P. Kerkoc

Surface damage of (-)2-(α-methylbenzylamino)-5-nitropyridine single crystals induced by pulsed laser radiation.

Pulsed laser-induced surface damage experiments were made on the cleaved (001) face of (-)2-(α-methylbenzylamino)-5-nitropyridine crystals at a pulse length of 25 ns FWHM. The highest single-pulse damage threshold value was 24.2 J/cm(2) at 532 nm for light polarized along the crystallographic b axis.

Thermal properties of the nonlinear optical crystal zinc tris (thiourea) sulphate

The heat capacity of crystalline zinc tris (thiourea) sulphate, has been measured in the range from 220 to 500 K by differential scanning calorimetry, and was found to obey the relationship Cp(T)=2.76×10−3 T+0.366 J g−1 K−1. Thermal expansion data have been measured in the range from 150 to 473 K. From these data, the principal thermal expansion coefficients were found to be α1=6.41×10−5 K−1, α2=4.52×10−5 K−1, and α3=−4.32×10−6 K−1. The thermal conductivity tensor of this orthorhombic crystal was calculated from values of the thermal diffusivity in the directions normal to the (100), (010), and (001) crystal planes by the laser flash method. The thermal conductivity coefficients at 295 K are k1=0.27 W m−1 K−1, k2=0.34 W m−1 K−1, and k3=0.54 W m−1 K−1.

Thermal conductivity of the molecular crystal (–)2–(α–methylbenzylamino)‐5‐nitropyridine

Thermal diffusivities of high quality (‐)2‐(α‐methylbenzylamino)‐5‐nitropyridine (MBANP) single crystals were measured in different directions by the flash diffusivity method. The complete thermal conductivity tensor at temperatures of 295, 323, and 349 K was then obtained for this monoclinic crystal from the thermal diffusivity, specific heat, and density data. For instance, the thermal conductivity coefficients at 295 K are k1=0.27 W/mK, k2=0.29 W/mK, and k3=0.20 W/mK. The peak melting point of MBANP lies at 357.3 K, whereas the corresponding enthalpy of melting ΔHm has a value 67.2 J/g.

Investigation of optical damage in the nonlinear optical crystal (−)2-(α-methylbenzylamino)-5-nitropyridine

Abstract Pulsed laser induced surface damage experiments were made on the cleaved (001) face of (—)2-(α-methylbenzylamino)-5-nitropyridine (MBANP) crystals using a pulse length of 25 ns FWHM. The highest single pulse damage threshold value was 24·2 J cm−2 at a wavelength of 1064 nm for light polarized along the crystallographic a axis, whereas the lowest was 1·8 J cm−2 at 532 nm for light polarized along the crystallographic b axis. The extent of the mechanical distortion of the (001) crystal plane consequent upon the absorption of a 25 ns FWHM, 10 J cm−2 pulse from a Nd:YAG laser operating at the wavelength 1064 nm has been measured by a non-destructive and non-invasive technique.

Thermal properties of the novel nonlinear optical crystal N‐methylurea

The heat capacity of crystalline N‐methylurea has been measured in the range from 223–303 K by differential scanning calorimetry, and was found to obey the relationship Cp(T)=(5.44±0.04) ×10−3 T−(0.02821±0.0016) J g−1 K−1. Thermal expansion data have also been measured in the range from 100–353 K, allowing the temperature dependent density to be calculated. From these data, the principal thermal expansion coefficients were found to vary linearly, e.g., over the range from 100–250 K. In this range α1=−(5.84±0.42)×10−5 K−1 and α2 and α3 were found to be (1.31±0.14)×10−4 K−1 and (1.04±0.10)×10−4 K−1, respectively. The thermal conductivity tensor of this orthorhombic crystal was then calculated from values of the thermal diffusivity in the directions normal to the (100), (010), and (001) planes determined by the laser flash method. The thermal conductivity coefficients at 295 K were found to be k1=0.47 W m−1 K−1, k2=0.26 W m−1 K−1, and k3=0.30 W m−1 K−1.

Thermal properties of the organic nonlinear optical crystal 4-nitro-4′-methylbenzylidene aniline

The thermal properties of high-quality nonlinear optical single crystals of 4-nitro- 4′-methylbenzylidene aniline (NMBA) have been measured in various temperature ranges. The specific heat was measured in the range from 273 to 373 K by differential scanning calorimetry and was found to obey the relationship Cp=2.3×10−3 T+0.487 J g−1 K−1. The peak melting point was detected at a temperature of 402 K with a corresponding enthalpy of melting ΔHm of 113.63 J g−1. Principal thermal expansion and thermal conductivity coefficients were determined at different temperatures. For example, at room temperature (295 K) they were α1=1.274×10−4 K−1, α2=0.826×10−4 K−1, and α3=0.239×10−4 K−1. The principal thermal conductivity coefficients were k1=0.40 W m−1 K−1, k2=0.19 W m−1 K−1, and k3=0.21 W m−1 K−1 and these values were independent of temperature up to 370 K.

Molecular crystals for applications in acousto-optics

An assessment of the acousto-optic figure of merit, M, was performed for the highly-polar non-centrosymmetric crystal, (-) 2--(methylbenzylamino)-5-nitropyridine. Its estimated value is as large as 1.3 × 10-13 s3 kg-1 at an ultrasound frequency of 15.4 MHz with light of wavelength 632.8 nm. This value is about four times as large as that of the widely used inorganic crystal, PbMoO4.

Low values of the tensor components of the non-resonant optical absorption in the molecular nonlinear optical single crystal (−)2-α-(methylbenzylamino)-5-nitropyridine

Abstract Low absorption coefficients for the light polarized along the crystallographic a, b and c ∗ axes and an additional direction bisecting the angle between the a and c ∗ axes of (−)2-α-(methylbenzylamino)-5-nitropyridine (MBANP) single crystals were measured at the wavelengths 1064 nm and 532 nm. They were found to be in the range from 0.022 cm−1 to 0.061 cm−1, i.e., of the same order of magnitude as some widely used crystals in the nonlinear optics. From these data all four absorption index coefficients of this crystal were determined.

Low nonresonant optical absorption in (-)2-α-(methylbenzylamino)-5-nitropyridine single crystals

Low absorption coefficients for the light polarizations along the crystallographic a, b, and c* axes of (-)2-α-(methylbenzylamino)-5-nitropyridine single crystals were measured at the wavelengths 1064 nm and 532 nm. They were found to be in the range from 0.02 cm-1 to 0.06 cm-1, i.e., of the same order of magnitude as some widely used crystals in nonlinear optics.

SECOND-HARMONIC GENERATION IN BIAXIAL CRYSTALS FOR A NON-DEPLETED FUNDAMENTAL GAUSSIAN LASER BEAM

The theory necessary for the optimization of second-harmonic (SHG) efficiency in biaxial crystals is developed and applied to the molecular crystal (-)2--(methylbenzylamino)-5-nitropyridine (MBANP). It is shown that, for the range of crystal lengths and beam walk-off angles available, the criteria for the selection of the parameters and for optimization of the second-harmonic signal are the same in biaxial and uniaxial crystals. The maximal possible SHG figure of merit, , is found to be for a 50 mm long crystal.