Guo Qi   Liu Tian   Wang Xiaoqian   Zheng Zhi-gang   Kudreyko Aleksey   Zhao Huijie   CHIGRINOV Vladimir G.   KWOK Hoi S.  

      摘要 + 此论文可免费阅读 (可能需要登录)

Diffractive optical elements attract considerable attention mainly due to its potential applications in imaging coding, optical sensing, etc. Application of ferroelectric liquid crystals (FLCs) with the photo-alignment technology in diffractive optical elements results in high efficiency and fast response time. In this study we demonstrate a circular Dammann grating (CDG) with the diffraction efficiency of 84.5%. The achieved response time of 64 µs is approximately two-order of magnitude faster than the existing response time of nematic liquid crystal devices. By applying low electric field (V=6 V) to the FLC CDG, it is switched between the eight-order diffractive state and the transmittive diffraction-free state.

       PDF全文 (下载：0)        Chinese Optics Letters ，2020年第18卷第8期 pp.08      

Sui Xiaomeng   He Zehao   Zhang Hao   Cao Liangcai   Chu Daping   Jin Guofan  

      摘要 + 此论文可免费阅读 (可能需要登录)

This letter describes an approach to encode complex-amplitude light waves with spatiotemporal double-phase holograms (DPHs) for overcoming the limit of the space-bandwidth product (SBP) delivered by existing methods. To construct DPHs, two spatially macro-pixel encoded phase components are employed in the SBP-preserved resampling of complex holograms. Four generated sub-DPHs are displayed sequentially in time for high-quality holographic image reconstruction without reducing the image size or discarding any image terms when the DPHs are interweaved. The reconstructed holographic images contain more details and less speckle noise, with their signal-to-noise ratio and structure similarity index being improved by 14.64% and 78.79%, respectively.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

Qi Wen-Rong   Liu Rui   Kong Ling-Jun   Wang Zhou-Xiang   Huang Shuang-Yin   Tu Chenghou   Li Yongnan   Wang Huitian  

      摘要 + 此论文可免费阅读 (可能需要登录)

Optical orbital angular momentum (OAM) is a special property of photons and has evoked research onto the light-matter interaction in both classical and quantum regimes. In classical, OAM is related to an optical vortex with a helical phase structure. In quantum, photons with a twisted or helical phase structure will carry a quantized OAM. To our knowledge, however, so far no experiment has demonstrated the fundamental property of the OAM at single photon level. In this Letter, we have demonstrated the average photon trajectories of twisted photons in a double-slit interference. We have experimentally captured the double-slit interference process of twisted photons by a time-gated intensified charge-coupled device camera, which is trigged by a heralded detection. Our work provides a new perspectives for understanding the micro-behaviours of twisted particles and enables new application in imaging and sensing.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

MORENO Yarien   Song Qingguo   Xing Zhikun   Sun Yuezhen   Yan Zhijun  

      摘要 + 此论文可免费阅读 (可能需要登录)

In this paper, we propose a hybrid tilted fiber gratings (polarizing grating and tilted fiber Bragg grating) based surface plasmon resonance (SPR) sensor. The hybrid tilted fiber gratings, consisted of a polarizing grating and tilted fiber Bragg grating (TFBG), is fabricated in a single-mode fiber in series by using UV inscription technique, in which the TFBG could generate a dense cladding mode resonance to excite SPR and polarizing grating could filter out S-polarization cladding mode of TFBG. Such proposed hybrid tilted fiber gratings could greatly simplify the interrogation system of the TFBG-based SPR sensor. The experiment results show that the hybrid tilted fiber gratings-based SPR sensor has the refractive index sensitivity of 522.8 nm/RIU. Finally, by using the proposed sensor, we have achieved the hemoglobin (Hb) concentrations detection within a sensing range from 0.1 mg/ml to 1.0 mg/ml and the sensitivity of 8.144 nm/(mg/ml).

       PDF全文 (下载：1)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

Liu Tiecheng   Hu Jingpei   Zhu Linglin   Zhou Ruyi   Zhang Chong   Wang Qinhua   zeng Aijun   Huang Huijie  

      摘要 + 此论文可免费阅读 (可能需要登录)

We present a kind of large effective aperture metalens based on optical sparse aperture (OSA) system. Each subaperture of the system is a metalens which is comprised of just a thin Au film with patterned subwavelength rectangular annular arrays on a SiO2 substrate and has a numerical aperture 0.46 with a diameter of 21.6μm. Ring6 design was selected to enlarge the effective aperture and enhance the spatial resolution. Compared with the absent in mid-frequency and high-frequency in modulation transfer function of individual metalens, Ring6 can offer a full-frequency band and show a better restored image quality by using Tikhonov regularization.

