Research On The Weak Laser Power Meter

Alongwiththe rapiddevelopment ofphotonics technology,thedemands ofoptical signal indetecting sensitivity, spectral response range and frequency characteristics become increasinglyhigh. Because silicon photodiode have fast response time, high sensitivity, linearity, low noise,stable performance, work in the visible and near infrared region and other characteristics inmeasuring light signals. Therefore, in recent years silicon photodiode has been used in laserpower measurement widely. Especiallyin measuring the laser signal below micro-watt becomesmore important. Because the development of self-calibration technology of silicon photodiode,wecansimplymeasuretheabsolutespectralresponsesensitivityofcorrespondingwavelengthofa laser radiation. Its uncertainty is from several per ten thousand to several per thousand. It canbeusedasthestandardoftinylaserpowermeasurement.Accordingly,this article is onthebasis ofconcludingresearchresults at homeandabroadinthe field of measurement continuous laser power, studying the method of using siliconphotodiode for probe components and making external circuits using of AT89C51 system andexpanding optical signal that collected by silicon photodiode and testing the voltage signal byamplification circuit for measuring laser power to achieve real-time measuring medical laserpower, we design and complete initial product of laser power measurement system. Themeasuring system has characteristics of measurement of a single wavelength power, goodlinearity,highsensitivity,fastresponse,highresolution,themoneyaccurately, reliableusingandlow-costproductioncomparedtothetraditionallaserpowermeter.In addition, after the probe of general power meter absorb laser, the surface of probe willaccumulate a large number of heat. If the cooling time is not fast enough will damage thephotosensitive components, so the demand of cooling effect for the probe is high. If probe isequipped with thermal devices, its overall volume will become large. In this study we use themethod of separating weak light from strong beam in proportion to measure its power so as toreflect the strong beam power. It does not need other thermal devices, another the volume ofsilicon photodiode itself is very small, the probe of measurement system is completely packageto inter of laser. It is no longer use the traditional digital or independent screen shows, themeasured power is finally showed by the PC real-timely. This is a main feature in this research.As the probe is completely packaged in inter of laser and the optical signal measured is weak.Thuseffectivelyavoidtheeffectsfrombackgroundnoiseandcircuitthermalnoise.