III–V semiconductor lasers: application in telecommunication systems - suitability for spectroscopy

The application of III–V semiconductor lasers in telecommunication systems is today an established technique for long haul data transmission. In optical fiber transmission links with data rates up to 2.5 Gbit/s (“data highways”) directly driven DFB lasers are used as transmitters. During the last years 1.3 μm and 1.55 μm DFB laser diodes have maturated from experimental devices to commercial products. In this paper several actual devices for telecommunication systems will be described. Single mode diode lasers might be also attractive for other applications, e.g. spectroscopy in the near infrared [D.E. Cooper and R.U. Martinelli, Laser Focus World 133 (Nov. 1992)]. For this purpose tuning properties of DFB lasers are very important. Typical thermal tuning and current tuning schemes will be discussed. However, single mode lasers are only available for very few specific wavelengths which generally do not coincide with the absorption lines of interesting gaseous species. A few nm tuning range can be achieved changing operation temperature. Larger wavelength ranges can be achieved with tunable lasers currently under development for future telecommunication systems. Widely tunable single mode lasers appear a very promising light source for tunable diode laser spectroscopy.