STABILIZING LEAD-SALT DIODE-LASERS - UNDERSTANDING AND CONTROLLING CHAOTIC FREQUENCY EMISSION

lead-salt tunable diode lasers (TDLs) are the only devices currently a vailable that can generate tunable monochromatic radiation at arbitrar y wavelengths between 3 and 30 micrometers and are particularly useful for high-resolution spectroscopy over a wide range of spectral regime s. Detailed observations oi TDLs show that the observed instrumental l inewidth is actually a temporal average of many narrow (less than 0.5 megahertz) emission ''modes.'' The lime scale characteristic of these ''modes,'' which appear to be of relatively constant intensity, is of the order of a microsecond. The laser's behavior is highly suggestive of a chaotic process, that is, seemingly random excursions of a dynami c variable (frequency) within a bounded range. This report shows exper imentally that TDL emissions are indeed chaotic. Furthermore, in a sim ple and robust fashion, this chaotic behavior has been successfully co ntrolled with the use of recent techniques that take advantage of chao s to produce a narrow band laser output.