The design of a compact and tunable extended-cavity semiconductor laser

The design of a tunable extended-cavity semiconductor laser based on the modified Littman configuration is described. The mechanics of the extended cavity is designed with respect to applications as a stabilized laser source for an etalon of optical frequency, a laser for interferometry where stability, narrow linewidth, and mode hop free tuning range are required and for spectroscopic purposes with similar requirements. It follows the contradicting demands for a rigid construction and fine adjustability of the optical components. Optimisation of the optical feedback level and its influence of the laser behaviour are discussed and a method for the feedback level adjustment by rotation of the polarization plane is proposed. The laser parameters are presented for a version based on a laser diode operating at a wavelength of 633 nm.