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Fourier Optics and Signal Processing|10 Article(s)
Characterizing a liquid crystal spatial light modulator at oblique incidence angles using the self-interference method
Zixin Zhao, Yiying Zhuang, Zhaoxian Xiao, Hangying Zhang, Chen Fan, Hehui Geng, and Hong Zhao
The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the +1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large (i.e. larger than 10°), the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM. The phase modulation characteristics of a reflective liquid crystal (LC) spatial light modulator (SLM) under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the +1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large (i.e. larger than 10°), the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.
Chinese Optics Letters
- Publication Date: Sep. 10, 2018
- Vol. 16, Issue 9, 090701 (2018)
Extracting cavity and pulse phases from limited data for coherent pulse stacking
Yilun Xu, Russell Wilcox, John Byrd, Lawrence Doolittle, Qiang Du, Gang Huang, Yawei Yang, Tong Zhou, Lixin Yan, Wenhui Huang, and Chuanxiang Tang
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. A Z-domain model targeting the pulsed laser is assembled to describe the optical interference process. An algorithm, extracting the cavity phase and pulse phases from limited data, where only the pulse intensity is available, is developed to diagnose optical cavity resonators. We also implement the algorithm on the cascaded system of multiple optical cavities, achieving phase errors less than 1.0° (root mean square), which could ensure the stability of CPS. Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. A Z-domain model targeting the pulsed laser is assembled to describe the optical interference process. An algorithm, extracting the cavity phase and pulse phases from limited data, where only the pulse intensity is available, is developed to diagnose optical cavity resonators. We also implement the algorithm on the cascaded system of multiple optical cavities, achieving phase errors less than 1.0° (root mean square), which could ensure the stability of CPS.
Chinese Optics Letters
- Publication Date: Apr. 10, 2018
- Vol. 16, Issue 4, 040701 (2018)
Compact optoelectronic oscillator based on a Fabry–Perot resonant electro-optic modulator
Jian Dai, Yitang Dai, Feifei Yin, Yue Zhou, Jianqiang Li, Yuting Fan, and Kun Xu
A novel compact optoelectronic oscillator (OEO) employing a Fabry–Perot (FP) resonant electro-optic (EO) modulator is proposed and experimentally demonstrated. The resonant modulator is used as the optical storage element as well as the mode selection element, which can greatly reduce the system complexity and make the system more portable. Moreover, the optical resonance and electrical transmission response for the FP resonant EO modulator are theoretically and experimentally studied. The proposed OEO oscillates at 10 and 20 GHz in the proof-of-concept experiment, and the corresponding single-sideband phase noise can reach below 118 and 108 dBc/Hz at 1 MHz offset frequency, respectively. A novel compact optoelectronic oscillator (OEO) employing a Fabry–Perot (FP) resonant electro-optic (EO) modulator is proposed and experimentally demonstrated. The resonant modulator is used as the optical storage element as well as the mode selection element, which can greatly reduce the system complexity and make the system more portable. Moreover, the optical resonance and electrical transmission response for the FP resonant EO modulator are theoretically and experimentally studied. The proposed OEO oscillates at 10 and 20 GHz in the proof-of-concept experiment, and the corresponding single-sideband phase noise can reach below 118 and 108 dBc/Hz at 1 MHz offset frequency, respectively.
Chinese Optics Letters
- Publication Date: Nov. 10, 2016
- Vol. 14, Issue 11, 110701 (2016)
Filtering characteristics of spatial filter for spatial filtering velocimeter
Xin He, Jian Zhou, Xiaoming Nie, and Xingwu Long
In order to select a suitable spatial filter for the spatial filtering velocimeter, the filtering characteristics of the spatial filters with a rectangular window and rectangular transmittance are investigated by the power spectrum of transmittance function method. The filtering characteristics of differential filters are investigated and compared with that of common ones. The influences of the number of spatial periods on the spectral bandwidth, deviation to central frequency, and peak transmittance are deeply analyzed. The results show that the influence is due to the form of superposition of the signal components and other components, the pedestal and higher-order components, and the superposition results from the finite size of the spatial filter. According to the results, a method is proposed to compensate for the deviation to central frequency. In order to select a suitable spatial filter for the spatial filtering velocimeter, the filtering characteristics of the spatial filters with a rectangular window and rectangular transmittance are investigated by the power spectrum of transmittance function method. The filtering characteristics of differential filters are investigated and compared with that of common ones. The influences of the number of spatial periods on the spectral bandwidth, deviation to central frequency, and peak transmittance are deeply analyzed. The results show that the influence is due to the form of superposition of the signal components and other components, the pedestal and higher-order components, and the superposition results from the finite size of the spatial filter. According to the results, a method is proposed to compensate for the deviation to central frequency.
