Thermal Expansion of Lithium Tantalate and Lithium Niobate Single Crystals

Abstract

The principal thermal expansion coefficients of single crystals of LiTaO3, LiNbO3 and α quartz (for reference purposes) have been determined by an x-ray diffraction technique in the temperature range 25°–500°C. All three materials crystallize in the trigonal system, the first two in class 3m and the last one in class 32, and are characterized by only two principal expansion coefficients, parallel and normal to the c or Z axis. The Bragg x-ray angle data were fitted to suitable polynomials in the temperature deviations from an arbitrary reference of 25°C, and the expansion coefficients up to second order calculated from the coefficients of these polynomials. The Z-axis expansion of LiTaO3 showed a definite maximum at about 250°C. Similar behavior was indicated in the Z-axis expansion of LiNbO3, but at a much higher temperature (at the high extreme of the measurement range). The expansion of all three crystals normal to the Z axis was quite regular.

Strain engineering in graphene by laser irradiation

“…In particular, graphene has a negative thermal expansion of the order of about À8 Â 10 À6 K À1 , 25 whereas in the case of lithium niobate the thermal expansion coefficient is 7.5-15 Â 10 À6 K À1 (depending on orientation). 26 We argue that it is the high values and difference in sign of the thermal expansion coefficients for the two materials that leads to strain relaxation upon heating. This is also corroborated by the fact that in the case of the silica substrate, where the expansion coefficient is an order of magnitude smaller than that of lithium niobate, 27 no strain relaxation is observed.…”

15 W green light generation by single-pass second harmonic generation of a single-frequency tapered diode laser

“…Here λ is the laser wavelength, L is the crystal length, n is the refractive index and α is the coefficient of linear thermal expansion. Using the Sellmeier equations [16], its derivatives [17] and the thermal expansion coefficient [18] for MgO:LiNbO 3 we find that the measured results at low input power indicate an effective length of our crystal of 27 mm. The power stability of the green light was measured for a period of 1 hour at a green output power of 1.5 W. The output power was 1.5 W ± 0.04 W corresponding to a variation of ± 3 %.…”

A method to remotely measure temperature change in a lithium niobate crystal using birefringence

“…where d 298 is the crystal thickness at 298 K, α and β are the first and second order thermal expansion coefficients respectively [11], and T is the temperature of the crystal in Kelvin.…”

“…A change in temperature changes the values of d and ∆n. Thermal expansion of the material modifies d according to [11] …”