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Title: Single Mode Wavelength-Tunable Thulium Fiber.
Creator: Shin, Dong Jin, Richardson, Martin, Schulzgen, Axel, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: Thulium fiber lasers have the broadest emission wavelength bandwidth out of any rare-earth doped fiber lasers. The emission wavelength starts from 1.75(&)#181;m and ends at around 2.15(&)#181;m, covering a vast swath of the eye safe wavelength region and intersecting with a large portion of mid-infrared atmospheric transmission window. Also, thulium fiber lasers provide the highest average output power of any other rare-earth doped fiber lasers in these wavelength regimes, making them...
Show moreThulium fiber lasers have the broadest emission wavelength bandwidth out of any rare-earth doped fiber lasers. The emission wavelength starts from 1.75(&)#181;m and ends at around 2.15(&)#181;m, covering a vast swath of the eye safe wavelength region and intersecting with a large portion of mid-infrared atmospheric transmission window. Also, thulium fiber lasers provide the highest average output power of any other rare-earth doped fiber lasers in these wavelength regimes, making them uniquely suited for applications such as remote sensing. At the moment, high power beam propagation of continuous wave laser through the atmosphere in the mid-infrared range is yet to be investigated anywhere. In particular, the effects of atmospheric water vapors on the thulium fiber laser propagation are unknown and are of great research interest. This dissertation identifies the stringent requirements in constructing a high power, single frequency, wavelength tunable, continuous wave thulium fiber laser with the aim of using it to study various atmospheric transmission effects. A fine spectral control scheme using diffraction gratings is explored and improvements are made. Moreover, a fiber numerical simulation model is presented and is used for designing and implementing the thulium fiber laser system. The current limitations of the implemented system are discussed and an improved system is proposed. This will lay the foundation for the future high power atmospheric propagation studies.
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Date Issued: 2018
Identifier: CFE0007372, ucf:52084
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007372

Title: Mode-locked Laser Based on Large Core Yb3+-Doped Fiber.
Creator: Jia, Fei, Amezcua Correa, Rodrigo, Schulzgen, Axel, Fathpour, Sasan, University of Central Florida
Abstract / Description: The thesis reviews principle of laser cavity and gives a general introduction to mode-locked laser (MLL). By using Yb3+-doped fiber as gain medium, passive MLL cavity is developed in experiment, aiming to obtain femtosecond pulses with high pump power from 25W to 35W. The gain medium fiber with 65(&)#181;m core diameter is cleaved with one flat end and another angled. Pump laser with 976nm wavelength is coupled into Yb3+-doped fiber to excite signal from 1020nm to 1040nm in the core. 9W is...
Show moreThe thesis reviews principle of laser cavity and gives a general introduction to mode-locked laser (MLL). By using Yb3+-doped fiber as gain medium, passive MLL cavity is developed in experiment, aiming to obtain femtosecond pulses with high pump power from 25W to 35W. The gain medium fiber with 65(&)#181;m core diameter is cleaved with one flat end and another angled. Pump laser with 976nm wavelength is coupled into Yb3+-doped fiber to excite signal from 1020nm to 1040nm in the core. 9W is threshold for laser setup. After locking all modes, picosecond pulses are output from laser cavity and coupled into dispersion delay fiber. By compressing pulse width, pulses are in soliton mode and then femtosecond laser pulses are obtained pulses are obtained. To measure ultrafast pulse width effectively, an auto-correlator based on Mach(-)Zehnder interferometer is developed. In the receiver terminal, a photodiode with range 320 nm to 1000 nm is used to detect signal and two photon absorption (TPA) method is applied.
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Date Issued: 2018
Identifier: CFE0007199, ucf:52249
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007199

Title: System for metal coated fiber fabrication.
Creator: Zhang, Da, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
Abstract / Description: For many specific applications, such as sensors, aerospace, chemical industry, deep-well oil-field industry, metal-coated fiber shows strong abilities to satisfy people's requirement. With in-line coating technology, we are able to coat Aluminum on the fibers.Using electromagnetic induction, we can easily heat an electrically conducting thing such as a metal with the eddy current. This process is defined as Induction heating. And we will melt the Aluminum by this induction heating during...
Show moreFor many specific applications, such as sensors, aerospace, chemical industry, deep-well oil-field industry, metal-coated fiber shows strong abilities to satisfy people's requirement. With in-line coating technology, we are able to coat Aluminum on the fibers.Using electromagnetic induction, we can easily heat an electrically conducting thing such as a metal with the eddy current. This process is defined as Induction heating. And we will melt the Aluminum by this induction heating during drawing the fibers on the tower. Introduce the fiber tower system. The drawing process of in-line technology is formed of the following steps: Position, Melting, Forming into fibers, Checking the diameter, Revising, Protective coatings. We will follow these to make the Aluminum coating fiber.With the help of the software which is 123D Design, I have four 3D model of the coating systems. Show the details of the all the coating systems such as the shape and the length of coated-fiber we can get.Talk about the photonic lantern which is the first project that I took part in when I joined the group. Show the mode profiles of our 6 to 1 lantern.
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Date Issued: 2017
Identifier: CFE0006677, ucf:51251
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006677

