Exact frequency and phase control of a terahertz laser
- 3 September 2020
- journal article
- research article
- Published by Optica Publishing Group in Optica
- Vol. 7 (9), 1143-1149
- https://doi.org/10.1364/optica.395941
Abstract
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 Hz, 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 pi. These findings are expected to enable applications in phase-resolved high-precision terahertz gas spectroscopy and radiometry. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.Funding Information
- Engineering and Physical Sciences Research Council ((EP/P021859/1))
This publication has 42 references indexed in Scilit:
- Three-dimensional localization precision of the double-helix point spread function versus astigmatism and biplaneApplied Physics Letters, 2010
- Phase-locking of a 2.7-THz quantum cascade laser to a mode-locked erbium-doped fibre laserNature Photonics, 2010
- DFB Lasers Between 760 nm and 16 µm for Sensing ApplicationsSensors, 2010
- Phase locking of a 27 THz quantum cascade laser to a microwave referenceOptics Letters, 2009
- Cold Molecule Spectroscopy for Constraining the Evolution of the Fine Structure ConstantPhysical Review Letters, 2006
- Noninvasive laser-induced photoacoustic tomography for structural and functional in vivo imaging of the brainNature Biotechnology, 2003
- Terahertz semiconductor-heterostructure laserNature, 2002
- Optical injection locking and phase-lock loop combined systemsOptics Letters, 1994
- Raman lidar system for the measurement of water vapor and aerosols in the Earth’s atmosphereApplied Optics, 1992
- Stimulated Optical Radiation in RubyNature, 1960