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Swept source optical coherence tomography based on non-uniform discrete fourier transform

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Chinese Optics Letters 2009年第10期7卷 941-944页

作者：吴彤丁志华王凯王川 State key lab of modern optical Instrumentation Zhejiang University

A high-speed high-sensitivity swept source optical coherence tomography （SSOCT） system using a high speed swept laser source is developed. Non-uniform discrete fourier transform （NDFT） method is introduced in the SSOCT system for data processing. Frequency calibration method based on a Mach-Zender interferometer （MZI） and conventional data interpolation method is also adopted in the system for comparison. optical coherence tomography （OCT） images from SSOCT based on the NDFT method, the MZI method, and the interpolation method are illustrated. The axial resolution of the SSOCT based on the NDFT method is comparable to that of the SSOCT system using MZI calibration method and conventional data interpolation method. The SSOCT system based on the NDFT method can achieve higher signal intensity than that of the system based on the MZI calibration method and conventional data interpolation method because of the better utilization of the power of source.

关键词： Block codes Calibration Data processing Discrete Fourier transforms Integrated optoelectronics Interpolation optical tomography Tomography

Anomalous Variation of Beat Frequency in a Dual Frequency He-Ne Laser

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Chinese Physics Letters 2016年第2期33卷 51-54页

作者：刘维新孙明哲 Shandong Provincial key laboratory of optical astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong University

The beat frequency in a dual frequency He-Ne laser varies while the resonant cavity length is tuned. As to the laser with two longitudinal modes, the variation amplitude is commonly less than 500 kHz, proven by experiments and theories. This study reveals an anomalous variation of the beat frequency when a piece of element is put into the cavity and is aligned with the laser axis. Consequently the variation amplitude couM reach 22 MHz, several dozen times larger than that without the intra-cavity element. This cannot be explained only by laser mode pulling and pushing effects. Some influencing factors are investigated experimentally, including the tilted angle of the element and the distance between its surface and cavity mirror. The qualitative analysis is discussed, which agrees with the experimental results.

关键词： of on as it or Anomalous Variation of Beat Frequency in a Dual Frequency He-Ne Laser in is

Classification of stellar populations in globular clusters

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Research in astronomy and Astrophysics 2017年第5期17卷 107-112页

作者： Yue Wang Gang Zhao Hai-Ning Li key laboratory of optical astronomy National Astronomical Observatories Chinese Academy of Sciences School of astronomy and Space Science University of Chinese Academy of Sciences

Possessing multiple stellar populations has been accepted as a common feature of globular clusters（GCs）. Different stellar populations manifest themselves with different chemical features,e.g. the well-known O-Na anti-correlation. Generally, the first（primordial） population has O and Na abundances consistent with those of field stars with similar metallicity; while the second（polluted） population is identified by their Na overabundance and O deficiency. The fraction of the populations is an important constraint on the GC formation scenario. Several methods have been proposed for the classification of GC populations. Here we examine a criterion derived based on the distribution of Galactic field stars, which relies on Na abundance as a function of [Fe/H], to distinguish first and second stellar populations in GCs. By comparing the first population fractions of 17 GCs estimated by the field star criterion with those in the literature derived by methods related to individual GCs, we find that the field star criterion tends to overestimate the first population fractions. The population separation methods,which are related to an individual GC sample, are recommended because the diversity of GCs can be taken into consideration. Currently, more caution should be exercised if one wants to regard field stars as a reference for the identification of a GC population. However, further study on the connection between field stars and GCs populations is still needed.

关键词： stellar populations stars criterion distinguish scenario primordial abundance manifest constraint

Design of an augmented reality display based on polarization grating

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Chinese Physics B 2019年第7期28卷 216-221页

作者： Renjie Xia Changshun Wang Yujia Pan Tianyu Chen Ziyao Lyu Lili Sun State key laboratory of Advanced optical Communication Systems and Networks School of Physics and AstronomyShanghai Jiao Tong University

A new optical system for an augmented reality(AR) display is proposed in this *** optical system mainly includes a ray deflector, coupling input grating, optical waveguide, and coupling output *** the ray deflector and the coupling input grating are designed based on the diffraction characteristics of the polarization grating, and the coupling output grating is the Bragg reflection *** with other AR schemes, this AR optical system not only reduces the number of projections from two to one, but also improves the efficiency of light coupling into the optical *** energy loss is reduced by utilizing the single-order diffraction characteristics of the polarization grating in its coupling input *** light deflector uses the polarization selectivity of the polarization grating and the characteristics of the rotating light of the twisted nematic liquid crystal layer to realize beam *** working principle of the optical system is experimentally and theoretically demonstrated.

