Zongshu Shao

The quality and performance of the organometallic complex nonlinear optical material tri-allylthiourea cadmium chloride (ATCC)

Abstract Large (30x30x25 mm) crystals of the organometallic, nonlinear optical material ATCC have been prepared by growth from solution in optically and structurally highly perfect state. Type I phase-matched SHG was observed for 1.064 μm radiation incident at 36.8°. The whole nonlinear coefficient was carried out by Maker-fringe (MF) method.

Efficient self-frequency doubling of Nd:GdCOB crystal by type-I phase matching out of its principal planes

Abstract We report on the efficient self-frequency doubling of Nd:GdCOB crystal by type-I phase-matching at θ=66.3° and ϕ=134.4°, which is out of its principal planes. A CW output power of 225 mW at 530.5 nm is obtained at an absorbed pump power of 1.56 W with an optical conversion efficiency of 14.4% and an absorbed threshold pump power of 1.8 mW. To our knowledge, this is the highest output power, the highest efficiency and the lowest threshold obtained from a self-frequency-doubled Nd:GdCOB laser to date.

Novel organic molecular second harmonic generation crystal : 3-methoxy-4-hydroxy-benzaldehyde

In considering the trade‐off between second‐order nonlinearity and transparency, a new organic molecular crystal 3‐methoxy‐4‐hydroxy‐benzaldehyde (MHBA) has been grown from solution by the temperature lowering method for the first time. MHBA belongs to the monoclinic system, and its space group is P21. The unit cell dimensions are: a=14.057, b=7.875, c=15.037 A with β=115.45°. The powder second harmonic generation of MHBA is 30 times higher than that of urea and the cutoff wavelength is 370 nm.

Second harmonic generation and self-frequency doubling performance in Nd:GdCa4O(BO3)3 crystal

Abstract Second harmonic generation (SHG) conversion efficiency of Nd:GdCOB crystal is reported. Theoretical calculation has shown that the largest effective nonlinear coefficient is not in the principal plane. The SHG experimental results of samples cut in the phase-matching direction of θ =66.3°, φ =134.4° and θ =90°, φ =46° are presented. The self-frequency doubling laser performance of the two samples is investigated.

Phase-matched second harmonic generation in new organic MHBA crystal

Abstract Linear and nonlinear optical properties of new organic (NLO) materials, e.g. 3-methoxy-4-hydroxy-benzaldehyde, have been investigated, and the results have been compared with typical organic crystals. Especially, the efficient doubling frequency of a pulsed Ti: sapphire laser using MHBA crystals was obtained at lower power. An all solid-state tunable blue laser with a tuning range of 400–450 nm thus has been realized with this material.

Laser characteristics of Cr:Nd:GdCOB self-frequency-doubling crystal

The phase matching angle of GdCOB crystal is calculated. By using Xenon flash lamp as pump source, we have realized the free run from 1.06 μm to 0.53 μm in self-frequency-doubling Cr:Nd:GdCOB (bi-doped) crystal and Nd:GdCOB (uni-doped) crystal. The experimental results show that the threshold energies for bi-doped crystal and uni-doped crystal are 0.92 J and 1.00 J, respectively; when the pump energy is 10 J, the output energies of green laser for two kinds of crystals are 2.46 mJ and 1.96 mJ, respectively. The output energy of Cr:Nd:GdCOB crystal has an increase of 25% in comparison to that of Nd:Gd:COB crystal. In addition, we discuss ways to improve efficiency.

Self-pumped phase conjugation with high reflectivity by stimulated forward- and backward-scattering tetragonal potassium tantalate niobate crystal

Abstract Self-pumped phase conjugation in tetragonal Fe-doped KTa 1− x Nb x O 3 crystal with a Q -switched, frequency-doubled Nd:YAG laser with power in the milliwatt range is demonstrated. A phase conjugate reflectivity as high as 55% was measured. Both stimulated forward- and backward-scattering were involved in the self-pumping process simultaneously. The coupling characteristics of this crystal are analyzed and compared with those of BaTiO 3 crystal.

Growth and properties of (Cr3+, Nd3+) doped GdCa4O(BO3)3 crystals

Abstract Optical quality Nd:GdCa 4 O(BO 3 ) 3 (Nd:GdCOB) crystal and chromium sensitized crystal of Cr:Nd:GdCa 4 O(BO 3 ) 3 (Cr:Nd:GdCOB) were grown by the Czochralski (CZ) method. The transmittance spectra was measured at room temperature on 7at%Nd:GdCOB and lat%Cr:7at%Nd:GdCOB samples. The absorption in the blue-UV region of Cr:Nd:GdCOB was larger than that of Nd:GdCOB, which matched the xenon flash lamp very well. A 3×3×10mm 3 Nd:GdCOB sample without any antireflective coating was sidepumped using a pulsed dye-laser tuned to 595.4nm. The green-light output energy was 1.35mJ at a pump energy of 17.5mJ. The conversion efficiency was 7.7%, and the threshold energy was less than 1.2mJ which are the best results up to now to our knowledge. 3×3×7mm 3 Nd:GdCOB and Cr:Nd:GdCOB samples without antireflective coatings were pumped using a flash pump source. The threshold for Cr:Nd:GdCOB was 0.9J while for Nd:GdCOB it was I.O.J. The output green light energy was 2.46mJ for Cr:Nd:GdCOB at a 10J flash pump energy and was 1.96mJ for Nd:GdCOB at the same pump energy, which clearly shows that Cr 3+ ions have the sensitizing effect on the Nd 3+ ions in Nd:GdCOB crystal.

Planar waveguide refractive index distribution functions determined precisely from mode indices

The inverse WKB (IWKB) approximation has been extended to derive the index distribution functions from the measured mode indices of a planar waveguide. Through the use of this technique, the forms of the index distribution functions are obtained by IWKB approximation and a criterion is used to derive the functions accurately. The results are compared to the exponential and Fermi distributions. It is shown that the index profile, surface index, and waveguide depth can be obtained more accurately than with the original IWKB approximation. Finally, the index distribution function of a c-cut proton-exchanged LiTaO(3) waveguide is given by this technique, the mode indices calculated with this function agree with the experimental results in the range of 10(-4).

Study on the second-harmonic-generation of GdCa4O(BO3)3 crystals along various phase-matching directions

In this paper, the theoretical calculations of deff of GdCa4O(BO3)3 (GdCOB) along various phase-matching (PM) directions are reported. It is shown that the maximum deff is out of the main planes and the deff in the range of (0<θ≤90, 90<φ≤180) are larger than that in the range of (0<θ≤90, 0≤φ≤90). The PM direction along (θ=66.8, φ=132.6) for GdCOB crystal has the largest deff. Second-harmonic-generation (SHG) experiments were performed on GdCOB crystal along various PM directions. The results show that in GdCOB crystal, the intracavity SHG conversion efficiency is 27.6% along the PM direction (θ=66.8, φ=132.6) which is larger than that along PM directions in XY and XZ main planes, which are in good agreement with the theoretical calculations. The continuous-wave (cw) green laser output power is 1.22 W when LD pump power is 10 W in the Nd:YVO4/GdCOB laser.