Linear and nonlinear optical properties of ZnGeP2 crystal for infrared laser device applications: revisited

Measurement of refractive indices in the spectral bands 9-11 microm and 1.32 microm from a cw CO2 laser and a Q-switched Nd:YAG laser, respectively, is reported in a ZnGeP2 crystal. A new set of Sellmeier dispersion relations has been derived from the measured refractive indices data in this crystal. Second-harmonic generation (SHG) of CO2 laser radiation in this crystal is also reported. It is also seen that the previously reported phase-matching data for others experiments in SHG and optical parametric devices is explained satisfactorily with this new set of Sellmeier dispersion relation.     

Accurate determination of solid and liquid dispersions from spectra channeled with the Fabry-Perot interferometer

The band spacing of the fringes of equal chromatic order of a thin Fabry-Perot interferometer is compared when this interferometer contains air, a solid, or a liquid. This comparison enables the dispersion of the group velocity of light in these media to be known accurately to 2.4 parts in one thousand. The Sellmeier dispersion function is used to deduce the refractive indices with the same degree of accuracy. The order-transformation method is used to find the exact order values from the roughly known optical thickness. The exact order values for air and the sample are used to find the refractive index accurately to approximately 3 x 10(-5). A least-squares fitting of the accurate experimental data to the Sellmeier dispersion function enables the coefficients of the latter to be more precisely defined for solids such as glass and mica and for liquids such as glycerin and distilled water. The atomic parameters such as the density of states and the absorption wavelengths in the ultraviolet region of the spectrum for the given samples are deduced from the more precisely found Sellmeier coefficients.     

Chromatic dispersions of the ocular media of human eyes

Of the commonly used chromatic dispersion equations, only the Sellmeier and the Cauchy equations seem to be theoretically based. Cauchy's equation is derived from the Sellmeier equation, is simpler to implement, and was found to give an excellent fit to published refractive-index data of the human eye. We used Cauchy's equation to model the chromatic difference in refraction of the Gullstrand number 1 schematic eye with a gradient-index lens. To estimate the dispersion at different refractive-index levels within the lens, a single dispersion equation at one nominal refractive index was linearly scaled. This scaling was justified after exploring the effect of mean refractive index on dispersion by using Sellmeier's equation and finding that a dispersion equation for one wavelength is just a linearly scaled version of the dispersion equation at any other wavlength. Because Cauchy's equation is theoretically based and gives excellent fit to data in the visible spectrum, it can be used to extrapolate results into the near infrared with confidence.     

Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal

We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (β) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 μm is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C.     

200-mW-average power ultraviolet generation at 0.193 microm in K2Al2B2O7

K2Al2B2O7 has been found to be phase matchable for type-1 sum-frequency generation (SFG) at 0.193 microm by mixing the Nd:YAG laser wavelength at 1.0642 microm and the SFG output of the RbTiOAsO4 optical parametric oscillator tuned at 0.2358 microm. An average power of 200 mW at 10 kHz was obtained in a 7-mm-long crystal. In addition, the Sellmeier equations and the thermo-optic dispersion formula, which predict well the phase-matching conditions and temperature phase-matching bandwidths (FWHM) for second-harmonic generation and SFG in the 0.193-0.669-microm range, are presented.     

Temperature-dependent refractive index of potassium acid phthalate (KAP) in the visible and near-infrared

We report an investigation of the temperature-dependence of the refractive index of potassium acid phthalate (KAP) crystal. Refractive index measurements are based on a refractometer setup operating in a temperature range from 25 °C to 200 °C and using five different laser wavelengths in the visible and near-infrared. Temperature-dependent dispersion relations are proposed, with an average fitting quality that exceeds experimental accuracy, and compared to previous room-temperature Sellmeier equations. Consequently, the new relations are employed for the calculation of various linear and nonlinear optical properties of KAP.     

Determination of the optical properties of a monomode optical fibre by fringes of equal chromatic order

Abstract

Multiple beam fringes of equal chromatic order are used to study the optical properties of a monomode optical fibre. The material dispersion of the core and that of the cladding of the fibre are measured. A modified single term Sellmeier dispersion formula is adopted and fitted to the experimental data. A new simple scheme of calculation is applied to reduce the interferogram. A single interferogram is sufficient to give the whole dispersion information needed across the visible spectrum.     

Widely tunable continuous-wave mid-infrared radiation (5.5-11 microm) by difference-frequency generation in LiInS2 crystal

The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation (DFG) in LiInS2 crystal is reported. Wide spectral coverage (5.5-11.3 microm) has been obtained with angle and wavelength tuning for type II (eoe) critically phase-matched parametric interaction. The phase-matching conditions in cw DFG have been investigated, which allowed us to improve the Sellmeier parameters by use of a two-pole dispersion equation. An effective nonlinear coefficient deff = 6.9 +/- 0.8 pm/V has been determined at approximately 7 microm relative to the well-known nonlinear coefficient d36 of AgGaS2, which yields a power-conversion efficiency of approximately 12.4 microW/(W2 cm). We evaluated the high-resolution spectral characteristics of the DFG source by recording C2H2 and SO2 spectra.     

Second-harmonic and sum-frequency generation in ZnGeP(2)

ZnGeP(2) has been found to be phase matchable for type-1 second-harmonic generation of a CO(2) laser to as high as 10.78 mum at 20.0 degrees C. The Sellmeier equations and nonlinear optical constant of this crystal are reported.     

