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Koepf, G. A.

Publications and source records attributed to Koepf, G. A..

18 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Off-axis coherently pumped laser

A coherently optically pumped laser system is described. A pump laser beam propagates through a laser medium contained in a degenerate cavity resonator in a controlled multiple round trip fashion in such a way that the unused pump beam emerges from an injection aperture at a different angle from which it enters the resonator. The pump beam is angularly injected off of the central axis of the resonator body whereupon the pump beam alternately undergoes spreading and focusing while pumping the laser medium by a process of resonant absorption. The emergent pump beam can also be used as a second pump beam source by being reinjected back into the cavity or it can be used for pumping another laser.

Koepf, G. A.↗
NASA NTRS1982

Collisional narrowing in the optically pumped CH3OH and CH3F lasers

The gain linewidth of the optically pumped CH3F laser is observed to narrow and rebroaden with the addition of He. In addition, the same effect is observed in the CH3OH laser with the addition of the polyatomic buffer gases SF6 and CS2. These results offer conclusive evidence of the Dicke narrowing phenomena in these inverted pure rotational transitions. The effect is observed using a high harmonic mixing technique in a Schottky barrier diode.

Lawandy, N. M.↗
NASA NTRS1982

The excitation and distribution of CO (J = 6-5) emission in the Orion Nebula

Observations of the 691-GHz (J = 6-5) transition of CO in the BN/KL region of Orion obtained in February 1981, at the IR Telescope Facility at Mauna Kea are reported. The system employs a heterodyne receiver with an overall noise temperature of 3900 K DSB at 432 microns, 64 5-MHz IF-filter-bank channels, and a chopping secondary with 120-arcsec excursion, and has 35-arcsec resolution. Sample data are presented graphically and analyzed using a rate equation and a kinetic model. A 35 x 45-arcsec core with hot broad plateau emission (antenna temperature 180 + or - 36 K) surrounded by an area of strong narrow-line 120-K emission is found. It is suggested that the plateau emission originates in a wide thin sheet after a shock wave, with H2 density at least 10 to the 6th/cu cm and gas kinetic temperature greater than 500 K.

Buhl, D.↗
NASA NTRS1981

Submillimeter heterodyne detection of interstellar carbon monoxide at 434 micrometers

Laser heterodyne observations of submillimeter emissions from carbon monoxide in the Orion molecular cloud are reported. High frequency and spatial resolution observations were made at the NASA Infrared Telescope Facility on Mauna Kea by the use of an optically pumped laser local oscillator and quasi-optical Schottky diode mixer for heterodyne detection of the J = 6 - 5 rotational transition of CO at 434 microns. Spectral analysis of the 434-micron emission indicates that the emitting gas is optically thin and is at a temperature above 180 K. Results thus demonstrate the potential contributions of ground-based high-resolution submillimeter astronomy to the study of active regions in interstellar molecular clouds.

Fetterman, H. R.↗
NASA NTRS1981

Detection of the J = 6 - 5 transition of carbon monoxide

The J = 6 - 5 rotational transition of carbon monoxide has been detected in emission from the KL 'plateau source' in the Orion molecular cloud. The corrected peak antenna temperature is 100 K, and the FWHM line width is 26 km/sec. These observations were carried out using the 3 m telescope of the NASA IRTF (Infrared Telescope Facility) on Mauna Kea, Hawaii, and constitute the first astronomical data obtained at submillimeter wavelengths with a heterodyne system using a laser local oscillator. The data support the idea that the high-velocity dispersion CO in Orion is optically thin and set a lower limit to its temperature of approximately 180 K.

Goldsmith, P. F.↗
NASA NTRS1981

433 micron laser heterodyne observations of galactic CO from Mauna Kea

A submillimeter heterodyne radiometer, developed for astronomical applications, uses an optically pumped laser local oscillator and a quasi-optical Schottky diode mixer. The resultant telescope-mounted system, which has a noise temperature less than 4000 K (double sideband) and high frequency and spatial resolution, has been used to detect the J = 6 to 5 rotational transition of carbon monoxide at 434 micrometers in the Orion molecular clouds. The measurements, when compared with previous millimeter-wave data, indicate that the broad carbon monoxide emission feature is produced by an optically thin gas whose temperature exceeds 180 K.

Buhl, D.↗
NASA NTRS1980

A stable submillimeter laser local oscillator for heterodyne radiometry and spectroscopy

A submillimeter laser with off-axis pump beam injection is described. This design concept achieves complete isolation of the pump laser with respect to the pump radiation reflected from the submillimeter resonator. Active line independent stabilization of the pump laser is obtained by the use of an external tunable etalon as a frequency reference. The submillimeter output power is constant to within 4% over periods of hours. Mean frequency drifts of less than 2 parts in 100 million per minute were measured by mixing with very high harmonics of an X-band synthesizer in a planar Schottky diode.

