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Existing and prospective submillimeter local oscillator technologies are surveyed and compared wi... more Existing and prospective submillimeter local oscillator technologies are surveyed and compared with respect to criteria of suitability for application in spaceborne submillimeter heterodyne receivers as those proposed for the Large Deployable Reflector (LDR). Solid-state and plasma devices are considered in terms of fundamental limitations.
The Astrophysical Journal, 1993
... s~ 3UOUOdWOO siq~ JO ~31~3S [COisi~4d oq~ JO ~U!pU1~3SJ~pUfl ~O (L861 SOj!OH ~` iUJ1~)jjfl)~)... more ... s~ 3UOUOdWOO siq~ JO ~31~3S [COisi~4d oq~ JO ~U!pU1~3SJ~pUfl ~O (L861 SOj!OH ~` iUJ1~)jjfl)~) OU1~jd oq~ o~toq~ odj j JO ~q~pq i~ p~ `%Øj~ U~q3 J~U~J~ 03 `Ax1~[CD ~ jo ~U1?jd oq~ U! `%O1 ~ WOJJ ~U!S~OJOU! ...
Journal of Quantitative Spectroscopy and Radiative Transfer, 1986
Abstract The H 2 O-broadening of CO ro-vibrational lines, measured by Willis et al. and others, i... more Abstract The H 2 O-broadening of CO ro-vibrational lines, measured by Willis et al. and others, is fit by a calculation, after Anderson, Tsao and Curnutte, which invokes a dominant quadrupole-dipole interaction. Both temperature- and rotational-line dependence are inferred for the fundamental band and ground state.
The Astrophysical Journal, 1996
... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Sol... more ... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, MC 685, Greenbelt, MD 20771; MICHAEL R. HAAS, SEAN WJ COLGAN, EDWIN F. ERICKSON Space Science ...
The Astrophysical Journal, 1996
... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Sol... more ... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, MC 685, Greenbelt, MD 20771; MICHAEL R. HAAS, SEAN WJ COLGAN, EDWIN F. ERICKSON Space Science ...
AIP Conference Proceedings, 1992
ABSTRACT Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionize... more ABSTRACT Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionized gas, we propose state-selective photoionization of sulfur within neutral regions as a mechanism to explain the 1.5 power scaling between optical forbidden lines of N ii and S ii in M 82 and identify it with the 1.5 power scaling found between the far infrared emission lines of N ii and C ii associated with large scale structure of the Galaxy. While N ii emission can be attributed uniquely to ionized regions, C ii emission arises in neutral photodissociation regions as well. Boundaries between ionized and neutral regions are found to contribute significantly to the Galactic luminosity of both species. Forbidden line emission of ionized sulfur, it is suggested, similarly probes neutral photodissociation regions.
Lecture Notes in Physics, 1988
ABSTRACT Without Abstract
Infrared Physics, 1980
ABSTRACT A multilayer dielectric dichroic mirror has been designed for the reflection of infrared... more ABSTRACT A multilayer dielectric dichroic mirror has been designed for the reflection of infrared radiation and the transmission of far-infrared radiation in an optically pumped far-infrared laser. Silicon was chosen as the mirror substrate material and ZnS and Ge as the materials with which to construct the stack of one-quarter-wavelength layers deposited on the substrate. Mirrors have been designed to operate at normal incidence and at the Brewster angle, with reflectance at 10 microns. Transmission measurements are in agreement with a semiempirical model of mirror transmission, and reveal low absorption of wavelengths greater than 50 microns. The mirrors have been used as CW far-infrared laser output couplers and in TEA laser experiments at powers up to 1 MW with little evidence of damage.
Optical Fiber Communication, 1982
Infrared Physics, 1983
ABSTRACT The operating principles of a new kind of room-temperature thermal radiation detector ar... more ABSTRACT The operating principles of a new kind of room-temperature thermal radiation detector are described. In this device modulated light heats a gas, either directly or by conduction from a thin absorbing membrane, and the resultant change in density of the gas is detected by optical heterodyning. The performance of a membrane device of this kind agrees well with the predictions of theory.