Title: Design and Verification of a Multi-Terawatt Ti-Sapphire Femtosecond Laser System.
Creator: Roumayah, Patrick, Shah, Lawrence, Richardson, Martin, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: Ultrashort pulse lasers are well-established in the scientific community due to the wide range of applications facilitated by their extreme intensities and broad bandwidth capabilities. This thesis will primarily present the design for the Mobile Ultrafast High Energy Laser Facility (MU-HELF) for use in outdoor atmospheric propagation experiments under development at the Laser Plasma Laboratory at UCF. The system is a 100fs 500 mJ Ti-Sapphire Chirped-Pulse Amplification (CPA) laser, operating...
Show moreUltrashort pulse lasers are well-established in the scientific community due to the wide range of applications facilitated by their extreme intensities and broad bandwidth capabilities. This thesis will primarily present the design for the Mobile Ultrafast High Energy Laser Facility (MU-HELF) for use in outdoor atmospheric propagation experiments under development at the Laser Plasma Laboratory at UCF. The system is a 100fs 500 mJ Ti-Sapphire Chirped-Pulse Amplification (CPA) laser, operating at 10 Hz. Some background on the generation of very high intensity optical pulses is also presented, alongside an overview of the physics of filamentation. As part of the design of MU-HELF, this thesis focuses on a novel approach to manage the large amount of dispersion required to stretch the pulse for CPA utilizing a custom nonlinear chirped Volume Bragg Grating (VBG) as a pulse stretcher matched to a traditional Treacy compressor. As part of this thesis, the dispersion of the CPA system was thoroughly modeled to properly design the chirped VBG and fabricated VBGs were characterized using a scanning spectral interferometry technique. The work demonstrates the feasibility of using a compact monolithic pulse stretcher in terawatt class CPA lasers.
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Date Issued: 2017
Identifier: CFE0006651, ucf:51241
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006651

Title: Multi-Purpose device for analyzing and measuring ultra-short pulses.
Creator: Mehta, Naman Anilkumar, Schulzgen, Axel, Delfyett, Peter, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: Intensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picosecondsand femtoseconds. I have built an in-house, compact, portable, industry standard intensityauto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widthsfrom 500 ps to 50 fs. The impetus for developing this instrument stemmed from our developmentof a multicore-fiber laser for high power laser applications, which also produces very short pulsesthat cannot be...
Show moreIntensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picosecondsand femtoseconds. I have built an in-house, compact, portable, industry standard intensityauto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widthsfrom 500 ps to 50 fs. The impetus for developing this instrument stemmed from our developmentof a multicore-fiber laser for high power laser applications, which also produces very short pulsesthat cannot be measured with an oscilloscope. As techniques for measuring short pulse-widthshave been well studied, what made my journey exciting was the process of taking an idea and realizinga successful, cost-efficient device. In this study, I have analyzed a Q-switched laser and mymeasured pulse-width matched the theoretical value previously calculated. I have also analyzedour mode-locked multicore fiber laser and results were encouraging. The notion to build one intensityautocorrelator was based on our labs future work, which was with modelocked multicore fiberlaser, which at the moment is giving pulses on order of nanoseconds. Dr. Axel Schulzgen gavethe responsibility to build an intensity autocorrelator on my shoulders. As, Intensity autocorrelatorshave been around for long time, he encouraged me to make one in house, compact, portableintensity autocorrelator which measures pulse widths of 50 fs up to 500 ps quite easily.
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Date Issued: 2016
Identifier: CFE0006353, ucf:51508
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006353

Title: Picosecond Yb-Doped Fiber Amplifier.
Creator: Zhu, Weibin, Amezcua Correa, Rodrigo, Schulzgen, Axel, Fathpour, Sasan, University of Central Florida
Abstract / Description: Due to its versatility, rare earth doped fiber amplifier (RDFA) has attracted a lot of researchers worldwide in recent years. Depends on different kinds of rare earth ion, RDFA can be categorized into neodymium doped fiber amplifier (NDFA), erbium doped fiber amplifier (EDFA), thulium doped fiber amplifier (TDFA), and so forth. Among many kinds of RDFA, the ytterbium doped fiber amplifier (YDFA) has received even more interest, especially in high power application, mainly because of its broad...
Show moreDue to its versatility, rare earth doped fiber amplifier (RDFA) has attracted a lot of researchers worldwide in recent years. Depends on different kinds of rare earth ion, RDFA can be categorized into neodymium doped fiber amplifier (NDFA), erbium doped fiber amplifier (EDFA), thulium doped fiber amplifier (TDFA), and so forth. Among many kinds of RDFA, the ytterbium doped fiber amplifier (YDFA) has received even more interest, especially in high power application, mainly because of its broad gain bandwidth and high conversion efficiency which are due to its relatively simple electronic structure.The purpose of this research is to study the YDFA by developing a model and building a YDFA setup in free space configuration. The active fiber used in the setup is a few modes, polarization-maintaining double-cladding ytterbium-doped large mode area (LMA) fiber and the length is 1m. The pump used is a tunable 975nm laser diode and a 1064nm laser diode was used as the seed which has 630 ps pulse duration time and 9.59 kHz repetition rate. This setup produces 2.514W average power, corresponding to a pulse peak power of 423kW, with 15W absorbed pump power. The spectrum of the output power has also been investigated.
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Date Issued: 2017
Identifier: CFE0006678, ucf:51214
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006678

