Clayton H. Bair

High resolution spectral measurement of the HNO 3 11.3-μm band using tunable diode lasers

High resolution spectra in the region of the 2nu(9) band of nitric acid have been obtained for selected portions of the HNO(3) spectrum using tunable diode laser techniques. Continuous spectra are presented from 891.25 cm(-1) to 898.77 cm(-1), with a spectral resolution </=0.001 cm(-1) (30 MHz). Absolute line intensities and line positions are presented. Absolute wavelength calibration was obtained by frequency mixing the diode laser with a C(13)O(2)(16) isotope laser. Self and foreign gas (N(2)) broadening coefficients were iteratively calculated from the experimental data and were determined to be alpha(a) = 0.8 cm(-1)/atm and alpha(f) = 0.13 cm(-1)/atm, respectively.

Pulsed injection control of a titanium-doped sapphire laser

Injection control of a tunable Ti:sapphire laser using a narrow-bandwidth pulsed dye laser operating at a wavelength removed from the peak of the Ti:sapphire-laser gain curve is reported. The free-running Ti:sapphire laser had broadband laser emission from 750 to 790 nm. Injection at 727 nm resulted in essentially complete energy extraction at that wavelength in a 2.5-pm bandwidth matching the injection source.

Infrared vibration–rotation spectra of the CIO radical using tunable diode laser spectroscopy

Tunable diode laser spectroscopy is used to measure the infrared vibration-rotation spectra of the ClO radical. The radical is generated in a flow system where a Cl2-He mixture passes through a microwave discharge to dissociate the Cl2. An O3-O2 mixture from an ozone generator is injected into the system downstream of the microwave discharge where O3 combines with Cl to form ClO. By adjusting the gas flow rates to yield an excess of Cl atoms, all the ozone is combined. ClO concentration is measured with UV absorption at 2577 and 2772 A and a deuterium lamp as a continuous source. Total cell pressure is 5.5 torr. The diode laser spectrometer is calibrated with ammonia lines as a reference where possible. The frequency of vibration-rotation lines is expressed as a function of rotational quantum number, fundamental vibrational frequency, and the rotational constants of the upper and lower vibrational states.

Demonstration of frequency control and CW diode laser injection control of a titanium-doped sapphire ring laser with no internal optical elements

Theoretical and experimental frequency narrowing studies of a Ti-sapphire ring laser with no intracavity optical elements are reported. Frequency narrowing has been achieved using a birefringent filter between a partially reflecting reverse wave suppressor mirror and the ring cavity output mirror. Results of CW diode laser injection seeding are reported. >

Investigation of 2.1-μm lasing properties of Ho:Tm:Cr:YAG crystals under flash-lamp pumping at various operating conditions

Flash-lamp-pumped normal-mode and Q-switched 2.1-microm laser operations of Ho:Tm:Cr:YAG crystals have been evaluated under a wide variety of experimental conditions in order to determine an optimum lasing condition and to characterize the laser outputs. Q-switched laser-output energies equal to or in some cases more than the normal-mode laser energies were obtained in the form of a strong single spike by optimizing the opening time of a lithium niobate Q switch. The increase of the normal-mode laser slope efficiency was observed with the increase of the Tm concentration from 2.5 to 4.5 at. % at operating temperatures from 120 K to near room temperature. Laser transitions were observed only at 2.098 and 2.091 microm under various conditions. The 2.091-microm laser transition appeared to be dominant at high-temperature operations with low-reflective-output couplers and to have an energy-level assignment from 5313 cm(-1) to 534 cm(-1) or (and) from 5313 cm(-1) to 536 cm(-1).

Measurement of HCl absorption coefficients with a DF laser

Absorption coefficients in the fundamental P-branch of HCl at several DF laser transitions from 2439.02 cm(-1) to 2862.87 cm(-1) have been measured experimentally. The 2-1 P(3) DF laser transition has been shown to overlap the P(6) HCl(37) absorption line within the halfwidth of an atmospherically broadened line. The absorption coefficient k was measured to be 5.64 +/- 0.28 (atm-cm)cm(-1) for a 0.27% mixture of HCl in N(2) at a total pressure of 760 Torr. A theoretical and experimental comparison of the pressure dependence of k showed that the 2-1 P(3) DF transition lies 1.32 +/- 0.15 GHz from the center of the P(6) HCl absorption line. This line separation is in good agreement with published positions for this DF laser transition and the HCl absorption line. At least four other DF laser transitions in the spectral interval measured are reported showing measurable absorption (>/=10%) for a 10.2% mixture of HCl in N(2) across a 1-m pathlength. Applications of these results to differential absorption lidar (DIAL) and to heterodyne detection are also discussed.