Chinese Optics Letters
- Publication Date: Jun. 10, 2015
- Vol. 13, Issue 6, 060702 (2015)
Broadband shifting luminescence in Cr3+/Yb3+ codoped Y3Al5O12 thin films by pulsed laser deposition
Yinzhen Wang, Ning Li, Pingping Duan, Junyong Deng, Liaolin Zhang, Benli Chu, and Qinyu He
Cr3+/Yb3+ codoped Y3Al5O12 (i.e., YAG) thin films are prepared by pulsed laser deposition. The films are characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence spectra. Excitation at 446 or 587 nm, a broadband emission in the range of 610–800 nm, and an intense near-infrared at 1030 nm are obtained, showing cooperative energy transfer from Cr3+ to Yb3+ ions in the Cr3+/Yb3+ codoped YAG thin films; energy transfer efficiency is 71%. The YAG films may have potential application to enhance the efficiency of silicon solar cells. Cr3+/Yb3+ codoped Y3Al5O12 (i.e., YAG) thin films are prepared by pulsed laser deposition. The films are characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and photoluminescence spectra. Excitation at 446 or 587 nm, a broadband emission in the range of 610–800 nm, and an intense near-infrared at 1030 nm are obtained, showing cooperative energy transfer from Cr3+ to Yb3+ ions in the Cr3+/Yb3+ codoped YAG thin films; energy transfer efficiency is 71%. The YAG films may have potential application to enhance the efficiency of silicon solar cells.
Chinese Optics Letters
- Publication Date: Jun. 10, 2015
- Vol. 13, Issue 6, 060701 (2015)
Digital holographic shape measurement using Fizeau microscopy
D. G. Abdelsalam, Junwei Min, Daesuk Kim, and Baoli Yao
We present a Fizeau interferometer using a microscopic objective as a tool for surface contouring without the need for a numerical lens for reconstruction. The interferometer is associated with a telescope system to feature the object with collimated light. The experiment is conducted on two objects possessing different step heights. The phase maps from the captured off-axis holograms are calculated numerically, which allows us to deduce the contours of the objects. The great advantages of the presented technique are that it can be done in real time and there is no need for numerical lenses for micro-objects reconstruction. We present a Fizeau interferometer using a microscopic objective as a tool for surface contouring without the need for a numerical lens for reconstruction. The interferometer is associated with a telescope system to feature the object with collimated light. The experiment is conducted on two objects possessing different step heights. The phase maps from the captured off-axis holograms are calculated numerically, which allows us to deduce the contours of the objects. The great advantages of the presented technique are that it can be done in real time and there is no need for numerical lenses for micro-objects reconstruction.
Chinese Optics Letters
- Publication Date: Oct. 10, 2015
- Vol. 13, Issue 10, 100701 (2015)
Tunable rectangular array illuminator in periodically poled LiNbO3 crystal
Qiuying Li, Juan Huo, Xiaohui Zhao, and Xianfeng Chen
An electro-optic tunable rectangular array illuminator in one-dimensional periodically poled LiNbO3 (PPLN) crystal is presented experimentally which result is in good agreement with results from simulation. The illuminator is formed based on the Talbot self-imaging effect by applying an electric field on PPLN. The intensity distribution of rectangular array could be precisely modulated. Compared with other array illuminators, this tunable illuminator uses a lower voltage and could get a more concentrated intensity distribution. The influence of the incident angle to the self-imaging patterns is studied for the first time. An electro-optic tunable rectangular array illuminator in one-dimensional periodically poled LiNbO3 (PPLN) crystal is presented experimentally which result is in good agreement with results from simulation. The illuminator is formed based on the Talbot self-imaging effect by applying an electric field on PPLN. The intensity distribution of rectangular array could be precisely modulated. Compared with other array illuminators, this tunable illuminator uses a lower voltage and could get a more concentrated intensity distribution. The influence of the incident angle to the self-imaging patterns is studied for the first time.
