The Study Of Noise Measurement Virtual System Of Semiconductor Laser

In the 1960s, semiconductor lasers were devised, which brings thethriving future of the Optoelectronics fields. Along with the rapid extensionof applied fields, the semiconductor lasers' research and development aregoing forward with a very high speed. By now, the laser diodes have beenwidely used in optical fiber communication, CD, laser printing, informationmemory, medical treatment, pumping solid lasers, measuring, integratedoptics and so on. It becomes more important in advanced technology fields.Then, it is very important to measure the performance of LDs exactly andconveniently and to assess the quality and reliability of LDs. At present, theusual method of screen is electric aging in which all devices are aged with aconstant power or a constant current under high temperature and then theearly failed devices are selected. In the aging, the reliable devices are alsosubject to screening, and the lifetime of devices is affected because of thehot and electric hurt. It can cause batches of devices damage when someaccidence happens, for instance, the out of control system or power cut. Onthe other hand, electric aging is not sensitive for latent defects, for example,some devices after electric aging screening are usually found fail rapidly.Thus, the urgent problems are how to analyses the factors which affect thedevice reliability, and how to select the unqualified devices with a fast,nondestructive and conveniently method. Semiconductor laser noise includes light noise and electric noise ,lightnoise includes phase noise and intensity noise, electric noise includesthermal noise ,shot noise,1/f noise, g-r noise and so on. Electric noiseindicates the defect of material and device, especially, it is very sensitive forvarious reliability-dependent defects. So the electric noise is becoming auseful tool to characterize device quality and reliability. Of late years, it hasgiven rise to the person much interest. So since the semiconductor laserswere developed, the people have studied its noise characteristics. Especially 70吉林大学硕士学位论文of late years, with the semiconductor lasers' applying extensively in avariety of domains, the questions of the appliance noise have given rise tothe universal concerns of the people, and the studying about the noise ismore earnester and all-rounder. The low-noise measurement of the semiconductor lasers needsfrequency spectrum analyzer. Because it is very expensive, this paper putforward the noise testing system of semiconductor lasers. The system usesvirtual instruments instead of the analyzer, so the cost of the system isreduced. The system can carry out the function of the time domaindisplaying,the spectral analysis,the spectrum density analysis ,crossspectrum analysis and the frequency response analysis, and select themethods of windowing function and the data averaging according to thesignal feature. We expect the system can carry out the low-noisemeasurements and the reliability evaluation of the semiconductor lasers. First, the article introduces the noise characteristic of semiconductorlasers , especially, the electric noise characteristic is mainly summarized,including the varieties,the features,the generation mechanism and theprincipally applying. Secondly, the measuring methods of noise insemiconductor lasers are introduced, in which the ultralow-noise PC-Basedmeasurement system is especially studied. The system includes thehardware part and the software part: the hardware part adopts four circuits,the preamplifier,the second level amplifying circuit,the filtering circuit andthe acquisition card protection circuit. The system is to measure electricalnoise of semiconductor lasers and the other semiconductor devices, and thevoltage of noise is very small, usually between several nV and several tennV. So they need amplifying, in order to achieve the differentiating range ofthe data acquisition card,...