The Study Of The Influence Of Radiation Effect On Laser Diodes

In recent years, with the development of the aerospace industry and nuclear industry, the application of photonic technology is seriously considered for communication and monitoring fields. Laser diodes (LD) has been extensively used in optical communication systems, because of its, for example small volume, long life-span, high-power and low cost as well as easy to use etc. LD is one of the key devices in free-space optical communications. However, the radiation induce a seriously effect on the output of LD and this effect will lead to the increase of BER. For decreasing this kind of effect we can take the method of device strengthen and system regulation. Therefore in the one hand we can set up the theoretical model of the effect of radiation on LD's output power and then study the relationship between the LD's irradiation resistance and its structure and material parameters, which can give reference for the device strengthen. In the other hand we set up the model of the effect of radiation on BER,and then study the process and mechanism of this effect, which can give reference for the system regulation. Because of the different mechanism of radiation on LD the effect can be divided into two different effects that is transient ionizing effect and displacement effect,Based on the above describe, the content of this paper mainly includes the following aspects:(1) The study on the model that optical response of LD to the transient ionizing effect. The radiation will lead to the ionization of outer election in LD, and generate photocurrent in LD; this kind of current has no difference with the injection current, thus leading to an optical power increases. In this paper, we introduce ionization item to the carrier rate equation, combine the photon rate equation, and derive the optical response model of LD transient ionization effect under the single-mode lasing state. According to the reference [100], the experimental results are calculated. The results show that the experimental results in the reference [100] are in the range of calculated results, which verifies the correctness of the model. Based on this model, the definition of optical gain factor is given. The factor is determined by LD micro-structural parameters, and reflects the sensitive degree of ionization effect on the LD. In order to provide a reference for the reinforce design of the device. The impacts of the output mirror reflectivity and the active layer thickness on optical gain factor are analyzed.(2) The study of optical response model of LD to total dose effect. This part mainly includes two aspects: in the one hand, we deduce the optical response model of displacement effect and get the microscopic parameter expression of optical power decay factor. In the other hand, we set up the integrated optical response model of LD's radiation effect.First, we use the radiation damage model of LD threshold carrier density which is from O. Gilard, and then combine the carrier rate equation and photon rate equation; finally, we derive the model of optical response of LD to displacement effect. Based on this model we get the expression of optical power decay factor. Our decay factor expression includes the structure and material parameters. So it can give direct reference for devices strengthen. On this basis, the impact of the output mirror reflectivity and the cavity length on the factor is analyzed. The radiation experimental verification is carried out using 1550nm LD, and the experimental results verify the correctness of the model.The impact of radiation on LD's output optical power should be the integration results of both transient ionization effects and displacement effects. Therefore, based on the consideration of both photocurrent increase factor due to transient ionization effects and threshold current density decrease factor due to displacement effects, we obtain an integrated LD optical response model of radiation effect. As we consider the integrated factors in this model, it has more practical applications.(3) The effect of radiation on BER of the system and the improving method. In this part we analyze the effect of transient effect and accumulative damage effect on BER.First, according to the track statistics of the space radiation environment particle data which is from NOAA (National Oceanic and Atmospheric Administration), the probability distribution model of space radiation dose rate is given, it provides a basis for calculating the effect of ionization effect on space optical communication BER. Second, we deduce a model of LD transient ionization effect on BER. The model generally provides a BER calculation method in the role of the random fluctuations in the incident light power and the receive noise. Based on this model we simulated the effect of the optical response of LD to the transient ionization effects. At last, we introduce the output power reducing effect into the equation of BER, and deduce a model for calculating BER. Then we made research on simulation analysis for the effect some typical parameters. Based on the research we discuss how to lower the influence of the output power on BER through changing the threshold, the extinction ratio, the gain factor and the output power. In the end we deduce the model of the change of threshold and the best value range of extinction ratio...