Study On The Electro-opto-thermal Characteristics And Its Testing Technology Of Laser Diode With Pulse Injection

As a new type of light source, laser diode (LD) has the advantages of higher conversion efficiency, smaller volume, lighter weight, higher reliability, adjustable wavelength and higher integrable ability with other semiconductor devices, etc. These characteristics of LD have allowed many uses to be commercialized. And its problem about performance is the focus of attention all the time during it is widly used. In order to ensure the stability and reliability of LD, it is very neccesary to strictly test the device during the whole production process of wafer, chip and module. And it is demanded that new testing technology of characteristics should be presented. Therefore, this dissertation summarizes the current electro-opto-thermal characteristics development, and researches on the characteristics and testing technology of LD to solve the existent problems of LD characteristics testing.Based on single mode rate equation of LD, electrical and optical equivalent circuit models of pulsed LD are established in the paper, which take into account pulse current source, parasitic parameters, and heat dissipation. The new representation is verified feasibly to analyze the operating characteristics of LD. With the models, the performance of LD devices under transient conditions and steady conditions with pulse injection can be analyzed. Results of various properties about the operating characteristics from the simulator are discussed. And these results will be the theory foundation for research of LD pulsed driving and testing technology.In order to study LD thermal performance, a heat transfer model is presented to analyze the heat transfer characteristics of LD, which is based on the analyses for heat generation reasons and heat flux. It shows that the method is feasible and supplies a convenient thermal model for LDs with pulse injection. Then thermal analysis of LD is presented with the model. The simulation results show that the thermal response is closely related to pulse peak current, pulse width, pulse cycle and ambient temperature.Aiming at testing of the electro-opto-thermal characteristics for pulsed LD, a new testing system which combined temperature control module, pulse current source and data gathering unit is established. The pulsed current source is made of constant-current source and couple output interface controlled by square pulse signal, which ensures stability of pulsed current, rise time and fall time. It is convenient to adjust the pulse current amplitude, pulse width, pulse cycle and sampling gate independently. The data gathering unit, which adopting the sampling gate synchronizing with the pulse current to control the high speed sample-and-hold amplifier, obtains multiplex data. The pulsed LD automatic testing system, which combines FPGA technique with SCM as the controlling center, is presented. By the contrasting experiments for the pulsed system with other CW system, it is proved that the pulsed system is feasible and can implement testing operation with pulse width of 100ns. LD devices with poor thermal performance or unknown heat sink can be tested safely using the pulsed sysem.A new testing method of thermal characteristics is presented, which uses forward voltage by pulse injection as the temperature-sensitive parameter. The temperature coefficient of forward voltage is accurately calibrated using pulse current as the driving source, and the self-heat effect of the driving current can be ignored. Based on the influence rules of pulse width and pulse cycle to forward voltage, the feasible parameters of the pulse for calibration current is obtained, viz. pulse width is 100ns and pulse cycle is 10μs. The method makes the thermal characteristics testing convenient for LD in the stage of spontaneous emission and stimulated emission, and it is more versatile than other tesing methods.