Thermal conductivity measurements of laser crystals by infrared thermography. Application to Nd:doped crystals

Abstract

We present a thermal conductivity measurement method for laser crystals based on thermal mapping of the crystal face by an infrared camera. Those measurements are performed under end-pumping of the laser crystal and during laser operation. The calculation of the fraction of pump power converted into heat is therefore simplified, and it is possible to link easily the temperature in the crystal to the thermal conductivity. We demonstrate the efficiency of this measurement method with a Nd:YAG crystal, before using it to compare Nd:YVO(4) and Nd:GdVO(4) crystals.

Highly efficient Nd:YVO_4 laser by direct in-band diode pumping at 914 nm

“…This demonstrates the low contribution of upper-laser-level loss mechanisms to the thermal load in our setup. As the temperature gradient is very low compared with other experiments realized under pumping at 808 nm [10], we expected to have a very weak thermal lens in the crystal. To carry out this measurement, we took advantage of the sensitivity of our cavity to the thermal lens.…”

“…Moreover, the large beam size and the small absorption coefficient limited the local population inversion density and reduced locally upper-laser-level loss mechanisms such as Auger recombination, multiphonon decay, and concentration quenching [9]. To see the contribution of these effects to the thermal load, we measured the temperature of the pumped face with or without laser action with an IR camera in a setup reported elsewhere [10] at the maximum absorbed pump power ͑14.6 W͒. With laser action, the population inversion density is very low (clamped to its value at threshold), and we can assume that the rate for upper-laserlevel loss mechanisms is negligible compared with the rate of stimulated emission: we measured a tem- perature increase of 15°C between the center and the edge of the pumped face.…”

Megawatt peak power, 1 kHz, 266 nm sub nanosecond laser source based on single-crystal fiber amplifier

“…By assuming the heat flow in the BBO as radial, we can use the equations defined in [8]. The maximum axial temperature elevation in the center of the crystal between its entrance and its end can be expressed as follow [9]:…”

Output characteristics of Nd:GdVO4 crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers

“…Nd:GdVO 4 has a large absorption cross section of 5.2×10 -19 cm 2 , a large emission cross section of 7.6×10 -19 cm 2 at 1.06 μm and a wide absorption bandwidth at pump wavelength of 808 nm [6][7][8] . Especially, the thermal conductivity of GdVO 4 which is 12.3 W/mK along the 001 direction is twice higher than that of YVO 4 , and is even higher than that of YAG [9] . Such unique spectroscopic and thermal properties make Nd:GdVO 4 crystal be a promising gain medium substituting for Nd:YAG and Nd:YVO 4 in compact all-solid-state lasers.…”