Nobuhiro Umemura

Ultraviolet generation tunable to 0.185 µm in CsLiB 6 O 10

CsLiB6O10 has been found to be phase matchable for type-1 sum frequency generation to a minimum of 0.185 µm by mixing the fifth harmonic of a Nd:YAG laser at 1.0642 µm and the output of a KTP parametric oscillator pumped by the second harmonic of the same Nd:YAG laser at 20.0 °C. The improved Sellmeier equations and the thermo-optic constants of this crystal are reported.

90? Phase-Matching Properties of YCa4O(BO3)3 and GdxY1-xCa4O(BO3)3

YCa4O(BO3)3 has been found to be 90° phase-matchable for type-1 second-harmonic generation at 0.4168 µm along the z-axis at 20°C. The improved Sellmeier equations of YCa4O(BO3)3 that correctly reproduce our new experimental data for second-harmonic and sum-frequency generation in the 0.3547–1.9079 µm range are reported. In addition, the 90° phase-matching properties of GdxY1-xCa4O(BO3)3 as a function of the Gd molar concentration X are presented together with the empirical index formula.

Temperature-Insensitive Second-Harmonic Generation at 0.5321 µm in YCa4O(BO3)3

YCa4O(BO3)3 has been found to have the phase-matching points where the temperature variation of the phase-matching angle (dθobs/dT) becomes zero for type-1 second-harmonic generation at 0.5321 µm at θ=30.8° and =180°. We also found that the temperature sensitivity of the phase-matching angle in the zx plane differs between the =0° and =180° propagation directions in this material. In addition, the thermo-optic dispersion formula of YCa4O(BO3)3 is presented.

Thermo-optic dispersion formula for RbTiOAsO4

The thermo-optic constants of the flux grown RbTiOAsO4 (RTA) have been measured from 0.4577 to 0.7931 µm. These results were fitted to the temperature phase-matching bandwidths (FWHM) for harmonic generation of the Nd:YAG laser and the Nd:YAG laser-pumped KTiOAsO4 (KTA) optical parametric oscillator (OPO), and were used to construct the thermo-optic dispersion formula that can be used for good reproduction of the temperature-dependent phase-matching conditions in the 0.459–3.129 µm range. Applications to the quasi phase-matching are presented.

Phase-matching properties of KNbO 3 in the mid-infrared

KNbO(3) has been found to be phase matchable for type 1 second-harmonic generation up to 2.4 microm at 22 degrees C. The improved Sellmeier equations that correctly reproduce the nonlinear experiments thus far reported in the literature and our new experimental results for harmonic generation of CO(2) laser harmonics between 3.5303 and 5.2955 microm are presented.

90° phase-matched mid-infrared parametric oscillation in undoped KTiOAsO4

90° phase-matched parametric oscillation up to 4.3 µ m was obtained in the undoped KTiOAsO4 (KTA) crystal by pumping with the 1.928 µ m output of a KTiOPO4 (KTP) parametric oscillator pumped by an Nd:YAG laser at 1.064 µ m. The oscillator is continuously tunable from 3.4 to 4.3 µ m. The improved Sellmeiers equations are presented.

Wavelength dependence of laser-induced damage in fused silica and fused quartz

Laser-induced damage threshold (LIDT) of various types of vitreous silica at 1064, 532, 355 and 266 nm was investigated. At 1064 nm no difference of LIDT was observed for all samples. At 1064-355 nm, wavelength-dependence of LIDT of synthetic fused silica (SFS) can be well described by a relation Ith equals 1.45 (lambda) 0.43, where Ith is LIDT in J/cm2 and (lambda) is wavelength in nm. At 266 nm, however, LIDTs were smaller than a half of the calculated value from above relation. This difference can be explained by the damage mechanism; at 266 nm, two-photon absorption-induced defects lowered the LIDT same as a KrF-excimer-laser induced defects, whereas at longer wavelengths two photon process does not occur. LIDTs of fused quartz (FQ) at 532 and 355 nm, and that of a SFS containing about 1000 ppm of Cl and no OH at 355 nm were a little lower than that of the other SFSs. This may be related to the absorption of metallic impurities contained in FQ and dissolved Cl2 molecule in SFS.

Thermo-optic dispersion formula for BiB/sub 3/O/sub 6/

Thermo-optic constants for BiB/sub 3/O/sub 6/ were measured from 20.0 to 120.0/spl deg/C at 0.5435 and 1.0642 /spl mu/m. The thermo-optic dispersion formula that reproduces well the temperature-dependent phase-matching conditions in the 0.3547-1.621 /spl mu/m is presented.

Laser-induced bulk damage of various types of vitreous silica

Multiple-pulse laser induced bulk damage of various types of silica glasses at wavelengths of 532 and 355 nm with laser pulse width of approximately 6 ns repetition rate of 10 Hz were measured. At 532 n, no apparent difference was observed in multiple pulse laser-induced bulk damage threshold (MLIDT) except for As fused quartz (FQ) produced by electrical melting of natural quartz powder whose MLIDT at a constant number of pluses is less than those of the other silicas. MLIDT at 355 nm were different among samples. The MLIDT of FQ disperse much more than that of synthetic fused silica. This could be derived from the distribution of the metallic impurity content in FQ.

90º phase-matched Hg0.35Cd0.65Ga2S4 optical parametric oscillator pumped by a Nd:YAG laser

This paper reports the 90°phase-matched Hg0.35Cd0.65Ga2S4 optical parametric oscillator (OPO) pumped by a Nd:YAG laser at 1.0642 μm in the 8.24-9.40 μm range. The resulting data for the temperature tuning curves of the two idler wavelengths were found to agree well with the theoretical values calculated with the Sellmeier and thermo-optic dispersion formulas constructed from those of HgGa2S4 and CdGa2S4 presented in our previous paper (K. Kato et al. Opt. Commun. 386, 49-52, (2017)). The OPO threshold was ~ 0.3 W, which is 57% lower than ~ 0.7 W observed for the 8-mm-long HgGa2S4 crystal.