玻璃材料折射率及色散的高准确度测量

使用德国Triotics公司生产的SpectroMaster HR UV-VIS-IR型折射率测量设备,对FK5玻璃块的e、d、g、F′和C′谱线的折射率值进行高准确度测量,并修正至标准环境条件下的折射率值。用得到的折射率值进行曲线拟合,验证Cauchy色散公式和Sellmeier色散公式。     

Optical properties of BaCaBO3F crystal

The optical transmission spectra of BaCaBO₃F (abbr. BCBF) crystal have been measured at room temperature. The refractive indices have been measured with the minimum deviation method and fitted to the Sellmeier equations. The nonlinear optical coefficient d₂₂ of BCBF crystal determined by the Maker fringe technique is 0.74d₃₆(KDP).     

Sellmeier and thermo-optic dispersion formulas for RbTiOPO4

The thermo-optic constants for RbTiOPO₄ were measured from 20.0 to 120.0 °C in the 0.532–1.571 μm range. The Sellmeier and thermo-optic dispersion formulas that reproduce well the temperature-dependent phase-matching conditions for the normal and periodically poled crystals are presented.     

Optical constants of the nano-crystal and polymer composite thin film PbTiO3/PEK-c

Composite thin films of PbTiO₃ nano-crystals and high transparency PEK-c polymer were prepared by spin coating. The size of PbTiO₃ nanocrystals was evaluated to be 30–40 nm. The transparency spectra of PEK-c composite thin film in 360–800 nm were measured. The optical constants n, k of the film in the wavelength range 400–620 nm were investigated by the transmission spectrum. The dispersion of refractive index fits well to a three-term Sellmeier relation. At 633 nm wavelength the refractive index of PbTiO₃/PEK-c film was measured to be 1.6628 by a prism coupling method and showed a good agreement with the calculated value using the Sellmeier relation.     

Optical properties of BaCaBO3F crystal

The optical transmission spectra of BaCaBO₃F (abbr. BCBF) crystal have been measured at room temperature. The refractive indices have been measured with the minimum deviation method and fitted to the Sellmeier equations. The nonlinear optical coefficient d₂₂ of BCBF crystal determined by the Maker fringe technique is 0.74d₃₆(KDP).     

Sellmeier and thermo-optic dispersion formulas for KTP

KTP has been found to be phase matchable for type-2 second-harmonic generation of the third harmonics of the CO2 laser wavelengths at 9.2714 and 9.5525 microm at 20.0 degrees C. The resulting angle and temperature-tuning data combined with the literature values of the Nd:YAG laser-pumped optical parametric oscillator were used to improve the Sellmeier equations and the thermo-optic dispersion formula that reproduce well the temperature-tuned 90 degree phase-matching conditions of the flux-grown crystals. Applications to quasi phase matching are presented.     

High-accuracy measurements of the refractive index and its temperature coefficient of calcium fluoride in a wide wavelength range from 138 to 2326 nm

The refractive indices of synthetic calcium fluoride for 69 wavelengths from 138 nm in the deep ultraviolet to 2326 nm in the near infrared were measured by the minimum-deviation method in a nitrogen environment. We made these measurements at 20 degrees and 25 degrees C, respectively, to determine the thermal coefficients of the refractive index over this wide-wavelength region. These refractive indices were fitted to a four-term Sellmeier dispersion formula. The temperature coefficients of the refractive index were fitted to a Hoffman-type dispersion formula. The standard deviation of the residual between the observed values and the calculated values was 0.6 x 10(-6) for the refractive index and was 0.13 x 10(-6)/degrees C for the temperature coefficient of the refractive index.     

Measurement of refractive indices and thermal refractive-index coefficients of 7.5-mol.% Nb:KTiOPO4 crystal

The principal refractive indices and the thermal refractive-index coefficients of 7.5-mol.% Nb:KTiOPO(4) crystal were measured by autocollimation for wavelengths of 0.53975, 0.6328, 1.0795, and 1.3414 microm from room temperature to 143 degrees C. The Sellmeier equations at room temperature were obtained and used to calculate the optimal phase-matched angles for 1.0642 and 1.0795 microm. The calculated and experimental values are in good agreement.     

Optical Properties of Ca_(0.25)Ba_(0.75)Nb_2O_6 Thin Films Prepared by Spinning Coating

Ca0.25Ba0.75Nb2O6 (CBN25) thin film was prepared on quartz substrate by spinning coating and the optical properties were investigated by a Hitachi U-3410 spectrophotometer and a Metricon 2010 prism coupler. The optical band gap, thickness and refractive index at 632.8 nm of the CBN25 thin film were determined to be 3.65 eV, 529 nm and 2.2258, respectively. The dispersion of the refractive index fitted to Sellmeier relation well and optical waves could be guided into the thin film, which implied that CBN25 thin films were promising for integrated optics and optically active devices.     

Tunable coherent infrared generation near 2.5 microm from self-difference frequency mixing in YAl3(BO3)4:Nd3+

Idler generation from self-difference frequency mixing of the pump wave near 750 nm and the 1062-nm Nd3+ laser emission in the bifunctional laser and nonlinear optical YAl3(BO3)4:Nd3+ crystal was shown. The efficiency was 0.37%, and the infrared wavelength was tunable in the 2430-2600-nm range. New Sellmeier formulas that predict phase-matching polar angles for frequency conversion processes involving wavelengths up to 2600 nm were established.     

Ultraviolet generation tunable to 0.185 microm in CsLiB6O10

CsLiB(6) O(10) has been found to be phase matchable for type-1 sum frequency generation to a minimum of 0.185 mum by mixing the fifth harmonic of a Nd:YAG laser at 1.0642 mum and the output of a KTP parametric oscillator pumped by the second harmonic of the same Nd:YAG laser at 20.0 degrees C. The improved Sellmeier equations and the thermo-optic constants of this crystal are reported.