An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy] -4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene (M1) was synthesized. Polymer (PM1) p...An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy] -4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene (M1) was synthesized. Polymer (PM1) possessing optical phase conjugated response was obtained by homopolymerization of the optically active monomer (M1) using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could be easily fabricated by spin coating. The optical phase conjugated responses of the polymer PM1 were measured by degenerate four-wave mixing (DFWM). In comparison with polymer containing no chiral group, it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PM1 in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams (514.5 nm) and the irradiating number, presumably due to the chiral group in the PM1 molecular structure. For the case of the polymer investigated here, a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams, which aims originally at searching for a new photoactive material.展开更多
The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti：sapphire laser is studied experimentally and theoretically in this paper. At varying values o...The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti：sapphire laser is studied experimentally and theoretically in this paper. At varying values of phase- conjugation precision, we focus the corresponding beams into spots of the same size of 5.1 μm × 5.3 μm with a f/4 parabola in the 32 TW/36 fs Ti：sapphire laser system. The results show that the precision of conjugation can induce an intensity modulation but does not significantly affect the wavefront correction.展开更多
The technology for phase detection of liquid crystal optical device is a difficult research in current domestic and overseas. However, for the existing liquid crystal optical device, aiming at the poor anti-vibration ...The technology for phase detection of liquid crystal optical device is a difficult research in current domestic and overseas. However, for the existing liquid crystal optical device, aiming at the poor anti-vibration capability and poor versatile of phase detection, the complexity of phase retrieval algorithm, we propose a new phase measurement principle and experimental methods of liquid crystal optical device. It is a phase measurement method based on the combination of phase- shifting interferometer and phase conjugation technology. The deflection characteristics of the liquid crystal device means the device can implement phase modulation to only one direction of polarized light while is completely transparent to orthogonal polarized light. We put forward the phase shift of the orthogonal polarization phase shift interferometer method, using phase shifting interference as well as the combination of phase conjugate means to achieve its phase measurement. So we can retrieves devices modulation phase simply and efficiently combines with phase- shifting interferometer technology.展开更多
While propagating inside the strongly scattering biological tssue,photons lose their incident directions beyond one transport mean free path(TMFP,~1 millimeter(mm)),which makes it challenging to achieve optical focusi...While propagating inside the strongly scattering biological tssue,photons lose their incident directions beyond one transport mean free path(TMFP,~1 millimeter(mm)),which makes it challenging to achieve optical focusing or clear imaging deep inside tissue.By manipulating many degrees of the incident optical wavefront,the latest optical wavefront engineering(WFE)technology compensates the wavelfront distortions caused by the scattering media and thus is toward breaking this physical limit,bringing bright perspective to many applications deep inside tissue,eg,high resolution functional/molecular imaging,optical excitation(optogenetics)and optical tweezers.However,inside the dynamic turbid media such as the biological tissue,the wavefront distortion is a fast and continuously changing process whose decorrelation rate is on timescales from milliseconds(ms)to microseconds(μs),or even faster.This requires that the WFE technology should be capable of beating this rapid process.In this review,we discuss the major challenges faced by the WFE technology due to the fast decorrelation of dynamic turbid media such as living tissue when achieving light focusing/imaging and summarize the research progress achieved to date to overcome these challenges.展开更多
The optimized optical phase conjugation （OPC） configuration is proposed for the 40-Gb/s CO-OFDM system. The proposed configuration for nonlinear cancellation is systematically depicted in transmission links with lum...The optimized optical phase conjugation （OPC） configuration is proposed for the 40-Gb/s CO-OFDM system. The proposed configuration for nonlinear cancellation is systematically depicted in transmission links with lumped amplification. Numerical simulations are performed to demonstrate effectiveness. Simulation results show that mid-span spectral inversion （MSSI） can partially compensate for nonlinear distortions. Moreover, its optimized configuration can further improve system performances and increase nonlinear compensation effectiveness. Compared with MSSI, the maximal Q factor, nonlinear threshold, and transmission distance of optimized OPC configuration increase by over 1.6 dB, 2 dB, and 2 times, respectively.展开更多
A method is proposed to optimize the recording structure of the photorefractive volume grating to compensate high spatial frequency in the distorted wavefront by optical phase conjugation.Based on the coupled-wave equ...A method is proposed to optimize the recording structure of the photorefractive volume grating to compensate high spatial frequency in the distorted wavefront by optical phase conjugation.Based on the coupled-wave equation, the diffraction efficiency of the recorded grating formed by the scattered beams in different recording structures is simulated.The theoretical results show that the recorded modulations with high spatial frequency can be significantly improved in the small recording angle.In the experiment, three recording structures with the recording angles of 7.5°, 30°, and 45° are chosen to verify the compensation effect.Compared with the reconstructed image in the large recording angle of 45°, the signal to noise ratio of the image recorded at 7.5° increases to 3.2 times of that at 45°.展开更多
Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The...Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The results of numerical simulations are useful for improving compensation for pulse distortion.展开更多
Optical phase conjugation is a technique that employs nonlinear optical effects to precisely reverse both the direction of the propagation and the overall phase of a wavefront. It may be used in a variety of spheres, ...Optical phase conjugation is a technique that employs nonlinear optical effects to precisely reverse both the direction of the propagation and the overall phase of a wavefront. It may be used in a variety of spheres, such as adaptive optics, real-time holography, optical computing, photoresist technique and nonlinear optical spectroscopy. In a展开更多
Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numer...Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numerically. It is found that OPC cannot compensate for pulse waveform distortion due to SS. The initial chirp of pulses and dispersion can counteract SS and improve the compensation performance for the distortion.展开更多
基金This work was supported by National Natural Science Foundation of China (No. 59873001)Scientific Foundation for Returned Overseas Chinese Scholars, Ministry of Education.