       PDF全文 (下载：1)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

guo meng   He Hongbo   Yi Kui   Shao Shuying   Hu Guohang   Shao Jianda  

      摘要 + 此论文可免费阅读 (可能需要登录)

Ultrathin Ge films with thickness of about 15nm at different deposition temperatures were prepared by electron beam evaporation. Spectral measurement results showed that as the deposition temperature increases from 100 ° C to 300 ° C, the greater decrease in the transmittance of the films in the wavelength range from 350 nm to 2100 nm. After annealing in air at 500℃,tThe transmittance significantly increased and approached that of uncoated fused quartz after annealing. Based on Tauc plot method and Mott-Davis-Paracrystalline model, the optical band gap of Ge films was calculated and interpreted, the difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing, while has little effect on the optical band gap after annealing. Furthermore, due to oxidation of Ge films, the optical band gap was significantly increased to ~5.7eV after annealing.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

Chen Yiwei   He yi   Wang Jing   Li Wanyue   Xing Lina   Gao Feng   Shi Guohua  

      摘要 + 此论文可免费阅读 (可能需要登录)

An automated superpixels identification/mosaicking method is presented for the analysis of cone photoreceptor cells with the use of adaptive optics scanning laser ophthalmoscope (AO-SLO) images. This is an image oversegmentation method used for the identification and mosaicking of cone photoreceptor cells in AO-SLO images. It includes image denoising, estimation of the cone photoreceptor cell number, superpixels segmentation, merging of superpixels, and final identification and mosaicking processing steps. The effectiveness of the presented method was confirmed based on its comparison with a manual method with precision, recall and F1-score of 77.3%, 95.2% and 85.3%, respectively.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

Wang Cong   zhao mengfei   Hao Qianqian   Zou Zhengting   Fan xiuwei   Liu Jie   su liangbi  

      摘要 + 此论文可免费阅读 (可能需要登录)

We report on laser diode (LD) pumped passively Q-switched Yb,Gd:SrF₂ lasers with high single-pulse energy for the first time. In addition, a stable Q-switched laser based on a Cr⁴⁺:YAG saturable absorber was demonstrated. The maximum output power of Q-switched obtained was 495 mW, with a pulse width and pulse repetition rate of 233 ns and 1.238 kHz, respectively. The corresponding single-pulse energy and the peak power were as high as 400 µJ and 1.714 kW. The laser was operated at a TEM₀₀ mode, and the beam quality was near-diffraction-limited.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第10期 pp.10      

Chen Yung-Fu   Lee C. C.   Wang C. H.   Hsieh M. X.  

      摘要 + 此论文可免费阅读 (可能需要登录)

The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring the laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite-Gaussian (HG) and Laguerre-Gaussian (LG) modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite-Laguerre-Gaussian (HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of SU(2) in the Jordan–Schwinger map. Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials. Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes but also a pedagogical insight into quantum physics.

       PDF全文 (下载：5)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Xu Long   Zhu Ruiqi   Xu Caixia  

      摘要 + 此论文可免费阅读 (可能需要登录)

Broadband photochromic effect on pure and rare earth doped lead lanthanum zirconate titanate (PLZT) ceramics was studied under the illumination of ultraviolet light at 360 nm. Photocarriers trapping and detrapping processes of thermal disconnected traps played the vital role in both darkening and bleaching process. The interaction between photocarrier traps and rare earth ions energy levels has been demonstrated, which influenced the photochromatic darkening performance greatly. The transformation of photoluminescence spectra in Er3+ doped PLZT ceramics also improved the physical picture of the trap’s distribution of the materials. This work could be used to modulate the photoluminescence and lasing behavior.

       PDF全文 (下载：1)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Xiao Junyu   Xiao Ruiwen   Zhang Rongxuan   Shen Zhixiong   Hu Wei   Wang Lei   Lu Yanqing  

      摘要 + 此论文可免费阅读 (可能需要登录)

We demonstrate a tunable terahertz (THz) absorber based on an indium tin oxide (ITO) metamaterial. The upper ITO cross-shaped metasurface with different arm lengths is fabricated by femtosecond laser etching directly. The thickness of the middle dielectric layer is only 60 μm which makes the absorber very transparent and flexible. The experimental results show the THz resonant peaks have high-performance near 1 THz. By setting spacers of different thicknesses between the middle layer and the ITO mirror, a new type of tunable THz absorber is proposed. Its absorption peak frequency can be continuously adjusted from 0.92 to 1.04 THz between TE and TM polarization. This transparent THz metamaterial absorber is expected to be widely used in THz imaging, sensing, and biological detection.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Wang Gao   Zheng Huaibin   Tang Zhiguo   He Yuchen   Zhou Yu   Chen Hui   Liu Jianbin   Yuan Yuan   Li Fuli   Xu Zhuo  

