PNNL

Abstract

Following an introduction to the history of the invention of the quantum cascade (QC) laser and of the band-structure engineering advances that have led to laser action ocer most of the mid-infrared(IR) and part part of the far-IR spectrum, the paper provides a comprehensive review of recent developments that will likely enable important advances in areas such as optical communications, ultrahigh sensitivity gas-sensing systems. As we discuss the experimental observations of the remarkably different frequency response of QC lasers compared to diode lasers, i.e. the absence of relaxation oscillations, their high-speed digital modulation, and results on mid0IR optical wireless communication links, which demonstrate the possibility of reliably transmitting complex multimedia data streams. Ultra short pulse generation by gain switching and active and passive modelocking is subsequently discussed. Recent data on the linewidth of free-running QC lasers (~150 kHz) and their frequency stabilization down to 10 kHz are presented. Experiments of the relative frequency stability (~5Hz) of two QC lasers locked to optical cavities are discussed. Finally, developments in metallic waveguides with surface plamon modes, which have enabled extension of the operating wavelength to the far-IR are reported."