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Constitutive NF‐κB activation is associated with cellular senescence and stem cell dysfunction and rare variants in NF‐κB family members are enriched in centenarians. We recently identified a novel small molecule (SR12343) that inhibits IKK/NF‐κB activation by disrupting the association between IKKβ and NEMO. Here we investigated the therapeutic effects of SR12343 on senescence and aging in three different mouse models. SR12343 reduced senescence‐associated beta‐galactosidase (SA‐β‐gal) activity in oxidative stress‐induced senescent mouse embryonic fibroblasts as well as in etoposide‐induced senescent human IMR90 cells. Chronic administration of SR12343 to the Ercc1 −/ ∆ and Zmpste24 −/− mouse models of accelerated aging reduced markers of cellular senescence and SASP and improved multiple parameters of aging. SR12343 also reduced markers of senescence and increased muscle fiber size in 2‐year‐old WT mice. Taken together, these results demonstrate that IKK/NF‐κB signaling pathway represents a promising target for reducing markers of cellular senescence, extending healthspan and treating age‐related diseases., Constitutive IKK/NF‐κB activation is associated with cellular senescence and aging. Here we demonstrate that pharmacological inhibition of IKK/NF‐κB activation by the small molecule SR12343 reduced senescence and SAPS factors in cell culture, improved healthspan in mice with accelerated aging, and reduced markers of senescence and pathology in multiple tissues of both accelerated and naturally aged mice. Therefore, IKK/NF‐κB pathway is a promising target for aging interventions to treat age‐related diseases.

Objective To determine the clinical features of confirmed cases of severe fever with thrombocytopenia syndrome (SFTS) and to explore the early warning indicators of death from SFTS. Methods A retrospective case–control study was performed at a single medical institution in Yantai. A total of 20 SFTS patients who died (death group) during January 2014 to December 2015 and another 40 age- and sex-matched SFTS patients who survived (survivor group) were identified from the case records. The differences in demographic characteristics, clinical signs and symptoms, and laboratory parameters in the early stage of disease were compared between the two groups. Conditional logistic regression was used to identify the independent risk factors for mortality in SFTS patients. Results Univariate logistic regression analysis showed that a disturbance of consciousness, pulse–temperature deficit, neurological signs, hemorrhagic manifestations, pulmonary infection, decreased lymphocyte percentage, high lactate dehydrogenase and creatine kinase levels, increased serum creatinine, blood urea nitrogen, and C-reactive protein (CRP), hyponatremia, and prolonged activated partial thromboplastin time (APPT) and prothrombin time were associated with mortality. On multivariate logistic regression analysis, the independent predictors of death were neurological signs (odds ratio (OR) 31.247, 95% confidence interval (CI) 4.813–202.853), hemorrhagic manifestations (OR 20.251, 95% CI 2.056–199.443), disturbance of consciousness (OR 15.359, 95% CI 2.139–110.268), hyponatremia (OR 5.280, 95% CI 1.235–22.575), increased CRP (OR 2.641, 95% CI 1.090–6.396), increased serum creatinine (OR 6.776, 95% CI 1.047–43.840), and prolonged APTT (OR 6.018, 95% CI 1.450–24.975). Conclusions Neurological signs, hemorrhagic manifestations, disturbance of consciousness, hyponatremia, prolonged APTT, and increased CRP and serum creatinine are risk factors for death in SFTS.

Aldehyde dehydrogenase (ALDH) is a cancer stem cell marker. Retinoic acid has antitumor properties, including the induction of apoptosis and inhibition of proliferation. Retinal, the precursor of retinoic acid, can be oxidized to retinoic acid by dehydrogenases, including ALDH. We hypothesized that retinal could potentially be transformed to retinoic acid with higher efficiency by cancer stem cells, due to the higher ALDH activity. We previously observed that ALDH activity is greater in highly metastatic K7M2 osteosarcoma (OS) cells than in nonmetastatic K12 OS cells. We also demonstrated that ALDH activity correlates with clinical metastases in bone sarcoma patients, suggesting that ALDH may be a therapeutic target specific to cells with high metastatic potential. Our current results demonstrated that retinal preferentially affected the phenotypes of ALDH-high K7M2 cells in contrast to ALDH-low K12 cells, which could be mediated by the more efficient transformation of retinal to retinoic acid by ALDH in K7M2 cells. Retinal treatment of highly metastatic K7M2 cells decreased their proliferation, invasion capacity, and resistance to oxidative stress. Retinal altered the expression of metastasis-related genes. These observations indicate that retinal may be used to specifically target metastatic cancer stem cells in OS.

