Tunable lasers - An overview

The purpose oft his editorial and the SpeciaIls sue on Tunable Lasers is to highlight the large number of research opportunities in the area of tunable lasers. The extensive list of applications provides both justification and a sense of urgency for research on tunable lasers. The Guest Editors hope that the objective has been reached. Ever since laser sources were first demonstrated, the idea of a tunable "radio-like" coherent source has been recognized as having a large number of potential applications. If, however, one searches abstracting services such as the Defense Technical Information Center or Physics Abstracts, there does not appear to be an aggressive pursuit of the goal of tunable lasers. The research activity that has gone on resulted in commercial tunable sources realized mainly by dye lasers or by nonlinear processes such as parametric oscillators. The ultimate tunable laser (at any wavelength) has not been developed, but its characteristics can be imagined; the ultimate tunable lasers in terms of practicability and simplicity certainly would be a stable, longlife, easily servicable material operating at room temperature, which via external settings may be tuned within its tunable range to any selected frequency. Recently, the discovery of alexandrite has in fact provided the first material that provides these characteristics.