Fast tunable diode laser with digital control and multiple line selection

摘要

Abstract: Tunable diode lasers have become a light source of choice for spectroscopic applications because of their small size, high efficiency, reliability, and low cost. Tuning for a particular wavelength is commonly realized by using the Littman-Metcalf external cavity configuration with a diffractive grating and rotating mirror. Using this approach, mechanical moving parts and a high degree of precision in the rotation mechanism are required for wavelength selection. Because of this mechanical motion, the tuning process is relatively slow. In some spectroscopic applications sample probing at more than one wavelength is desirable, which currently requires two or more lasers. The development of a single laser source with fast selection over a definable set of wavelengths, also capable of simultaneous emission of a multi-line spectrum, is described. Such a laser can be used to match the spectral signature of the sample and would dramatically increase the speed and reliability of a laser spectrometer. The design is based on an external-cavity configuration with fast computer controlled (in the millisecond range) line selection and has no moving parts. The laser is capable of emitting sets of multi-line near infrared spectra, each spectrum stored as a record in a computer database and matching the spectral signature of a particular chemical component, thus facilitating rapid and reliable spectroscopic detection and analysis of compound samples. The laser design and experimental test results are presented and discussed in the paper.!6