Publications by authors named "Hongkai Ren"

In this paper, we report an efficient red-green-blue (RGB) laser based on the stimulated Raman scattering (SRS) of ethanol. The wavelengths of the three-color laser are 631, 532, and 447 nm, respectively, and the gamut space that can cover is 116% of the Rec. 2020 standard gamut in the CIE1976 color space.

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In current inertial confinement fusion (ICF) facilities, potassium dihydrogen phosphate (KHPO, KDP) type crystals are the only nonlinear optical (NLO) materials that can satisfy the aperture requirement of the ICF laser driver. Ammonium dihydrogen phosphate (NHHPO, ADP) crystal is a typical isomer of KDP crystal, with a large nonlinear optical coefficient, high ultraviolet transmittance, and large growth sizes, which is an important deep ultraviolet (UV) NLO material. In this paper, we investigated the effect of ADP temperature on its fourth-harmonic-generation (FHG) performance.

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Theoretical analysis indicated that partially deuterated ammonium dihydrogen phosphate (DADP) crystal with a deuterium content of 23% could realize spectral noncritical phase-matching (S-NCPM) for type-I frequency doubling of an Nd:glass laser. To explore the temperature dependence of the phase matching (PM) angle of the second harmonic generation (SHG) process and the output SHG bandwidth of DADP crystal at 1.053 μm, we used the point-seed rapid-growth method to grow targeted DADP crystal with 23% deuterium content.

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In this review, we introduce the progress in the growth of large-aperture DKDP crystals and some aspects of crystal quality including determination of deuterium content, homogeneity of deuterium distribution, residual strains, nonlinear absorption, and laser-induced damage resistance for its application in high power laser system. Large-aperture high-quality DKDP crystal with deuteration level of 70% has been successfully grown by the traditional method, which can fabricate the large single-crystal optics with the size exceeding 400 mm. Neutron diffraction technique is an efficient method to research the deuterium content and 3D residual strains in single crystals.

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For the first time, the temperature stability of second-harmonic-generation (SHG) is reported for the entire space of a YCaO(BO) (YCOB) crystal for a temperature range of -10 - 520 °C. Both theoretical calculations and experimental data indicate an optimum phase-matching (PM) direction of (θ = 149.2°, ϕ = 0°), which is located in the XZ principle plane (90° < θ < 180°).

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The temperature bandwidth of the second harmonic generation (SHG) phase-matching process was investigated for the GdCaO(BO) (GdCOB) crystal. GdCOB exhibits a much broader temperature bandwidth in comparison with many familiar nonlinear optical (NLO) crystals. For a fundamental wave of 1,064 nm, the maximum temperature bandwidth appeared at (θ=135°, ϕ=47.

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Cascaded longitudinal stimulated Raman scattering (LSRS) and the frequency doubling process are reported for the first time. When potassium dihydrogen phosphate (KDP) crystals are used as the type I and type II frequency doublers of picosecond, focused 1064 nm laser pulses, strong LSRS effects are observed. Three new laser spectrum lines appeared successively, i.

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KDP single crystals were grown in aqueous solution by using "point seeds" with a defined crystallographic direction of 59° to the Z axis. When hillock slopes on the (100) face of KDP crystals were measured within the supersaturation (σ) range of 0 < σ ≤ 0.06, the slope of hillocks with hollow cores depended nonlinearly on supersaturation.

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