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An optimized design for a broadband Raman optical amplifier in standard single-mode fiber covering the C and L bands is presented, to be used in combination with wideband optical phase conjugation (OPC) nonlinearity compensation. The use of two Raman pumps and fiber Bragg grating reflectors at different wavelengths for the transmitted (C band) and conjugated (L band) WDM channels is proposed to extend bandwidth beyond the limits imposed by single-wavelength pumping, for a total 10 THz. Optimization of pump and reflector wavelength, as well as pump powers, allows us to achieve low asymmetry across the whole transmission band for optimal nonlinearity compensation. System performance is simulated to estimate OSNR, gain flatness and nonlinear Kerr distortion.

We present a quantum theory of nondegenerate phase-sensitive parametric amplification in a ?(3) nonlinear medium. The nonzero response time of the Kerr (?(3)) nonlinearity determines the quantum-limited. noise figure of the ?(3) parametric amplification, as well as the limit on quadrature squeezing. This nonzero response time of the nonlinearity requires coupling of the parametric process to a molecular vibration phonon bath, causing the addition of excess noise through spontaneous Raman scattering. We present analytical expressions for the quantum-limited noise figure of frequency nondegenerate and frequency degenerate ?(3) parametric amplifiers operated as phase-sensitive amplifiers. We also present results for frequency nondegenerate quadrature squeezing. We show that our nondegenerate squeezing theory agrees with the degenerate squeezing theory of Boivin and Shapiro as degeneracy is approached. We have also included the effect of linear loss on the phase-sensitive process. © 2006 Optical Society of America.

We present a quantum theory of nondegenerate phase-sensitive parametric amplification in a ?(3) nonlinear medium. The nonzero response time of the Kerr (?(3)) nonlinearity determines the quantum-limited. noise figure of the ?(3) parametric amplification, as well as the limit on quadrature squeezing. This nonzero response time of the nonlinearity requires coupling of the parametric process to a molecular vibration phonon bath, causing the addition of excess noise through spontaneous Raman scattering. We present analytical expressions for the quantum-limited noise figure of frequency nondegenerate and frequency degenerate ?(3) parametric amplifiers operated as phase-sensitive amplifiers. We also present results for frequency nondegenerate quadrature squeezing. We show that our nondegenerate squeezing theory agrees with the degenerate squeezing theory of Boivin and Shapiro as degeneracy is approached. We have also included the effect of linear loss on the phase-sensitive process. © 2006 Optical Society of America.

In this paper, we review different designs of distributed Raman amplifiers which have been proposed to minimize the signal power profile asymmetry in mid-link optical phase conjugation systems. We demonstrate how the symmetrical signal power profiles along the fiber can be achieved using various distributed Raman amplification techniques in the single-span and more realistic multi-span circumstances. In addition, we show the theoretically predicted results of the Kerr nonlinear product reduction with different Raman techniques in mid-link optical phase conjugator systems, and then in-line/long-haul transmission performance using numerical simulations.

A novel vortex-transform is proposed. This transform allows for generating complex-valued functions from modulated intensity patterns, including high frequency components from modulation, without the generation of unstable phase singularities. From these complex-valued functions it is possible to obtain intensity and pseudo-phase maps to analyze the intensity recordings without the necessity of phase retrieval techniques. The intensity and pseudo-phase maps obtained by using this transform preserve the modulation structure onto the intensity and phase modulo 2? maps, including stable phase singularities. ©2013 Optical Society of America.

In this study, the effect of the shift in the refractive index between two dispersive elements on the output phase-conjugated (PC) wave power of waveband-shift-free optical-phase conjugators based on difference-frequency generation (DFG-OPCs) is analyzed. First, a numerical model of the DFG-OPC is built by considering the shift ∆n in the refractive index. The derived formula shows that the output PC wave power of DFG-OPCs depends on the shift in the refractive index. Subsequently, the dependence of the output PC wave power on the shift is confirmed analytically. Calculations indicate that the output PC wave power varies according to the shift. For a relatively fractional shift ∆n = 1.0e-6, the output PC power is degraded by 3 dB. Finally, acceptable values of the shift and temperature difference are calculated as functions of the length of the dispersive element. It is illustrated in this study that the acceptable value of shift in the refractive index increases as the length of the dispersive element is reduced and that the output PC wave power can be stabilized against changes in temperature.

Normal development of the visual system in infants relies on clear images being projected onto the retina, which can be disrupted by lens opacity caused by congenital cataract. This disruption, if uncorrected in early life, results in amblyopia (permanently decreased vision even after removal of the cataract). Doctors are able to prevent amblyopia by removing the cataract during the first several weeks of life, but this surgery risks a host of complications, which can be equally visually disabling. Here, we investigated the feasibility of focusing light noninvasively through highly scattering cataractous lenses to stimulate the retina, thereby preventing amblyopia. This approach would allow the cataractous lens removal surgery to be delayed and hence greatly reduce the risk of complications from early surgery. Employing a wavefront shaping technique named time-reversed ultrasonically encoded optical focusing in reflection mode, we focused 532-nm light through a highly scattering ex vivo adult human cataractous lens. This work demonstrates a potential clinical application of wavefront shaping techniques. © 2017 The Authors.

