Guangyong Jin

Study on the mechanism of a charge-coupled device detector irradiated by millisecond pulse laser under functional loss

The damage mechanism of a CCD detector was studied by building an experimental system containing a millisecond pulse laser irradiating a CCD detector. The experimental results show that the damage on the CCD detector was mainly thermal damage, along with mechanical damage. A melting phenomenon was caused by the thermal damage, so that a crater was observed on the surface of the CCD detector. Caused by melting of the polysilicon electrodes and a temperature rise in the silicon dioxide, the shift register impedance values were sharply reduced. Most of the substrate clock signals were broken and disappeared due to melting of channels in the silicon substrate layer, which caused a functional loss for the CCD detector. The mechanical damage on the melting edge of the CCD detector created heave; the temperature gradient caused this damage. In this paper, the decrease in vertical shift register impedance values was consistent with previous test results.

Analysis of thermodynamic effect in Si irradiated by pulsed-laser

According to the heat conduction equation, thermoelastic equation and boundary conditions of finite, using the finite element method(FEM), established the three-dimensional finite element calculation model of thermal elastic ,numerical simulation the transient temperature field and stress field distribution of the single crystal silicon materials by the pulsing laser irradiation, and analytic solution the temperature distribution and stress distribution of laser irradiation on the silicon material , and analyzes the different parameters such as laser energy, pulse width, pulse number influence on temperature and stress, and the intrinsic damage mechanism of pulsed laser irradiation on silicon were studied. The results show that the silicon material is mainly in hot melt under the action of ablation damage.According to the irradiation of different energy and different pulse laser ,we can obtain the center temperature distribution, then get the law of the change of temperature with the variation of laser energy and pulse width in silicon material; according to the principal stress and shear stress distribution in 110 direction with different energy and different pulse, we can get the law of the change of stress distribution with the variation of laser energy and pulse width ;according to the principal stress distribution of single pulse and pulse train in 110 direction, we can get the law of the change of stress with pulse numbers in silicon.When power density of laser on optical material surface (or energy density) is the damage threshold, the optical material surface will form a spontaneous, periodic, and permanent surface ripple, it is called periodic surface structure laser induced (LIPSS).It is the condensed optical field of work to generate low dimensional quantum structures by laser irradiation on Si samples. The pioneering work of research and development and application of low dimensional quantum system has important academic value.The result of this paper provides theoretical foundation not only for research of theories of Si and substrate thermal stress damage and its numerical simulation under laser radiation but also for pulse laser technology and widening its application scope.

Plasma characteristics of single crystal silicon irradiated by millisecond pulsed laser

In the air, Mach-zehnder interference system was set up to study the plasma expansion process of single crystal silicon induced by millisecond pulsed laser. Electron density is the main parameter of laser plasma characteristics. Calculation electron density of silicon plasma based on the relationship between the FWHM of Stark broadening of spectral line and the electron density. Experimental results show that: The existence material splash phenomenon is existence in silicon plasma generated by millisecond laser, the long pulse laser interaction with material has the thermal effect. Silicon plasma emission spectrum is strong in the distribution of the continuous spectrum, the discrete series of atoms and ions are superimposed on it. With the increase of the laser energy density, the electron density of the plasma increases.

Delay time dependence of thermal effect of combined pulse laser machining

The research focused on the effect of delay time in combined pulse laser machining on the material temperature field. Aiming at the parameter optimization of pulse laser machining aluminum alloy, the combined pulse laser model based on heat conduction equation was introduced. And the finite element analysis software, COMSOL Multiphysics, was also utilized in the research. Without considering the phase transition process of aluminum alloy, the results of the numerical simulation was shown in this paper. By the simulation study of aluminum alloy’s irradiation with combined pulse, the effect of the change in delay time of combined pulse on the temperature field of the aluminum alloy and simultaneously the quantized results under the specific laser spot conditions were obtained. Based on the results, several conclusions could be reached, the delay time could affect the rule of temperature changing with time. The reasonable delay time controlling would help improving the efficiency. In addition, when the condition of the laser pulse energy density is constant, the optimal delay time depends on pulse sequence.

