Presently, very efficient and compact laser sources can be obtained using semiconductor laser diodes based on 2-dimensional quantum well(s) in their active gain region. Such state-of-the-art semiconductor laser diodes can produce hundreds of milliwatts of laser light emitted over a narrow range of wavelengths of a few nanometers (nm) or smaller. Typically, to obtain a different wavelength, a distinct laser diode must be fabricated with the appropriate quantum well(s) in its active region. For several applications, a wide range of wavelengths are necessary. This limits the usefulness of semiconductor laser diodes based on quantum wells because the 2-dimensional density-of-states of the electronic structure results in a gain spectrum which can be tuned at most by tens of nanometers using external cavities, or using integrated tuning elements.
The current state-of-the-art technology used to obtain laser sources tunable over hundreds of nanometers using external cavity configurations with a solid-state crystal such as a Ti-Sapphire lasers (Ti-Saph lasers), or with dyes mixed in a liquid medium (Dye lasers). These lasers have major limitations because they are not compact and are very inefficient since they have to be aligned and optically pumped with another powerful laser operated at shorter wavelengths.
There exists a real need for compact and efficient lasers, tunable over a broad range of wavelengths for multimedia and telecommunication applications, as well as for diagnostic and research/development tools. New applications will also emerge with the development and availability of such laser sources.
It is therefore an object of the invention to provide an apparatus and method capable of generating laser light tunable over a wide range of wavelengths in a compact and efficient way.