Abstract:Tm-doped Fiber Lasers (TDFL) have the advantages of compact structure, excellent cooling capacity, good beam quality and high non-linear effect threshold etc. Theoretically, its quantum conversion efficiency can be up to 200%. The laser generated by TDFLs at the wavelengths from 1.7 μm to 2.1 μm has wide applications in many fields. The absorption spectrum and level structure of Tm3 , the advantages and disadvantages of three different pumping methods and the research progress of high power TDFLs at home and abroad are presented in brief. Finally, the preliminary view on the future development of high power TDFLs is given.

Abstract:To meet the requirements of a satellite platform, the lightweight design is needed for a certain electronic control cabinet. The structure style of a small, light and highly stable electronic control cabinet is given. According to the complex operation condition of electronic devices of remote sensors in orbit, a protective design method for electronic control cabinets is proposed. An active thermal control measure is taken for high power consumption devices. Finally, the electronic control cabinet is analyzed by using the Finite Element Method (FEM). The result shows that the first-order modal of the electronic control cabinet is 240 Hz which is much greater than the specification of 140 Hz and can meet the requirements of space application.

Abstract:As a kind of traditional optical components, prisms are limited in the application of modern optical instruments because of their nonlinear dispersion. By analyzing the dispersion nature of prisms, a dispersion model of material was established and a design method of compound prisms with linear dispersion was proposed. Two kinds of materials with close nonlinear dispersion coefficients T1 and T2 and different linear dispersion coefficient V were used. By controlling the parameters of the compound prism and the incident angle, linear dispersion could be achieved. Finally, the evaluation index was established for the linear dispersion compound prism. The designed result was evaluated scientifically and reasonably. The correctness of the design theory was verified. It was found that the nonlinear dispersion of the compound prism was improved effectively. The improvement of nonlinear dispersion was dependent on the absolute nonlinear coefficient P of two kinds of materials. When $P$ was greater than 0.01, the compound prism could achieve linear dispersion. The nonlinear (NL) of the dispersion curve was better than 5%.

Abstract:On the basis of a 384×288 uncooled staring focal plane array detector with pixel size of 25 μm, a 20-fold uncooled long wavelength infrared continuous zoom optical system is designed. The operation waveband of the system is 8～12 μm and its F number is 1.3. It has the advantages of larger relative aperture, higher zoom ratio and smooth zoom path etc. The system consists of seven lenses which are made from a combination of two kinds of materials. Most of the lenses are made from common germanium material so as to reduce the use of expensive materials and be easy for processing. By using one diffraction optical element and two aspheric elements, a compact structure of the system is realized. The system has its Nyquist spatial frequency of 20 lp/mm, Modulation Transfer Function (MTF) greater than 0.4 for short focus and long focus and MTF greater than 0.58 for middle focus. These MTF values show that the system has excellent image quality.

Abstract:Since Infrared Focal Plane Arrays (IRFPA) have become the main stream in the development of infrared detectors, the use of IRFPA parameters to evaluate the comprehensive performance of an infrared detection system is very important. The operating range equation of an infrared detection system represented by Noise Equivalent Temperature Difference (NETD) is deduced. Considering the influence of background radiation and target imaging dispersion effect on detection, the operating range of a system for a point target under different visibility conditions is calculated. The result shows that the better the visibility is, the farther the operating range of the infrared detection system is. The variation of the detecting capability of the infrared detection system with NETD is analyzed. With the increase of NETD, the operating range of the infrared detection system for the target decreases remarkably. The research result is of referential value to the design and performance index evaluation of infrared detection systems.

Abstract:A high frequency moving-magnet linear compressor was designed for a 120 Hz coaxial pulse tube cold finger and a motor model was designed by means of finite element analysis. The experimental results showed that the crycooler could achieve 1 W@80 K cooling capacity with input power of 34 W. On the basis of this compressor model, the compressor was used to drive a Stirling cold finger with same frequency. By redesigning the flexure-bearing and moving mass, the Stirling cold finger achieved 1 W@80 K cooling capacity with input power of 34 W. This showed that this design method was effective.

Abstract:Scanning mirrors are often used to acquire space electro-optical information. Some applications have higher requirements for the fast start-stop response and pointing accuracy of scanning mirrors. According to the motion mode of a permanent magnet synchronous motor when it is driving a scanning mirror, a motor Simulink simulation model using three-closed-loop vector control strategy is established. A method which uses the sectional Proportional Integration Differentiation (PID) algorithm to control position loop is proposed. The results show that compared with the traditional PID, the sectional PID can enhance the response speed of the system. At the same time, it can also improve the control accuracy and stability of the system to a certain extent.

Abstract:Under the frame of thought experiment, the concept of generalized particle which has variable volume or shape is proposed. The origin of the concept of the speed of light is analyzed. The impossibility of faster-than-light is discussed. The view that the universe originated from the split of an initial photon black hole is proposed. The quasars that are moving close to the speed of light are the first evidence to support the photon splitting model. The photon can be divided into high energy and low energy photon. The problems of arrangement and selection of photonic data are discussed. The concept of blackbody can be derived from the blackhole. The derivation process of the blackbody radiation formula based on MATLAB is introduced in this paper. The blackbody radiation formulae for low energy photons (i.e., the Planck’s formulae) can be obtained by adding a zero in the photonic data sequence; otherwise, the blackbody radiation formula, which includes high energy photons, is obtained, and the result tends to infinity. For the description of the ultimate fate of the universe, without introducing any other concepts or terms such as entropy, the photon splitting model plus the radiative heat transfer model can be used to obtain the conclusions which are equivalent to that from the theories of heat silence or dissipative structure. The dark matter particle (or simply, the darklet) model which is based on photon splitting is presented. The darklets are the second evidence to support the photon splitting model. A cycle model between the speed of light and the non speed of light is proposed for the evolution of the universe.