Simulation study on thermal effect of long pulse laser interaction with CFRP material

Laser machining is one of most widely used technologies nowadays and becoming a hot industry as well. At the same time, many kinds of carbon fiber material have been used in different area, such as sports products, transportation, microelectronic industry and so on. Moreover, there is lack of the combination research on the laser interaction with Carbon Fiber Reinforced Polymer (CFRP) material with simulation method. In this paper, the temperature status of long pulse laser interaction with CFRP will be simulated and discussed. Firstly, a laser thermal damage model has been built considering the heat conduction theory and thermal-elasto-plastic theory. Then using COMSOL Multiphysics software to build the geometric model and to simulate the mathematic results. Secondly, the functions of long pulse laser interaction with CFRP has been introduced. Material surface temperature increased by time during the laser irradiating time and the increasing speed is faster when the laser fluence is higher. Furthermore, the peak temperature of the center of material surface is increasing by enhanced the laser fluence when the pulse length is a constant value. In this condition, both the ablation depth and the Heat Affected Zone(HAZ) is larger when increased laser fluence. When keep the laser fluence as a constant value, the laser with shorter pulse length is more easier to make the CFRP to the vaporization material. Meanwhile, the HAZ is becoming larger when the pulse length is longer, and the thermal effect depth is as the same trend as the HAZ. As a result, when long pulse laser interaction with CFRP material, the thermal effect is the significant value to analysis the process, which is mostly effect by laser fluence and pulse length. For laser machining in different industries, the laser parameter choose should be different. The shorter pulse length laser is suitable for the laser machining which requires high accuracy, and the longer one is better for the deeper or larger ablation holes.

Numerical analysis of the temperature field in silicon avalanche photodiode by millisecond laser irradiation

Recent years, millisecond laser become a research hotspot. Avalanche photodiode (APD) based on silicon structure has excellent characteristics such as low noise and high-sensitivity. It is key components in receives for long-haul high-bit-rate optical communication system. The failure mechanism of silicon APD remains quite unknown, although some silicon p-i-n photodiode failure modes have been speculated. The COMSOL Multiphysics finite element analysis software was utilized in this paper. And the 2D model, which based on heat conduction equation, was established to simulate the temperature field of the silicon avalanche photodiode irradiated by millisecond laser. The model presented in the following section is a work which considers only melting of silicon by a millisecond laser pulse. The temperature dependences of material properties are taken into account, which has a great influence on the temperature fields indicated by the numerical results. The pulsed laser-induced transient temperature fields in silicon avalanche photodiode are obtained, which will be useful in the research on the mechanism of interactions between millisecond laser and photodiode. The evolution of temperature at the central point of the top surface, the temperature distribution along the radial direction in the end of laser irradiation and the temperature distribution along the axial direction in the end of laser irradiation were considered. Meanwhile, the fluence threshold value was obtained through the model. The conclusions had a reference value for revealing the mechanism of interactions between millisecond laser and the silicon avalanche photodiode.

The Process of a Laser-Supported Combustion Wave Induced by Millisecond Pulsed Laser on Aluminum Alloy

We study the process of a laser-supported combustion wave (LSCW) when an aluminum alloy is irradiated by a millisecond pulse laser based on the method of laser shadowgraphy. Under the condition of different laser parameters, the obtained results include the velocity, ignition threshold of LSCW and the variation law. The speed of LSCW increases with the laser energy under the same irradiation laser pulse width, and the speed of LSCW reduces with the increase of the laser pulse width under the same irradiation laser energy. Moreover, the ignition time of LSCW becomes shorter by increasing the laser number of the pulse and is not effected by changing the frequencies, when keeping the laser pulse width and energy unchanged. The results of the study can be applied in the laser propulsion technology and metal surface laser heat treatment, etc.