We demonstrate that interface optical phonons can efficiently pump electrons from the quasi-X states to the quasi-/spl Gamma/ states in short-period type-II GaAs-AlAs superlattices. As a result, peculiar behaviors on these superlattices have been observed. First, photoluminescence intensity for the quasi-direct transition drastically increases as the temperature or pump power increases. Second, the dependence of the integrated photoluminescence intensity on the pump power exhibits a square power law.

Among almost all the work done on parametric processes in the past, two-photon absorption (TPA) has been intentionally avoided by properly choosing the pump wavelength. On the contrary, we have purposely explored how TPA sets the fundamental limit on the optical parametric generation (OPG) and oscillation (OPO) by using periodically poled LiNbO 3 (PPLN) as a testing nonlinear medium. Indeed, we have demonstrated that the TPA dramatically affects the characteristics of these two parametric processes. To our surprise, the OPO is actually not a preferred parametric process anymore compared with the OPG due to the presence of the strong TPA. In addition, the TPA can further be enhanced by self-focusing effect caused by accumulated thermal effect (ATE).

This paper presents the experimental results of two-wave mixing and self-pumped phase conjugation (SPPC) in barium titanate (BaTiO3) crystals doped with Rh or Ce. It has been shown that the main parameters of SPPC depend very strongly on the concentrations of dopants, the incident angles and the crystal cut used. High gain in two-wave mixing corresponds to low phase-conjugate reflectivity in all samples. It is impossible to maintain the highest reflectivity and gain simultaneously, because the gain will definitely be limited when we try to get the highest reflectivity, and vice versa. Some qualitative explanation of the experimental results is also given.

The gain of forward two-wave mixing (FTWM) and time response of a Cu-doped barium strontium potassium sodium niobate (KNSBN) crystal are investigated at 514.5 nm in the temperature range 20–120°C. It is found that the gain reaches its maximum value at about 90°C. The effective photorefractive charge density decreases with temperature. The response and erasure rates increase with increasing temperature. Moreover, the erasure process can be described by a diexponential function. A band diagram of the two-center charge transport model is presented. The phenomena are explained qualitatively.

Expressions of the coupling constant for contradirectional two-wave mixing (CTWM) have been derived. The calculations show that the energy transfer in CTWM has some unique characteristics different from the forward two-wave mixing (FTWM), in which the energy transfer direction is dependent on the two beam orientations with respect to the crystal polar axis and the sign of the light-induced carriers as well as the electro-optic coefficients. As a result, the CTWM can have a reverse energy transfer direction to the FTWM under a certain condition. The experimental results in two typical crystals of Rh-doped BaTiO3 and in Ce-doped strontium barium niobate (SBN:Ce) demonstrate the theoretical investigations very well.

The dependence of the threshold coupling strength on the loss parameter and the incident-beam ratio is calculated and shown for a new mutually pumped phase conjugator with a novel photorefractive crystal of copper-doped potassium sodium strontium barium niobate, in which both incoherent beams are incident upon the negative-c face and they travel in geometric paths similar to the outline of two arches. The maximum reflectivity attained is 21%. The tolerances of the output to both incident angles and positions are assessed. A curve fit is also made between the measured results and theoretical calculation.

Both multistage and a great number of four-wave mixing interaction region models arising from contradirectional two-wave mixing to generate phase conjugation beam are suggested for the first time to our knowledge with a beam entering negative c face of the crystal. The mechanism transformation with geometric parameters is also observed and discussed. The backscattering beams from random noise beams may be expected to be amplified by contradirectional two-wave mixing under the beam entering negative c face of copper-doped potassium sodium strontium barium niobate. The maximum of reflectivity attains 33%.

We have implemented a THz source based on intracavity difference frequency generation in stacked GaP plates as an output coupler of an optical parametric oscillator. The total THz output peak power approaches 200 W.

