The paper discusses optimization of gain and output power and scaling of a pulser-sustainer discharge excited
oxygen-iodine laser. For this, NO addition to the laser mixture and iodine vapor dissociation in an auxiliary high-voltage,
nanosecond pulse duration, repetitively pulsed discharge ("side" discharge) are used. Iodine dissociation fraction
generated in the side discharge and measured in the M=3 laser cavity is up to 50%. The experiments showed that
additional iodine dissociation generated in the side discharge only moderately increased laser gain, by 10-15%.
Parametric gain optimization by varying main discharge pressure, O2 and NO fractions in the flow, I2 flow rate, pulsed
discharge frequency, and sustainer discharge power, with the side discharge in operation produced gain up to 0.08 %/cm.
Two parameters that critically affect gain are the energy loading per molecule in the discharge and the NO flow rate
controlling the O atom concentration in the flow. Operation at the main discharge pressure of 60 torr resulted in
significantly higher gain than at 100 torr, 0.080 %/cm vs. 0.043 %/cm, due to high discharge energy loading per
molecule at the lower pressure. Laser output power measured at the gain optimized conditions is 1.4 W. Experiments
with a scaled-up laser with a large volume pulser-sustainer discharge (10 cm x 10 cm x 2 cm vs. 5 cm x 5 cm x 2 cm)
and longer gain path (10 cm vs. 5 cm) demonstrated stable discharge operation at discharge powers up to at least 2.9 kW.
Singlet delta yield and gain measurements in the scaled-up laser are underway.
The paper presents results of singlet delta oxygen yield (SDO) measurements in a high-pressure, non-self-sustained discharge and small signal gain measurements on the 1315 nm iodine atom transition in the M=3 supersonic cavity downstream of the discharge. The results demonstrate operation of a stable pulser-sustainer discharge in O2-He flows at pressures of up to 120 torr and discharge powers of up to 2.2 kW. The reduced electric field in the DC sustainer discharge ranges from 6 to 12 Td. SDO yield in the discharge is up to 5.0-5.7% at the discharge temperatures of 400-420 K. The results suggest that SDO yield exceeds the gain threshold yield at the M=3 cavity temperature by up to a factor of three, which is confirmed by gain measurements. The highest gain measured in the supersonic cavity is 0.01%/cm.
The kinetic modeling and design of a carbon monoxide (CO) gas laser is presented. In contrast to the more widely known fundamental band CO laser, this laser is designed to operate on the first overtone bands, the Δν = 2 vibrational quantum transitions. Lasing on these bands is known to produce multi-line output at wavelengths from 2.5 microns to beyond 4.0 microns in the infrared. The present study is to develop a compact, wall-cooled CO overtone laser, that can develop average powers O[100 W]. A kinetic modeling code has been developed to guide the design, and to calculate both continuous wave (c.w.) and Q-switched performance. There are distinct advantages in Q-switched operation of this laser, which is potentially one of the few truly efficient lasers scalable to very high average powers.
The electric-discharge-excited carbon monoxide laser is one of the most efficient laser sources known that is scalable to very high continuous wave powers. We review work at Ohio State where such lasers are used to excite flowing molecular gas plasmas, in mixtures of CO and other diatomic gases, including air. These plasmas are stable, diffuse, and can be operated at high gas pressures and low gas kinetic temperature. They are being employed for various plasma chemistry applications. Recent results are presented in which such an optically pumped plasma reactor is used to synthesize single-walled carbon nanotubes, which show surprising order and alignment.