Method for narrowing line width of semiconductor laser by means of improved phase modulation heterodyning technology based on electric feedback

Abstract

The invention discloses a method for narrowing the line width of a semiconductor laser by means of an improved phase modulation heterodyning technology based on electric feedback. The method for narrowing the line width comprises the steps: an output signal of the laser is connected to a frequency shifting MZ interferometer through an acoustic optical modulator, the frequency noise of the laser is converted into phase noise, coherent demodulation is carried out by a radio-frequency signal with controllable frequency deviation, then, frequency correction signals are obtained through amplification and filtering, a part of the frequency correction signals enter a driving current of the laser, the other part of the frequency correction signals are connected to an electric input end of the acoustic optical modulator behind a photoelectric detector, the frequency of the laser is corrected, the phase noise is reduced, and therefore the aim of narrowing the line width is achieved. The method for narrowing the line width has the advantages that the device is simple and easy to achieve, and a high-fineness FP cavity is not required; the line width is narrowed, and the frequency can be modulated at the same time; a high-quality light source is provided for a coherent light communication and high-resolution spectrograph; the requirements for the frequency of the laser do not exist, and therefore narrowing of the line width of the laser in various wavebands can be achieved.

Description

technical field [0001] The invention belongs to the field of narrowing the line width of semiconductor lasers, in particular to a method for narrowing the line width of semiconductor lasers based on the improved phase modulation heterodyne technology of electrical feedback. Background technique [0002] Ideally, a semiconductor laser outputs a single longitudinal mode optical signal with high purity and good monochromaticity. In 1982, Henry proposed the theory of line width broadening of single longitudinal mode semiconductor lasers, which clarified the reason for the wide line width of semiconductor lasers. The actual semiconductor laser has a certain line width due to the spontaneous emission of the internal gain medium, and the change of the carrier concentration also causes the line width to broaden. Therefore, a lot of researches have been done on how to narrow the linewidth of lasers at home and abroad, and some methods for narrowing the linewidth have been proposed....

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Problems solved by technology

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies existing in the prior art, and to propose a method for narrowing semiconductor lasers based on an improved phase modulation heterodyne technology based on electric feedback. The frequency discriminator is difficult to operate, high in cost, prone to frequency drift, and the frequency cannot be continuously tuned

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