The Astrophysical Journal, 1989
The Astrophysical Journal, 1991
Water vapor may be one of the most abundant constituents of shocked molecular clouds. The nonequi... more Water vapor may be one of the most abundant constituents of shocked molecular clouds. The nonequilibrium distribution of population among its rotational energy states requires the observation of a multiplicity of transitions to constrain its abundance and excitation state. Flux limits are presented for emission due to the (010) 4(14) - 3(21) rotational transition of ortho-H2O at 67.804 GHz in several nebular and stellar sources. Upper limits for a beam-averaged column density of H2O in its nu2 vibrational manifold are derived for Orion BN-KL. Constraints placed by these observations on an internal source of infrared radiation in the Orion shock are discussed.
The Astrophysical Journal, 1990
ABSTRACT Absorption of orthoformaldehyde (HâCO) toward the giant H II region W51A (G49.5 - 0.4) h... more ABSTRACT Absorption of orthoformaldehyde (HâCO) toward the giant H II region W51A (G49.5 - 0.4) has been used as a remote probe of the cosmic microwave background (CMB) at a distance of 7.5 kpc. VLA observations of the 6 cm and 2 cm wavelength transitions provided sufficient resolution and sensitivity to resolve condensations within the foregound clouds. Solutions to the equations of statistical equilibrium within each condensation in the context of a large velocity gradient model yielded an estimate for the CMB temperature at 2.1 mm wavelength of 3.2 + or - 0.9 K. The uncertainty is dominated by modeling of collisional pumping by neutral hydrogen molecules (H2). 25 refs.
Optics Letters, 1979
The generation of mode-locked far-infrared pulses by synchronous, mode-locked optical pumping by ... more The generation of mode-locked far-infrared pulses by synchronous, mode-locked optical pumping by CO 2 lasers is demonstrated for the first time. The gain bandwidth implied by the observed short pulses (<1 nsec) exceeds the homogeneous linewidth of 40 MHz (T 2 = 8 nsec) under the experimental conditions and is attributed to an effective inhomogeneous broadening in molecules with a K-multiplet structure such as 12 CH 3 F and also to the presence of near-resonant stimulated Raman emission from each frequency component of the pump. This implies that the duration of pulses generated in low-pressure gases by this technique is determined by the greater of the pumpingpulse bandwidth or the linewidth of the lasing transition.
This patent describes an optical sensor sensing various kinds of physical fields, comprising: a s... more This patent describes an optical sensor sensing various kinds of physical fields, comprising: a semiconductor diode lasing medium, with a first and a second end facet oriented perpendicularly to the optical axis of the medium, producing coherent optical energy at a lasing frequency. The first facet is highly reflective at the lasing frequency and the second facet is highly nonreflective at the lasing frequency; a fiber optic coupler with first second, third and fourth ports for distributing optical energy incident on any one of the ports in predetermined ratios between the remainder of the ports; a first optical fiber or first optical waveguide with a first end optically coupled to the second facet of the lasing medium and with a second end optically coupled to the first port of the coupler. The first optical fiber or the first optical waveguide transmits optical energy between the lasing medium and the coupler; and a resonant cavity having a response curve, the cavity including the...
International Journal of Infrared and Millimeter Waves, 1980
A signal flow graph representation of the density matrix equations appropriate to a serial three-... more A signal flow graph representation of the density matrix equations appropriate to a serial three-wave interaction is introduced, from which perturbation theory and AC Stark shift information may be extracted. The conditions for a large interaction cross section for the three-photon transition are deduced and applied to selected experimental situations with the main conclusion being that the effect may be present in a large number of CW and pulsed experiments.
