The developement of concepts leading to semiconductor lasers

Claude Weisbuch

We introduce the various physical concepts which have been put to good use in the past 60+ years since the invention of the semiconductor laser diode. We then evaluate the various advances which led to the modern quantum well laser, including the use of strain effects and quantum barriers. This has resulted in a improvement of the threshold current density by 5 orders of magnitude, a unique achievement in semiconductor devices.
Semiconductor lasers are nowadays fabricated and used in a wide range of realizations. We give a number of recent illustrations such as high-power arrays, high-speed lasers, short and long wavelengths lasers etc… To obtain still better light-emitters one needs to obtain sharp optical features and enhanced light-matter interaction in solids. We describe the recent advances in lower dimensionality quantized systems such as 1D quantum well wires and 0D quantum dots. While most of the effort has been, and still is, devoted to the quantization of electron motion in low-dimensional structures, a new promising scheme has recently appeared based on photon mode quantization in optical microcavities, photonic bandgap materials and other photon localization structures. It leads to many features similar to those obtained by electron motion quantization, such as sharp emission lines, but also to several better ones: directionality, “thresholdless” lasers, strong light-matter coupling etc… We also discuss the challenge for higher power efficiency and why LEDs are fundamentally a better device in that direction, hence their dominance in lighting applications. On the other hand, as sources for solid-state laser pumping, semiconductor lasers are superior based on their directionality allowing efficient coupling and are thus ubiquitous for this application.

Claude Weisbuch is a semiconductor physicist. He held positions in academia, industry, government. He is now emeritus “Directeur de Recherches” Ecole Polytechnique, France and professor in the materials department of University of California at Santa Barbara, USA, working on high-efficiency LEDs. He was at Bell Laboratories (1979-1981), Saint-Gobain (1983), Thomson-CSF (now Thales) (1983-1992). He was chief scientist of DGA (procurement), ministry of defense, France (1992-1998). In CNRS from 1997, he co-founded in 2002 a high-tech company, Genewave, Paris, devoted to fluorescence-based molecular diagnostics systems , based on his work on light extraction in LEDs. He has authored more than 300 papers and 35 patents.