Osteosarcoma (OS) is the most common primary malignancy of bone. Mortality is determined by the presence of metastatic disease, but little is known regarding the biochemical events that drive metastases. Two murine OS cell lines, K7M2 and K12, are related but differ significantly in their metastatic potentials: K7M2 is highly metastatic whereas K12 displays much less metastatic potential. Using this experimental system, the mammalian target of rapamycin (mTOR) pathway has been implicated in OS metastasis. We also discovered that aldehyde dehydrogenase (ALDH, a stem cell marker) activity is higher in K7M2 cells than K12 cells. Rapamycin treatment reduces the expression and enzymatic activity of ALDH in K7M2 cells. ALDH inhibition renders these cells more susceptible to apoptotic death when exposed to oxidative stress. Furthermore, rapamycin treatment reduces bone morphogenetic protein-2 (BMP2) and vascular endothelial growth factor (VEGF) gene expression and inhibits K7M2 proliferation, migration, and invasionin vitro. Inhibition of ALDH with disulfiram correlated with decreased mTOR expression and activity. In conclusion, we provide evidence for interaction between mTOR activity, ALDH activity, and metastatic potential in murine OS cells. Our work suggests that mTOR and ALDH are therapeutic targets for the treatment and prevention of OS metastasis.

By mixing three optical frequencies generated by an optical parametric oscillator under a novel configuration based in nonlinear crystals, multiple THz frequencies are efficiently generated. They can be used to pursue variety of novel applications.

We have observed quasiphase-matched second-harmonic generation in the reflection geometry from GaAs/AlAs multilayers. By using GaAs/AlGaAs multilayers and Fresnel reflection as a cavity, we have also achieved cavity-enhanced nonphase-matched second-harmonic generation from GaAs/AlAs multilayers. The linewidth for the first order reflection-second-harmonic generation is limited only by wave-vector mismatch. In addition, we have demonstrated two-order-of-magnitude enhancement on the conversion efficiency by using the cavity.

This letter presents the experimental results of self-pumped phase conjugation (SPPC) in barium titanate (BaTiO3) crystals doped with Rh or Ce. It has been shown that the main parameters of SPPC depend very strongly on the concentration of dopants, the incident angles, and the cut type of the crystals. Some qualitative explanation of the experimental results are also given.

Spatial walk-off can severely increase the threshold of critical phase-matched optical parametric oscillations (OPOs) and distort the output beam quality. With 16-layer KTP stacks for walk-off compensation, noncritical phase-match-like (NCPM-like) and quasi-phase-match-like OPOs with enhanced angular acceptance have been demonstrated based on two different KTP bonding orientations. In the NCPM-like composite, output pulse energy of 49 microJ has been achieved at pump energy of 523 microJ with pulse duration of 15 ns and repetition rate of 1 KHz. The OPO threshold as low as 254 microJ(44.6 MW/cm(2)) has been achieved.

Quasi-noncritical phase-matched and quasi-phase-matched 2-µm optical parametric oscillations have been demonstrated and characterized in adhesive-free bonded multilayer walk-off compensated KTP composites with low pulse energy 1.064-µm pump laser.

Backward terahertz pulses were converted from ultrafast pulses of a laser amplifier within multiperiod periodically poled LiNbO3 (PPLN) wafers. The average output powers of more than 2 microW were obtained from all six domain periods, corresponding to the frequency range of 217 GHz-2.373 THz. Among the six periods, the highest output power of 10.7 microW and the narrowest linewidth of 5.98 GHz were achieved at the periods of 66.5 microm and 150.0 microm, respectively.

We used pump-probe technique to investigate recombination dynamics of photogenerated carriers in photodiodes consisting of InAs/GaInSb W-structured superlattices. Recombination time constants of 1.6 ns and 10 ns were measured under high and low powers, respectively.

Multilayer walk-off corrected nonlinear crystal composites not only can correct the spatial walk-off, but also can compensate the phase-mismatching caused by incident angle deviation. The noncritical phase-matching-like properties can be engineered to all wavelengths.

We have generated the backward terahertz pulses with record-high average powers of 2.3-11 µW and narrowest bandwidth of 6 GHz from multi-grating periodically-poled lithium niobate by optical rectification at room temperature.

Phonon-assisted anti-Stokes fluorescence has been observed in GaN film grown on Si (111) substrate. The donor-acceptor pairs and bound excitons have played primary roles in the generation of anti-Stokes fluorescence.

In this work, we present our new findings following our studies of the THz generation from InGaN/GaN multiple quantum wells (MQW's), pumped by a frequency-doubled sub-picosecond Ti:sapphire amplifier at the output wavelength of 395 nm. For the pump power of 320 mW, an average output power of 32 nW was measured in the frequency range of 300 GHz - 4.28 THz. Based on the photo luminescence (PL) spectra measured on these InGaN/GaN MQW's, quantum dots (QD's) were formed.