Power modulated visible lasers are interesting for a number of applications within areas such as laser displays and medical laser treatments. In this paper, we present a system for modulating the second-harmonic light generated by single-pass frequency doubling of a distributed feedback (DFB) master oscillator power amplifier (MOPA) laser diode with separate electrical contacts for the MO and the PA. A modulation depth in excess of 97% from 0.1 Hz to 10 kHz is demonstrated. This is done by wavelength tuning of the laser diode using only a 40 mA adjustment of the current through the MO. The bandwidth of the modulation is limited by the electronics. This method has the potential to decrease the size as well as cost of modulated visible lasers. The achievable optical powers will increase as DFB MOPAs are further developed. (C) 2017 Optical Society of America

Kerr nonlinearity compensation by optical phase conjugation is demonstrated in a WDM PDM 16-QAM system. Improved received signal quality is reported for both dispersion-compensated and dispersion-uncompensated transmission and a comparison with digital backpropagation is provided.

A collaborative experiment was made in Paris, between CREOL, University of Central Florida and LOA, Ecole Polytechnique, on filament interaction. Recent studies have proven that crossing two filaments can give interesting phenomena (plasma grating, energy exchange). In this collaborative work we study the possibility and the characterization of Optical Phase Conjugation (OPC) created by two counter propagating filaments interacting with a probe beam.

This letter presents the experimental demonstration of degenerate two-beam phase conjugation (2BPC) by using a one-dimensional ZnS-YF photonic crystal (PhC) with central defect mode. The effective third-order nonlinearity of the PhC sample is (2.3 +/- 0.1) x 10(-9) which is almost four orders of magnitude larger in comparison with bulk ZnS (chi((3))(ZnS) = 3.1 x 10(-13) esu). This large nonlinearity enhancement is attributed to the high density of mode and the electric field localization around the central defect layer near the defect mode wavelength. The realization of 2BPC utilizing defect mode in a simple PhC structure will greatly reduce the complexity to achieve compact and low-power nonlinear optical devices.

This work reports the properties of stimulated Rayleigh-Bragg scattering (SRBS) from a two-photon absorbing CdSe-Cds-ZnS quantum-rods (QRs) solution in chloroform, excited by 1064-nm and similar to 13-ns laser pulses. The two-photon absorbing capability of the scattering medium, as well as the pump threshold, spectral structure, and pulse waveforms of the backward stimulated scattering were measured. Comparing to a pure solvent or an organic dye-solution, the semiconductor QR system has many advantages such as the lower pump threshold, higher energy transfer efficiency, and better photo-physical and photo-chemical stability. The measured output/input characteristic curve shows that the backward SRBS can enhance the optical power limiting performance that is based on two-photon absorption, backward stimulated scattering, and other nonlinear absorption mechanisms. In addition, the backward SRBS beam from our sample medium exhibits a fairly good optical phase-conjugation capability, so that the distortion influence from an inserted aberrator can be automatically removed., QC 20100525

For packet-switched metro networks, one of the key functional blocks is the transmission, extraction and update of in-band packet control information, which is commonly known as packet label swapping. The use of phase modulation to carry the control information can facilitate easy swapping process. By combining phase modulated label with intensity modulated optical packets in non-overlapping manners, we demonstrated that optical packet label swapping using differential phase-shift keyed labels could be achieved without any sacrifices in packet signal quality., In packet-switched optical networks, packets are routed using IP-based distributed routing algorithms. Inconsistencies in routing information among routing nodes may result in routing loop formation in the network and may cause severe impact on the network performance. We proposed a novel packet routing loop mitigation scheme based on the principle of packet 'time-to-live' value countdown. This scheme enables loop mitigation to be performed asynchronously in optical domain, causing little packet processing delay. Two implementations were proposed. One was based on differential optical phase shift keying and the other was based on self-phase modulation in semiconductor optical amplifier., The continuous increase in Internet-bound data traffic in recent years has placed higher requirement on network bandwidth and flexibility. In view of this, packet-switched metro networks and broadband passive optical access networks have emerged as the promising network solutions in the near future. The focus of this thesis is on the improvement of functionality and reliability as well as the reduction of system complexity in optical metro area and access networks with the use of optical phase modulation techniques. In access network, constant-intensity optical phase modulation formats were studied for their applications in wavelength-division-multiplexed passive optical networks with centralized light source. Using them as downstream modulation formats, the downstream optical carrier can be utilized to carry upstream intensity-modulated data. It can greatly simplify upstream transmission and facilitate network management. Experimental and numerical analyses shows promising upstream re-modulation performance with a simple optical network unit (ONU) configuration., Hung Wai., Adviser: Lian-Kuan Chen., Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: ., Thesis (Ph.D.)--Chinese University of Hong Kong, 2004., Includes bibliographical references (leaves 130-135)., Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web., Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web., s in English and Chinese., School code: 1307., isbn: 9781109405132, Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)

