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We have investigated a novel configuration of optical parametric oscillation whereby signal twins and idler twins are simultaneously generated by both of two oppositely-oriented nonlinear crystals forming twins. Our theory is supported by our experiment.
Phonon-polariton resonances are manifestation of the strong interaction between an electromagnetic wave interacts and transverse-optical phonons in a crystalline solid. Such resonances result in great enhancements of ionic second-order nonlinearities [1]. For LiNbO3, dominant element of the ionic second-order nonlinear susceptibility tensor coefficients d33 at 7.5 THz is a factor of about 50 larger...
Previously, we demonstrated that recovery of image blurred by phase aberration [1] and atmospheric turbulence [2] through optical phase conjugate beams generated by difference-frequency generation. In Refs. [1,2], the images were restored by the phase-conjugation in the transmission configuration. Based on such a scheme, the image system overcomes the disadvantages which were suffered in the past,...
Consider an optical parametric oscillator (OPO) in a single (KTiOPO4) KTP crystal where type-II non-critical phase-matching condition based on birefringence is satisfied. A pair of the signal and idler is generated. It was demonstrated previously [1] that each signal is split into the twin signals whereas each idler is split into the twin idlers in periodically-inverted KTP stack composite. The wavelengths...
Up-converted photoluminescence of GaN nanowires is observed at the temperature above 375 K. At 475 K, the mechanism of the photoluminescence was identified as phonon-assisted bandtail emission. Such a phenomenon contributes to optical refrigeration.
We have shown that Raman oscillation, frequency upconversion, and Raman amplification can be achieved in a second-order nonlinear medium at the phonon-polariton resonance.
A phase conjugate replica of the complex incident signal electric field can be generated by through optical phase conjugation (OPC) based on one of the nonlinear optical processes. One of the important applications for OPC is the full recovery of an image after it transmits through a phase distorting medium. Such distortion makes the image have a poor contrast, reduces the spatial resolution, and...
When adhesive free bonded (AFB) periodically-inverted potassium titanyl phosphate (KTiOPO4, KTP) plates were used as a nonlinear medium inside a cavity, coupled optical parametric oscillators (OPOs) were implemented [1]. As a result, two signal waves and two idler waves can be simultaneously generated. In singly resonant OPOs, two idler waves were used to efficiently generate THz waves [2]. When a...
We have observed enhancements of forward and backward anti-Stokes Raman signals generated in lithium niobate waveguides by one order of magnitude. Forward and backward exhibit different spectral features, unique for two configurations.
THz radiation was generated by mixing idler-idler waves from coupled optical parametric oscillators based on stacked KTP plates. Power enhancement, noise reduction, and linewidth narrowing have been attributed to noise reduction between idler waves.
We demonstrate that surface-emitting second-harmonic generation is an effective technique for evaluating domains of periodically-poled lithium niobate waveguide: domain period, linear taper, and poling depth. Such a method reaches nanoscale spatial resolution of 0.5 nm.
We investigated multiple coupled optical parametric oscillators, exhibiting behaviors of strong coupling. Conversion efficiency and slope efficiency stay the same as those for conventional and two coupled optical parametric oscillators whereas linewidths are significantly reduced.
Using phase-conjugate beam generated by second-order nonlinear process, blurred images caused by atmospheric turbulence were fully recovered. Due to instantaneous response, it is perhaps the only scheme for efficiently recovering image distorted by atmospheric turbulence.
We show that waveguides made of GaN/AlGaN heterostructures can be used for efficient parametric up and down conversion under transverse geometry. The conversion efficiency for generation of coherent ultraviolet radiation reaches 1%.
We investigated hot phonons based on Stokes Raman scattering from a GaN/AlN high electron mobility transistor. Such a simple method is advantageous compared with the method based on Stokes and anti-Stokes Raman scattering.
We have observed frequency upconversion of the incoming photons within the communication band to a visible band in a gallium phosphide crystal. Such a crystal is capable of reaching the single-photon detection level.
Laser cooling of solids based on anti-Stokes photoluminescence was proposed in 1929 [1]. Indeed, through the light emission based on phonon-assisted anti-Stokes photoluminescence, the average photon energy emitted is larger than that for the absorbed pump photons. The difference between the emitted and absorbed photon energies is made up by the energy of each removed phonon. Since phonons represent...
Since the last special issue on terahertz science and technology, nearly three years have been passed. During this period, while there have been further developments in terahertz (THz) sources, detectors, materials, and applications, there have been new discoveries. The purpose of this issue of the IEEE Journal of Selected Topics in Quantum Electronics (JSTQE) is to highlight the advances in materials,...
Efficient Terahertz output is generated from InGaN/GaN dot-in-a-wire light emitting diodes (LEDs) grown on Si(111). Under reverse bias, the THz output power is enhanced more than 4 times.
We have observed enhancement factors of at least 21 for backward-propagating anti-Stokes Raman signals generated by Ti-diffused lithium niobate waveguides under the microwatt pump power and using a single-photon detector.
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