Y. X. Fan

Absolute and relative nonlinear optical coefficients of KDP, KD*P, BaB/sub 2/O/sub 4/, LiIO/sub 3/, MgO:LiNbO/sub 3/, and KTP measured by phase-matched second-harmonic generation

Both absolute and relative nonlinear optical coefficients of six nonlinear materials measured by second-harmonic generation are discussed. A single-mode, injection-seeded, Q-switched Nd:YAG laser with spatially filtered output was used to generate the 1.064- mu m fundamental radiation. The following results were obtained: d/sub 36/(KD*P)=0.38 pm/V, d/sub 36/(KD*P)=0.37 pm/V, mod d/sub 22/(BaB/sub 2/O/sub 4/) mod =2.2 pm/V, d/sub 31/(LiIO/sub 3/)=-4.1 pm/V, d/sub 31/(5%MgO:MgO LiNbO/sub 3/)=-4.7 pm/V, and d/sub eff/(KTP)=3.2 pm/V. The accuracy of these measurements is estimated to be better than 10%. >

Second harmonic generation and accurate index of refraction measurements in flux-grown KTiOPO 4

Accurate index of refraction measurements have been performed in flux-grown KTiOPO(4). These measurements give good agreement between experiment and theory for angle phase matching in Type II second harmonic generation at 1.064 microm. These refractive-index data have allowed us to calculate the propagation angles for second harmonic generation at wavelengths of interest other than 1.064 microm such as 1.34 microm. Type II second harmonic energy conversion efficiency of 1.064 micro m of up to 59% in this material has also been demonstrated with higher efficiencies possible. Limits to conversion efficiency are discussed.

AgGaS2 infrared parametric oscillator

We report the first operation of an optical parametric oscillator in a chalcopyrite crystal, AgGaS2. Tuning from 1.4 to 4.0 μm is demonstrated for 1.06‐μm Nd:yttrium aluminum garnet pumping. The potential tuning range extends to the 12‐μm transparency limit of the crystal.

Visible BaB2O4 optical parametric oscillator pumped at 355 nm by a single-axial-mode pulsed source

A visible BaB2O4 optical parametric oscillator (OPO) pumped by a single‐axial‐mode 355‐nm source has been demonstrated. An average output power of 140 mW with a signal wave conversion efficiency of 13% and an idler conversion efficiency of 11% for a total conversion efficiency of 24% has been achieved. The oscillator has continuously tuned from 412 nm to 2.55 μm limited by the infrared transmission range of the crystal. Through injection seeding we obtained single‐axial‐mode OPO operation with a corresponding OPO linewidth of less than 3 GHz.

Broadly tunable infrared parametric oscillator using AgGaSe2

The first successful operation of a AgGaSe2 infrared parametric oscillator is reported. Continuous tuning ranges of 1.6–1.7 μm, 6.7–6.9 μm, and 2.65–9.02 μm were achieved using 1.34‐μm neodymium and 2.05‐μm holmium pump lasers. Pulse energies exceeding 3 mJ, peak powers near 100 kW, and conversion efficiencies of 18% were obtained. Operation of the parametric oscillator was possible well below the 13–40 MW/cm2 surface damage threshold of this nonlinear material.

Barium borate optical parametric oscillator

Experimental results of the first BaB/sub 2/O/sub 4/ optical parametric oscillator (OPO) are presented. The pump source was the second harmonic output of a Q-switched TEM/sub 00/ mode Nd:YAG laser. The OPO had 1 mJ output energy with a peak power of 80 kW in a tuning range from 0.94 to 1.22 mu m. >

Recent Developments In Barium Borate

The nonlinear optical properties of β-BaB204 (beta barium borate) are demonstrated in the generation of second through fifth harmonics of 1.06 μm neodymium laser radiation and in optical parametric oscillation pumped by 532-nm radiation. βBaB204 is particularly useful for high average power applications and nonlinear frequency generation in the ultraviolet to wavelengths as short as 200 nm. An internal energy conversion efficiency of 84% for 1064-nm to 532-nm second harmonic generation, and cascaded harmonic conversion to the 213-nm fifth harmonic with 11% overall conversion were obtained. The observed performance agrees well with that predicted by modeling.

Efficient second harmonic generation of 10‐μm radiation in AgGaSe2

AgGaSe2 crystals for nonlinear infrared applications are being grown reproducibly. Using high‐quality, 2‐cm‐long crystals, 14% energy and 60% peak intensity conversion efficiency have been demonstrated for second harmonic generation of the pulsed output of a CO2 miniature transversely excited atmospheric laser.

Coherent 70. 9-nm radiation generated in neon by frequency tripling the fifth harmonic of a Nd:YAG laser

We have produced coherent radiation in the XUV region at 70.9 nm by frequency tripling the fifth harmonic of Nd:YAG laser radiation in neon. BaB(2)O(4) was used to generate the fifth harmonic at 212.8 nm with an output pulse energy of 20 mJ and a pulse width of 5 nsec. Subsequent frequency tripling in neon gas generated 10 W of peak power at 70.9 nm.

Recent Developments in Nonlinear Optical Materials

Advances in nonlinear frequency conversion involve developments in laser pump sources, and nonlinear optical materials and techniques. There is a renewed interest in the development of nonlinear optical materials that has resulted from advances in the other areas, and from applications requiring tunable coherent radiation. Recent materials developments have included improvements in available size and optical quality of established nonlinear materials and the development of new materials that extend the conditions under which nonlinear frequency conversion can be used. There is a large amount of earlier materials work that is the subject of reviews [1]. The current effort in nonlinear optical materials development is also extensive, and the discussion here is limited to bulk inorganic materials used in second order nonlinear frequency conversion processes. Silver gallium selenide, lithium niobate and barium borate are discussed to provide examples.