Title: Design of a hydrogen-filled hollow-core Raman fiber laser.
Creator: Qin, Yangyang, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
Abstract / Description: The purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process...
Show moreThe purpose of this study is to investigate the design of a Raman fiber laser based on a molecule hydrogen-filled hollow-core fiber with non-touching single ring of capillaries structure. O-hydrogen vibrational frequency shift of 4155 cm-1 and rotational frequency shift of 587 cm-1 were employed to generate Raman scattering from a 1064nm pump source.A thorough exploration was made to show how all Raman fiber laser components made up: gas chamber, hollow-core fibers, windows. The whole process of chamber design, modification and fabrication were demonstrated. Besides, two kinds of anti-resonant hollow-core fibers were studied and tested. The transmission and loss spectrum of these fibers were measured thus it's easier to make a choice. Through the whole thesis a Raman fiber laser can be set up and tested very soon.
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Date Issued: 2017
Identifier: CFE0006645, ucf:51213
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006645

$LP fiber mode converters using holographic phase mask in photo-thermo-refractive glass$

Title: LP fiber mode converters using holographic phase mask in photo-thermo-refractive glass.
Creator: Patil, Aniket, Schulzgen, Axel, Delfyett, Peter, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: In this study, an investigation was undertaken to research the use of holographic phase masks (HPMs) in photo-thermo-refractive (PTR) glass as mode converters for linearly polarized (LP) fiber modes. A Spatial Light Modulator (SLM) was used to generate higher-order transverse fiber modes LPm,n. Under proper incidence condition on the holographic device, LPm,n modes are diffracted and simultaneously converted into higher order or lower order LP modes. The process was analyzed by imaging the...
Show moreIn this study, an investigation was undertaken to research the use of holographic phase masks (HPMs) in photo-thermo-refractive (PTR) glass as mode converters for linearly polarized (LP) fiber modes. A Spatial Light Modulator (SLM) was used to generate higher-order transverse fiber modes LPm,n. Under proper incidence condition on the holographic device, LPm,n modes are diffracted and simultaneously converted into higher order or lower order LP modes. The process was analyzed by imaging the far field on a CCD camera. It is demonstrated that using this novel method of converting transverse fiber modes several combinations of LP modes can be converted to each other with mode conversion efficiencies up to 70%. Mode purities were found to be around 85% for up conversion and around 90% for down conversion, respectively. It is noticed that this approach has several promising applications such as mode multiplexing, beam cleaning and power scaling of higher-order mode fiber lasers and amplifiers by combining mode conversion and beam combining.
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Date Issued: 2014
Identifier: CFE0005396, ucf:50459
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005396

Title: Peak Power Scaling of Nanosecond Pulses in Thulium based Fiber Lasers.
Creator: Gaida, Christian, Richardson, Martin, Shah, Lawrence, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: Thulium based fiber lasers represent a promising alternative for pulse energy scaling and highpeak power generation with ytterbium based systems at 1 micrometer. Advantages of thulium arise fromthe operation at longer wavelengths and a large gain bandwidth (1.8-2.1 micrometer). Nonlinear effects,such as self phase modulation, stimulated Raman scattering and stimulated Brillouin scattering generally limit peak power scaling in fiber lasers. The longer wavelength of thulium fiber lasersand...
Show moreThulium based fiber lasers represent a promising alternative for pulse energy scaling and highpeak power generation with ytterbium based systems at 1 micrometer. Advantages of thulium arise fromthe operation at longer wavelengths and a large gain bandwidth (1.8-2.1 micrometer). Nonlinear effects,such as self phase modulation, stimulated Raman scattering and stimulated Brillouin scattering generally limit peak power scaling in fiber lasers. The longer wavelength of thulium fiber lasersand large mode field areas can significantly increase the nonlinear thresholds. Compared to 1 micrometer systems, thulium fiber lasers enable single mode guidance for two times larger mode field diameterin step index fibers. Similar behavior is expected for index guiding thulium doped photonic crystalfibers.In this work a novel thulium doped rod type photonic crystal fiber design with large mode field diameter (>50 micrometer) was first characterized in CW-lasing configuration and then utilized as finalamplifier in a two stage master oscillator power amplifier. The system generated MW-level peakpower at 6.5ns pulse duration and 1kHz repetition rate. This world record performance exemplifiesthe potential of thulium fiber lasers to supersede ytterbium based systems for very high peak powergeneration in the future.As part of this work a computer model for the transient simulation of pulsed amplification inthulium based fiber lasers was developed. The simulations are in good agreement with the experimentalresults. The computer model can be used for efficient optimization of future thulium basedfiber amplifier designs.
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Date Issued: 2013
Identifier: CFE0004845, ucf:49699
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004845