Existing and prospective submillimeter local oscillator technologies are surveyed and compared wi... more Existing and prospective submillimeter local oscillator technologies are surveyed and compared with respect to criteria of suitability for application in spaceborne submillimeter heterodyne receivers as those proposed for the Large Deployable Reflector (LDR). Solid-state and plasma devices are considered in terms of fundamental limitations.
The Astrophysical Journal, 1993
... s~ 3UOUOdWOO siq~ JO ~31~3S [COisi~4d oq~ JO ~U!pU1~3SJ~pUfl ~O (L861 SOj!OH ~` iUJ1~)jjfl)~)... more ... s~ 3UOUOdWOO siq~ JO ~31~3S [COisi~4d oq~ JO ~U!pU1~3SJ~pUfl ~O (L861 SOj!OH ~` iUJ1~)jjfl)~) OU1~jd oq~ o~toq~ odj j JO ~q~pq i~ p~ `%Øj~ U~q3 J~U~J~ 03 `Ax1~[CD ~ jo ~U1?jd oq~ U! `%O1 ~ WOJJ ~U!S~OJOU! ...
Journal of Quantitative Spectroscopy and Radiative Transfer, 1986
Abstract The H 2 O-broadening of CO ro-vibrational lines, measured by Willis et al. and others, i... more Abstract The H 2 O-broadening of CO ro-vibrational lines, measured by Willis et al. and others, is fit by a calculation, after Anderson, Tsao and Curnutte, which invokes a dominant quadrupole-dipole interaction. Both temperature- and rotational-line dependence are inferred for the fundamental band and ground state.
The Astrophysical Journal, 1996
... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Sol... more ... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, MC 685, Greenbelt, MD 20771; MICHAEL R. HAAS, SEAN WJ COLGAN, EDWIN F. ERICKSON Space Science ...
The Astrophysical Journal, 1996
... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Sol... more ... OF IONIZED GAS IN THE INNER GALAXY SJ PETUCHOWSKI CL BENNETT Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, MC 685, Greenbelt, MD 20771; MICHAEL R. HAAS, SEAN WJ COLGAN, EDWIN F. ERICKSON Space Science ...
AIP Conference Proceedings, 1992
ABSTRACT Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionize... more ABSTRACT Although emission in the [S ii] λ6716 forbidden line is commonly assumed to trace ionized gas, we propose state-selective photoionization of sulfur within neutral regions as a mechanism to explain the 1.5 power scaling between optical forbidden lines of N ii and S ii in M 82 and identify it with the 1.5 power scaling found between the far infrared emission lines of N ii and C ii associated with large scale structure of the Galaxy. While N ii emission can be attributed uniquely to ionized regions, C ii emission arises in neutral photodissociation regions as well. Boundaries between ionized and neutral regions are found to contribute significantly to the Galactic luminosity of both species. Forbidden line emission of ionized sulfur, it is suggested, similarly probes neutral photodissociation regions.
Lecture Notes in Physics, 1988
ABSTRACT Without Abstract
Infrared Physics, 1980
ABSTRACT A multilayer dielectric dichroic mirror has been designed for the reflection of infrared... more ABSTRACT A multilayer dielectric dichroic mirror has been designed for the reflection of infrared radiation and the transmission of far-infrared radiation in an optically pumped far-infrared laser. Silicon was chosen as the mirror substrate material and ZnS and Ge as the materials with which to construct the stack of one-quarter-wavelength layers deposited on the substrate. Mirrors have been designed to operate at normal incidence and at the Brewster angle, with reflectance at 10 microns. Transmission measurements are in agreement with a semiempirical model of mirror transmission, and reveal low absorption of wavelengths greater than 50 microns. The mirrors have been used as CW far-infrared laser output couplers and in TEA laser experiments at powers up to 1 MW with little evidence of damage.
