The design and fabrication of an optical 2×490°hybrid based on birefringent crystals for a coherent receiver in a free−space optical communication system are presented.For the quadrature receiver,two pairs o...The design and fabrication of an optical 2×490°hybrid based on birefringent crystals for a coherent receiver in a free−space optical communication system are presented.For the quadrature receiver,two pairs of 180°phase−shift outputs are obtained and one pair has a phase difference of 90°with respect to the other.The 90°hybrid comprises two pairs of stacked birefringent plates,a phase retardation plate and an analyser birefringent plate.The testing results measured by the heterodyne method verify that the 2×4 optical 90°hybrid can work correctly and effectively.The phase compensation and further optimization schemes are also proposed.展开更多
Synthetic aperture imaging ladar (SAIL) technique belongs fully coherent processing in both the time domain and space domain and has a rather high implement difficulty. To solve this problem, the concept of circular...Synthetic aperture imaging ladar (SAIL) technique belongs fully coherent processing in both the time domain and space domain and has a rather high implement difficulty. To solve this problem, the concept of circular incoherently SAIL is introduced. A speckle version image of a two-dimensional (2D) letter 'E' target is reconstructed from E-field projection data detected by a circular incoherently SAIL system. The experimental system is constructed by three subsystems using chirped-pulse laser as the light source and heterodyne detection to get the range information of the target. The reconstruction of the image and the noise effect are also discussed in detail.展开更多
We apply phase retrieval method to align projection data for tomographic reconstruction in reflective tomography laser radar imaging. In our experiment, the target is placed on a spin table with an unknown, but fixed,...We apply phase retrieval method to align projection data for tomographic reconstruction in reflective tomography laser radar imaging. In our experiment, the target is placed on a spin table with an unknown, but fixed, axis. The oscillatory motion of the target in the incident direction of the laser pulse is added at each view to simulate the real satellites random motion. The experimental simulation results demonstrate the effectiveness of this method to improve image reconstruction quality. Future research also includes the development of projection registration based on phase retrieval for targets with more complicated structure.展开更多
A compact passively Q-switched Yb:YAG microchip laser is demonstrated. Featuring a semiconductor saturable-absorber mirror (SESAM), the laser yields pulses of 219 ps when the length of the microchip Yb:YAG crystal...A compact passively Q-switched Yb:YAG microchip laser is demonstrated. Featuring a semiconductor saturable-absorber mirror (SESAM), the laser yields pulses of 219 ps when the length of the microchip Yb:YAG crystal is 100 #m and the beam quality is M2 〈 1.3. To the best of our knowledge, pulses from the proposed laser are the shortest Q-switching pulses obtained from Yb:YAG microchip lasers currently available.展开更多
We report a switchable dual-wavelength fiber grating laser in linear overlapping cavity. The laser features two overlapping cavities sharing a single Yb-doped gain medium fiber and two sets of fiber Bragg gratings. A ...We report a switchable dual-wavelength fiber grating laser in linear overlapping cavity. The laser features two overlapping cavities sharing a single Yb-doped gain medium fiber and two sets of fiber Bragg gratings. A coiling fiber setup is inserted into the 1035 nm laser cavity. Given that the bending loss is inversely related to the bending radius, the cavity loss of 1035-nm can be modulated. Modulating the bending loss facilitates the switching of the fiber grating laser to a single-or dual-wavelength output at 1030 or 1035 nm and convenient tuning of the power ratio of the two wavelengths. An approximately 152.6-mW output power and up to 38-dB polarization extinction ratio are observed. The simultaneous lasing at I030 and 1035 nm is a qualified seeder source for amplification to high power scale and can be applied to difference frequency generation of a terahertz signal. This dual-wavelength fiber grating laser is a potential pump source for generating terahertz radiation using a novel approach.展开更多
基金by the Chinese Academy of Sciences,the National Natural Science Foundation of China under Grant No 60908029the Natural Science Foundation of Shanghai under Grant No 09ZR1435300the National High-Tech Research and Development Program of China under Grant No 2007AA01Z298.
文摘The design and fabrication of an optical 2×490°hybrid based on birefringent crystals for a coherent receiver in a free−space optical communication system are presented.For the quadrature receiver,two pairs of 180°phase−shift outputs are obtained and one pair has a phase difference of 90°with respect to the other.The 90°hybrid comprises two pairs of stacked birefringent plates,a phase retardation plate and an analyser birefringent plate.The testing results measured by the heterodyne method verify that the 2×4 optical 90°hybrid can work correctly and effectively.The phase compensation and further optimization schemes are also proposed.
基金supported by the Key Laboratory of Space Laser Communication and Testing Technology of the Chinese Academy of Sciences and the National Nature Science Foundation of China (No. 61108069)
文摘Synthetic aperture imaging ladar (SAIL) technique belongs fully coherent processing in both the time domain and space domain and has a rather high implement difficulty. To solve this problem, the concept of circular incoherently SAIL is introduced. A speckle version image of a two-dimensional (2D) letter 'E' target is reconstructed from E-field projection data detected by a circular incoherently SAIL system. The experimental system is constructed by three subsystems using chirped-pulse laser as the light source and heterodyne detection to get the range information of the target. The reconstruction of the image and the noise effect are also discussed in detail.
基金supported by the National Natural Science Foundation of China under Grant No.0803371-X00
文摘We apply phase retrieval method to align projection data for tomographic reconstruction in reflective tomography laser radar imaging. In our experiment, the target is placed on a spin table with an unknown, but fixed, axis. The oscillatory motion of the target in the incident direction of the laser pulse is added at each view to simulate the real satellites random motion. The experimental simulation results demonstrate the effectiveness of this method to improve image reconstruction quality. Future research also includes the development of projection registration based on phase retrieval for targets with more complicated structure.
文摘A compact passively Q-switched Yb:YAG microchip laser is demonstrated. Featuring a semiconductor saturable-absorber mirror (SESAM), the laser yields pulses of 219 ps when the length of the microchip Yb:YAG crystal is 100 #m and the beam quality is M2 〈 1.3. To the best of our knowledge, pulses from the proposed laser are the shortest Q-switching pulses obtained from Yb:YAG microchip lasers currently available.
基金supported by the Shanghai Rising-Star Program(No.12QH1401100)the Chinese Academy of Sciences Comprehensive Strategic Cooperation Projects in Guangdong Province(No.2010B090300063)
文摘We report a switchable dual-wavelength fiber grating laser in linear overlapping cavity. The laser features two overlapping cavities sharing a single Yb-doped gain medium fiber and two sets of fiber Bragg gratings. A coiling fiber setup is inserted into the 1035 nm laser cavity. Given that the bending loss is inversely related to the bending radius, the cavity loss of 1035-nm can be modulated. Modulating the bending loss facilitates the switching of the fiber grating laser to a single-or dual-wavelength output at 1030 or 1035 nm and convenient tuning of the power ratio of the two wavelengths. An approximately 152.6-mW output power and up to 38-dB polarization extinction ratio are observed. The simultaneous lasing at I030 and 1035 nm is a qualified seeder source for amplification to high power scale and can be applied to difference frequency generation of a terahertz signal. This dual-wavelength fiber grating laser is a potential pump source for generating terahertz radiation using a novel approach.