Title: Broad Bandwidth, All-fiber, Thulium-doped Photonic Crystal Fiber Amplifier for Potential Use in Scaling Ultrashort Pulse Peak Powers.
Creator: Sincore, Alex, Richardson, Martin, Shah, Lawrence, Amezcua Correa, Rodrigo, University of Central Florida
Abstract / Description: Fiber based ultrashort pulse laser sources are desirable for many applications; however generating high peak powers in fiber lasers is primarily limited by the onset of nonlinear effects such as self-phase modulation, stimulated Raman scattering, and self-focusing. Increasing the fiber core diameter mitigates the onset of these nonlinear effects, but also allows unwanted higher-order transverse spatial modes to propagate. Both large core diameters and single-mode propagation can be...
Show moreFiber based ultrashort pulse laser sources are desirable for many applications; however generating high peak powers in fiber lasers is primarily limited by the onset of nonlinear effects such as self-phase modulation, stimulated Raman scattering, and self-focusing. Increasing the fiber core diameter mitigates the onset of these nonlinear effects, but also allows unwanted higher-order transverse spatial modes to propagate. Both large core diameters and single-mode propagation can be simultaneously attained using photonic crystal fibers.Thulium-doped fiber lasers are attractive for high peak power ultrashort pulse systems. They offer a broad gain bandwidth, capable of amplifying sub-100 femtosecond pulses. The longer center wavelength at 2 ?m theoretically enables higher peak powers relative to 1 ?m systems since nonlinear effects inversely scale with wavelength. Also, the 2 ?m emission is desirable to support applications reaching further into the mid-IR.This work evaluates the performance of a novel all-fiber pump combiner that incorporates a thulium-doped photonic crystal fiber. This fully integrated amplifier is characterized and possesses a large gain bandwidth, essentially single-mode propagation, and high degree of polarization. This innovative all-fiber, thulium-doped photonic crystal fiber amplifier has great potential for enabling high peak powers in 2 ?m fiber systems; however the current optical-to-optical efficiency is low relative to similar free-space amplifiers. Further development and device optimization will lead to higher efficiencies and improved performance.
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Date Issued: 2014
Identifier: CFE0005260, ucf:50611
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005260

Title: Nonlinear Dynamics in Multimode Optical Fibers.
Creator: Eftekhar, Mohammad Amin, Christodoulides, Demetrios, Amezcua Correa, Rodrigo, Li, Guifang, Kaup, David, University of Central Florida
Abstract / Description: Multimode optical fibers have recently reemerged as a viable platform for addressing a number of long-standing issues associated with information bandwidth requirements and power-handling capabilities. The complex nature of heavily multimoded systems can be effectively exploited to observe altogether novel physical effects arising from spatiotemporal and intermodal linear and nonlinear processes. Here, we have studied nonlinear dynamics in multimode optical fibers (MMFs) in both the normal...
Show moreMultimode optical fibers have recently reemerged as a viable platform for addressing a number of long-standing issues associated with information bandwidth requirements and power-handling capabilities. The complex nature of heavily multimoded systems can be effectively exploited to observe altogether novel physical effects arising from spatiotemporal and intermodal linear and nonlinear processes. Here, we have studied nonlinear dynamics in multimode optical fibers (MMFs) in both the normal and anomalous dispersion regimes. In the anomalous dispersion regime, the nonlinearity leads to a formation of spatiotemporal 3-D solitons. Unlike in single-mode fibers, these solitons are not unique and their properties can be modified through the additional degrees of freedom offered by these multimoded settings. In addition, soliton related processes such as soliton fission and dispersive wave generation will be also drastically altered in such multimode systems. Our theoretical work unravels some of the complexities of the underlying dynamics and helps us better understand these effects. The nonlinear dynamics in such multimode systems can be accelerated through a judicious fiber design. A cancelation of Raman self-frequency shifts and Blue-shifting multimode solitons were observed in such settings as a result of an acceleration of intermodal oscillations. Spatiotemporal instabilities in parabolic-index multimode fibers will also be discussed. In the normal dispersion regime, this effect can be exploited to generate an ultrabroad and uniform supercontinuum that extends more than 2.5 octaves. To do so, the unstable spectral regions are pushed away from the pump, thus sweeping the entire spectrum. Multimode parabolic pulses were also predicted and observed in passive normally dispersive tapered MMFs. These setting can obviate the harsh bandwidth limitation present in single-mode system imposed by gain medium and be effectively used for realizing high power multimode fiber lasers. Finally, an instant and efficient second-harmonic generation was observed in the multimode optical fibers. Through a modification of initial conditions, the efficiency of this process could be enhanced to a record high of %6.5.
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Date Issued: 2018
Identifier: CFE0007399, ucf:52063
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007399

