The thermal focal length of the side-pumped module was first measured at different pump currents, revealing a relationship between thermal focal length and pump current. Then, a linear resonant cavity was designed and optimized. A 1064 nm pulsed laser was generated by using LD side-pumped Nd:YAG laser and acousto-optic(AO) Q-switching technology. BBO and LBO crystals were utilized for second-harmonic generation (SHG) and sum-frequency generation (SFG), respectively. At a repetition rate of 8 kHz, the maximum average power of the 355 nm ultraviolet (UV) output reached 2.13 W, with a pulse width of 32.7 ns. The optical-to-optical conversion efficiency from 1064 nm to 355 nm was 24.3%. At last an analysis was conducted on the impact of the 1064nm to 532 nm photon number ratio's impact on SFG, and the optimal power ratio is close to 1:2 for achieving high conversion efficiency of 355 nm laser output.
A compact dual wavelength Nd:YVO4/MgO:PPLN infrared laser was developed successfully which was composed of Nd:YVO4 crystal, MgO:PPLN crystal and a cavity mirror(M1). The fundamental laser was consisted of the first face of Nd:YVO4 and M1, and the optical parametric oscillation(OPO) cavity defined by the second face of Nd:YVO4 and M1. The infrared laser output with wavelengths of 1539 nm and 3447 nm was obtained using intracavity cw OPO technology. The output power of 1539nm and 3447nm were 670mW and 236mW at the pumped LD power of 6.0 W, and the optical conversion efficiency was 15.1%. The higher conversion efficiency was mainly attributed the 2mm thickness of MgO:PPLN crystal. Intracavity dual wavelength laser can be used in spectrum detection, drunk driving test and so on.
This system uses SOI optical waveguide ring resonator chip. By using the method of selecting single direction light path, we got the resonance curve and backscattering curve of the resonant, while the system is working under different light powers. The changing rules of FWHM and resonant depth under different light powers is analyzed. And the action mechanism of optical power on the cavity resonance curve and backscattering is analyzed. Finally, the optimal working optical power of SOI integrated optical gyroscope system is determined.
Based on the asymmetric directional coupler, a polarization beam splitter based on silicon on Insulator (SOI) platform is designed for the wavelength range of 1500nm-1600nm in optical communication in this letter. The asymmetric directional coupler is composed of a regular strip shape waveguide and a sub-wavelength grating waveguide. The influence of the grating period, grating depth, and duty cycle on its polarization characteristics is analyzed. The simulation results show that the polarization extinction ratio (PER) of TE polarization is 20-23 dB and the insertion loss (IL) is 0.01-0.04dB, in the wavelength range of 1500–1600nm, while the PER of TM polarization is 15-26 dB and the IL is 0.3-0.6dB. Especially, the PER and IL are 21 dB (26 dB) and 0.31 dB (0.26 dB) for TE (TM) at the wavelength of 1550 nm. Moreover, the minimum feature size of this device is 25 μm2 . It can be effectively used in semiconductor photoelectronic devices.
Alexandrite crystal is a broadband tunable gain medium with good performance in near infrared band. At room temperature, the wavelength tuning range of the alexandrite laser is about 700~818nm, UV or deep-UV (DUV) lasers can be obtained by single or multiple optical nonlinear frequency conversions. The laser oscillations can be generated when alexandrite crystals absorb pumping light energy, and a considerable part of pumping energy will be converted into thermal energy of crystals which will lead to a thermal effect. It will affect the output laser efficiency, the stability of resonator and the quality of output laser beam. In this paper, by establishing the thermal conduction model of the crystal, the stable temperature field distribution, deformation field distribution, and thermal stress field distribution in the crystal can be obtained by solving the corresponding equations. Then the thermal effects caused by these three fields are analyzed respectively, and the corresponding focal lengths of thermal are calculated which shows an inverse relationship between the focal length of the thermal and the absorption pumping power when other conditions remain unchanged. The stable parameter range of the laser cavity can be obtained according to the stable conditions of the resonator, and it will play a guiding role in solving the thermal effect of the crystal and improving the performance of the laser.
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