Ralph F. Tate

Spatial gain measurements in a chemical oxygen iodine laser (COIL)

The spatial distribution of small signal gain has been investigated on the RADICL device, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F=3/spl rarr/F=4 hyperfine levels of the (/sup 2/P/sub 1/2/) to (/sup 2/P/sub 3/2/) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle, which is about two times greater than measurements made on ReCOIL by Hager et al. (1988) and compares favorably with measurements made on the RotoCOIL device by Keating et al. (1990). Gain distribution was investigated under three I/sub 2/ flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena. >

Results of small-signal gain measurements on a supersonic chemical oxygen iodine laser with an advanced nozzle bank

High-resolution diode laser spectroscopy has been used to probe the gain in the active medium formed by an advanced supersonic chemical oxygen iodine laser (COIL), ejector nozzle bank. The probe beam was directed through the medium at 90/spl deg/ (normal) to the flow velocity and at an angle of 27.5/spl deg/ away from normal incidence. Analysis of the small-signal gain spectrum allowed for the determination of the gain, average gas velocity, static pressure, and temperature. The dependence of gain, temperature, and gas velocity on the primary nitrogen molar flow rate and basic hydrogen peroxide temperature was obtained. A maximum small-signal gain of 7 /spl times/ 10/sup -3/ cm/sup -1/, average gas velocity of 575 m/s, static temperature of 172 K were measured for flow rates of 270 mmole/s of primary nitrogen, 39.2 mmole/s of chlorine, 11 mmole/s of secondary nitrogen, and 0.8 mmole/s of iodine. Estimation of the static pressure in the flow core from spectroscopic data is very close to the static sidewall pressure. The role of transverse velocity components in the gas flow and their effect on the interpretation of gain profiles is discussed.

The Measurement of Gain on the 1.315 Micrometers Transition of Atomic Iodine in a Subsonic Flow of Chemically Generated NCl(a(1) delta)

Abstract Gain is measured on the electronic I( 2 P 3/2 )– I ∗ ( 2 P 1/2 ) transition of atomic iodine at 1.315 μm when hydrazoic acid HN 3 is injected into a flow of iodine and chlorine atoms. The inversion was generated in a transverse subsonic flow device that produced electronically excited I ∗ ( 2 P 1/2 ) atoms from the efficient energy transfer reaction between NCl(a 1 Δ ) metastable and ground state I ( 2 P 3/2 ) atoms. The population inversion was directly observed using a 1.315 μm tunable diode laser that scanned the entire line shape of the (3,4) hyperfine transition of iodine.

Supersonic RF discharge CO laser operating in fundamental (Δ=1) and overtone (Δ=2) spectral bands

Radio frequency (RF)-excitation of carbon monoxide (CO) in a supersonic cavity with only a 10 cm gain length has yielded an observed fundamental band (Δv=1) multi-line lasing output power of 2.1 kW utilizing a one-pass resonator, with an electrical efficiency of 21%. More importantly, this work generated 50 W of overtone multi-line lasing around 2.7 micron. This was the first time lasing on CO overtone bands (Δv=2) had been demonstrated with a RF-pumped supersonic system.

Measurement of gain on the 1.315-μm transition of atomic iodine as produced from the NCl(a1Δ) + I(2P3/2) energy transfer reaction

A direct measurement of gain on the electronic I (2P3/2) - I*(2Pi/2) transition of atomic iodine at 1.315 jam using tunable diode laser is demonstrated. The population inversion results from the efficient energy transfer between NCI (alA) metastables and I (2P3/2) atoms. Ground state iodine atoms and NCI (a1 A) metastables are produced in a transverse subsonic flow device from the stepwise reaction of Cl atoms with HI followed by the reaction of Cl with azide (N3) radicals, respectively. Under current experimental conditions, a gain of 0.020%/cm is obtained and appears to be limited by reagent number density. A kinetic model was constructed to simulate the experimental gain profile using a mechanism consisting of fully coupled finite rate chemistry and 1-D fluid dynamics. Good agreement with experimental and theoretical calculations are obtained. Keywords: Gain, population inversion, atomic iodine, NCI (a*A) metastables, azides, energy transfer

Dynamics of a mode-locked low-pressure photolytic I* laser

A longitudinally pumped photolytic iodine laser has been reliably mode-locked over a broad range of iodide pressures (1-30 Torr). Average mode-locked pulse widths ranging from 1.4-2.5 ns were observed as a function of CF/sub 3/I iodide pressure and added buffer gas (Ar). Low-pressure data indicate an increased gain bandwidth as a result of an initial nonthermal I* atom distribution following rapid ( >

Two-dimensional gain measurements in a chemical oxygen-iodine laser (COIL) device

The spatial distribution of gain has been investigated on the Research Assessment and Device Improvement Chemical Laser, a supersonic chemical oxygen-iodine laser (COIL). A frequency-stabilized, narrow linewidth diode laser system operating on the F equals 3 yields F equals 4 hyperfine levels of the (2P1/2) to (2P3/2) spin-orbit transition in atomic iodine was used as a small signal probe. A peak gain of 1.2%/cm was measured along the horizontal centerline of the single-slit, supersonic nozzle is about two times greater than measurements made on ReCOIL and compares favorably with measurements made on the Rotating Disk Generator (RotoCOIL) device. Gain distribution was investigated under three I2 flow conditions. Scans across the supersonic expansion indicate a gradient in gain distribution due to higher gas temperatures along the walls and mixing phenomena.

Progress report on the development of a repetitively pulsed frequency-shifted COIL laser

This paper summarizes recent progress that has occurred in several research areas related to the development of a repetitively-pulsed, frequency-shifted chemical oxygen iodine laser (COIL). COIL gain- switch experiments at 10 kHz pulse rates are described using a novel solid state pulsed magnetic field system. Raman conversion experiments in hydrogen using a pulsed photolytic iodine laser as a COIL surrogate are also described.

Dynamics of low‐pressure gain‐switched iodine lasers

The dynamics of gain‐switched, low‐pressure photolytic iodine lasers were investigated experimentally and theoretically as a function of pressure and buffer gas. The behavior of the pulse shape, build‐up, and duration can be explained by relaxation from a nonthermalized to a thermalized velocity distribution of the gas.

The direct observation of gain on the 1.315 μm transition of atomic iodine produced by the energy transfer from NCl(a1Δ) to I(2P3/2)

Gain between the I(2P3/2) and I*(2P1/2) states of atomic iodine at 1.315 μm was detected in a transverse subsonic flow reactor that produced electronically excited I*(2P1/2) atoms from the efficient energy transfer reaction between NCl(a1Δ) metastables and ground state I(2P3/2) atoms. The population inversion was directly observed using a 1.315 μm tunable diode laser that scanned across the entire I(2P3/2)−I*(2P1/2) hyperfine transition with complete resolution.