Title: 2 micron fiber lasers: power scaling concepts and limitations.
Creator: Sincore, Alex, Richardson, Martin, Amezcua Correa, Rodrigo, Schulzgen, Axel, Shah, Lawrence, University of Central Florida
Abstract / Description: Thulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin...
Show moreThulium- and holmium-doped fiber lasers (TDF and HDF) emitting at 2 micron offer unique benefits and applications compared to common ytterbium-doped 1 micron lasers. This dissertation details the concepts, limitations, design, and performance of four 2 micron fiber laser systems. While these lasers were developed for various end-uses, they also provide further insight into two major power scaling limitations. The first limitation is optical nonlinearities: specifically stimulated Brillouin scattering (SBS) and modulation instability (MI). The second limitation is thermal failure due to inefficient pump conversion. First, a 21.5 W single-frequency, single-mode laser with adjustable output from continuous-wave to nanosecond pulses is developed. Measuring the SBS threshold versus pulse duration enables the Brillouin gain coefficient and gain bandwidth to be determined at 2 micron. Second, a 23 W spectrally-broadband, nanosecond pulsed laser is constructed for materials processing applications. The temporally incoherent multi-kW peak power pulses can also efficiently produce MI and supercontinuum generation by adjusting the input spectral linewidth. Third, the measured performance of in-band pumped TDF and HDF lasers are compared with simulations. HDF displays low efficiencies, which is explained by including ion clustering in the simulations. The TDF operates with impressive (>)90% slope efficiencies. Based on this result, a system design for (>)1 kW average power TDF amplifier is described. The designed final amplifier will be in-band pumped to enable high efficiency and low thermal load. The amplifier efficiency, operating bandwidth, thermal load, and nonlinear limits are modeled and analyzed to provide a framework for execution. Overall, this dissertation provides further insight and understanding on the various processes that limit power scaling of 2 micron fiber lasers.
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Date Issued: 2018
Identifier: CFE0007374, ucf:52105
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007374

Title: Mode coupling in space-division multiplexed systems.
Creator: Liu, Huiyuan, Li, Guifang, Likamwa, Patrick, Amezcua Correa, Rodrigo, Chanda, Debashis, University of Central Florida
Abstract / Description: Even though fiber-optic communication systems have been engineered to nearly approach the Shannon capacity limit, they still cannot meet the exponentially-growing bandwidth demand of the Internet. Space-division multiplexing (SDM) has attracted considerable attention in recent years due to its potential to address this capacity crunch. In SDM, the transmission channels support more than one spatial mode, each of which can provide the same capacity as a single-mode fiber. To make SDM practical...
Show moreEven though fiber-optic communication systems have been engineered to nearly approach the Shannon capacity limit, they still cannot meet the exponentially-growing bandwidth demand of the Internet. Space-division multiplexing (SDM) has attracted considerable attention in recent years due to its potential to address this capacity crunch. In SDM, the transmission channels support more than one spatial mode, each of which can provide the same capacity as a single-mode fiber. To make SDM practical, crosstalk among modes must be effectively managed. This dissertation presents three techniques for crosstalk management for SDM. In some cases such as intra-datacenter interconnects, even though mode crosstalk cannot be completely avoided, crosstalk among mode groups can be suppressed in properly-designed few-mode fibers to support mode group-multiplexed transmission. However, in most cases, mode coupling is unavoidable. In free-space optical (FSO) communication, mode coupling due to turbulence manifests as wavefront distortions. Since there is almost no modal dispersion in FSO, we demonstrate the use of few-mode pre-amplified receivers to mitigate the effect of turbulence without using adaptive optics. In fiber-optic communication, multi-mode fibers or long-haul few-mode fibers not only suffer from mode crosstalk but also large modal dispersion, which can only be compensated electronically using multiple-input-multiple-output (MIMO) digital signal processing (DSP). In this case, we take the counterintuitive approach of introducing strong mode coupling to reduce modal group delay and DSP complexity.
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Date Issued: 2019
Identifier: CFE0007831, ucf:52806
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007831

Title: High performance liquid crystal devices for augmented reality and virtual reality.
Creator: Talukder, Md Javed Rouf, Wu, Shintson, Moharam, Jim, Amezcua Correa, Rodrigo, Dong, Yajie, University of Central Florida
Abstract / Description: See-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time...
Show moreSee-through augmented reality and virtual reality displays are emerging due to their widespread applications in education, engineering design, medical, retail, transportation, automotive, aerospace, gaming, and entertainment. For augmented reality and virtual reality displays, high-resolution density, high luminance, fast response time and high ambient contrast ratio are critically needed. High-resolution density helps eliminate the screen-door effect, high luminance and fast response time enable low duty ratio operation, which plays a key role for suppressing image blurs. A dimmer placed in front of AR display helps to control the incident background light, which in turn improves the image contrast. In this dissertation, we have focused three crucial display metrics: high luminance, fast motion picture response time (MPRT) and high ambient contrast ratio.We report a fringe-field switching liquid crystal display, abbreviated as d-FFS LCD, by using a low viscosity material and new diamond-shape electrode configuration. Our proposed device shows high transmittance, fast motion picture response time, low operation voltage, wide viewing angle, and indistinguishable color shift and gamma shift. We also investigate the rubbing angle effects on transmittance and response time. When rubbing angle is 0 degree, the virtual wall effect is strong, resulting in fast response time but compromised transmittance. When rubbing angle is greater than 1.2 degree, the virtual walls disappear, as a result, the transmittance increases dramatically, but the tradeoff is in slower response time. We also demonstrate a photo-responsive guest-host liquid crystal (LC) dimmer to enhance the ambient contrast ratio in augmented reality displays. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with negative dielectric anisotropy. In this device, transmittance changes from bright state to dark state by exposing a low intensity UV or blue light. Reversal process can be carried out by red light or thermal effect. Such a polarizer-free photo-activated dimmer can also be used for wide range of applications, such as diffractive photonic devices, portable information system, vehicular head-up displays, and smart window for energy saving purpose. A dual-stimuli polarizer-free dye-doped liquid crystal (LC) device is demonstrated as a dimmer. Upon UV/blue light exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. Such an electric-field-assisted reversal time can be reduced from ~10s to a few milliseconds, depending on the applied voltage. Considering power consumption, low manufacturing cost, and large fabrication tolerance, this device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.
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Date Issued: 2019
Identifier: CFE0007731, ucf:52425
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007731