Numerical simulation of different pulse width of long pulsed laser on aluminum alloy

Established a physical model to simulate the melt ejection induced by long pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. This simulation is based on the interaction between single pulsed laser with different pulse width and different peak energy and aluminum alloy material. By comparing the theoretical simulation data and the actual test data, we discover that: the theoretical simulation curve is well consistent with the actual experimental curve, this two-dimensional model is with high reliability; when the temperature at the center of aluminum alloy surface increases and evaporation happens after the surface temperature at the center of aluminum alloy surface reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium vaporization; the keyhole appears on the surface of the target, an increment of the keyhole, the maximum temperature at the center of aluminum alloy surface gradually moves inwardly. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.

Experimental study on photodiode damage by millisecond pulse laser irradiation

The photoelectric detector is a very significance part in laser and its application system, but when photoelectric detector irradiated by high energy laser, the laser may cause thermal damage to the photoelectric detector, when the temperature more than its melting point and vaporization point, there will be a permanent damage in PIN photodetector, leading to the failure of photoelectric detector. In order to study the photodiode damage mechanism by millisecond pulse laser irradiation, a set of experimental system has been built, choosing appropriate pulsed laser parameters to irradiate silicon-based PIN photodiode and monitoring the surface temperature in the process of irradiation, until the PIN photodiode complete failure. The measurement results of real-time temperature, responsivity change and damage morphology were analyzed to conclude the failure reason of the PIN photodiode. The results showed that with the increase of laser energy, the PIN photodiode surface temperature would be also increased accordingly. Before the laser irradiation, the responsivity of PIN photodiode was the same. But after the laser irradiation, the responsivity of the PIN photodiode would be changed and with the increase of laser energy, the decline extent of responsivity would be also increased. Judging from the ablation, crack and fold zone on the surface of PIN photodiode after the laser irradiation, the damage was for thermal stress effect. The continuity of material confined its free expansion. Therefore, the uneven thermal expansion induced the great thermal stress. At the same time, the silicon transited from brittle to ductile and the yield strength dramatically decreased. Once the maximum thermal stress exceeded the critical stress, the plastic deformation and the brittle cracks of silicon would be generated. With the increase of laser energy, the thermal stress damage extent of PIN photodiode would be also increased accordingly and the black area of laser ablation would be also larger. In this paper, the damage mechanism of silicon-based PIN photodiode irradiated by millisecond pulse laser is that the thermal stress causes the phenomena of ablation, fold and responsivity change. The conclusions have a vital significance in improving the performance of PIN photodiode in the field of laser application.

Numerical simulation of temperature field and thermal stress field in silicon-based positive-intrinsic-negative photodiode irradiated by multipulsed millisecond laser

Laser induced morphological damage have been observed in silicon-based positive-intrinsic-negative photodiode. This paper adopted the methods of the theoretical calculation and finite element numerical simulation to model, then solved the temperature field and thermal stress field in silicon-based positive-intrinsic-negative photodiode irradiated by multipulsed millisecond laser, and researched the features and laws of the temperature field and thermal stress field. As for the thermal-mechanical problem of multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, based on Fourier heat conduction and thermoelasticity theories, we established a two-dimensional axisymmetric mathematical model .Then adopted finite element method to simulate the transient temperature field and thermal stress field. The temperature dependences of the material parameters and the absorption coefficient were taken into account in the calculation. The results indicated that there was the heat accumulation effect when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode. The morphological damage threshold were obtained numerically. The evolution of temperature at the central point of the top surface, the temperature distribution along the radial direction in the end of laser irradiation and the temperature distribution along the axial direction in the end of laser irradiation were considered. Meanwhile, the radial stress, hoop stress, axial stress on the top surface and the R=500μm axis were also considered. The results showed that the morphological damage threshold decreased with the increased of the pulse number. The results of this study have reference significance of researching the thermal and thermal stress effect evolution’s features when multipulsed millisecond laser irradiating silicon-based positive-intrinsic-negative photodiode, then revealing the mechanism of interactions between millisecond laser and photodiode.