Generation of high-quality petawatt pulses. Final report
- Michigan Univ., Ann Arbor, MI (United States)
CPA sources need a front-end capable of generating very short seed pulses. To meet this requirement, present CPA sources rely on actively modelocked solid-state oscillators used in conjunction with non-linear fiber stages. This approach generates pulses with a residual frequency chirp, resulting in a limited peak-to-background intensity contrast ratio. The availability of an oscillator capable of producing directly (i.e. without fiber stage) picosecond or sub-picosecond pulses would significantly improve the quality of CPA sources. We have pursued different approaches to replace the standard modelocked oscillator front-end. In an initial phase, we investigated the possible use of Additive Pulse Modelocking (APM) color-center lasers as oscillators for CPA Nd:glass sources. Lately we have developed a Ti:Sapphire modelocked oscillator operating in the one-micron range. In order to generate pulses with very high peak to background contrast ratio, we have built a non-linear coupled-cavity oscillator generating 200-fs pulses. This color-center laser operates in the 1.5--1.6 micron range. A diagram of the oscillator is shown in Fig. 1. The laser is pumped with a modelocked Nd:YAG source. Both KCl and NaCl crystals were tested as gain media. NaCl was found to have a larger tuning range and to generate a higher average power (up to 150 mW). When synchronously mode-locked, the color-center generates pulses in the 10--20 ps range. Once interferometrically coupled to non-linear external-cavity, this oscillator produces very short pulses (85 to 260 fs). This oscillator was first operated with a 2 mm birefringent plate. 85 fs, near transform-limited pulses were generated at 1.54 micron. As the laser was tuned to longer wavelength, the pulse duration increased, as well as the bandwidth-duration product. With a 4 mm birefringent plate, 125 fs, transform-limited pulses were generated over the full tuning range.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 10104911
- Report Number(s):
- UCRL-CR-108460; ON: DE92003965
- Resource Relation:
- Other Information: PBD: [1991]
- Country of Publication:
- United States
- Language:
- English
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