Lawrence E. Myers

Quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO 3

We review progress in quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3. Using the electric-field poling process, we can reliably fabricate 0.5-mm-thick crystals with uniform domain structures over a 15-mm length. Periodically poled material retains the low-loss and bulk power handling properties of single-domain LiNbO3, and quasi phase matching permits noncritical phase matching with d33, the highest-valued nonlinear coefficient. Optical parametric oscillators pumped by 1.064-μm pulsed Nd:YAG lasers have been operated over the wavelength range 1.4–4 μm with tuning by temperature or by quasi-phase-matched period. We have shown an oscillation threshold as low as 0.012 mJ with a Q-switched pump laser and pumping at greater than ten times threshold without damage. We have also demonstrated a cw doubly resonant oscillator near 1.96 μm pumped directly with a commercial cw diode laser at 978 nm.

Multigrating quasi-phase-matched optical parametric oscillator in periodically poled LiNbO 3

We report a widely tunable quasi-phase-matched optical parametric oscillator that uses periodically poled LiNbO(3)with a multigrating structure. The device is tuned by translation of the crystal through the resonator and pump beam, with no realignment needed. With a 1.064-microm acousto-optically Q-switched Nd:YAG pumplaser, we produced noncritically phase-matched tunable IR output from 1.36 to 4.83 microm. The threshold was 6 microJ for a 26-mm interaction length. The extraordinary polarization of LiNbO(3) has better IR transmission than does the ordinary polarization, permitting operation at longer wavelengths with d(33) quasi-phase matching than with conventional Type I birefringent phase matching.

Periodically poled lithium niobate and quasi-phase-matched optical parametric oscillators

Since their introduction two years ago, quasi-phase-matched (QPM) optical parametric oscillators (OPOs) have moved into the mainstream of OPO research. This has been made possible by continuing improvements and availability of the microstructured nonlinear material periodically poled lithium niobate (PPLN). Demonstrations of PPLN OPOs now span the range of pulse formats and power levels. The most significant area of development is low-peak-power devices where operation with conventional materials is difficult. In this paper, we describe the current state of this research, including OPOs pumped by high-repetition-rate (>30 kHz) Q-switched diode-pumped solid state lasers, and CW singly resonant OPOs with >3-W output power in the 3-4-/spl mu/m range.

93% pump depletion, 3.5-W continuous-wave, singly resonant optical parametric oscillator.

We report two cw, singly resonant optical parametric oscillator (OPO) configurations based on periodically poled lithium niobate that result in significantly higher efficiency and output power than in previous studies. Using four-mirror OPO cavities and pumping with a 1.064-microm Nd:YAG laser, we observe 93% pump depletion and obtain ~86% of the converted pump photons as useful idler output. The single-beam, in-the-bucket idler output power of 3.55 W at 3.25 microm corresponds to ~80% of quantum-limited performance. We measure and compare the amplitude noise and spectral bandwidth of the two configurations. We also demonstrate >1 W of tunable cw output over the 3.3-3.9-microm spectral range.

Quasi-phase-matched 1.064-μm-pumped optical parametric oscillator in bulk periodically poled LiNbO 3

We report a quasi-phase-matched optical parametric oscillator, using bulk periodically poled LiNbO(3). The optical parametric oscillator, pumped by a 1.064-microm Q-switched Nd:YAG laser, was temperature tuned over the wavelength range 1.66-2.95 microm. The oscillation threshold of approximately 0.1 mJ was more than a factor of 10 below the damage limit. The LiNbO(3) crystal, fabricated by application of an electric field to a sample with liquid and metal surface electrodes, was 0.5 mm thick with a 5.2-mm interaction length and a quasi-phase-matched period of 31 microm.

Continuous-wave singly resonant optical parametric oscillator based on periodically poled LiNbO 3

We report a continuous-wave singly resonant optical parametric oscillator (OPO) based on periodically poled lithium niobate. The simple, two-mirror OPO, pumped by a 1.064-microm Nd:YAG laser, had a 2.6-4.5-W threshold and an output of >1.2 W at 3.3 microm and was tuned over 1.45-1.62 microm (signal) and 3.98-3.11 microm (idler). The noise characteristics and the spectral properties of the device are described.

2.5-W, continuous-wave, 629-nm solid-state laser source

We report an efficient, high-power, cw, 629-nm laser source based on a diode-pumped Nd:YAG laser and a periodically poled lithium niobate (PPLN) frequency converter. This device integrates two separate frequency-conversion steps in a single crystal, taking advantage of the ability to fabricate PPLN with nearly arbitrary grating periods and phase-matching temperatures. This device uses a single PPLN crystal that has two grating regions in series. The first region quasi-phase matches a standard optical parametric oscillator process (1064nm?1540nm +3450nm), and the second region quasi-phase matches a sum-frequency process whereby the pump and the signal light make red light (1064nm+1540nm ?629nm). Using a four-mirror ring cavity, we were able to convert 21% of the 1064-nm pump to 629-nm output, yielding 2.5W of red output with 11.8W of input.

UV and visible absorption in LiTaO3

The effects of reduction, oxidation, Li-enrichment and impurity on LiTaO3 crystals were studied. It is demonstrated that the best LiTaO3 crystals show less absorption than LiNbO3, less photorefraction and no green-light-induced infrared absorption.

Progress in quasi-phase-matched optical parametric oscillators using periodically poled LiNbO3

We review progress on quasi-phasematched optical parametric oscillators (OPOs) in bulk periodically poled LiNbO3. We have extended the electric-field poling process so that we now reliably fabricate crystals over 60-mm long in full 3-inch-diameter, 0.5-mm-thick wafers. Periodically poled material retains the low loss and bulk power handling properties of single domain LiNbO3, and QPM allows noncritical phasematching with the highest value of the nonlinear coefficient. OPOs pumped by 1.064-micrometers Nd:YAG lasers have been operated over the wavelength range 1.36 micrometers to 4.9 micrometers with tuning by temperature or QPM period. We have shown oscillation threshold as low as 0.006 mJ with a Q-switched pump laser, and pumping over 25 times threshold without damage. We have also demonstrated a doubly resonant OPO pumped directly with a commercial cw diode laser at 978 nm, and a 1.064-micrometers -pumped cw singly-resonant OPO with threshold < 3 W.

Quasi-phasematched optical parametric oscillators using bulk periodically poled LiNbO3

We review progress of quasi-phasematched (QPM) optical parametric oscillators (OPOs) in bulk periodically poled LiNbO3. Using the electric field poling process, we can reliably fabricate 0.5-mm thick crystals with uniform domain structures over 15-mm long. Periodically poled material retains the low loss and bulk power handling properties of single domain LiNbO3, and QPM allows noncritical phasematching with the highest value of the nonlinear coefficient. OPOs pumped by 1.064-micrometers pulsed Nd:YAG lasers have been operated over the wavelength range 1.45 micrometers to 4.0 micrometers with tuning by temperature or QPM period. We have shown oscillation threshold as low as 0.020 mJ with a Q-switched pump laser, and pumping over two times threshold without damage. We have also demonstrated a doubly resonant oscillator near 1.96 micrometers pumped directly with a cw diode laser at 978 nm.