Viscosity of F and GeO/sub 2/ codoped silica glass

The dopant concentration dependence of the viscosity of fluorine (F) and GeO/sub 2/ codoped silica glass is investigated experimentally. The viscosity of these glasses at various dopant concentrations is measured using the drawing method in the 1700-2000 degrees C temperature range. The change in the viscosity logarithm of F and GeO/sub 2/ codoped silica glass was found to be the linear sum of the changes induced individually by F and GeO/sub 2/.<>     

Second harmonic generation in optical fibers

We describe second harmonic generation in silica based optical fibers as a function of time and the preliminary explanations published so far in the literature. The latter deal essentially with the electromagnetic aspect of the phenomenon. By a different way of analysis (closer to material science), we emphasize on the structural defects active in this non-linear property.     

Sol-gel ZnO-SiO/sub 2/ composite waveguide ultraviolet lasers

Random laser action with coherent feedback is realized in ZnO-SiO/sub 2/ composite films, which consists of ZnO clusters embedded in SiO/sub 2/ dielectric matrix prepared by sol-gel technique. The films are deposited on silicon substrate with a SiO/sub 2/ buffer layer to form a waveguide structure. Ultraviolet lasing at room temperature is observed from the composite films with ZnO : SiO/sub 2/ molar ratio varying between 1 : 5 and 1 : 30. The corresponding lasing wavelength and linewidth under 355-nm optical excitation are found to be /spl sim/388 nm and less than 0.6 nm, respectively. Our experiment has shown that the proper control of light confinement inside the random cavities leads to coherent random lasing.     

Quasi-phase-matched second harmonic generation in a LiTaO3 waveguide

The authors report third-order quasi-matched (QPM) second harmonic generation (SHG) in a LiTaO₃ channel waveguide. A deep domain-inverted region is first fabricated by a proton-exchange and heat treatment technique. Then a uniform and low-pass channel waveguide is fabricated by pyrophosphoric acid proton exchange. Consequently, 12 mW of blue light is obtained at 424 nm wavelength with a conversion efficiency of 6%. The observed FWHM (full-width half maximum) temperature acceptance width for SHG power is 3.2°C and FWHM wavelength acceptance bandwidth for that is 0.2 nm. It is also shown that diffraction limited focusing of the generated blue light may be obtained     

半导体激光的倍频

用碘酸锂(α-LiIO_3)晶体对GaAlAs DH激光二极管的脉冲输出进行了倍频。对于0.83μm的基波激光,第一类相位匹配角为40°。二次谐波的平均功率和基波平均功率成近似的平方关系。     

Local normal-mode analysis of second harmonic generation in aperiodic waveguide

A new theoretical analysis method based on the local normal-mode expansion is proposed for analysis of optical second harmonic generation (SHG) under quasi-phase-matching in a waveguide with a periodic structure. Nonlinear coupled mode equations, SHG efficiency, and effective SHG coefficient are derived. In addition, SHG devices quasi-phase-matched with corrugation and with periodic domain inversion are studied analytically and numerically. The results are compared to those obtained by the conventional ideal normal-mode expansion. It is shown that in a corrugated waveguide the local normal-mode expansion method presents a different result from the ideal normal-mode expansion since the periodic variation of the modal field profile is dominant in the quasi-phase-matching process. On the other hand, in the periodically domain-inverted ferroelectric waveguide, it is shown that the variation of the modal field profile is sufficiently small and both expansion methods coincide with each other     

Noncritical quasi-phase-matched second harmonic generation in anannealed proton-exchanged LiNbO3 waveguide

We report the demonstration of dimensional noncritical phase matching, a phase-matched interaction length exceeding 10 mm, and an internal conversion efficiency of 204%/W for second harmonic generation of 976 nm radiation in a periodically poled, annealed proton-exchanged LiNbO₃ waveguide. Using models for the linear and nonlinear optical properties of annealed proton-exchanged LiNbO₃ waveguides and the observed ferroelectric domain grating, the phase-matching wavelength was predicted to within several nm and the conversion efficiency to within ≈20% of the measured values. Optimization of waveguide second harmonic generation devices is discussed     

A highly damage-resistant Zn:LiNbO/sub 3/ ridge waveguide and its application to a polarization-independent wavelength converter

We have fabricated a periodically poled ridge waveguide using a liquid phase epitaxy (LPE)-grown Zn:LiNbO/sub 3/ substrate. The waveguide can confine both the transverse electric and transverse magnetic mode. Its strong resistance to photorefractive damage enables stable parametric amplification. We demonstrate polarization-independent wavelength conversion using polarization diversity in a single waveguide.     

