| Summary: | 博士 === 國立清華大學 === 電機工程學系 === 95 === Periodically poled lithium niobate (PPLN) has become the nonlinear-optical material of choice in many infrared optical parametric processes due to its high nonlinearity, readily engineered tuning characteristics, and repeatable fabrication. The fabricating techniques are well developed and can produce device-quality PPLN crystals. Lithium niobate itself is a common material for photonics applications, such like electro-optics and acousto-optics modulation. The focus of the research was designing advanced electo-optic domain inverted devices based on PPLN, and investigating the performances and characteristics of these PPLN laser devices. A series of designs for advanced PPLN laser devices were realized and characterized.
We report an electro-optic Bragg modulator using a periodically poled lithium niobate (PPLN) crystal. We measured a half-wave voltage of 160 V when transmitting a 1064-nm laser through a 14.2-mm-long, 780-�慆-thick, 20.13-�慆-period PPLN crystal at the Bragg angle. We also demonstrated a Q-switched Nd:YVO4 laser using such a PPLN Bragg modulator as its Q-switch, producing 7.8-ns, 201-�寙 pulses at 10 kHz repetition rate when pumped by a 19.35-W diode laser at 808 nm.
We report a single-longitudinal-mode CW diode-pumped Nd:YVO4 laser emitting at both 1064 and 1342 nm with 10% optical efficiency at 20-W pump power. The measured spectral widths at 1064 and 1342 nm were less than 450 MHz and 400 MHz, respectively. The two emission wavelengths can be independently tuned over the lasing bandwidths of the dual-wavelength laser.
We report the observation of light-enhanced electro-optic spectral tuning in annealed proton-exchanged, asymmetric domain-duty-cycle PPLN channel waveguides for second harmonic generation. The spectral tuning rate was increased rapidly from 0.07 nm/(kV/mm) to a saturated value 0.32 nm/(kV/mm) in a 30%/70% domain-duty-cycle PPLN waveguide when the fundamental pump power near 1534 nm was increased from 0.6 mW to 46 mW. The second harmonic laser power at 767 nm was identified to be the source enhancing the spectral tuning.
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