2011 Vol. 4, No. 4
To achieve the applications of micro-Laser Plasma Propulsion(LPP) to aerospace fields, the development of the LPP technologies during 10 years was introduced. The different working modes for the LPP were discussed and their advantages and disadvantages were analyzed briefly. The effects of laser micro ablation of a target on LPP properties were also introduced, which involves the state of target, structure of target, doped target, and the liquid target. For the purpose of the micro satellite orbit and posture control, the micro-Laser Plasma Thrusters(LPTs) developed by Phipps group in America were analyzed. Finally, the shortcomings in the research were pointed out and the further development of LPP technology was given.
This paper introduces the applications and development of laser 3D detection imaging systems at home and abroad and reviews the basic compositions and technical configurations of the JIGSAW system, LADS system, helicopter 3D-LZ Imaging LADAR and the airborne high-resolution detailed investigation system. Especially, it gives different characteristics of these systems. Furthermore, it describes their working principles, different scanning modes and emphasizes the core technologies of these systems, including laser ranging , laser optical axis control, pointing measurement and data processing image display. Finally, this paper outlines the developing prospects of the airborne laser 3D imaging detection systems.
Innovation capability is the major driving force for the technology and economic development of a country. Establishment of a scientific evaluation method for innovation capability can be helpful to enhance such a capability for those institutes in a country and can provide references for government to make policies in science and technology development. In this paper, a new evaluation method is created based on the hawk-dove game theory. Corresponding to basic factors of quantum game theory, the physical meanings in an innovation system are introduced and a evaluation model of technology innovation capability is established based on the hawk-dove game theory. Then, the relation between entanglement and benefits matrix is analyzed and a method is established in which the entanglement from various participants in hawk-dove quantum game theory is used to indicate innovation capability. Furthermore, the capacity of independent innovation of research institutes is explained with hawk-dove quantum game theory, an index system for independent innovation capability is constructed and a combinational calculation method, namely, the calculation of quantum entanglement, is also set up. Finally, institutes of Chinese Academy of Sciences are chosen as the evaluation examples and evaluation data from this method and the simple statistical method of China Academy of Engineering Physics are compared. The result shows that this new method is rational and operable.
On the basis of coherently induced photonic gap structures, a new all-optical routing control scheme is proposed to simultaneously control the propagation dynamics of two weak light signals. With the transfer-matrix method to describe the coherent scattering of light waves in periodic media and the density-matrix equations to describe the resonant interaction between monochromatic laser fields and multi-level atoms, the steady reflection and transmission spectra are calculated for a coherently driven ultra-cold atomic ensemble as the control medium. The results show that, by changing the spatial patterns, intensity, and frequencies of two strong laser fields, a pair of special frequency bands(with ~95% reflectivity or 95% transmissivity) can be first established near the probe resonance and then be manipulated at any time to induce two weak light signals of different frequencies into the desired network channels. This scheme well satisfies the basic requirements of low-deformation and low-loss for all-optical routing control of weak light signals in the field of quantum information processing.
Sub-wavelength metallic gratings have extraordinary transmission efficiency and local field enhancement in resonant wavelengths. In order to deeply understand the resonant discipline, the resonant origins of the sub-wavelength metallic gratings were investigated. Three resonant wavelengths were analyzed by adjusting the geometric parameters and materials of the gratings, and the physical disciplines of three different resonant wavelengths were obtained. In the simulation, the periodical boundary method based on the boundary integral equation combined with a plane wave expansion method was used to process the period structures with arbitrary shapes. The numerical results show that three resonant center wavelengths can be tuned by the materials, periods, and the thicknesses of the gratings. It is believed that this study will provide useful information for further designing micro-nano optical elements.
In order to resolve the problem on calibration for a lunar-based ultraviolet camera in deep space, an ultraviolet star simulator with large dynamic ranges and high precision simulating magnitudes was developed. By taking an off-axis collimator with the focal length of 5 000 mm as a collimating system and a double integrating sphere as the uniform source of light, it can simulate the star magnitude from 3 to 16 with the system minimum resolution of star magnitude of 0.2 and the uncertainty of 5.48%. The experimental result shows that the star simulator satisfies the requirement of ground-based calibration for the lunar-based ultraviolet camera in deep space. It not only can calibrate the detection ability and sensitivity of the ultraviolet camera, but also can measure its other technological parameters, which provides the foundation of ground-based calibration for developing the high altitude orbit camera in deep space.
A design method for the optical system with a large relative aperture was researched and the initial optical power distribution of optical lenses was discussed. A F/0.9 infrared athermalized objective with a large relative aperture was proposed. Firstly, an athermal design model for the multiple-lens composed optical system was established. Then, by considering the systematic structure form and the selected optical materials, the initial optical power distribution among the lenses was accomplished. Finally, the aberration of the design was corrected by computer aid optimization design. The analysis of environment temperature shows that the image quality of the objective is stable in the change of temperature from 40 ℃ to 60 ℃ and its Modulation Transfer Function(MTF) approximates to the diffraction limit. The result of the implemented design agrees well with that of the theoretic computation.
