Analysis of multipass laser amplifier systems for storage laser media
Highly efficient short pulse high power lasers have many potential applications, including laser fusion drivers. One technique for achieving high powers in short pulses is to use a storage laser amplifier. A storage laser amplifier uses a laser medium with a long lived upper laser level. The upper laser level can accumulate energy from a pumping source over a relatively long time. This stored energy is then extracted by stimulated emission over a relatively short time. Examples of such storage laser media are Nd:YAG, Nd:Glass, V:MgF/sub 2/, Tm:Glass, CO/sub 2/, and Group VI media (e.g., sulfur and selenium). The single pass amplifier system depicted in (top) is the simplest approach to amplifying a laser light pulse. The laser beam is passed once through the laser medium. The beam is amplified as it extracts energy stored in the medium's upper laser level. The single pass amplifier performance is limited in that it cannot simultaneously provide high energy gain and high efficiency. Under certain conditions these limitations can be overcome by using a multipass system such as the one depicted in the lower part. In this paper a single pass amplifier is investigated first using the Frantz-Nodvik theory of short pulse laser amplification. The multipass system is then treated by sequentially applying the single pass extraction equations for each extraction pass. In order to find the gain coefficient for each extraction, the changes occurring in the laser medium and in the laser beam fluence between extraction passes are determined using a simple three level laser kinetics model.
- Research Organization:
- California Univ., Livermore (USA). Lawrence Livermore National Lab.
- OSTI ID:
- 6874536
- Report Number(s):
- AD-A-090400
- Country of Publication:
- United States
- Language:
- English
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