Koepf, G. A.↗
NASA NTRS1980

Pressure shift in the 170-micron emission of the CW optically pumped CH3OH laser

Pressure shifts of +15 MHz torr were observed in 16(8)-16(7) 170-micron CW CH3OH optically pumped laser emission. The experiments were performed using a harmonic mixing technique in a Schottky diode. The results are explained in terms of a second-order dipole-dipole interaction in a statistical formulation.

Lawandy, N. M.↗
NASA NTRS1980

Sub mm laser local oscillators: Design criteria and results

Diagnostic results are given of the spectral features and the power conversion efficiency of submillimeter (SMM) laser local oscillators. Several criteria are obtained for the design of frequency stable and efficient smm lasers for local oscillator applications. Finally, a design is described and results on the power output and power and frequency stability are given. The mode pattern is very close to a Gaussian profile so that efficient coupling to a quasioptical mixer is possible. The laser provides sufficient output power at a large number of lines to drive the mixer into the low conversion loss regime. Radiometric integration times of several minutes with a spectral resolution of 1 MHz will be possible. With present state-of-the-art Schottky mixers and low noise preamplifiers a radiometric temperature resolution of a few K can be expected over a spectral range from 500to 900 GHz.

Koepf, G. A.↗
NASA NTRS1980

Energy-transfer mechanisms in the CH3F-SF6 optically pumped laser

The power of an optically pumped CH3F laser operating on the 496-micron line has been doubled with the addition of SF6 without any corresponding increase in pump absorption. It is suggested that a near-resonant energy transfer between CH3F and SF6 followed by SF6 deactivation is the mechanism responsible for the enhancement.

Lawandy, N. M.↗
NASA NTRS1980

Collisional narrowing by polyatomic buffer gases in an optically pumped CH3F laser

The gain linewidth of an optically pumped CH3F molecular laser is observed with the addition of various polyatomic buffer gases. This is interpreted as collisional (Dicke) narrowing. The measurement is the first observation of collisional narrowing by polyatomic buffer gases. It is also the first observation of the effect in a laser oscillator. The effect was observed using a heterodyne mixing technique at the laser emission frequency of 604 GHz. Collision cross sections for SF6-CH3F and CS2-CH3F are obtained.

Lawandy, N. M.↗
NASA NTRS1980

Relaxation oscillations in optically pumped molecular lasers

The observation of relaxation oscillations in both the (C-13)H3F and (C-12)H3F optically pumped lasers is reported. Expressions are derived for the oscillation frequency and its temperature and pressure dependences using a four-level rate equation model. Excellent agreement between measured frequencies and the theory presented is observed. Models are considered for using this phenomenon to determine the rotational and vibrational relaxation mechanisms of the laser gases.

Lawandy, N. M.↗
NASA NTRS1979

Laser apparatus

A laser apparatus having a pump laser device for producing pump laser energy upon being excited is disclosed. The pump laser device has a resonating cavity for oscillating and amplifying the pump laser energy. A source laser device is used for producing source laser energy upon being excited by the pump laser energy. The source laser device has a resonating cavity for oscillating and amplifying the source laser energy. The source laser's resonating cavity is coupled within a portion of the pump laser's resonating cavity.

Koepf, G. A.↗
NASA NTRS1979

Common-cavity pumped laser

Two lasers linked by dichroic coupler are packaged in single cavity. Resulting system is more compact, efficient, and durable than conventional two-cavity lasers. Such instruments (portable pumped lasers) are needed for spectroscopy in plasma diagnostics in atmospheric research, and in radar-like devices for seeing through dense fog or smoke.

Koepf, G. A.↗
NASA NTRS1977

CW operation of an intracavity pumped molecular submillimeter-wave laser

The 373-micron line of CH3CN was operated in a CW mode in an arrangement where the submillimeter (SMM)-wave laser is placed inside the resonator of the CO2 pump laser. 1 mW of CW output power was obtained; this is five times the power of a comparable SMM-wave laser in the common extracavity arrangement. In a pulsed mode, a peak power of 46 mW was measured.

Koepf, G. A.↗
NASA NTRS1977

Submillimeter-wave laser operating in a passive Q-switched intracavity pump mode

Pulsed operation of submillimeter gas lasers was achieved with the laser gas inside the resonator of the CO2 pump laser acting as a saturable absorber for passive Q switching the CO2 laser. With a metal-oxyde-metal whisker detector 1-5-microsec-wide pulses could be detected at 118, 373, and 496 micron wavelength.

Koepf, G. A.↗
NASA NTRS1977

Design criteria for FIR waveguide laser cavities

The geometrical design parameters of coherently pumped far infrared waveguide laser cavities are analyzed with respect to minimization of pump power losses. The advantages of highly degenerate cavities and off axis displacement of the injection hole are outlined. Relations between the cavity parameters are given which simplify the design of cavities with high pumping efficiency.

Koepf, G. A.↗