Investigation of laser-induced damage in DKDP under multi-color irradiation
Laser-induced initiation of bulk damage sites in DKDP crystals is investigated under simultaneous exposure to 532- and 355-nm nanosecond laser pulses in order to simulate the operational conditions during harmonic conversion as well as probe the damage mechanisms. The results demonstrate synergetic damage effects under the dual-wavelength excitation. Furthermore, the damage performance is directly related to and can be predicted from the damage performance at each wavelength separately. The measured relative effective absorption coefficients at the two wavelengths are found to depend on the laser fluence. Laser-induced damage sites initiated within the bulk of optical components is a key limiting factor in the development of high power laser systems. Potassium dihydrogen phosphate (KH{sub 2}PO{sub 4} or KDP) and its deuterated analog (KD{sub 2-x}H{sub x}PO{sub 4} or DKDP) have been widely used for over three decades as Pockels cells and frequency converters and are still the only nonlinear materials suitable for large-aperture laser systems [1,2]. Damage thresholds in these materials have increased over time, primarily due to purer raw materials and improvement in growth processes, though localized damage sites still arise from laser intensities far below that necessary for intrinsic dielectric breakdown [3]. The damage precursors and their absorption mechanism leading to damage initiation are still unknown despite more than four decades of research [4,5]. In the case of KDP and DKDP crystals, recent work has highlighted the importance of synergetic effects between the second and third harmonics in Nd:glass lasers present during harmonic conversion to the observed damage density [6]. In this work, we quantitatively assess the damage performance of KDP/DKDP crystals under simultaneous exposure to the second and third harmonics of a nanosecond Nd:YAG laser system in order to (a) probe the underlying mechanism of damage initiation and (b) simulate the conditions taking place during harmonic conversion towards developing predictive models.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 900095
- Report Number(s):
- UCRL-JRNL-224169; TRN: US200709%%385
- Journal Information:
- Applied Physics Letters, vol. 89, no. 18, October 30, 2006, pp. 181922, Journal Name: Applied Physics Letters, vol. 89, no. 18, October 30, 2006, pp. 181922
- Country of Publication:
- United States
- Language:
- English
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