Abstract
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. These optical parametric processes require quasi-phase-matching (QPM) periods typically ranging from 20 µm to 30 µm. 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 QPM devices based on PPLN, and demonstrating the performance and characteristics of these QPM devices. This dissertation presents a series of designs for advanced PPLN devices Novel 1064-nm second harmonic generation (SHG) with built-in electro-optics based amplitude modulation was modeled and characterized. The measured half-wave voltage for the amplitude modulation is 1.1V*d(um)/ld(cm), where d is the separation of the electrodes and ld is the length of the electrodes. We demonstrate optical parametric generation from a 532 nm-pumped PPLN with a wavelength spectrum covering the sodium D1, D2 wavelengths 589.6 nm and 589.0 nm. Despite the 8 cm-1 attenuation at the 5.45 um idler wavelength, the PPLN generates a 9 uJ/pulse energy near the 589-nm sodium wavelength when pumped by a 130 uJ/pulse frequency-doubled Nd:YAG Q-switched laser. The observed effective nonlinear coefficient is about 30% higher than its value at the visible and near infrared wavelengths. We believe this is the first observation of ionic susceptibility enhanced parametric gain in the mid-infrared absorption region of lithium niobate. Also demonstrated is a 1064-nm passively Q-switched Nd:YAG laser pumped PPLN OPG; the overall efficiency exceeds 20 %. Based on a double-pass configuration, we demonstrate conversion efficiency which is 2 times single-pass configuration. We report the first demonstration of 220-psec visible laser generation from a passively Q-switched laser pumped PPLN in a single-pass, cascaded frequency conversion process. The monolithic PPLN consists of a 1-cm section for frequency doubling the 1064-nm Nd:YAG pump laser to a 532-nm laser, and a subsequent 4-cm section for generating the visible laser in a 532-nm pumped optical parametric generation (OPG) process. When generating the 622.3 nm OPG signal wavelength, we measured 16 % overall efficiency, and 35 % slope efficiency at 6.45-□J pump energy. At 10-6 pump duty cycle and 20-mW average power in the visible, photorefractive damage was not observed at the phase matching temperature 40.3□ C. By seeding a 1064-nm pumped PPLN OPG with a 30-MHz-linewidth, 1549.6-nm-wavelength diode laser, we produced narrow-line optical parametric amplification (OPA) pulses. The pulse width is 200 ps and the line width is less than 10 GHz. Gain competitions were observed in the OPA process. Finally, we demonstrate distributed-feedback (DFB) optical parametric oscillation (OPO) by writing photorefractive gratings in periodically poled lithium niobate (PPLN). The photorefractive DFB structures were fabricated by illuminating PPLN with ultraviolet light through a photomask, and by interfering 532-nm laser beams in the PPLN. Evidence of DFB OPO was observed from the spectral narrowing at the 1438.8-nm and the 619.3-nm idler wavelengths from 1064-nm and 532-nm pumped PPLN crystals having the DFB grating periods phase-matched to the 4084.5-nm and 3774-nm signal wavelengths, respectively.