Ozone Air Broadening Coefficients In The 9 μm Region

Air broadening coefficients and line strengths are reported for selected ozone lines in the 8.8 to 10μm spectral region. These parameters were obtained from a least squares fit of the Voigt line shape to experimental ozone absorption spectra obtained with a tunable diode laser. Analysis of 11 lines in the νl and 18 lines in the ν3 band suggest a transition dependent coefficient although no definitive relationship was identified., The average air broadening coefficient for the νl and ν3 ozone lines is 0.077 and 0.083cm-1/atm, respectively. The measured line strengths are typically 10% to a factor of 2 larger than those given in the AFGL compilation.

Recent advances in efficient long-life, eye-safe solid state and CO2 lasers for laser radar applications

There is increasing interest in the comparative roles of CO2 and the more recently developed eye-safe solid-state lasers for long-life efficient laser radar applications. This paper assesses recent technology advances in each area and their roles in laser radar and especially Doppler lidar and DIAL development. The key problems in eye-safe solid-state lasers are discussed relating to the energy transfer mechanisms between the complicated energy level manifolds of the Tm,Ho,Er ion dopants in hosts with decreasing crystal fields such as YAG or YLF. One concerns optimization of energy transfer for efficient lasing through choice of dopant concentration, power density, crystal field and temperature, with the highly practical goal of minimal cooling needs. Another key problem, specific to laser radar and lidar, involves tailoring of energy transfer times to provide efficient energy extraction for short, e.g., Q-switched pulses used in DIAL and Dopper lidar. Special emphasis is given to eye-safe lasers in the 2 μm range because of the high efficiency applications to DIAL and (windshear) Doppler lidar and because they are well suited for Optical Parametric Oscillator frequency conversion into the important ≈ 4 to 5 μm DIAL range. The discussion of CO2 lasers concerns recent advances in Pt/Sn02 oxide catalysts and other noble metal/metal oxide combinations. Emphasis is given to the dramatic effects of small quantities of H20 vapor for increasing the activity and lifetime of Pt/Sn02 catalysts and to increased lifetime operation with rare isotope 12C18O2 lasing mixtures; iL-the 12C18O2 laser wavelengths in the 9.1 μm range are of special interest for space-based Doppler lidar such as the proposed Laser Atmospheric Wind Sounder.

Ozone Air-Broadening Coefficients In The 9ÃÂÃÂÃÂõm Region

Air-broadening coefficients and line strengths are reported for selected ozone lines in the 8.8 to 10 um spectral region. These parameters were obtained from a least squares fit of the Voigt line shape to experimental ozone absorption spectra obtained with a tunable diode laser. Analysis of 11 lines in the vi and 18 lines in the v3 band suggest a transition-dependent coefficient although no definitive relationship was identified. The average air-broadening coefficient for the vi and v3 ozone lines is 0.077 and 0.083 cm-1/atm, respectively. The measured line strengths are typically 10% to a factor of two larger than those given in the Air Force Geophysics Laboratory compilation.

Alexandrite Laser Pumped Ho:Tm:YLF Laser Performance

The performance of Ho:Tm:YLF pumped by an Alexandrite laser was compared to previously obtained results for comparable Ho:Tm:YAG experiments. We have used an Alexandrite laser with pulse durations of 650μs and 200μs to longitudinally pump Ho:Tm:YLF crystal with 1.5% and 0.5% Ho concentration and length of 4 to 6mm. For a 1.5% Ho concentration in YLF, with pump pulse of 200μs, a slope efficiency as high as 50% is obtained for 6mm long crystal. In general, higher slope efficiencies are achieved in Ho:Tm:YLF than in Ho:Tm:YAG. Previous Ho:Tm:YAG experimental measurements are in good agreement with an improved rate equation model.