To achieve the positioning optical components of a reference sphere in a interferometer accurately, a flexure barrel was designed. The mechanical model, structure parameter, positioning accuracy and lens deformation of the structure was studied. Firstly, a spring model system was established based on the principle of material mechanics. According to the mechanical equation and geometry relations, a binary equation of the center position of lens and the flexure's deformation was given. Then, the effects of assemble position, temperature, and structure parameters on the the positions and force of the lens were analyzed. Finally, the mechanical performance of the designed structure was analyzed by using the FEA method. The results indicate that the results of numerical simulation is coincident with that of finite element simulation well, and the best thickness of the flexure barrel is 1.5 mm, which fully meet the requirements of the reference sphere in the interferometer for the positioning accuracy and stability of the lens barrel.
To decrease the influence of external loads and temperature changes on the surface deformation and alignment of a lens, a typical lens support structure was investigated based on the characteristics and technical requirements of carbon dioxide detectors for optical systems and specifications. A radial support structure was proposed and its 3D model was established. In order to verify the reasonability of the structure, the dynamic and static rigidities as well as thermal characteristics were analyzed by using a nonlinear analysis method through CAD engineering analytical software. The analysis results indicate that the first frequency of lens subassembly is 1 301 Hz, and lens surface shape error is as follows:PV/10, RMS/50, Tilt error1. The radial support structure can keep lens centration well and reduce the influence of temperature diversification on the lens surface deformation.These results validate the rationality of structure and satisfy the design requirements.
An efficient CO2 laser at 10.6 m pumped by a generator with an Inductive Energy Storage(IES) generator and a Semiconductor Opening Switch(SOS) was described. Theoretical evaluation and experimental results on the second harmonic generation in GaSe and GaSe0.7S0.3 nonlinear crystals pumped by the laser were presented. Results show that for GaSe crystal, the maximum energy conversion efficiency is 0.38% at the energy of the incident radiation of 180 mJ, and the peak power of converted radiation is about 8 kW.
Based on the working principles of a pyroelectric detector, the transient response of the detector to the pulse laser is researched. The model of pyroelectric detector is built, and the response in practical application is simulated according to the parameters of materials and structures. Signal process circuits which are suitable for a high-repetition-rate pulse laser are designed. Finally, a number of the repetition frequency laser radiation experiments on the pyroelectric detector are carried out. The experiments on frequency response and pulse width of the detector are completed, and the feasibility of applying the pyroelectric detector to the energy measurement of the high-repetition-rate and narrow pulse laser is verified.
It shows larger conversion errors and stronger electromagnetic interference when the AD converter(ADC) built in DSPF2812 of the control system for a high-power TEA CO2 laser based on the DSP is used to acquire analog signals. To overcome the backcomings, a method to correct the ADC built in the DSPF2812 was proposed based on both the hardware and software. In hardware processing, the analog filtering and isolation module were adopted to process the input analog signals and the median average filtering method was used to eliminate the occasional glitch. With software correction, two given reference voltages were sent to the two channels of the A/D converter of the DSPF2812 to calculate the offset error and gain error, then it was used to correct other channels of the A/D converter. Furthermore, the impact of the reference voltage and A/D sample clock on the A/D conversion precision was analyzed by experiments. The experimental results show that the method can improve the precision of the A/D converter effectively. The A/D conversion error has been within 3 LSB, which can ensure the stability and reliability of data acquisition for the control system in high-power TEA CO2 lasers.
An integrated vector sum microwave photonic phase shifter(MWPPS) based on the asymmetric Mach-Zendner structure in Silicon on Insulator(SOI) rib waveguides was designed and fabricated for the first time. A fixed true time delay of 47 ps was achieved by a length difference of 3 983 m between the two asymmetric arms. Then two thermo-optical Variable Optical Attenuators(VOAs) were integrated in the two arms respectively to tune the optical power individually. The phase shift ranging from 0 to near 180 for a 10 GHz microwave signal has been achieved by the RI variation of 0.610 in VOAs. The device which has a very compact size could be easily integrated in silicon optoelectronic chips and expected to be widely used in Optically Controlled Phased Array Radars(OCPARs).
The spatial encoding principle of the modulation disk in a laser-beam riding guided sighting instrument is introduced. The design procedure of the modulation disk is described, and a single disk is selected to reduce the volume and weight of the guided sighting instrument. By considering every influencing factor of guided sighting instrument, the width, start-stop positions of inner and outer code paths and five kinds of frequencies are designed. The principle of defining deviation information, modulation coefficient characterizing the position information of a missile and the method of computing frequency are given. To avoid error codes of two fields' alternation, the design method to change angles is presented to rotate every frequency pattern 45 along the radial of the modulation disk. Experiments show that the method ensures the field cycle of 5 ms, and improve the guided precision.