Semiconductor Laser Engineering, Reliability and Diagnostics: A Practical Approach to High Power and Single Mode Devices

Part I

DIODE LASER ENGINEERING

Overview

The impressive technological advances that resulted in semiconductor diode laser technologies in the last decade can be grouped roughly into four areas: higher optical output power, higher single transverse mode and diffraction-limited output, increased range of lasing wavelengths, and significantly improved reliability (see Part II). Most noteworthy commercial demonstrations in high-power continuous wave (cw) outputs of single-emitter and multi-element emitter laser products, for example, in the 980 nm band, include 0.75 W ex-fiber for single spatial mode, narrow-stripe emitters, 12 W for tapered master oscillator power amplifier emitters with single-mode, diffraction-limited operation, 25 W for standard 100 μm wide aperture single-emitter devices, and 1000 W quasi-cw for standard 1 cm multi-element linear laser arrays with nearly diffraction-limited beams.

The development of novel design approaches including strained quantum wells and quantum cascade structures, as well as the advanced maturity of material systems such as compounds based on GaN, CdS, and GaSb, have significantly extended the operating wavelength range of semiconductor lasers throughout the visible spectrum into the ultraviolet regime down to about 0.375 μm on the short-wavelength side and far into the infrared regime with cw operation within 3–10 μm at room temperature, and beyond 10 μm up to 300 μm at operating temperatures around 77 K on the very long wavelength side. ...