Method and means for generation of tunable laser sidebands in the far-infrared region

A method for generating tunable far-infrared radiation is described. The apparatus includes a Schottky-barrier diode which has one side coupled through a conductor to a waveguide that carries a tunable microwave frequency; the diode has an opposite side which is coupled through a radiating whisker to a bias source. Infrared light is directed at the diode, and infrared light with tunable sidebands is radiated by the whisker through an open space to a reflector. The original infrared is separated from a tunable infrared sideband by a polarizing Michelson interferometer

Performance of multiplexed Ge:Ga detector arrays in the far infrared

The performance of two multi-element, multiplexed Ge:Ga linear arrays under low-background conditions was investigated. The on-focal switching is accomplished by MOSFET switches, and the integrated charge is made available through MOSFET source followers. The tests were conducted at 106 microns, and the radiation on the detectors was confined to a spectral window 1.25 microns wide using a stack of cold filters. At 4.2 K, the highest responsivity was 584 A/W, the noise equivalent power was 1.0 x 10(exp -16) W/square root of Hz, and the read noise was 6100 electrons/sample. A detailed description of the test setup and procedure is presented

Resonant infrared detector with substantially unit quantum efficiency

A resonant infrared detector includes an infrared-active layer which has first and second parallel faces and which absorbs radiation of a given wavelength. The detector also includes a first tuned reflective layer, disposed opposite the first face of the infrared-active layer, which reflects a specific portion of the radiation incident thereon and allows a specific portion of the incident radiation at the given wavelength to reach the infrared-active layer. A second reflective layer, disposed opposite the second face of the infrared-active layer, reflects back into the infrared-active layer substantially all of the radiation at the given wavelength which passes through the infrared-active layer. The reflective layers have the effect of increasing the quantum efficiency of the infrared detector relative to the quantum efficiency of the infrared-active layer alone

Direct measurement of the fundamental rotational transitions of the OH radical by laser sideband spectroscopy

We report for the first time the direct (zero-field) spectra of the fundamental rotational transitions of the OH radical in its Ω = 3/2 and 1/2 states at 2509.9 and 1834.7 GHz using a recently developed far-infrared laser sideband spectrometer. These measurements have verified and refined the predictions of previous laser magnetic resonance (LMR) work, thereby confirming the far-infrared detection of interstellar OH. The increased accuracy of these direct measurements will be useful to future astronomical and atmospheric studies of these important transitions

The Far-Infrared Rotational Spectrum of X^2∏ OH Notes

We have previously reported the direct (zero-field) measurement of the fundamental rotational transitions of the hydroxyl radical using a recently developed far-infrared (FIR) laser sideband spectrometer (/). This note presents a more extensive set of measurements of the pure rotational spectrum of OH, which we combine with existing microwave, infrared, and optical data to produce an optimized set of molecular constants

Generation Of Tunable Laser Sidebands In The Far-Infrared Region

Continuously tunable laser sidebands have been generated by mixing radiation from an optically pumped far infrared (FIR) molecular laser, operated at 693, 762, 1627, and 1839 GHz, with that from millimeter‐wave klystrons in a Schottky‐barrier diode. An enhancement in conversion efficiency over similar systems reported previously is obtained by using a Michelson interferometer to separate the sidebands from the carrier and by placing the Schottky diode in an open structure corner cube mount. With 4 mW of laser power at 693 and 762 GHz the sideband power was measured to be 3.0 μW. This is at least an order of magnitude better than the previously reported results. At higher frequencies, 22 mW of 1627‐GHz laser power produced about 2.5 μW of sideband output, while 3mW of 1839‐GHz laser power generated about 100 nW of sideband radiation. The lower efficiency at the higher frequencies is due primarily to the mismatch between the laser radiation and the fixed‐length diode antenna. To demonstrate the tunability of the generated far‐infrared radiation, the laser sidebands were swept through absorption lines of HDO and H_2CO near 600 and 800 GHz. The absorption signals were easily seen, using either video or lock‐in detection techniques

GENERATION OF TUNABLE LASER SIDEBANDS IN THE FAR-INFRARED REGION

Author Institution: Jet Propulsion Laboratory, California Institute of Technology; Jet Propulsion Laboratory, California Institute of Technology; Department of Chemistry, California Institute of Technology; Jet Propulsion Laboratory, California Institute of Technology; Jet Propulsion Laboratory, California Institute of TechnologyContinuously tunable laser sidebands have been generated by mixing radiation from an optically pumped far infrared (FIR) molecular laser beyond 3000 GHz with that from millimeterwave klystrons in a Schottky-barrier diode. An enhancement in conversion efficiency over similar systems reported previously is obtained by using a Michelson interferometer to separate the sidebands from the carrier and by placing the Schottky diode in an open structure corner cube mount. With 4 mW of laser power at 693 and 762 GHz the sideband power was measured to be $10\mu$W. This is at least an order of magnitude better than the previously reported results. At higher frequencies, 22 mW of 1627 GHz laser power produced about $7.5\mu W$ of sideband output while 3mW of 1839 GHz laser power generated about 200 nW of sideband radiation. The lower efficiency at the higher frequencies is due primarily to the mismatch between the laser radiation and the fixed-length diode antenna. Spectral lines have been observed up to 3200 GHz. The molecular absorbtion signals are easily seen using either video or lock-in detection techniques. The combination of various lines from FIR lasers, the continuous tunability of klystrons, and the high efficiency of this system promises nearly complete coverage of the entire submillimeter and far-infrared regime, and provides a powerful tool for spectroscopic measurements. Some of these recent measurements to provide frequency calibration throughout the region will be described