Difference-frequency tunable single-frequency terahertz source with external cavity strengthened

Abstract

The invention discloses a difference-frequency tunable single-frequency terahertz source, with an external cavity strengthened, on the basis of pumping of two single-frequency fiber lasers. As the two tunable single-frequency fiber lasers are taken as pumping sources, a periodical reversal crystal in quasi-phase-matching is utilized as a difference-frequency crystal, and a four-mirror ring resonant cavity is utilized to form an external cavity strengthened structure, the single-frequency terahertz radiated output is realized. Single-frequency fiber laser is output and coupled into the quasi-phase matching crystal by means of a pumping coupling system, pumping light passes through the crystal repeatedly by the aid of the four-mirror ring cavity structure to increase photon utilization efficiency to strength the external cavity, and finally terahertz wave is output through a terahertz radiated output mirror set on the right side of the quasi-phase-matching crystal. The difference-frequency tunable single-frequency terahertz source with the external cavity strengthened has the advantages of compact structure, high efficiency, high reliability and the like.

Description

technical field [0001] The invention belongs to the field of terahertz technology, in particular to a External-cavity enhanced difference-frequency tunable single-frequency terahertz source pumped by single-frequency fiber laser. Background technique [0002] The terahertz band is between microwaves and light waves, and contains rich physical and chemical information when interacting with matter. Therefore, terahertz waves are widely used in basic research fields such as molecular spectroscopy and biological spectrum imaging analysis. The current terahertz spectral imaging technology mainly uses ultrashort pulses to excite photoconductive and nonlinear materials to obtain broadband terahertz radiation sources, but the output of terahertz waves excited by ultrashort pulse lasers is a broadband spectrum, and its spectral resolution has a large gap. Limitations, the current time-domain spectral analysis system - TDS can only achieve a spectral resolution greater than 10 GHz, ...

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Problems solved by technology

[0004] However, free electron lasers are bulky and difficult to apply in practice. Although optically pumped gas lasers and return wave tubes have high output power, their tuning range is narrow, coherent optical mixing has low output power and narrow tuning range, and quantum cascade lasers need to operate at low temperatures. , and the defects such as narrow tuning range

In recent years, optical terahertz radiation sources based on optical nonlinear frequency down-conversion technology have made great progress, but due to the lack of high nonlinear coefficient terahertz difference-frequency crystals and high-efficiency pumping methods, their output power levels and tuning ranges still exist. Very limited, unable to fully meet the relevant applications of terahertz

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