Two-frequency MOPA laser system generates terahertp waves

March 1, 1999
In January at Photonics West (San Jose, CA), researchers from the California Institute of Technology and Jet Propulsion Laboratory (CalTech and JPL; Pasadena, CA) described generation of coherent terahertp waves by photomixing in low-temperature-grown gallium arsenide photoconductive antennas, using a tunable, two-frequency, high-power laser-diode system emitting at 850 nm. Three diode lasers generated the difference frequency in the CalTech-JPL device. Two were locked to adjacent modes of an ul

Two-frequency MOPA laser system generates terahertp waves

In January at Photonics West (San Jose, CA), researchers from the California Institute of Technology and Jet Propulsion Laboratory (CalTech and JPL; Pasadena, CA) described generation of coherent terahertp waves by photomixing in low-temperature-grown gallium arsenide photoconductive antennas, using a tunable, two-frequency, high-power laser-diode system emitting at 850 nm. Three diode lasers generated the difference frequency in the CalTech-JPL device. Two were locked to adjacent modes of an ultrastable Fabry-Perot cavity, and a micro wave source was used to offset-lock the third diode laser to the cavity-locked laser. A master oscillator-power amplifier (MOPA) amplified the difference-frequency signal to 500 mW. The system was calibrated to an accuracy of 107 using molecular lines over 250-1400 GHz.

Remote sensing of the atmosphere using terahertp spectroscopy offers a particularly sensitive measure of the diurnal behavior of stratospheric hydroxyl (OH), and the Microwave Limb Sounder on the Earth Observing System CHEM-1 polar satellite will use heterodyne OH measurement at 2.5 THz. Contact Herbert Pickett at [email protected].

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