Research Of Narrowing Linewidth Technology Based On Electrical Feedback Semiconductor Laser

With the development of coherent optical communication, interferometric sensing andother related fields, the semiconductor laser has developed rapidly based on several uniqueadvantages. After a few decades development, lasers are widely applied in communicationfiled as optical source. With higher requirements of monochromaticity and collimation inmany fields, the laser needs to develop to narrower line width, so the semiconductor laserearned wider application prospect in different fields.Semiconductor laser has played a significant role in optical communication,interferometric sensing, etc, with advantages of smaller size, lighter weight, Higher reliability,longer life, higher electro-optical conversion efficiency, more convenient modulation, can bedirectly modulated and so on. Meanwhile. In recent years, a lot of technologies of narrowinglinewidth are put forward, but the linewidth of semiconductor laser is not as good as fiberlaser, Which bring the new blossom on the research of narrowing linewidth.This paper mainly studied several existing methods of narrowing linewidth ofsemiconductor laser and presented two approaches of reducing linewidth: based on singleside-band modulation in an electro-optical feed-forward technology and enhanced PDH(heterodyne phase modulation) technology based on electricity feedback are studied, strictanalysis in the thesis, through building simulation system confirmed the effectiveness of theproposed solution. The details are as follows:1. Firstly, In the paper the current situation and development of the semiconductor laserare emphatically described. Secondly, several methods of narrow linewidth ofsemiconductor laser are analyzed in detail and concluded merits and demerits.Furthermore, kinds of line width measurement method is given at the same time, theprinciple of measurement of narrow linewidth are studied emphatically.2. Firstly, we introduce the characteristics of semiconductor laser and basic structure.Secondly, expounds the optical properties and electrical properties of semiconductorlaser, Thirdly, the reason of produce linewidth and the theory of electronic negativefeedback technology narrow linewidth are analyzed.3. Analyzed the electro-optic effects of lithium niobate crystal and the operatingprinciple of intensity modulator&phase modulator which based on thecharacteristics of lithium niobate, provided the simulate result of all kinds ofmodulation system based on lithium niobate. Proposed a method of narrowlinewidth which is feed-forward line width compression system based on singleside-band (SSB) modulation, basic principle as following: take the initial phasenoise extracted from feed forward branch as modulate signal, connected on the SSBmodulator which after the laser device (intensity modulate realized by phase modulate), to narrow the linewidth by remove the phase noise of laser. The outputspectrum of DFB laser device by experiment, by the means of the characteristic ofoutput spectrum, combine with simulation environment set up with software,narrowed the linewidth from0.5nm to0.016nm successfully.4. Presented a method of narrowing linewidth which is an improved PDH（Phasemodulation heterodyne）technology base on electronic negative feedback. Combinethe frequency shift MZ interferometer with electric negative feedback technology,make the initial noise signal feedback to the injection current of laser device, toreach the purpose of frequency stabilization and reduce phase noise, so the linewidthcan be narrowed. Compare with traditional PDH technology, this method don’t needhigh fineness feedback cavity, so it’s low cost and easy to implement. Narrow thelinewidth from0.5nm to0.02nm successfully through simulation environment set upwith software.