Chinese Optics Letters
- Publication Date: Apr. 30, 2014
- Vol. 12, Issue 5, 050701 (2014)
Self-accelerating and self-breathing Bessel-like beams along arbitrary trajectories
Juanying Zhao, Peng Zhang, Dongmei Deng, Cibo Lou, Daohong Song, Jingjiao Liu, and Zhigang Chen
We theoretically and experimentally study self-accelerating and self-breathing Bessel-like beams that follow arbitrary trajectories, including hyperbolic, hyperbolic secant, and three-dimensional (3D) spiraling trajectories. The beams have an overall Bessel-like profile in transverse dimensions; however, the intensity of their central main lobe breathes while traveling along a curved trajectory. Such beams can be readily generated experimentally through appropriate phase modulation of the optical wavefront. The beams contribute to the design of new families of self-accelerating beams. We theoretically and experimentally study self-accelerating and self-breathing Bessel-like beams that follow arbitrary trajectories, including hyperbolic, hyperbolic secant, and three-dimensional (3D) spiraling trajectories. The beams have an overall Bessel-like profile in transverse dimensions; however, the intensity of their central main lobe breathes while traveling along a curved trajectory. Such beams can be readily generated experimentally through appropriate phase modulation of the optical wavefront. The beams contribute to the design of new families of self-accelerating beams.
Chinese Optics Letters
- Publication Date: Nov. 06, 2013
- Vol. 11, Issue 11, 110701 (2013)
Experimental investigation on a software synchronous optical sampling technique based on periodically poled lithium niobate
Lin Zuo, Aiying Yang, Junsen Lai, and Yunan Sun
A software synchronous optical sampling system is constructed based on sum frequency generation (SFG) in periodically poled lithium niobate (PPLN). Five gigahertz of a non-return-to-zero (NRZ) data signal is sampled by sampling pulse with the repetition frequency of 29.31 MHz. The power of the SFG light is set at -23 dBm, and an eye diagram is successfully recovered. A band-pass filter is added before the sampling pulse is subjected to erbium-doped fiber amplifier to reduce gain competition and ensure a high power level of SFG. A software synchronous optical sampling system is constructed based on sum frequency generation (SFG) in periodically poled lithium niobate (PPLN). Five gigahertz of a non-return-to-zero (NRZ) data signal is sampled by sampling pulse with the repetition frequency of 29.31 MHz. The power of the SFG light is set at -23 dBm, and an eye diagram is successfully recovered. A band-pass filter is added before the sampling pulse is subjected to erbium-doped fiber amplifier to reduce gain competition and ensure a high power level of SFG.
Chinese Optics Letters
- Publication Date: Aug. 03, 2012
- Vol. 10, Issue 10, 100701 (2012)
Fiber nonlinearity mitigation by PAPR reduction in coherent optical OFDM systems via biased clipping OFDM
Yaohong Hao, Yuquan Li, Rong Wang, and Weiwei Huang
A new method incorporating biased clipping orthogonal frequency division multiplexing (OFDM) is presented, which mitigates fiber nonlinear effects in a long-haul coherent optical OFDM (CO-OFDM) system. Under the scheme of the method, the wanted signal carried by odd subcarriers is orthogonal to clipping noise and a Mach-Zehnder modulator (MZM) performs the optimal OFDM signal up-converter from the radio frequency (RF) domain to the optical domain. Analysis and simulation results show that fiber non-linear effects can be effectively mitigated by reducing the peak-to-average power ratio (PAPR) in biased clipping CO-OFDM system. The nonlinearity threshold (NLT) is improved by 5 dB with a reach of 240 km. With a fiber length up to 800 km, system Q value is improved by approximately 2.3, 1.2, and 0.6 dB at a chromatic dispersion of 6, 12, and 16 ps/(nm￠km), respectively. Additionally, system Q reaches the maximum when direct currect (DC) bias is equal to the mean value of the OFDM waveform. A new method incorporating biased clipping orthogonal frequency division multiplexing (OFDM) is presented, which mitigates fiber nonlinear effects in a long-haul coherent optical OFDM (CO-OFDM) system. Under the scheme of the method, the wanted signal carried by odd subcarriers is orthogonal to clipping noise and a Mach-Zehnder modulator (MZM) performs the optimal OFDM signal up-converter from the radio frequency (RF) domain to the optical domain. Analysis and simulation results show that fiber non-linear effects can be effectively mitigated by reducing the peak-to-average power ratio (PAPR) in biased clipping CO-OFDM system. The nonlinearity threshold (NLT) is improved by 5 dB with a reach of 240 km. With a fiber length up to 800 km, system Q value is improved by approximately 2.3, 1.2, and 0.6 dB at a chromatic dispersion of 6, 12, and 16 ps/(nm￠km), respectively. Additionally, system Q reaches the maximum when direct currect (DC) bias is equal to the mean value of the OFDM waveform.
Chinese Optics Letters
- Publication Date: Aug. 30, 2011
- Vol. 10, Issue 1, 010701 (2012)
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