A method has been demonstrated by holographic interference in photorefractive media for real-time image subtraction requiring only a single pass through an aberrating medium. Image enhancement by passing the conjugate beam back through the aberration (double pass) has been previously demonstrated. For various applications, a single pass is required. The theory and experiments for double- and single-pass arrangements are presented.

Lam Sio Kuan., Thesis (Ph.D.)--Chinese University of Hong Kong, 1998., Includes bibliographical references (p. 111-116)., Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web., Mode of access: World Wide Web., s in English and Chinese., http://library.cuhk.edu.hk/record=b6073111, Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)

by Tong Wai Yin Alex., Thesis (M.Phil.)--Chinese University of Hong Kong, 1996., Includes bibliographical references (leaf 55)., Acknowledgement, Biographical Sketch, Table of contents, Chapter Chapter 1 --- Introduction --- p.1, Chapter Chapter 2 --- Nonlinear Optics in dye-doped solid --- p.4, Chapter 2.1 --- Nonlinear Optics --- p.4, Chapter 2.2 --- Photophysics of dye molecules --- p.6, Chapter 2.3 --- Nonlinear effect in dye-doped solid --- p.8, Chapter Chapter 3 --- Sol-Gel Silica --- p.11, Chapter 3.1 --- The formation of dye-doped sol-gel silica --- p.11, Chapter 3.2 --- The physical properties --- p.15, Chapter 3.3 --- The optical properties --- p.16, Chapter Chapter 4 --- Saturation Absorption --- p.18, Chapter 4.1 --- Saturation Absorption in Fluorescein 548 dye-doped solid --- p.18, Chapter 4.2 --- Experimental Details --- p.19, Chapter 4.3 --- Results and Discussion --- p.19, Chapter 4.4 --- Conclusion --- p.30, Chapter Chapter 5 --- Optical Phase Conjucation --- p.31, Chapter 5.1 --- OPC Theory --- p.31, Chapter 5.11 --- The Distortion Correction Theorem --- p.32, Chapter 5.12 --- The Proof of the Distortion Theorem --- p.32, Chapter 5.13 --- The generation of Phase Conjucate Waves --- p.34, Chapter 5.2 --- Degenerate Four Wave Mixing --- p.35, Chapter 5.21 --- Geometries of DFWM --- p.35, Chapter 5.22 --- DFWM Theory --- p.37, Chapter 5.23 --- DFWM in Absorbing Media --- p.40, Chapter 5.3 --- Experimental Details --- p.44, Chapter 5.4 --- Results and Discussion --- p.46, Chapter 5.5 --- Conclusion --- p.53, Chapter Chapter 6 --- Conclusion and Suggestions for future work --- p.54, Reference, http://library.cuhk.edu.hk/record=b5888954, Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)

The main objective of this research is to theoretically investigate the physics of various optical phase conjugation processes (e.g., four-wave mixing, stimulated Brillouin scattering, photorefractive self- or mutually pumped phase conjugators) in nonlinear optical media (photorefractive crystals, optical fibers, etc.), and to explore theoretically and/or experimentally various kinks of applications of optical phase conjugation and nonlinear optical processes

The work described in this dissertation can be divided into two parts. The first part is an investigation of the transient behavior and stability property of a phase conjugate resonator (PCR) below threshold. The second part is an experimental and theoretical study of the PCR's spatiotemporal dynamics above threshold. The time-dependent coupled wave equations for four-wave mixing (FWM) in a photorefractive crystal, with two distinct interaction regions caused by feedback from an ordinary mirror, was used to model the transient dynamics of a PCR below threshold. Analytical expressions of the steady state cavity's fields for the case of nondepleted pumps and an absorption free medium were derived and used to determine the self-oscillation conditions. The solutions, through simple frequency domain transformation techniques, were used to define the PCR's transfer function and analyse its stability. Taking into account pump depletion and medium absorption, the transient buildup and decay times of the cavity's fields as well as the specularly reflected and phase conjugate reflected intensities were numerically calculated as functions of a number of system parameters such as the coupling parameter and the pump and probe ratios. General trends were unveiled and discussed in view of the possible use of the PCR in image storage or processing architectures. Experimental results for the buildup and decay times confirmed qualitatively the predicted behavior.