文摘An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy] -4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene (M1) was synthesized. Polymer (PM1) possessing optical phase conjugated response was obtained by homopolymerization of the optically active monomer (M1) using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could be easily fabricated by spin coating. The optical phase conjugated responses of the polymer PM1 were measured by degenerate four-wave mixing (DFWM). In comparison with polymer containing no chiral group, it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PM1 in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams (514.5 nm) and the irradiating number, presumably due to the chiral group in the PM1 molecular structure. For the case of the polymer investigated here, a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams, which aims originally at searching for a new photoactive material.
基金Project supported by the National Basic Research Program of China(Grant No.2011CB808101)the National Natural Science Foundation of China(Grant No.60921004)
文摘The phase conjugation between the deformable mirror and the wavefront sensor in the aberration correction of a terawatt Ti：sapphire laser is studied experimentally and theoretically in this paper. At varying values of phase- conjugation precision, we focus the corresponding beams into spots of the same size of 5.1 μm × 5.3 μm with a f/4 parabola in the 32 TW/36 fs Ti：sapphire laser system. The results show that the precision of conjugation can induce an intensity modulation but does not significantly affect the wavefront correction.
文摘The technology for phase detection of liquid crystal optical device is a difficult research in current domestic and overseas. However, for the existing liquid crystal optical device, aiming at the poor anti-vibration capability and poor versatile of phase detection, the complexity of phase retrieval algorithm, we propose a new phase measurement principle and experimental methods of liquid crystal optical device. It is a phase measurement method based on the combination of phase- shifting interferometer and phase conjugation technology. The deflection characteristics of the liquid crystal device means the device can implement phase modulation to only one direction of polarized light while is completely transparent to orthogonal polarized light. We put forward the phase shift of the orthogonal polarization phase shift interferometer method, using phase shifting interference as well as the combination of phase conjugate means to achieve its phase measurement. So we can retrieves devices modulation phase simply and efficiently combines with phase- shifting interferometer technology.
文摘While propagating inside the strongly scattering biological tssue,photons lose their incident directions beyond one transport mean free path(TMFP,~1 millimeter(mm)),which makes it challenging to achieve optical focusing or clear imaging deep inside tissue.By manipulating many degrees of the incident optical wavefront,the latest optical wavefront engineering(WFE)technology compensates the wavelfront distortions caused by the scattering media and thus is toward breaking this physical limit,bringing bright perspective to many applications deep inside tissue,eg,high resolution functional/molecular imaging,optical excitation(optogenetics)and optical tweezers.However,inside the dynamic turbid media such as the biological tissue,the wavefront distortion is a fast and continuously changing process whose decorrelation rate is on timescales from milliseconds(ms)to microseconds(μs),or even faster.This requires that the WFE technology should be capable of beating this rapid process.In this review,we discuss the major challenges faced by the WFE technology due to the fast decorrelation of dynamic turbid media such as living tissue when achieving light focusing/imaging and summarize the research progress achieved to date to overcome these challenges.
基金supported in part by the National Natural Science Foundation of China (No. 60932004)the National "863" Program of China (No. 2009AA01A345)the National "973" Program of China (No.2007CB310705)
文摘The optimized optical phase conjugation （OPC） configuration is proposed for the 40-Gb/s CO-OFDM system. The proposed configuration for nonlinear cancellation is systematically depicted in transmission links with lumped amplification. Numerical simulations are performed to demonstrate effectiveness. Simulation results show that mid-span spectral inversion （MSSI） can partially compensate for nonlinear distortions. Moreover, its optimized configuration can further improve system performances and increase nonlinear compensation effectiveness. Compared with MSSI, the maximal Q factor, nonlinear threshold, and transmission distance of optimized OPC configuration increase by over 1.6 dB, 2 dB, and 2 times, respectively.
基金supported by the National Natural Science Foundation of China(No.11774364)the Shanghai Sailing Program(No.18YF1425900)
文摘A method is proposed to optimize the recording structure of the photorefractive volume grating to compensate high spatial frequency in the distorted wavefront by optical phase conjugation.Based on the coupled-wave equation, the diffraction efficiency of the recorded grating formed by the scattered beams in different recording structures is simulated.The theoretical results show that the recorded modulations with high spatial frequency can be significantly improved in the small recording angle.In the experiment, three recording structures with the recording angles of 7.5°, 30°, and 45° are chosen to verify the compensation effect.Compared with the reconstructed image in the large recording angle of 45°, the signal to noise ratio of the image recorded at 7.5° increases to 3.2 times of that at 45°.
文摘Relationship between the initial chirp of super-Gaussian pulse and dispersion and nonlinearity effects of a single-mode fiber in the optical communication system using midway optical phase conjugation is analyzed. The results of numerical simulations are useful for improving compensation for pulse distortion.
文摘Optical phase conjugation is a technique that employs nonlinear optical effects to precisely reverse both the direction of the propagation and the overall phase of a wavefront. It may be used in a variety of spheres, such as adaptive optics, real-time holography, optical computing, photoresist technique and nonlinear optical spectroscopy. In a
文摘Effects of self-steepening (SS) of chirped Gaussian pulses on optical fiber communication system using midway optical phase conjugation (OPC) are analyzed. Dynamic evolution of the ultrashort pulses is simulated numerically. It is found that OPC cannot compensate for pulse waveform distortion due to SS. The initial chirp of pulses and dispersion can counteract SS and improve the compensation performance for the distortion.