Broadband THz pulses have been generated from InGaN/GaN multiple quantum wells pumped by a frequency-doubled sub-picosecond laser amplifier at 395 nm. Enhanced THz emissions are strongly correlated with reduced photoluminescence intensities.

We observed the strong enhancement of photoluminescence intensities close to electron Fermi energy as the result of the breakdown of k-selection rule for radiaitive recombination due to the localization of holes in InN films.

Under relatively high pump intensities, photoluminescence intensities across the miniband were greatly reduced, which was attributed to the existence of periodic electric fields caused by spatially-separated photogenerated electrons and holes in short-period type-II InAs/GaSb superlattices.

We demonstrate that longitudinal-optical phonons in type-II InAs/GaSb quantum wells can be used to up-convert photoluminescence. Such a phenomenon could be used to achieve laser-induced cooling of lattices.

Our experimental results indicate that the two-photon absorption sets the fundamental limits to optical parametric generation and oscillation in periodically-poled lithium niobate. The investigation of how the strong TPA affects the OPG and OPO pumped by a nanosecond 532-nm beam in a PPLN crystal. To our surprise, the OPG becomes more efficient for the signal generation. In addition, the TPA can be further enhanced by self-focusing caused by accumulated thermal effect (ATE) by multiple laser pusles

In this paper we investigate short period GaAs/AlAs type-II superlattices(SL) for efficient amplification of radiation. Typical photoluminescence spectrum of type II SL's are measured at different temperatures and pump intensities.

We have studied the coupling between the InAs quantum dots and coupled quantum wells strained by the InAs quantum dots (i.e. coupled-quantum-well dots) by measuring photoluminescence spectra. By comparing the photoluminescence spectra of the coupled-quantum-well dots in which either the narrow well or wide well is grown next to the InAs quantum dots, we have evidenced the spatially inhomogeneous strains applied by the InAs quantum dots on the coupled quantum wells. Moreover, we have also investigated the three coupling regimes, i.e. when the dot level is higher than, lower than, and aligned to the lowest quantum-well transition. Based on our measurements, we conclude that the optical properties for the coupled-quantum-well dots have been significantly improved over the quantum dots.

We have demonstrated that type-II InAs/GaSb superlattices exhibit anomalously strong band-filling effects. By varying the width of the barrier or well, we have investigated the effects from 2-D quantum wells to quasi-3-D superlattices.

We show a mutually pumped phase conjugator with a high coupling efficiency in a novel crystal of copper‐doped potassium sodium strontium barium niobate. A twisting around of one another and self‐curving coupling channel is observed. A theory is developed to simulate the coupling channel. The shape of curved trajectories has also been calculated. We verify that one, two, three, and more four wave mixing interaction regions exist in photorefractive bridge mutually pumped phase conjugators with the simulations. The calculated results are essentially consistent with our experimental observations, and they may be used in other photorefractive phase conjugators after making a modification.

We have systematically designed, fabricated, and tested chalcogenide-glass waveguides. Among all the characterization techniques, we have found that the prism-coupling method is the most effective and accurate for determining all the parameters describing the performance of the slab waveguides. Furthermore, we have also achieved the end-fire coupling in these waveguides to study the characteristics of the transmitted beams. These waveguides can be optimized eventually for the biosensor applications.

We demonstrate that longitudinal-optical (LO) phonons efficiently pump electrons from the quasi-X states to the quasi-Γ states in short-period type-II GaAs/AlAs superlattices. At a very low temperature, the phonon-assisted electron up-transfer can occur if the energy difference between the lowest quasi-Γ states and quasi-X states is equal to or less than the LO phonon energies. As the temperature increases, however, kinetic energies of the electrons can facilitate the electron up-transfer. As a result, we have observed peculiar behaviors on these superlattices. First, photoluminescence intensity for the quasi-direct transition drastically increases as the temperature or pump power increases. Second, the dependence of the integrated photoluminescence intensity on the pump power exhibits a square power law.