Title: Imaging through Glass-air Anderson Localizing Optical Fiber.
Creator: Zhao, Jian, Schulzgen, Axel, Amezcua Correa, Rodrigo, Pang, Sean, Delfyett, Peter, Mafi, Arash, University of Central Florida
Abstract / Description: The fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be...
Show moreThe fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be insensitive to environmental perturbations, such as mechanical bending or temperature variations. Besides, both coherent and incoherent light sources should be compatible with the imaging system. It is extremely challenging for current technologies to address all these issues simultaneously. The limitation mainly lies in the deficient stability and imaging capability of fiber-optic devices and the limited image reconstruction capability of algorithms. To address these limitations, we first develop the randomly disordered glass-air optical fiber featuring a high air-filling fraction (~28.5 %) and low loss (~1 dB per meter) at visible wavelengths. Due to the transverse Anderson localization effect, the randomly disordered structure can support thousands of modes, most of which demonstrate single-mode properties. By making use of these modes, the randomly disordered optical fiber provides a robust and low-loss imaging system which can transport images with higher quality than the best commercially available imaging fiber. We further demonstrate that deep-learning algorithm can be applied to the randomly disordered optical fiber to overcome the physical limitation of the fiber itself. At the initial stage, a laser-illuminated system is built by integrating a deep convolutional neural network with the randomly disordered optical fiber. Binary sparse objects, such as handwritten numbers and English letters, are collected, transported and reconstructed using this system. It is proved that this first deep-learning-based fiber imaging system can perform artifact-free, lensless and bending-independent imaging at variable working distances. In real-world applications, the gray-scale biological subjects have much more complicated features. To image biological tissues, we re-design the architecture of the deep convolutional neural network and apply it to a newly designed system using incoherent illumination. The improved fiber imaging system has much higher resolution and faster reconstruction speed. We show that this new system can perform video-rate, artifact-free, lensless cell imaging. The cell imaging process is also remarkably robust with regard to mechanical bending and temperature variations. In addition, this system demonstrates stronger transfer-learning capability than existed deep-learning-based fiber imaging system.
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Date Issued: 2019
Identifier: CFE0007746, ucf:52405
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007746

Title: Hybrid integration of second- and third-order highly nonlinear waveguides on silicon substrates.
Creator: Camacho Gonzalez, Guillermo Fernando, Fathpour, Sasan, Likamwa, Patrick, Amezcua Correa, Rodrigo, Peale, Robert, University of Central Florida
Abstract / Description: In order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film...
Show moreIn order to extend the capabilities and applications of silicon photonics, other materials and compatible technologies have been developed and integrated on silicon substrates. A particular class of integrable materials are those with high second- and third-order nonlinear optical properties. This work presents contributions made to nonlinear integrated photonics on silicon substrates, including chalcogenide waveguides for over an octave supercontinuum generation, and rib-loaded thin-film lithium niobate waveguides for highly efficient second-harmonic generation. Through the pursuit of hybrid integration of the two types of waveguides for applications such as on-chip self-referenced optical frequency combs, we have experimentally demonstrated fabrication integrability of chalcogenide and thin-film lithium niobate waveguides in a single chip and a pathway for both second- and third-order nonlinearities occurring therein. Accordingly, design specifications for an efficient nonlinear integrated waveguide are reported, showing over an octave supercontinuum generation and frequency selectivity for second-harmonic generation, enabling potentials of on-chip interferometry techniques for carrier-envelope offset detection, and hence stabilized optical combs.
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Date Issued: 2019
Identifier: CFE0007607, ucf:52560
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007607