CHD/sub 2/OH optically pumped by a waveguide CO/sub 2/ laser: new far-infrared laser lines from the CD/sub 2/ wagging vibrational mode

For the first time, a wide tunability waveguide CO/sub 2/ laser was used to pump the CHD/sub 2/OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD/sub 2/ wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements.     

Continuous-wave erbium-diffused LiNbO/sub 3/ waveguide laser

The first integrated optical laser in LiNbO/sub 3/, doped by an indiffusion of Er/sup 3+/ prior to channel-guide fabrication by Ti diffusion is reported. Pumped by a colour centre ( lambda /sub p/=1.477 mu m), CW operation at lambda =1.532 mu m ( Delta lambda approximately 0.3 nm) with a threshold of approximately 8 mW absorbed power was achieved.<>     

Large-scale and high-density planar lightwave circuits with high- Delta GeO/sub 2/-doped silica waveguides

GeO/sub 2/-doped silica waveguides with a high refractive index difference ( Delta ) of 2% and a propagation loss of 0.1 dB/cm are fabricated on Si substrates. 200 cm-long test circuits and ring resonators are demonstrated, both with a minimum curvature of 2 mm.<>     

吖啶酮衍生物粉末微晶的二次谐波测量

建立了有机物粉末二次谐波(SHG)的测量系统。测定了N-烃基口丫啶酮衍生物粉末的SHG,并以溶剂变色法测定了一些口丫啶酮衍生物的分子超极化率与分子基态偶极矩的复合量(βCTμg).从分子结构特征与分子折射率等方面对其所表现出的非线性光学性质进行了分析。具有“Λ”型多极结构、分子间氢键、支化烷基和甲基的口丫啶酮衍生物,粉末SHG较强;βCTμg与SHG相对强度近似线性关系;分子折射率与SHG不满足Kurtz-Pery关系。     

A high-power short-pulse laser diode for waveguide second harmonic generation

This paper describes successful development of a high-power short-pulse i.r. laser diode, together with numerical analyses giving a clear understanding of the operation. The novel aspect of the present laser diode is that a saturable absorber is incorporated for gain switching into the buried-twin-ridge substrate (BTRS) structure which allows a high-stability fundamental spatial mode operation. Peak powers as high as 1.23 W and pulse widths as narrow as 34.1 ps have been obtained in an efficient gain-switching operation with the high mode stability. The experimental observations are well-explicable by the numerical analyses in substantial respects. We also report picosecond-pulse blue-light generation which has been attained by applying the frequency doubling technique to the above laser in a LiNbO₃ waveguide.     

Polarisation-insensitive Si/sub 3/N/sub 4/ strip-loaded BaTiO/sub 3/ thin-film waveguide with low propagation losses

A low-loss and polarisation-insensitive singlemode BaTiO/sub 3/ thin-film waveguide is reported. Polarisation-dependent loss as low as 0.1 dB/cm at a wavelength of 1.55 /spl mu/m has been achieved by a novel Si/sub 3/N/sub 4/ strip-loaded BaTiO/sub 3/ waveguide structure. Propagation loss of less than 0.9 dB/cm for both TE and TM polarisations was measured     

TEA CO_2 10.6微米激光在AgGaS_2晶体中的倍频

研究了AgGaS_2晶体对TEA CO_2 10.6微米激光的倍频特性。晶体厚度4.3毫米时倍频转换效率为0.122％。实测相位匹配角71.5％,调节宽度8°±1°。实验结果与理论计算值非常一致。     

Second harmonic generation in ion-exchanged waveguides of semiconductor microcrystallite-doped glasses

Waveguides written in semiconductor microcrystalline-doped glasses using the ion-exchange method have been optically encoded for second harmonic generation of Nd:YAG radiation.<>     

Measurements on waveguide properties of GeO2-SiO2-cored optical fibres

Total attenuation and scatter loss measurements have been made on optical-fibre waveguides produced with graded refractive-index profiles in GeO-2-SiO2 cores. The total attenuation of the fibres at semiconductor-laser wavelengths has been reduced to less than 4 dB/km.     

铌酸锂薄膜波导上二次谐波产生中的色散分析

基于绝缘体上铌酸锂平台,设计了周期极化的铌酸锂薄膜波导结构,利用铌酸锂良好的非线性性质并结合灵活的相位匹配方案,分析了结构色散对极化周期的影响。此外,借助波导模式有效折射率随温度变化的不同,通过改变材料温度,有效扩展了频率转换的带宽,实现了1.5～1.6μm范围内的倍频,最终获得562%的归一化转换效率,为芯片光子学参量转换的进一步研究提供了理论基础。