In this final report, we summarize the design and performance of an optically phase-conjugated tunable visible dye laser system, and the frequency doubled Q- switched Nd:YAG laser used to drive it. This high-brightness laser source utilized optical phase-conjugation (OPC) via Stimulated Brillouin Scattering (SBS) in a double-passed dye laser cell containing Rhodamine 6G in methanol. The dye cell it-self served as the SBS active medium. The use of SBS to remove optical abberrations in laser systems is relatively well-known; the implementation described herein is unique and can be used to provide a very compact tunable laser source. We have produced a 561 improvement in beam brightness and a 2.74 times improvement in beam jitter using the SBS in the double passed amplifier over using an ordinary retro mirror. This increase in beam brightness is due to a significant improvement in beam quality, and some pulse compression, obtained by using SBS. Output energy/pulse of 23 mJ has been demonstrated at 10 Hz and 560 nm output wavelength; tunability from 554 to 574 nm has also been demonstrated. jg

Parametric investigation of volume holographic gratings and optical phase conjugation are studied through coherent and incoherent beam couplings in barium titanate BaTiO(3) and through the study of bistability in phase conjugate resonators. Experiments have been done on the effect of color centers in the formation of resonant systems and holographic grating formation. A summary of the important results appears in the final report.

An optical image feedback system utilizing a cavity with a phase-conjugate mirror (PCM) has been studied. A new theory, based on operators, is developed to describe the steady-state output of the cavity. The use of operators allows one to describe the various optical operations and transformations needed in the optical implementation of iterative algorithms. The characteristics of the cavity are discussed using an expansion of the cavity fields in the cavity eigenfunctions. Several image processing applications using a PCM cavity are proposed and are studied using computer simulations. These theoretical studies indicate that a PC11 cavity can be useful in many applications. Optical phase conjugation was realized using a single crystal of photorefractive BaTi0₃ in a degenerated four-wave mixing geometry. The reflectivity gain from the PCM was optimized experimentally by the geometrical parameters and by the beamintensity ratios. The ability of the PCM to remove phase distortion as predicted theoretically, was demonstrated experimentally. The output of a PCM cavity can be substantially influenced by self-oscillations of the cavity above threshold. This was experimentally studied by observing the time evolution of the input. To avoid the influence of self-oscillation, the cavity must be operated below threshold. It is found that the cavity decay time constant diverges at and about threshold. This can be used as an indicator to show whether the cavity has crossed the threshold or to measure how close to threshold the cavity operates. To verify that a PCM cavity can be used in iterative image processing, an experiment was set up to implement an image restoration scheme based on the Gerchberg algorithm. It is shown that an optical implementation of the Gerchberg algorithm is feasible for objects made of few pixels. The experiment confirmed .that image iteration in a PCm cavity is possible. The limitations of the cavity and the technical difficulties are discussed.

Experimental investigations have been carried out on forward mode optical phase conjugation in Hg(1-x)CdxTe using CO2 Q-switched and TEA lasers. The temperature dependence of the degenerate four-wave mixing signal at 10.6 um has been studied for four n-type samples (x=0, 211, 0.216, 0.229, 0.233) and one p-type (x=0, 236) between 80K and 300K. Formation and erasure of a dynamic electron grating in an n-type x=0, 216 sample has been studied. Keywords: Mercury cadmium tellurides; Laser materials; Q switching; Laser pumping; TEA lasers; Carbon dioxide lasers.

This thesis presents a detailed interpretation of published theory of nonlinear optical phase conjugation by degenerate four wave mixing and by the photorefractive effect. Photorefractive phase conjugation is shown to be a low incident intensity alternative to degenerate four wave mixing (which requires high intensity incident light to achieve the nonlinear polarization of a medium. The derivations of two models for the photorefractive effect, Feinberg's Hopping Model and Kukhtarev's Solid State Model, are presented. The significance of Kukhtarev's model is his development of criteria for which spatially sinusoidal incident light (interference fringes) produces a spatially sinusoidal electro-static field in the crystal-an assumption casually made in much photorefractive work. Both models culminate in expressions for the magnitude of the space-charge field and the spatial phase shift between the field and the incident interference pattern for small modulation conditions. Feinberg's model is extended to develop expressions for two-beam coupling, diffraction efficiency and phase conjugate reflectivity. An alternative development for these expressions assumes the electro-static field exists in the crystal and modulates the crystal's refractive index by the linear electro-optic (Pockel's) effect.

When a beam of extraordinarily polarized light is directed through a poled, single crystal of Barium titanate it fans in the direction of the optic axis. This thesis research investigates the origin of this fanning, or asymmetric self-defocusing, in barium titanate. Experimental observations and theoretical simulation suggest that this phenomenon is due to near forward stimulated photorefractive scattering. Additionally, observations of unique variegated beam patterns during phase conjugation are reported, including internally pumped rings and motion invariant patterns.