Abstract: A laser spectrometer includes a tunable laser assembly, a periodically-poled nonlinear optical crystal, with parallel polished input and output end faces, and a mechanism for controlling an entrance location of a pump input beam of the tunable laser on the input end face of the periodically-poled nonlinear optical crystal, such that the pump input beam traverses different grating periods of the periodically-poled nonlinear optical crystal.

Abstract: The present invention relates to a laser system and method which enables fast, accurate laser frequency tuning. In particular, the present invention includes only one laser and only one absolute frequency locking loop to perform the same fast frequency tuning than previous seed laser systems.

Abstract: RF modulation spectroscopy of a near-infrared tunable laser diode source is used to determine the oxygen concentration in a sample medium. A reference cell containing a known concentration of oxygen is used to calibrate the apparatus as well as to lock the laser on an oxygen absorption line. The temperature of the reference cell is monitored from which the pressure in the reference cell can be determined. Both the temperature and the pressure in the sample cell are monitored, either directly using independent transducers or indirectly using spectroscopic techniques. The oxygen content of the sample is determined, correcting for both temperature and pressure effects.

Abstract: RF modulation spectroscopy of a near infrared laser diode source is used to determine the amount of a target substance in a breath sample. In this type of modulation the laser output is modulated to produce sidebands displaced from the laser carrier by the modulation frequency. The modulated beam is passed through a gas sample which differentially absorbs the sidebands, the result of which is the conversion of some of the laser frequency modulation into amplitude modulation which is subsequently detected using a broadband photodetector. In certain tests, the target substance is a particular isotope, whose concentration is measured as an isotope ratio. In order to measure the presence of first and second isotopic species, provision is made to provide laser illumination at characteristic wavelengths for absorption lines for the first and second isotopic species of the gas.