Wavelength and pulselength dependence of laser conditioning and bulk damage in doubler-cut KH 2 PO 4

Abstract

An experimental technique has been utilized to measure the variation of bulk damage scatter with damaging fluence in plates of KH 2 PO 4 (KDP) crystals. Bulk damage in unconditioned and laser-conditioned doubler-cut KDP crystals has been studied using 527 nm (2ω) light at pulselengths of 0.3 -10 ns. It is found that there is less scatter due to damage at fixed fluence for longer pulselengths. In particular, there is~4X increase in fluence for equivalent scatter for damage at 2ω, 10 ns as compared to 0.30 ns in unconditioned KDP. The results for the unconditioned and conditioned KDP show that for all the pulselengths the scatter due to the bulk damage is a strong function of the damaging fluence (φ~5). It is determined that the 2ω fluence pulselength-scaling for equivalent bulk damage scatter in unconditioned KDP varies as τ 0.30±0.11 and in 3ω, 3ns ramp-conditioned KDP varies as τ 0.27±0.14 . The effectiveness of 2ω and 3ω laser conditioning at pulselengths in the range of 0.30-23 ns for damage induced 2ω, 3 ns is analyzed in terms of scatter. For the protocols tested (i.e. peak conditioning irradiance, etc.), the 3ω, 300 ps conditioning to a peak fluence of 3 J/cm 2 had the best performance under 2ω, 3 ns testing. The general trend in the performance of the conditioning protocols was shorter wavelength and shorter pulselength appear to produce better conditioning for testing at 2ω, 3 ns.

Does complex absorption behavior leading to conditioning and damage in KDP/DKDP reflect the electronic structure of initiators?

“…Our theoretical values can be compared by assuming a relation between fluence φ and density ρ. We chose a power law dependence of damage density on total absorbed energy fluence, r~φ 3 and found the results shown in Fig. 5b.…”

“…In KDP, the bulk damage threshold has been found [1][2][3] to scale with pulselength τ roughly as τ 0.24-0.35 for wavelengths of 355 and 532 nm. Pulselength scaling for conditioned material 4 is similar to that for unconditioned material.…”

Transparent-media characterization dedicated to laser damage studies: a key task, multi-faceted, and always renewed

“…We can define an effective 3 ω fluence which leads to equivalent damage effects under simultaneous 2 ω and 3 ω irradiation and plot it as a function of 2 ω fluence (fig 3 left). The wavelength and pulselength dependence of conditioning of KDP has been studied 47 . In figure 4 is presented a result of KDP conditioning at 3ω with 3ns pulses.…”

“…Study of KDP Conditioning47 . Example of plot of ordered pairs of scatter curves versus 2ω damaging fluence, for 3ω, 3ns conditioned KDP at the pulse lengths labeled for the 2ω damaging pulses.…”

Optics Performance at 1(omega), 2 (omega), and 3 (omega): Final Report on LDRD Project 03-ERD-071

“…Also, we see that 300-ps conditioning at 10 GW/cm 2 provided the best conditioning effectiveness. Conditioning results for KDP are presented in [33]. …”