A Spectral Beam Combining Device Using a Reflective Film-Coated Transmission Grating to Realize Two Diffractions

Abstract

The invention discloses a spectrum beam combination device for realizing twice diffraction by using the transmission grating of a plated reflecting film. The spectrum beam combination device comprises a semiconductor laser unit light source, a slow-axis collimated column lens, a conversion lens, a transmission grating and an output coupling mirror. The transmission grating of the back plated reflecting film is used as a diffraction element, namely the reflecting film is plated at the back of a grating surface, so that the dispersive power of the grating can be doubled by an incident beam through the diffraction of the transmission grating twice. According to the spectrum beam combination device, the restriction that the dispersive power of the diffraction grating is limited in traditional spectrum beam combination is overcome, the number of beam combination elements can be increased in the gain line width of the material and the high-efficiency diffraction wavelength range of the grating, and the output power is obviously improved, or the length of a resonant cavity can be shortened when certain output spectrum width is guaranteed, so that the structure of a laser unit is compacter, and the mode of the laser unit is stabler.

Description

technical field [0001] The invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser spectral combining device for realizing laser output with narrow line width and high power by using a transmission grating coated with a reflective film and feeding back through an external cavity. Background technique [0002] Semiconductor lasers have the advantages of low cost, long life, small size and high reliability, and have been widely used in industrial processing, pumping, medical treatment, communication and other fields. An important factor restricting the future development of semiconductor lasers is brightness. The brightness of the laser beam is determined by the output power and beam quality, the higher the power, the better the beam quality and the higher the brightness. [0003] Beam combining technology is a common method to realize high-brightness semiconductor lasers. Spectral beam combining is a novel beam combining techn...

AI Technical Summary

Problems solved by technology

[0004] How to compress the spectral width of the beam combining laser is the main problem of increasing the number of combining units. The spectral width is determined by many factors, mainly in the following three categories: 1. Reducing the distance between adjacent combining units can produce high-density semiconductors The laser array or the use of optical imaging systems to compress the beam combining unit spacing, but limited by semiconductor technology, increases crosstalk between different units, cannot be fully fed back, and reduces beam combining efficiency; 2. Increase the focal length of the conversion lens, but the beam combining system The length of the coupling cavity and the length of the coupling cavity will increase accordingly, the volume of the system will become larger and the stability of the resonator system will decrease, the overall optical path will increase, and crosstalk between beam combining units is more likely to occur when the divergence angle remains the same ; 3. To increase the linear density of the diffraction grating means to reduce the grating period of the diffraction grating, but the grating period is limited by the wavelength of the semiconductor laser, and the minimum grating period cannot be less than half of the wavelength. Assuming that the wavelength of the semiconductor laser is 940nm, the theoretical maximum of the diffraction grating The linear density is 2127lines / mm, the linear density cannot be further improved, and the feasibility is not high

Improving the linear density of the grating is to improve the diffraction ability of the grating. The diffraction ability of the grating can also be improved by using two non-parallel gratings. In the patent, it is proposed to use two gratings placed non-parallel, and the beam combining unit passes through the diffraction effect of the grating twice. Although the spectral width is compressed by half, two gratings are used to improve the diffraction ability of the grating, and the adjustment accuracy of the system and Difficulty increases, raster cost is high

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