Title: Sensing with Specialty Optical Fibers.
Creator: Van Newkirk, Amy, Schulzgen, Axel, Delfyett, Peter, Amezcua Correa, Rodrigo, Raghavan, Seetha, University of Central Florida
Abstract / Description: Fiber optic based sensing is a growing field with many applications in civil and aerospace engineering, oil and gas industries, and particularly in harsh environments where electronics are not able to function. Optical fibers can be easily integrated into structures, are immune to electromagnetic interference, can be interrogated from remote distances, and can be multiplexed for distributed measurements. Because of these properties, specialty fiber designs and devices are being explored for...
Show moreFiber optic based sensing is a growing field with many applications in civil and aerospace engineering, oil and gas industries, and particularly in harsh environments where electronics are not able to function. Optical fibers can be easily integrated into structures, are immune to electromagnetic interference, can be interrogated from remote distances, and can be multiplexed for distributed measurements. Because of these properties, specialty fiber designs and devices are being explored for sensing temperature, strain, pressure, curvature, refractive index, and more. Here we show a detailed analysis of a multicore fiber (MCF) for sensing, including its design and optimization in simulation, as well as experimental operation when used as sensor. The multicore fiber sensor's performance as a function of temperature, strain, bending, and acoustic waves are all explored. The MCF sensors are shown to be able to withstand temperatures up to 1000(&)deg;C, making them suitable to be harsh environment sensors. Additionally, a simple method for increasing the sensitivity of the MCF to longitudinal force is shown to multiple the sensitivity of the MCF sensor by a factor of seven. Also, a configuration for decoupling force and temperature will be presented. Finally, a developing all-fiber device, a photonic lantern, will be shown in conjunction with the MCF in order to increase sensitivity, add directional sensitivity, and lower the cost of the sensor interrogation for bending measurements. In addition to the multicore fiber, an analysis of anti-resonant hollow core fiber (ARHCF) is also presented. The fibers' design-dependent propagation losses are explored, as well as their higher order mode content. Also, a potential application of an ARHCF for an in-fiber Raman air sensor is introduced, and the design optimization in simulation is shown.
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Date Issued: 2016
Identifier: CFE0006409, ucf:51490
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006409

Title: Mode Evolution in Fiber Based Devices for Optical Communication Systems.
Creator: Huang, Bin, Li, Guifang, Amezcua Correa, Rodrigo, Abouraddy, Ayman, Chen, Haoshuo, University of Central Florida
Abstract / Description: Space division multiplexing (SDM) is the most promising way of increasing the capacity of a single fiber. To enable the few mode fiber (FMF) or multi-mode fiber (MMF) transmission system, several major challenges have to be overcome. One is the urgent need of ideal mode multiplexer, the second is the perfect amplification for all spatial modes, another one is the modal delay spread (MDS) due to group velocity difference of spatial modes. The main subject of this dissertation is to model,...
Show moreSpace division multiplexing (SDM) is the most promising way of increasing the capacity of a single fiber. To enable the few mode fiber (FMF) or multi-mode fiber (MMF) transmission system, several major challenges have to be overcome. One is the urgent need of ideal mode multiplexer, the second is the perfect amplification for all spatial modes, another one is the modal delay spread (MDS) due to group velocity difference of spatial modes. The main subject of this dissertation is to model, fabricate and characterize the mode multiplexer for FMF transmission. First, we designed a novel resonant mode coupler (structured directional coupler pair). After that, we studied the adiabatic mode multiplexer (photonic lantern). 6-mode photonic lantern using graded-index (GI) MMFs is proposed and demonstrated, which alleviates the adiabatic require-ment and improves mode selectivity. Then, 10-mode photonic lantern is demonstrated using novel double cladding micro-structured drilling-hole preform, which alleviates the adiabatic requirement and demonstrate a feasible way to scale up the lantern modes. Also, multi-mode photonic lantern is studied for high order input modes. In addition, for the perfect amplification of the modes, cladding pump method is demonstrated. The mode selective lantern designed and fabricated can be used for the characterization of few mode amplifier with swept wavelength interferometer (SWI). Also, we demonstrated the application of the use of the few mode amplifier for the turbulence-resisted preamplified receiver. Besides, for the reduction of MDS, the long period grating for introducing strong mode mixing is demonstrated.
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Date Issued: 2017
Identifier: CFE0006884, ucf:51720
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006884

