Dr. Dafu Liu Profile

Dr. Dafu Liu

at Shanghai Institute of Technical Physics

SPIE Involvement:

Author

Proceedings Article | 30 January 2019 Paper

Research of suppressing stray light of cold shield with different black coating

Yang Wang, Yizhang Shen, Junlin Chen, Lin Xu, Defeng Mo, Dafu Liu

Proceedings Volume 10841, 1084117 (2019) https://doi.org/10.1117/12.2504898

KEYWORDS: Stray light, Light sources, Sensors, Infrared detectors, Infrared radiation, Nickel, Light, Bidirectional reflectance transmission function, Imaging systems, Plating

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With the development of infrared imaging technology, especially high resolution imaging instrument for space remote sensing, the requirement of suppressing stray light the optical system is more and more high, thus suppression of stray light of IR detector module as the core device of target detection and imaging is important. The design and processing cold shield is the key of infrared focal plane detector dewar for suppressing stray light, which mainly play a role in suppressing stray light outside of field view and improving background limited detectivity of IR detector. The structure of the cold shield is mainly effect Geometry Composing Function (GCF) of the stray radiation transmission, while Black coatings of cold shield influence bidirectional reflectance distribution function (BRDF) of stray radiation transmission. This paper mainly study suppressing stray light of cold shield with black phosphating process and black nickel plating and point source transmittance (PST) is used as the evaluation index for suppression of stray light, which can be measured accurately. A PST test system in near infrared wave band has been set up for measurement of cold shield’s PST, which coupling infrared light source with light guide tube for greatly improving the uniformity of infrared light source, while the dynamic range of test system decrease slightly. After testing and verification, light source instability is less than 1% , Non uniformity of light source at the exit of the parallel light tube is 7.4%@ 87.5mm×87.5mm.and dynamic range of test system is 0～1.5×10^-5, thus the test facility can satisfy PST test of stray light. The PST curve with angle for one stage cold shield with black phosphating process and black nickel plating are measured and consistent with numerical simulation, which first decrease rapidly with increase of the angle, then slowly vary after 35 angle for the structure of one stage cold shield, the results is useful for optimizing design of infrared detector modules for control of stray light.

Proceedings Article | 24 October 2017 Paper

An introduction of resistive arrays and packaging technology

Quan Sun, Dafu Liu, Haimei Gong

Proceedings Volume 10462, 104624G (2017) https://doi.org/10.1117/12.2285546

KEYWORDS: Packaging, Infrared technology, Resistors, Infrared radiation, Scene simulation

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Proceedings Article | 23 November 2010 Paper

Research of thermal stress between long linear MCT arrays and lead board using FEM

Wen Wu, Yonghong Wu, Dafu Liu

Proceedings Volume 7847, 78471U (2010) https://doi.org/10.1117/12.868754

KEYWORDS: Ceramics, Finite element methods, Cryogenics, Sapphire, Metals, Lead, Mercury cadmium telluride, Thermography, Lithium, Fabrication

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For the long wavelength infrared detection, HgCdTe (MCT) photoconductive devices are selected as the core of next-generation meteorological because of its mature fabrication technique and stable performance. During the assembly process, an innovative multilayer ceramic board providing mechanical support is designed as the electrical interconnection between MCT chips and external circuits for cryogenic application. Furthermore, due to its brittleness, long linear MCT device is normally glued to sapphire substrates on the multilayer ceramic board with cryogenic glue. Thus, it can be seen clearly that the assembly structure is a multilayer configuration which comprises various kinds of materials, including ceramic broad, sapphire, MCT and glues. As a result, the difference in Thermal Expansion Coefficient (TEC) between the layers could create the potential to introduce thermal stress at working environmental temperature (approximately 70K), which could result in device performance degradation, even die crack. This article analyzes the thermal stress between long linear MCT devices and a multilayer ceramic board by using Finite Element Method (FEM). According to analysis results, two factors are revealed as the most significant causes for introducing thermal stress: one is the sapphire substrate thickness; the other is the parameters of various materials, for instance Yong's modulus and TEC. Since the structure of MCT detector is determined by system requirements and is under the limitation of manufacture technology, this article reveals two effective approaches to reduce the unavoidable thermal stress: first, choosing the appropriate thickness of ceramic board which is made by Al₂O₃; second, adding another metal cushion Invar. With the above considerations, the distribution of thermal stress is simulated using FEM under different parameter conditions. Based on the results of simulations, an optimal design of package structure which could improve the reliability of linear MCT with minimum thermal stress is demonstrated.

Proceedings Article | 18 November 2010 Paper

InGaAs detector arrays hermetic encapsulation technology

Qinfei Xu, Dafu Liu

Proceedings Volume 7847, 78472H (2010) https://doi.org/10.1117/12.870098

KEYWORDS: Indium gallium arsenide, Detector arrays, Packaging, Sensors, Thermoelectric materials, Structural design, Infrared detectors, Short wave infrared radiation, Infrared imaging, Physics

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Proceedings Article | 17 November 2010 Paper

Vacuum packaging design and analysis for UFPA

Dafu Liu, Qinfei Xu

Proceedings Volume 7847, 78471Y (2010) https://doi.org/10.1117/12.868893

KEYWORDS: Packaging, Staring arrays, Convection, Analytical research, Reliability, Structural design, Ceramics, Metals, Protactinium, Sensors

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Proceedings Article | 15 October 2005 Paper

Failure analysis of PC MCT caused by current

Dafu Liu, Ligang Wu, Yonggang Yuan, Lianmei Zhang, Xiufang Jin, Haimei Gong

Proceedings Volume 5964, 596415 (2005) https://doi.org/10.1117/12.625046

KEYWORDS: Sensors, Combustion, Failure analysis, Photoresistors, Absorption, Signal detection, Sensor performance, Semiconductors, Mercury cadmium telluride, Black bodies

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Proceedings Article | 10 January 2005 Paper

Low-frequency noise studies in SWIR HgCdTe photodiodes

Yangcheng Huang, Dafu Liu, Yan Zhang, Haimei Gong

Proceedings Volume 5640, (2005) https://doi.org/10.1117/12.572547

KEYWORDS: Mercury cadmium telluride, Photodiodes, Diodes, Short wave infrared radiation, Sensors, Diffusion, Temperature metrology, Infrared imaging, Infrared radiation, Resistors

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Proceedings Article | 10 January 2005 Paper

Electrical shock effect on HgCdTe photoconductive detectors

Dafu Liu, Guosen Xu, Yangcheng Huang, Xiangyang Li, Haimei Gong

Proceedings Volume 5640, (2005) https://doi.org/10.1117/12.573139

KEYWORDS: Sensors, Resistance, Mercury cadmium telluride, Liquids, Nitrogen, Epoxies, Electrodes, Interfaces, Reliability, Mercury

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Proceedings Article | 10 January 2005 Paper

A feasible thermal-cycle screening system for cryogenic semiconductor components

Ligang Wu, Dafu Liu, Yimin Huang, Sangen Zhu, Haimei Gong

Proceedings Volume 5640, (2005) https://doi.org/10.1117/12.572718

KEYWORDS: Infrared detectors, Semiconductors, Sensors, Liquids, Nitrogen, Cryogenics, Indium, Mercury cadmium telluride, Long wavelength infrared, Infrared sensors

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Showing 5 of 9 publications

Conference Committee Involvement (1)

Optical Sensing and Imaging Technology and Applications

4 June 2017 | Beijing, China

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