David Kurt Neumann

High power 7-GHz bandwidth external-cavity diode laser array and its use in optically pumping singlet delta oxygen

Spectral bandwidth of a diode laser array is narrowed to 7 GHz FWHM by using a thick volume Bragg grating. Total output power reaches 13.5 W cw, of which 86% is in the 7-GHz band.

2.3-kW continuous operation cryogenic Yb:YAG laser

We present our recent developments in high-power, high-efficiency cryogenic Yb:YAG laser systems. Specifically, we will discuss our 2.3-kW master oscillator power amplifier (MOPA) which has shown optical wall-plug efficiencies above 30-% (diode-driver input to optical output). This laser system has been operated for long run times with continuous wave and pulsed output formats. The beam quality factor, M2, of the MOPA has been measured to be less than 2 and it is currently limited by the master oscillator. We are working to improve the devices beam quality and output power. In addition, we have demonstrated an all-cryogenic Yb:YAG laser that produced 29 W of optical power. Use of cryogenic diode laser pumps represents our next step towards achieving greater than 50% efficient high-power laser systems.

High-power deuterium Raman laser at 632 nm

We demonstrate a continuous-wave deuterium Raman laser that generates more than 100 mW of Stokes output power despite severe thermal effects. This output power represents a five-fold increase over any previously reported continuous-wave Raman laser.

Highly efficient, resonant Raman molecular iodine laser.

A highly efficient 1.3-microm molecular iodine Raman laser is demonstrated. Multiwavelength output powers of 600 mW and photon-conversion efficiencies of 78% are demonstrated for a 532-nm pump source. Single-wavelength output powers of 480 mW and photon-conversion efficiencies of 67% are also realized. A simple thermal lensing model is used to optimize the pump and Stokes mode sizes.

If(B3II) chemiluminescence resulting from laser photolysis of mixtures of O3 and C3F7I

Abstract IF(B 3 Π) chemiluminescence has been observed following 248 nm photolysis of O 3 in a mixture of O 3 and C 3 F 7 I. Measurements of the IF(B) vibrational and rotational temperatures are presented along with the conversion efficiency of energy from the absorbed 248 nm photons into IF(B). A kinetic model is postulated to explain the results.

Absorption measurements on collision-induced transitions in supercritical and liquid oxygen

Collision-induced absorption spectra have been measured in a wide temperature (80 - 300 K) and pressure (10 - 150 atm) range for the a ← X and b ← X absorption bands of oxygen. The peak and integrated absorption coefficients and monomolecular and multimolecular collision-induced cross-sections are measured for an oxygen density range of 4x1020 cm-3 to liquid. No temperature dependence was found in the absorption of the high density oxygen.

Singlet delta oxygen kinetics in optically excited liquid oxygen

A kinetics model to describe the behavior of singlet delta O2 in optically pumped liquid oxygen has been developed and tested against experimental data. The model was developed to study alternative methods of O2(a1Δg) production for the Chemical Oxygen Iodine Laser (COIL), and has been used in conjunction with experimental data to determine a value for the pooling rate constant in liquid oxygen of 1± 0.5 x 10-17 cm3molecule-1s-1.

Photochemically pumped I2(D’3Π2g→A’3Π2u) emission in mixtures of I2+C3F7I and I2+O3: Implications for chemically initiated, broadband optically pumped I2(D’→A’) lasers

We report the first observation of photochemically initiated I2(D’→A’) emission at 342 nm. Mixtures of I2 and C3F7I or I2 and O3 were excited by a KrF laser at 248 nm photodissociating the C3F7I or O3. The process believed responsible for the intense D’→A’ emission is rapid energy transfer from the excited I(2P1/2) or O2(a 1Δ) photodissociation products to I2(X,v‘=0) producing I2(X,v‘=25→43) which is optically pumped by 248 nm photons to I2(D 1∑+u) and I2(F 1∑+u). Rapid collisional redistribution results in the F,D→D’ crossover. Gain of several percent per centimeter on the D’→A’ transition may be possible with the appropriate gas mixture and pump source.

High Power 7-GHz Bandwidth External-Cavity Diode Laser Array

Spectral bandwidth of a diode laser array is narrowed to 7 GHz FWHM by using a thick volume Bragg grating. Total output power reaches 13.5 W cw, of which 86% is in the 7-GHz band.

Experimental demonstration of lasing in liquid oxygen

We report the first experimental demonstration of lasing in liquid oxygen at 1588 nm when pumped by a pulsed dye laser operating at 632 nm. Results from fluorescence and loss measurements are also presented.