We have studied coupling between InGaAs/GaAs coupled quantum wells and self-assembled InAs quantum dots by measuring the linewidths, peak energies and peak intensities of photoluminescence peaks for different pump powers and lateral locations

Summary form only given. Additional confinement in semiconductor quantum wires is expected to significantly improve the performances of semiconductor devices due to the increased density of states at the band edge. We report our result on the fabrication of self-assembled InAs/InP quantum wires (QWRs) with single and 10 vertical-periods. Our InAs QWRs were grown on InP [001] substrates in a Riber 32 MBE system at the temperature of 430/spl deg/C and a growth rate of 0.3 ML/s. The photoluminescence (PL) spectra and PL polarizations of the two samples were investigated at different pump wavelengths, different pump intensities and sample temperatures. Our results exhibited unique behaviors, especially on the stacked quantum wires. Following our detailed analyses, we determined the structure of the stacked quantum wires from the bottom to the top, which is different from the designed one. Furthermore, we have provided a new design that will result in the narrowing of the PL linewidth for the stacked self-assembled quantum wires.

Summary form only given. We have grown three structures of GaAs/AlAs superlattices and characterized them by using PL spectra. Our results show that for GaAs and AlAs layer thicknesses somewhere between 50 /spl Aring/ and 20 /spl Aring/ the superlattices start to behave as quasi-indirect semiconductor materials or type II superlattices. Our results presented here serve as a first step towards eventually using type-II superlattices in optical amplifiers with reduced cross talk and Q-switched lasers.

Summary form only given. Periodically-segmented ion-exchanged KTiOPO/sub 4/ (KTP) waveguides can be used for not only quasi-phase-matched (QPM) second-harmonic generation (SHG), but also acting as a distributed Bragg reflector (DBR) due to index grating to enhance conversion efficiency for SHG. In this case, a submicron-period index grating is desirable because it can reach a given reflectivity in a short length. One way to characterize the waveguide containing a submicron-period index grating is to measure reflection spectrum of an incident beam. Due to the presence of the index grating, it is also possible to use SHG to characterize the grating. However, in such a short-period grating, the forward SHG can never be phase-matched. Therefore, backward SHG can be used as a novel and unique technique to characterize a short-period grating. This technique has advantage for determining interface roughness, fluctuation of index layer thickness from one period to the next, and duty cycle. In addition, one can use this technique to determine whether the domain is inverted after ion exchange. Previously, it was demonstrated that domain inversion can still occur for the period as short as 3 /spl mu/m. Here, we report our results of achieving QPM backward SHG in periodically-segmented ion-exchanged KTP waveguide with the period of 0.7 /spl mu/m. We have fabricated 4-/spl mu/m-wide periodically-segmented KTP waveguides on a z-cut flux-grown KTP substrate by ion-exchange in a RbNO/sub 3//Ba(NO/sub 3/)/sub 2/ melt at 350/spl deg/C for 45 minutes. The diffused segments were 0.4-/spl mu/m-long RTP separated by 0.3-/spl mu/m-long KTP. There are 3200 periods in the center of the waveguide, which corresponds to a total length of 2.24 mm for the segment portion. A mode-locked Ti:sapphire laser with a pulse width of /spl sim/130 fs and repetition rate of 76 MHz was used as the pump source. The polarization of the fundamental beam is always parallel to the z-axis of the crystal for utilizing d/sub 33/. We first measured the average power of the backward SH beam while scanning the fundamental wavelength from 750 to 910 nm with a constant average pump power across the spectrum. For each center pump wavelength, we measured the SH spectrum. We then determined the peak power and corresponding SH wavelength. By varying the center pump wavelength, we obtained a spectrum for backward SH beam.

We report our recent results on characterization of GaAs/AlAs superlattices exhibiting evidence of a quasi- indirect transition between minibands. These structures have potential applications in semiconductor optical amplifiers with greatly-reduced cross-talk at high bit rates and Q-switched lasers.

Self-assembled InP/InAs/InP quantum wires have been successfully stacked for 10 vertical periods and characterized based on photoluminescence (PL) studies. Compared with single-period quantum wires, unique behaviors appear in the PL spectra and some fundamental effects have been observed. Through the detailed analyses of the PL shapes, linewidths, and polarizations at different pump wavelengths, pump intensities and sample temperatures, it is evidenced that the wire width and subband energy gradually decrease while the average wire thickness increases from the bottom period to the top one, period by period. Meanwhile, the average wire width gradually decreases. In addition, from the bottom to the top period the size fluctuation within each period decreases. Furthermore, above certain temperature or pump intensity all the quantum wires are vertically coupled among one another. Following these results, new growth conditions have been suggested, which can be essential to improving the optical quality of these self-assembled quantum wires.

