High energy laser technology
2016, 45(11): 1136001.
doi: 10.3788/IRLA201645.1136001
Laser plasma ignition(LPI) is viewed as a promising ignition technique for aerospace propulsion systems with its many merits over conventional ignition techniques, including easier control of the ignition position and timing, wider working condition, less electromagnetic interference, rapid response and feasibility of reliable r-ignitions, etc.. Firstly, an introduction to the technical benefits and physical processes of the LPI technique was given. Then the developments in the applications of the LPI in aerospace propulsion systems were summarized, especially the achievements that had been made in National Key Laboratory of Science and Technology on Tunable Laser, Harbin Institute of Technology. Finally, the challenges and prospects in the application of the LPI in aerospace propulsion systems were analyzed. The LPI has demonstrated great prospects in reliable r-ignition of the rocket engines fueled with no-toxic no-hypergolic propellants and scramjet engines fueled with hydrocarbon fuels. However, to facilitate the in orbit and on board applications, further progress should be made in the integrated system design of the LPI system with the propulsion systems, and in the miniaturization and engineering design of the LPI system.
2016, 45(11): 1136002.
doi: 10.3788/IRLA201645.1136002
The thermal distortions of deformable mirror with such materials as mon-crystalline silicon, silica and nucleated glass (ULE), irradiated with diod-pumped soli-state laser (DPL) were calculated and analyzed using FEA software. The results show that when the power density of input laser is 0.225 kW/cm2, and the reflectivity of the deformable mirror thin film are 99.9%, the temperature rising and thermal distortions of the deformable mirror are separately 0.804, 6.751 and 7.122℃, and 0.049 3, 0.034 8 and 0.005 4m respectivel, under the radiation time of 10 seconds. By comparison, the temperature rising of deformable mirror with mon-crystalline silicon substrate is smaller; the deformation and stress of ULE is the lowest, which would be a kind of more promising material for producing deformable mirror in future DPL laser system. In the end, some results of the long pulse laser irradiation were calculated and analysis.
2016, 45(11): 1136003.
doi: 10.3788/IRLA201645.1136003
Laser induced plasma ignition (LIPI) is a new technique for engine ignition. It is revealed that LIPI has benefits in many aspects, including reduction of erosion effects, increase of engine efficiency, shorter combustion time, more accurate location of ignition, and multipoint ignition simultaneously. Therefore it has a wide developing prospect. This paper mainly aimed at the key componen-laser source, of LIPI and made a comprehensive review for the development of the laser source and the latest achievements. Furthermore, the development prospect of this kind laser was also predicted.
2016, 45(11): 1136004.
doi: 10.3788/IRLA201645.1136004
Based on the Nonlinear Schdinger Equation(NLSE), the theoretical model of psssively mod-locked Er3+-doped fluorid fiber laser using a saturable absorber was set up, by which the mechanism of generating mi-infrared ultrashort pulse in the fiber laser was investigated. The numerical simulation focused on the evolution process of the mi-infrared ultrashort pulse in fluorine fiber laser. The impact of the Er3+:fluorine gain fiber length and the saturable absorber unsaturated loss on the generation of mod-locked pulse was analyzed in detail, and the reasonable parameter range was determined. It is found that for a given set of smal-signal gain, unsaturated loss, and net intracavity dispersion, the stable mod-locked pulses are achieved by tuning the Er3+:fluorine gain fiber length within a certain range. With increasing the Er3+:fluorine gain fiber length, the output pulse duration decreased gradually, while the increase of the spectrum width (FWHM) and the peak power are observed. Meanwhile, for a given set of Er3+:fluorine gain fiber length, net intracavity dispersion and smal-signal gain, the stable mod-locked pulses are also obtained by adjusting the saturable absorber unsaturated loss within a certain range. With the increase of the saturable absorber unsaturated loss, the output pulse duration decreases gradually, however spectral width broadens and then narrows, and peak power increases gradually.
