MICROCHIP LASERS (Mini DPSS lasers)

Microchip lasers are perhaps the ultimate in miniaturisation of diode-pumped solid-state lasers. A thin etalon of gain material (shown below in purple) has dielectric coatings applied to its plane surfaces, and a diode laser (shown black with red beam) provides a strongly localised pump source. The pump also produces thermal and gain related effects that provide cavity stability mechanisms, allowing the production of a high quality TEM00 beam. As first demonstrated a decade ago in Nd containing gain materials by Dixon and by Zayhowski and Mooradian, the short length of these devices allows the generation of single-frequency radiation in a readily mass produced laser. Scientists at Milan extended this concept into telecoms applications by using Er-Yb:glass as the gain material to generate tens of milliwatts of high-purity radiation at 1.5um.

Work at St Andrews and at Hamburg has explored intracavity frequency-doubled Nd lasers and produced tens to hundreds of milliwatts of cw red, green, and blue light. The short cavities had low loss and a small beam waists. This allowed the generation of significant circulating IR fields, and thus efficient second harmonic generation. The short cavity lengths also contributed to reduced intermodal coupling, and hence could remove the intensity instability known as "green noise". This type of technology was marketed by Uniphase, amongst others, as a replacement for air-cooled argon ion lasers in the reprographics and biomedical industries, for example.

Microchip lasers have found their own distinctive role. Their robust and readily mass-produced structures are very attractive. Couple this with their single-frequency CW performance, or their excellence at generating sub-nanosecond pulses, and one sees that they are well suited for many applications.

    

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