Chapter 2 - Long Wavelength (λ > 2 μm) Semiconductor Lasers

Abstract

This chapter considers some results for lasers of both types operating in the range λ > 2 μm with attention to material and structure problems. It presents the state of the art of semiconductor lasers emitting in the wavelength range λ > 2 μm with some historic excursions. It also describes laser types based on both interband and intraband optical transitions. The material systems of III–V, II–VI, and IV–VI semiconductor compounds and alloys for laser heterostructures are presented. The most important actual problems are the laser action at room temperature, the longest wavelength limit, the lowest threshold for laser oscillations, and the increase of the mode tuning range in tunable lasers. The applications of long-wavelength semiconductor lasers are also reviewed. The research of long wavelength semiconductor lasers is important with respect to the practical applications in a wide spectral range. There is an active field of the competitive developments of laser versions based on quite different operation mechanisms: either interband transition with a bipolar pumping or intraband transition with a unipolar pumping. The former mechanism is more traditional, with a great experience of commercial production of GaAs- and InP-based devices and large-scale applications. The aim in a further development is the improvement of laser structure with InSbAsP active materials lattice-matched to GaSb or InAs, which are suitable for emission in the spectral range of 2.5–3.5 μm.