T. J. Bridges

cw SUBMILLIMETER LASER ACTION IN OPTICALLY PUMPED METHYL FLUORIDE, METHYL ALCOHOL, AND VINYL CHLORIDE GASES

cw laser action is obtained on two lines in methyl fluoride, three lines in vinyl chloride, and 23 lines in methyl alcohol by optically pumping the gases with various lines of the CO2 laser. The laser wavelengths range from 70 to 700 μm.

Phase‐matched submillimeter wave generation by difference‐frequency mixing in ZnGeP2

Using two step‐tunable CO2 lasers, we have observed phase‐matched generation of frequencies 70 <ν<110 cm−1 by nonlinear mixing in a birefringent ternary semiconductor, ZnGeP2. An observed power of ∼1.7 μW at 83.37 cm−1 gave a signal‐to‐noise ratio of ∼1000 with a Ge:Ga detector. In combination with tunable optical lasers, this technique should yield a tunable source of submillimeter wave radiation for high‐resolution spectroscopy.

CO2 Waveguide Lasers

Compact cw single‐mode CO2 : He : N2 lasers with a 1‐mm‐diam dielectric waveguide discharge tube have exhibited gains of up to 37 dB/m, volumetric power outputs of 15 W/cm3, and saturation parameters of 3600 W/cm2 with a coolant temperature of −70°C. With tap water cooling at 20°C the corresponding values were 24 dB/m, 9.5 W/cm3, and 2100 W/cm2. All of these values are substantially larger than those obtained with conventional CO2 lasers. A 12.5‐cm‐long waveguide tube with an active volume of 0.096 cm3 gave a power output of 1.4 W at −70°C and 0.9 W at 20°C coolant temperature.

cw LASER ACTION AT 81.5 AND 263.4 μm IN OPTICALLY PUMPED AMMONIA GAS

cw laser action at 81.5 and 263.4 μm, corresponding to a rotational transition and an inversion transition in the v2 state of NH3, has been obtained by optically pumping the gas with an N2O laser.

Gain recovery time of traveling-wave semiconductor optical amplifiers

We propose a mechanism which may shorten the gain recovery time in semiconductor optical amplifiers. The mechanism is carrier diffusion from nearby carrier storage regions (carrier reservoirs), which enhances the carrier recovery process in the active region and consequently reduces the gain recovery time. Bias‐independent recovery times as short at 100 ps are demonstrated in a 1.3‐μm traveling‐wave amplifier.

MODE LOCKING OF A TRANSVERSELY EXCITED ATMOSPHERIC PRESSURE CO2 LASER

Mode locking of a transversely excited atmospheric‐pressure CO2 laser has been achieved through the use of a germanium acousto‐optic modulator. Subnanosecond pulse widths and peak powers in excess of 1 MW have been obtained.

High‐frequency constricted mesa lasers

InGaAsP cw constricted mesa lasers at 1.3 μm are described which have a small‐signal 3‐dB bandwidth of 20 GHz at −70 °C. Large‐signal pseudorandom modulation at 8 Gb/s resulted in 100% optical modulation. The lasers were gain switched at 12 GHz with 100% optical modulation.

SPONTANEOUS SELF‐PULSING AND CAVITY DUMPING IN A CO2 LASER WITH ELECTRO‐OPTIC Q‐SWITCHING

Spontaneous self‐pulsing has been observed in a 10.6‐μ CO2 laser, Q‐switched in ≈10 nsec by an internal GaAs electro‐optic cell, with no saturable absorber present. Each Q‐switched event consists of a train of ten or more 20‐nsec pulses with a total duration of ≈400 nsec in a single P(20) line. Electro‐optic dumping of the cavity energy near the peak of oscillation gives a single output pulse of ≈10‐kW peak power and 25‐nsec duration. A numerical comparison is made with the circulating π pulse theory of spontaneous pulsing.

ABSOLUTE FREQUENCY MEASUREMENT OF THE 118.6‐μm WATER‐VAPOR LASER TRANSITION

The frequency of the 118.6‐μm water‐vapor laser transition has been measured as 2,527,952.8 MHz in a harmonic mixing experiment. Accuracy of several parts in 108 has been obtained by phase locking the klystron harmonic source to a tunable crystal oscillator and by centering the laser to the Lamb dip.

ERRATUM: HIGH‐PRESSURE LASER ACTION IN 13 GASES WITH TRANSVERSE EXCITATION

Laser action has been achieved in 13 gases at high pressures using pulsed transverse excitation. A total of 149 wavelengths from 0.8 to 28μ was observed. Pulse lengths were found to lie in the range 0.2–5μsec. Several gases operate at atmospheric pressure and above and promise to give very high power outputs.