We have observed first-, second- and third-order quasi- phase-matched second-harmonic generation in the reflection geometry from GaAs/AlAs multilayers. We have measured phase- matching curves and identified all the peaks. The linewidth for the first order is limited only by wave-vector mismatch. We have demonstrated two-order-of-magnitude enhancement solely using quasi-phase-matched multilayers. We have also achieved cavity-enhanced quasi-phase-matched second-order and non-phase-matched second-harmonic generation from GaAs/Al0.8Ga0.2As multilayers. We have determined the element of the second-order susceptibility tensor used for quasi-phase matching. We have measured the conversion efficiencies and discussed possibilities for further enhancements.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Summary form only given. Recently, we reported obtaining THG by cascading non-phase-matched SHG and sum frequency generation in a single cerium-doped KTiOPO/sub 4/ (Ce:KTP) crystal from femtosecond laser pulses at 1.32 /spl mu/m. A conversion efficiency of 0.17% was achieved at a pump intensity of 3.2/spl times/10/sup 11/ W/cm/sup 2/. In order to improve the conversion efficiency, we have designed a new KTP structure by using quasi phase-matched (QPM) SHG to replace the previous non-phase-matched SHG. Here, we report our first result of efficiently generating coherent blue light in this crystal.

Summary form only given. GaAs and AlGaAs have very large second-order susceptibilities. To achieve efficient frequency conversion, multilayers have been used to achieve, quasi-phase matching (QPM). Our investigation of the reflection-SHG from multilayers serves as a first step towards eventual applications of GaAs/AlGaAs multilayers for generating and amplifying mid-IR waves based on a novel configuration.

A mutually pumped phase conjugator is demonstrated with a novel photorefractive crystal of copper-doped potassium sodium strontium barium niobate, in which the beams travel in a geometric path similar to the outline of a sickle. The maximum reflectivity is up to 168%. Faster response times are measured and are also simulated as a function of incident beam power ratio. Four available input geometries are found. The phase conjugation signals exist wide range of angular and position alignment.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The authors have introduced a technique to investigate the carrier dynamics of semiconductor nanostructures. Such a technique is based on the measurement of time-resolved differential photoluminescence spectra induced by subpicosecond pump and probe laser pulses by adjusting the temporal delay between them. Their results obtained on the InAs quantum dots embedded in InGaAs∕GaAs quantum wells using such a technique indicate that the exciton decay time, integrated photoluminescence intensity, and photoluminescence linewidth exhibit unique dependences on temperature.

A partly periodically poled KTiOPO(4) (KTP) crystal has been designed to integrate quasi-phase-matched second-harmonic generation (QPM SHG) with sum-frequency generation in one crystal for generating a third-harmonic beam. The highest conversion efficiencies of 45% and 3% have been achieved in our experiments for QPM SHG and third-harmonic generation, respectively, by use of picosecond laser pulses at 1.327 microm . We have also discovered that periodically poled KTP has slightly different indices (n(z)) from bulk KTP.

A new mutually pumped phase conjugator with a photorefractive copper-doped potassium sodium strontium barium niobate crystal is demonstrated, in which the beams travel along a geometric path similar to the outline of a sickle. The maximum reflectivity is as high as 168%. Phase-conjugate images are obtained. The two-interaction region theory, based on the coupled plane wave amplitude, is used to account for the main characteristics of the new phase conjugator. The threshold coupling strength which depends on the reflection loss and the incident beam ratio, is also investigated and calculated.

We describe a high-efficiency mutually pumped phase conjugator with ring channels in a bird-wing incident geometry in copper-doped potassium sodium strontium barium niobate. A transmissivity as great as 35% is measured. Optical switching is obtained. The dependence of phase-conjugation fidelity on the geometric parameters and the input-beam ratio is discussed. Some suggestions are proposed to improve the fidelity further. The response times as a function of the input-beam ratio with the input beam kept constant are measured, and the least-squares minimum is used to simulate the fitting curve equations and to explain the formation of optical switching and the reduction or improvement of image fidelity.

By mixing three nearly-even-spaced optical frequencies generated by coupled optical parametric oscillators based in KTP stacks and bulk KTP in a nonlinear medium, we demonstrate coherent interference of THz waves.