Optical Fiber Communication, 1982
Infrared Physics, 1983
ABSTRACT The operating principles of a new kind of room-temperature thermal radiation detector ar... more ABSTRACT The operating principles of a new kind of room-temperature thermal radiation detector are described. In this device modulated light heats a gas, either directly or by conduction from a thin absorbing membrane, and the resultant change in density of the gas is detected by optical heterodyning. The performance of a membrane device of this kind agrees well with the predictions of theory.
The Astrophysical Journal, 1989
The Astrophysical Journal, 1991
Water vapor may be one of the most abundant constituents of shocked molecular clouds. The nonequi... more Water vapor may be one of the most abundant constituents of shocked molecular clouds. The nonequilibrium distribution of population among its rotational energy states requires the observation of a multiplicity of transitions to constrain its abundance and excitation state. Flux limits are presented for emission due to the (010) 4(14) - 3(21) rotational transition of ortho-H2O at 67.804 GHz in several nebular and stellar sources. Upper limits for a beam-averaged column density of H2O in its nu2 vibrational manifold are derived for Orion BN-KL. Constraints placed by these observations on an internal source of infrared radiation in the Orion shock are discussed.
The Astrophysical Journal, 1990
ABSTRACT Absorption of orthoformaldehyde (HâCO) toward the giant H II region W51A (G49.5 - 0.4) h... more ABSTRACT Absorption of orthoformaldehyde (HâCO) toward the giant H II region W51A (G49.5 - 0.4) has been used as a remote probe of the cosmic microwave background (CMB) at a distance of 7.5 kpc. VLA observations of the 6 cm and 2 cm wavelength transitions provided sufficient resolution and sensitivity to resolve condensations within the foregound clouds. Solutions to the equations of statistical equilibrium within each condensation in the context of a large velocity gradient model yielded an estimate for the CMB temperature at 2.1 mm wavelength of 3.2 + or - 0.9 K. The uncertainty is dominated by modeling of collisional pumping by neutral hydrogen molecules (H2). 25 refs.
Optics Letters, 1979
The generation of mode-locked far-infrared pulses by synchronous, mode-locked optical pumping by ... more The generation of mode-locked far-infrared pulses by synchronous, mode-locked optical pumping by CO 2 lasers is demonstrated for the first time. The gain bandwidth implied by the observed short pulses (<1 nsec) exceeds the homogeneous linewidth of 40 MHz (T 2 = 8 nsec) under the experimental conditions and is attributed to an effective inhomogeneous broadening in molecules with a K-multiplet structure such as 12 CH 3 F and also to the presence of near-resonant stimulated Raman emission from each frequency component of the pump. This implies that the duration of pulses generated in low-pressure gases by this technique is determined by the greater of the pumpingpulse bandwidth or the linewidth of the lasing transition.
This patent describes an optical sensor sensing various kinds of physical fields, comprising: a s... more This patent describes an optical sensor sensing various kinds of physical fields, comprising: a semiconductor diode lasing medium, with a first and a second end facet oriented perpendicularly to the optical axis of the medium, producing coherent optical energy at a lasing frequency. The first facet is highly reflective at the lasing frequency and the second facet is highly nonreflective at the lasing frequency; a fiber optic coupler with first second, third and fourth ports for distributing optical energy incident on any one of the ports in predetermined ratios between the remainder of the ports; a first optical fiber or first optical waveguide with a first end optically coupled to the second facet of the lasing medium and with a second end optically coupled to the first port of the coupler. The first optical fiber or the first optical waveguide transmits optical energy between the lasing medium and the coupler; and a resonant cavity having a response curve, the cavity including the...
International Journal of Infrared and Millimeter Waves, 1980
A signal flow graph representation of the density matrix equations appropriate to a serial three-... more A signal flow graph representation of the density matrix equations appropriate to a serial three-wave interaction is introduced, from which perturbation theory and AC Stark shift information may be extracted. The conditions for a large interaction cross section for the three-photon transition are deduced and applied to selected experimental situations with the main conclusion being that the effect may be present in a large number of CW and pulsed experiments.