关键词： augmented reality polarization grating azo liquid crystal

Numerical Simulation of Bell Inequality＇s Violation Using optical Transverse Modes in Multimode Waveguides

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Chinese Physics Letters 2008年第7期25卷 2350-2353页

作者：符建高淑娟 State key lab of Modern optical Instrumentation Department of Optical Engineering Zhejiang University Hangzhou 310027

We numerically demonstrate that ＇mode-entangled states＇ based on the transverse modes of classical optical fields in multimode waveguides violate Bell＇s inequality. Numerically simulating the correlation measurement scheme of Bell＇s inequality, we obtain the normalized correlation functions of the intensity fluctuations for the two entangled classical fields. By using the correlation functions, the maximum violations of Bell＇s inequality are obtained. This implies that the two classical fields in the mode-entangled states, although spatially separated, present a nonlocal correlation.

关键词： BEAM-PROPAGATION METHOD QUANTUMLIKE FIELDS PHOTON MEDIA

Gaia calibrated UV luminous stars in LAMOST

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Research in astronomy and Astrophysics 2018年第12期18卷 123-130页

作者： Yu Bai Ji-Feng Liu Song Wang key laboratory of optical astronomy National Astronomical Observatories Chinese Academy of Sciences College of astronomy and Space Sciences University of Chinese Academy of Sciences

We take advantage of Gaia Data Release 2 to present 275 and 1774 ultraviolet luminous stars in the far ultraviolet(FUV) and near ultraviolet(NUV), *** stars exceed their expected values by 5σ with respect to over one million ultraviolet stars in the log g *** extinction is corrected with a 3 D dust *** order to limit the Lutz-Kelker bias to an insignificant level, we select stars with relative uncertainties in luminosity less than 40% and trigonometric parallaxes less than 20%.We cross-identified our sample with the catalogs of RR Lyr stars and possible white dwarf main-sequence binaries, and find they compose ～62% and ～16% of our sample in the FUV and NUV, *** catalog provides a unique sample to study stellar activity, spectrally unresolved compact main-sequence binaries and variable stars.

关键词： stars:activity stars:general ultraviolet:stars

The age of the halo as determined from halo field stars

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Research in astronomy and Astrophysics 2016年第3期16卷 73-80页

作者： Jin-Cheng Guo Chao Liu Ji-Feng Liu key laboratory of optical astronomy National Astronomical Observatories Chinese Academy of Sciences College of astronomy and Space Sciences University of Chinese Academy of Sciences

The age of the Galactic halo is a critical parameter that can constrain the origin of the stellar halo. In general, the Galactic stellar halo is believed to be very old. However, different independent measurements and techniques based on various types of stars are required so that the age estimates of the Galactic halo are accurate, robust, and reliable. In this work, we provide a novel approach to determine the age of the halo with turn-off stars. We first carefully select 63 field halo turn-off stars from the literature. Then, we compare them with the GARSTEC model, which takes the process of atomic diffusion into account in the B - V vs. metallicity plane. Finally, we run Monte Carlo simulations to consider the uncertainty of the color index and obtain the age of 10.5 ± 1.5 Gyr. This result is in agreement with previous studies. Future works are needed to collect more turn-off samples with more accurate photometry to reduce the uncertainty of the age.

关键词： galaxies: halos -- Galaxy: evolution -- stars: kinematics and dynamics

Evaluation of Slow Light Periodic Signals Considering the Distortion in EDF

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Chinese Physics Letters 2014年第3期31卷 82-85页

作者： WANG WU Chong-Qing WANG Zhi LIU Guo-Dong LIU Lan-Lan SUN Zhen-Chao Institute of optical Information and key lab of Luminescence and optical Information Technology Beijing Jiaotong University Beijing 100044

Based on the fundamental harmonic phase delay, a new definition of fundamental harmonic fractional delay （FHFD） is proposed to evaluate slow light with the consideration of signal distortion, to eliminate the dependence on the choice of the reference point. By solving the rate equation of erbium-doped fiber （EDF）, it is shown that the slow light always accompanies the signal distortion when the periodic signal propagates in EDF, and FHFD depends on the signal distortion, as well as the average input power, the modulation depth and the length of EDF. The results of simulations and experiments indicate that the definition of FHFD is reasonable and effective to evaluate the slow light of periodic signals.

关键词： Signal distortion

Broad-Band All-optical Wavelength Conversion of Differential Phase-Shift keyed Signal Using an SOA-Based Nonlinear Polarization Switch

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Chinese Physics Letters 2016年第3期33卷 44-47页

作者：毛雅亚盛新志吴重庆余贶碌 Institute of optical Information and Key Lab of Luminescence and Optical Information Technology(Ministry of Education)Beijing Jiaotong University

Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.

关键词： SOA for length as is of Broad-Band All-optical Wavelength Conversion of Differential Phase-Shift keyed Signal Using an SOA-Based Nonlinear Polarization Switch DPSK