| Laser diodes is a physical device that uses semiconductor material as an optical gain medium to complete the corresponding laser work.At present,it has been widely used in laser detection,radar communication,etc.,and has become one of the research focuses of the National Defense Science and Technology Commission.The semiconductor that commonly used include Ga As,In P,Cd S,Zn S,etc.As a ubiquitous physical phenomenon in semiconductor devices,1/f noise is the fluctuation phenomenon inside the carrier.Its characteristics and parameters can characterize the quality and performance of semiconductor devices to a certain extent.The reliability evaluation method has obvious advantages.Since lasers are light-emitting devices and have optical properties compared with conventional semiconductor devices,the study of optical 1/f noise characteristics in lasers is of great significance.In view of the above problems,this paper proposes to build a set of optical 1/f noise measurement system based on discrete components,which is verified by noise detection algorithm.The main contents of the paper include the following two points:Based on the basic characteristics of semiconductor laser optical 1/f noise,this paper establishes a semiconductor laser optical 1/f noise measurement system for cross-spectrum measurement of dual-channel preamplifiers.The measurement system is composed of a bias module,a photoelectric detection module,a filter module,a low-noise amplifying module,a data acquisition part and a shielding part.The bias circuit provides a continuously variable bias current for the laser to be tested,so that the laser reaches the luminous threshold and is in a luminous state;the photodetector converts the optical signal from the laser at the receiving end of the fiber into an electrical signal;the filter suppresses electromagnetic interference Since the low-frequency current noise is as low as p A/ Hz level,in order to ensure the normal operation of the data acquisition card,a preamplifier is used to convert the current signal converted by the photodetector into a voltage signal,and then amplify it.Data is uploaded to a computer,stored and analyzed.Based on the low-frequency noise measurement system,a measurement scheme is designed to verify the optical 1/f noise detection technology of semiconductor lasers,and the optical 1/f low-frequency noise power spectral density curve is measured.Analysis of the power spectral density curve shows that within 0-600 Hz,the power spectral density of low-frequency noise decreases with the increase of frequency.At the same time,the threshold method based on the optimal predictor variable is used to detect the data collected by the system,and the wavelet transform is used for denoising processing in a strong white noise environment.The power spectral density curve strictly follows the 1/f noise variation law.It can be seen that the system designed in this paper can accurately measure the 1/f low-frequency noise data of the 980 nm wavelength semiconductor laser,which provides experimental support for further research on the relationship between low-frequency noise and the reliability of semiconductor lasers. |
