Tunable Semiconductor Diode Laser Research Articles

Infrared spectroscopy of free radicals and transient molecules using a tunable diode laser

High resolution infrared spectra of transient species have been measured in the gas phase using tunable semiconductor diode lasers in the 9 and 11 uni regions. The spectra were recorded after a singLe pass of the laser either along a dischargeflow tube or through a convenCi-onal inErared sample cell. The laser spectrum of the chlorine atom at 11.3 pm has been assigned to the 2P12←2P32 fine structure transition and shows several resolved hyperfine features. The spectra of NF2 arise from absorptions in ehe γ1, and γ3, fundamental bands, and many components in the RQK branches of the γ1 band have been assigned. Two other transient species have also been detected and tentatively identified as CF2γ3 and HO2γ3.

High sensitivity point monitoring of ozone, and high resolution spectroscopy of the ν_3 band of ozone using a tunable semiconductor diode laser

Accurate measurements of the wavenumbers of more than 100 lines in the nu(3) band of ozone have been made using a tunable semiconductor diode laser and a temperature-stabilized germanium etalon. The accuracy for the line centers is estimated to be within 3-10 MHz and compares well with the accuracy attained using more complicated heterodyne techniques. The relevance of these results to ozone monitoring instruments based on CO(2) lasers is discussed. The tunability of the diode laser is also exploited to monitor ambient concentrations of ozone in the presence of interfering molecular species. A detection sensitivity of ~0.5 ppb of ozone is demonstrated.

High resolution spectroscopy of the OsO4 stretching fundamental at 961 cm−1

The ν3 bands of 187Os16O4, 189Os16O4, and 192Os16O4 have been recorded using both a Michelson interferometer (resolution 0.06 cm−1) and a tunable semiconductor diode laser (resolution limited by the Doppler width, ∼0.0007 cm−1). The rotational fine structure differs from that of most other spherical-top molecules, for only rotational levels of A symmetry exist. A total of 112 individual vibration–rotation lines in the P and R branches of the three isotopic species were calibrated against stimulated emission lines from a high-voltage CO2 gain cell, and were used to determine three scalar and two tensor spectroscopic constants for each species; an additional scalar constant was obtained from an analysis of the Q branch of 192OsO4. The strength of P (11) A2 0 was measured for 192OsO4 and yields a vibrational transition moment for ν3 of 0.17±0.02 D. Transitions of all isotopic species that are expected to fall near CO2 laser lines in the region 949–972 cm−1 are tabulated as an aid in the interpreation of saturation spectroscopy experiments. The general quadratic symmetry and valence force constants of OsO4 were redetermined, using the isotope shifts in ν3 as the additional constraints for the F2 symmetry block.

(Invited) Recent Advances in Laser Devices

This talk discusses some of the recent advances at M.I.T. Lincoln Laboratory in the area of tunable semiconductor diode lasers (including lead-salt diode lasers as well as GalnAsP/InP and GaAs external cavity controlled lasers), miniature Nd-compound lasers, and submillimeter Schottky detectors.

Wavenumber measurement of weak CO 2 laser lines around 10.6 μm

An experimental method is described in which a tunable semiconductor diode laser and the regular CO 2 laser lines are utilized to measure the wavenumber of CO 2 laser lines to an accuracy of about ±5 × 10 −4 cm −1. Twenty new CO 2 laser lines have been measured over the 943 to 951 cm −1 region.

Line shape of the Doppler-limited infrared magnetic rotation spectrum of nitric oxide

A fully resolved, Doppler-limited magnetic rotation spectrum of the R (13/2)1/2 absorption line in the fundamental (ν = 0 → ν = 1) vibration-rotation band of NO has been obtained using a cw, tunable PbSSe semiconductor diode laser.

Collisional narrowing of infrared water-vapor transitions

Water-vapor absorption lines in the ν2 band involving transitions between states of high rotational energy have been found to undergo substantial collisional narrowing in the presence of buffer gases. Measurements were carried out near 5.35 μm, using tunable lead sulfide selenide semiconductor diode lasers.

Tunable-Laser Spectroscopy of the ν1 Band of SO2

Individual transitions of the ν1 vibration-rotation band of SO2 in the 8.7-μm-wavelength region have been observed, using tunable semiconductor diode lasers, and compared with theoretical calculations based on pure-rotation data from microwave absorption measurements. A new value of 1151.71 ± 0.01 cm−1 has been found for the ν1-band center. Pressure-broadening coefficients and intensities of individual lines were determined from the high-resolution data, and a value was obtained for total band intensity.