Title: High power fiber lasers and fiber devices.
Creator: Sanjabieznaveh, Zeinab, Amezcua Correa, Rodrigo, Chang, Zenghu, Argenti, Luca, Richardson, Martin, Schulzgen, Axel, University of Central Florida
Abstract / Description: Fiber lasers and fiber amplifiers have experienced considerable improvements in recent years and demonstrated remarkable power scalability. However, due to high optical intensity in the core, the performance of high power fiber lasers is limited by detrimental nonlinear processes, such as four-wave mixing, self-phase modulation, stimulated Brillouin scattering, and stimulated Raman scattering. To mitigate nonlinear effects, very large mode area (LMA) fibers, which exhibit a mode field...
Show moreFiber lasers and fiber amplifiers have experienced considerable improvements in recent years and demonstrated remarkable power scalability. However, due to high optical intensity in the core, the performance of high power fiber lasers is limited by detrimental nonlinear processes, such as four-wave mixing, self-phase modulation, stimulated Brillouin scattering, and stimulated Raman scattering. To mitigate nonlinear effects, very large mode area (LMA) fibers, which exhibit a mode field diameter larger than 30 ?m have been developed. However, for larger core sizes the discrimination capabilities of conventional fiber designs decrease, consequently, LMA fibers are not strictly single mode which ultimately at high average powers results in sudden degradation of the output beam of a fiber laser or amplifier, namely, modal instability (MI). To suppress higher order modes (HOMs) in LMA fibers, various techniques have been proposed such as large pitch fibers (LPFs), differential bend loss for HOMs, leakage channel fibers, mode filtering with tapers, and chirally coupled cores. This thesis is divided into two parts. In the first two chapters, I focus on simulation, design and characterization of advanced high power fiber amplifiers. In the first chapter, I study the numerical modeling of the MI in active LMA fibers. Using a high fidelity time dependent computer model based on beam propagation method (BPM), taking laser gain and thermal effects into account, I show that engineering pump scheme is a promising technique leading to an appreciable threshold increase in a fiber amplifier. As an example I demonstrate that bi-directional pump scheme increases the instabilities threshold by a factor of ~30% with respect to the forward pump configuration. In the second chapter, I present a novel design of microstructured large pitch, LMA asymmetric rod-type fiber to achieve higher MI threshold. By eliminating mirror symmetries in the cladding of the LPF through six high refractive index germanium-doped silica inclusions, we reduce the overlap of the LP1m-like modes with the core region, which leads to strong HOM delocalization and enhanced preferential gain for the fundamental mode in active fibers. The third and fourth chapters of this thesis are focused on all-fiber mode multiplexers for communication applications. In the third chapter, I present an all-fiber mode selective photonic lantern mode multiplexer designed for launching into few-mode multicore fibers (FM-MCFs). This device is capable of selectively exciting LP01, LP11a and LP11b modes in a seven core configuration resulting in 21 spatial channels, with less than 38 dB crosstalk and with insertion loss below 0.4 dB. This device can be a critical component for the evolution of high capacity, high-density space division multiplexing (SDM) transmission networks based on MCFs.In the fourth chapter, I demonstrate for the first time, an all-fiber orbital angular momentum (OAM) mode multiplexer to efficiently generate and simultaneously multiplex multiple OAM modes within a broad spectral range of at least 550 nm. This innovative all-fiber passive design provides simultaneous multiplexing of multiple orthogonal OAM modes in a single fiber device with low loss and at low design complexity, therefore, it is of grand utility in variety of applications in classical and modern optical studies.
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Date Issued: 2017
Identifier: CFE0006956, ucf:51632
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006956

Title: Fiber Optimization for Operation Beyond Transverse Mode Instability Limitations.
Creator: Bradford, Joshua, Richardson, Martin, Gaume, Romain, Amezcua Correa, Rodrigo, Shah, Lawrence, University of Central Florida
Abstract / Description: Transverse Mode Instabilities (TMIs) stand as a fundamental limitation to power and brightness scaling in laser systems based upon optical fiber technologies. This work comprises experimental and theoretical investigations into fiber laser design that should minimize the effects of Stimulated Thermal Rayleigh Scattering. Theoretical discussions and simulations focus on how fiber parameters affect transverse mode coupling. These include core geometry optimization, pump geometry optimization,...
Show moreTransverse Mode Instabilities (TMIs) stand as a fundamental limitation to power and brightness scaling in laser systems based upon optical fiber technologies. This work comprises experimental and theoretical investigations into fiber laser design that should minimize the effects of Stimulated Thermal Rayleigh Scattering. Theoretical discussions and simulations focus on how fiber parameters affect transverse mode coupling. These include core geometry optimization, pump geometry optimization, in addition to the effects of HOM content and losses on the TMI threshold. Experimentally, a high-power laser facility is commissioned with beam quality diagnostics to quantify the thresholds of the onset of modal interferences and their impacts on beam quality. These diagnostics include high-resolution Fourier Transform Interferometry (FTI) and in-situ power-in-the-bucket measurements. The design and characterization capabilities developed here are crucial to the development of next-generation high-power fiber laser capabilities.
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Date Issued: 2018
Identifier: CFE0006980, ucf:51646
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006980

Fiber Laser (2)	+ -
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fiber laser (2)	+ -
optical fiber (2)	+ -
thulium (2)	+ -

2 ?m (1)	+ -
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Augmented reality (1)	+ -
Auto-correlator (1)	+ -
Azobenzene (1)	+ -
Chiral agent (1)	+ -
Chirped Pulse Amplification (1)	+ -
Dichroic dye (1)	+ -
Dispersive Waves (1)	+ -
Fast motion picture response time (1)	+ -
Fast response LCD (1)	+ -
Fiber Amplifier (1)	+ -
Fiber Lasers (1)	+ -
Fiber mode converter (1)	+ -
Filamentation (1)	+ -
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Amezcua Correa, Rodrigo (21)	+ -
University of Central Florida (21)	+ -
Schulzgen, Axel (11)	+ -
Richardson, Martin (7)	+ -
Shah, Lawrence (7)	+ -

Delfyett, Peter (4)	+ -
Fathpour, Sasan (3)	+ -
Li, Guifang (3)	+ -
Likamwa, Patrick (3)	+ -
Christodoulides, Demetrios (2)	+ -
Sincore, Alex (2)	+ -
Abouraddy, Ayman (1)	+ -
Argenti, Luca (1)	+ -
Bradford, Joshua (1)	+ -
Camacho Gonzalez, Guillermo Fernando (1)	+ -
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