A single-longitudinal mode (SLM) dual-cavity pulsed Ti: sapphire laser is presented. It is self-seeded by means of an active feedback mirror (AFM) consisting of a partially reflecting mirror and additional active medium. The use of AFM results in an increase of both the laser output energy and overall conversion efficiency by a factor of about 1.4 compared to results achieved with a passive feedback mirror, under equivalent conditions. A reliable, temporally stable SLM regime of operation is achieved in the 740-820 nm spectral range.
IntroductionLittman-type cavity configuration [1] Ti:sapphire (Ti:S) lasers produce broadly tunable single-longitudinal-mode (SLM) radiation with a high peak power [2]. Standard Littman-cavity SLM lasers are simple and compact, but they are characterized by extremely high threshold, low conversion efficiency, and low output energy.Classical Ti:S injection-seeding systems [3-5] exhibit much better energy parameters. However, such systems are usually bulky and complex in terms of design and control.Self-seeded pulsed Ti:S lasers, pumped by lasers [6][7][8] or by flashlamps [9], combine compactness and tunability with high efficiency and output energy. Ko et al.[7] developed a dual-cavity self-seeded Ti:S laser by placing a partially reflecting feedback mirror at the output of a standard Littman cavity laser. Merriam and Yin [8] reported enhanced operation of a Ti:S laser using such a cavity configuration. The retroreflectors mentioned above are simple mirrors, i.e. they represent passive optical elements. Scheps and Myers [10] described a twowavelength Ti:S laser with an active mirror positioned in one of the two cavity channels. The active mirror represents a combination of a diode-pumped Nd:YAG crystal and a passive end reflector. The use of an active mirror in the cavity results in enhanced laser operation at the wavelength having lower emission cross-section. However, the active mirror operates at one fixed spectral line only.In this work, a self-seeded coupled-cavity pulsed Ti:S laser with an active feedback mirror (AFM) in the cavity is described. The AFM comprises an active element of the same type as the laser medium. This ensures enhanced SLM operation of the laser over its broad tuning range.