Exact frequency and phase control of a terahertz laser
| Autor: | Paul Dean, Lianhe Li, Edmund H. Linfield, A. Giles Davies, Reshma A. Mohandas, Lalitha Ponnampalam, Alwyn J. Seeds, Joshua R. Freeman |
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| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Heterodyne
Materials science Terahertz radiation business.industry Far-infrared laser Physics::Optics Laser Atomic and Molecular Physics and Optics Electronic Optical and Magnetic Materials law.invention Injection locking Phase-locked loop Frequency comb Laser linewidth Optics law Physics::Atomic Physics business |
| ISSN: | 2334-2536 |
| Popis: | The accuracy of high-resolution spectroscopy depends critically on the stability, frequency control, and traceability available from laser sources. In this work, we report exact tunable frequency synthesis and phase control of a terahertz laser. The terahertz laser is locked by a terahertz injection phase lock loop for the first time, with the terahertz signal generated by heterodyning selected lines from an all-fiber infrared frequency comb generator in an ultrafast photodetector. The comb line frequency separation is exactly determined by a Global Positioning System-locked microwave frequency synthesizer, providing traceability of the terahertz laser frequency to primary standards. The locking technique reduced the heterodyne linewidth of the terahertz laser to a measurement instrument-limited linewidth of < 1 H z , robust against short- and long-term environmental fluctuations. The terahertz laser frequency can be tuned in increments determined only by the microwave synthesizer resolution, and the phase of the laser, relative to the reference, is independently and precisely controlled within a range ± 0.3 π . These findings are expected to enable applications in phase-resolved high-precision terahertz gas spectroscopy and radiometry. |
| Databáze: | OpenAIRE |
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