Laser-Induced Damage Threshold of Nonlinear GaSe and GaSe:In Crystals upon Exposure to Pulsed Radiation at a Wavelength of 2.1 μm

Abstract

The paper defined the laser-induced damage threshold from the fluence and the peak power of GaSe and GaSe:In single crystals upon exposure to nanosecond radiation in the two micron range and assessed the influence of test radiation energy parameters (pulse repetition rate, pulse duration) on the damage threshold. Laser-induced damage threshold was determined with the parameters of the incident radiation close to the pump radiation parameters of promising dual-wavelength optical parametric oscillators (effective pump sources for THz difference frequency oscillators): wavelength was ≈2.1 μm; pulse repetition rates were 10, 12, 14, and 20 kHz; and pulse durations were 15, 18, 20, and 22 ns. The obtained results made it possible to conclude that the value of GaSe damage threshold at a wavelength of 2.091 μm of the incident radiation was influenced by the accumulation effects (the damage threshold decreased as the pulse repetition rate increased). The accumulation effects were more significant in the case of the In-doped sample, since a more significant decrease in the damage threshold was observed with increasing frequency in terms of the peak power and the fluence.

Study on the mechanism of surface pressure of optical films formed by laser plasma shock wave

“…´-8.1 10 s. Literature [19] studied the pressure versus time curve of the shock wave front of an aluminum target under the action of a mJ 0.05 laser. The results showed that the highest pressure peak was about -10 N m , 7 2 and p decreased with the increase of the action time t. This is basically consistent with the results of this paper. Due to the different target materials and excitation energy, the highest pressure peak is different.…”

“…´t 8.1 10 s, 0 6 which shows that the total interaction time between laser plasma and shock wave is ´-8.1 10 s. 6 From equation (13), the pressure rises sharply from = ´p 1.013 10 N m 0 5 2 to ´-1.9 10 N m 8 2 during the interaction of laser pulse t , p and the pressure changes by three orders of magnitude. The plane decay model is used in   t t t .…”

“…Taking single-layer HfO 2 film as an example, if = -P 10 W cm 9 2 and r = -9.68 g cm , 3 the p I is about ´-3.6 10 N m . 5 2 Because the mass of splash material is too small, the pressure of this order of magnitude is not dominant in the interaction between laser and optical film surface, and can also be ignored.…”

“…For optical thin film elements in a high power laser system, when the laser acts on the optical thin film surface, the initial stage is the heat action, heat action heats the film and makes it locally heated, which leads to the increase of free electrons or gasification of the film. When the concentration of free electrons and ions reaches a certain amount, optical breakdown occurs (indicating that the optical film has undergone irreversible changes), and then the plasma is formed [1][2][3][4][5]. The absorption of subsequent laser energy by plasma causes its own temperature to rise sharply, and its volume expands outward after reaching high temperature and overheating state, that is, plasma shock wave is formed [6][7][8], and the initial propagation speed of plasma shock wave reaches the order of magnitude of -10 m s .…”

Honeycomb layered topology construction for exceptional long-wave infrared nonlinear optical crystals

“…GaSe is a state-of-the-art long-wave IR and THz NLO crystal with honeycomb double layered structure, possessing large NLO coefficients ( d 22 = 54 pm V −1 ), large birefringence (0.4@2 μm) and wide IR transparent range (0.62–19 μm). 8 Unfortunately, its perfect cleavage along the (0001) direction due to weak van der Waals force between layers, and low hardness, cause bad mechanical stability and service life. 9 Therefore, it is worth exploring new honeycomb layered-type IR NLO crystals.…”