Research On Key Technology Of Detector Response Calibration Device Based On Tunable Laser

Since the advent of lasers,various types of lasers have been developed and have driven the development of various applications based on laser sources.Compared with other light sources,laser is widely used with high power,high monochromaticity,wide spectrum and extremely low wavelength uncertainty.With the development of laser technology,the previous calibration device based on the lamp-monochromator system was gradually replaced by the device based on the laser source.In recent years,scientific research institutions in many developed countries such as Germany,the United Kingdom,the United States,and other developed countries have successively established measurement devices based on laser source,which has promoted the development of the optoelectronic industry and the improvement of product quality,and has realized the high-precision calibration of spectral response and characteristic measurement research of detectors and remote sensing instruments.(1)Firstly,a scheme for converting pulsed light into continuous light is proposed to avoid the nonlinear saturation of the detector caused by high peak power of pulsed light.The pulse of the laser was tested by the combination of an oscilloscope and a high-speed photodetector.The period of the original laser pulse was approximately 12.5 ns and the pulse width was approximately 130 fs.By using fiber bundles with different lengths of fiber,the laser pulse can be broadened into continuous laser,which can reduce the peak power of laser pulse.At the same time,the laser pulse stretcher based on fiber has the advantages of stable performance and high efficiency.And a pulse laser stretcher composed of 100 optical fibers was produced.Through experimental testing and analysis of the output beam of the laser pulse after the stretcher,the high peak power pulse was converted into many small pulses,and the pulse width was expanded in the time domain,and the peak power of laser pluse is reduced.The impact of the original pulse broadening on the silicon photodetector output signal before and after analysis is analyzed.When the original laser is input,the detector output signal jitter range is 6?V;while the laser output corresponding to the laser output through 100 fiber stretchers corresponds to the detector output signal jitter of 1.4?V.Signal jitter has been reduced by approximately76.7%.The method of using 200 optical fibers and pairing them in pairs is proposed to optimize the problem of uneven intensity distribution of continuous light in the time domain.The detector output signal jitter corresponding to the laser output of200 fiber stretchers is 1?V,and the signal jitter is further reduced,which is 83.3%lower than that of the detector corresponding to the original pulse.Therefore,converting the pulsed light into continuous light through the fiber bundle can not only reduce the high peak power of the pulse,but also optimize the jitter amplitude of the output signal of the detector.The pulse stretcher has a positive role in the calibration of the detector response.(2)It is proposed to shape the incident laser beam based on the microlens array to achieve a uniform light field for the calibration device.Combined with a wide-spectrum tunable laser source,it is analyzed that a single compact microlens array has the advantages of simple structure and high energy utilization rate,so a software simulation is carried out for this optical system.By using microlens array modeling and simulation,a uniform light field with an inhomogeneity about 0.2% is theoretically obtained.Based on the microlens array,a set of laser uniform beam shaping optical path was built,and the data of 20mm×20mm in the range of interest was measured by a uniformity scanner.The best uniform radiation field was obtained at ?=600nm,and the unevenness was 0.24 %,which has good consistency with the theoretical results.Theoretical derivation analyzes that the radiation field with good uniformity can reduce the relative standard uncertainty of the calibration measurement.Therefore,the highly uniform radiation field plays an important role in the application of high-precision calibration and has a wide range of applications in the field of metrology.(3)A tunable laser system based on titanium-doped sapphire laser was built.The titanium-doped sapphire laser source can continuously output laser in the range of 680nm-1080 nm,and the average spectral power of the laser source is about1000 m W.By combining an optical parametric oscillator(OPO)and a laser parametric oscillator frequency multiplier(SHG+THG+FHG),a continuously tunable broadband spectrum can be generated.The laser system can cover the190nm-4000 nm band.Combining the pulse-to-continuous optical converter and the optical uniform beam collimating optical path,a detector response calibration device based on the tunable laser source is built.The device has the advantages of high wavelength accuracy,easy adjustment,narrow spectral bandwidth,and high signal-to-noise ratio.