      摘要 + 此论文可免费阅读 (可能需要登录)

A new architecture, naked-eye ghost imaging via photoelectric-feedback, is developed, which avoids computer algorithm processing. Instead, the proposed scheme uses a photoelectric-feedback-loop to firstly realize the correlation (multiplication) process of the traditional ghost imaging system. Then, the vision persistence effect of the naked-eye is exploited to implement the integral process and to generate negative images. Two kinds of feed-back circuits, the digital circuit and the analog circuit, are presented, which can achieve a feedback operation. Based on this design, a high-contrast real-time imaging of moving objects is obtained via a special pattern-scanning architecture on a low-speed light-modulation mask.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Lu Shaowen   Zhou Yu   Zhu Funan   Hou Xia   Hu Shengnan   Sun Jianfeng   Yang Yan   Zhang Xiaoxi   Zhu Ren   Zhu Xiaolei   Chen Weibiao  

      摘要 + 此论文可免费阅读 (可能需要登录)

We analyze a feasible high-sensitivity homodyne coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK). A fourth-power phase-lock loop based on digital look-up table is used. Considering the nonnegligible loop delay, we optimize the loop natural frequency. Without error correction coding, a sensitivity of -37dBm/-35dBm are achieved while the bit error rate is below 10-9 at 2.5Gbaud/5Gbaud rate. For the QPSK communication system, the bit rate is twice the baud rate.The loop natural frequency is 0.645Mrad/s and the minimized steady-state phase error standard deviation is 3.83°.

       PDF全文 (下载：4)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Kwiatkowski Jacek  

      摘要 + 此论文可免费阅读 (可能需要登录)

Detailed power and spectral analysis of a diode-pumped c-cut Pbnm 3 at.% Tm:YAP laser in a continuous wave (CW) operation is presented. The laser was experimentally examined in terms of the dependence on the transmittance and radius of curvature of the output coupling mirrors. At room temperature, for an output coupling transmission of 10.8%, the maximum output power of 6.35 W was obtained under a total absorbed pump power of 13.67 W with an optical-to-optical conversion efficiency of 46.5%. The highest slope efficiency of 60.4% was indicated. A detailed spectral analysis was presented. For its dependence on output coupler transmission, the Tm:YAP laser generates wavelengths at approximately 1940 nm or 1990 nm.

       PDF全文 (下载：13)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

hu junjiang   Zhang Liyab   Ni Chuan   Men Tao   Wen Lei   Chen You   Tang Jingping   Wang Biao   Chen Bin   chen wei   Hu Lili  

      摘要 + 此论文可免费阅读 (可能需要登录)

A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at cladding interface was measured using the technique. Residual reflectance could be in the order of 10-5 by matching refractive index of Nd:glass, polymer, cladding glass, and eliminating defects in adhesive layer. Residual reflection spatial distribution appears to be similar with Newton rings due to the edge surface flatness. Relationship between residual reflectance and edge surface flatness was discussed, and results revealed the significance of the edge surface flatness is very important during cladding process.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Sun Hao   Tang Yuhua   Hu Yuze   You Jie   Liu Hengzhu   Zheng Xin  

      摘要 + 此论文可免费阅读 (可能需要登录)

We experimentally demonstrate for the first time, an active all-optical ultrafast modulation of electromagnetically induced transparency like effect, in a hybrid device of sapphire/Si/metamaterial. From numerically simulations, it can be deducted that the tuning process is attributed to the coupling between the dark mode existed in split-ring resonators and the bright mode existed in cut wire resonators. The transmission amplitude modulation is accompanied with the slow-light effect. In addition, the ultrafast formation process is measured to be as fast as 2 ps. This work should make an important contribution to novel chip-scale photonic devices and terahertz communications.

       PDF全文 (下载：1)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Shi Jingzhang   Zhang Fangzheng   Ben De   Pan Shilong  

      摘要 + 此论文可免费阅读 (可能需要登录)

We propose a photonic-assisted single system for measuring the frequency and phase noise of microwave signals in a large spectral range. Both the frequency and phase noise to be measured are extracted from the phase difference between the signal under test and its replica delayed by a span of fiber and a variable optical delay line (VODL). The system calibration, frequency measurement, and phase noise measurement are performed by adjusting the VODL at different working modes. Accurate frequency and phase noise measurement for microwave signals in a large frequency range from 5 to 50 GHz is experimentally demonstrated.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Dong Junqing   Li Qinghui   Hu Yongqing  

      摘要 + 此论文可免费阅读 (可能需要登录)

In this letter, we report a combination of non-invasive analysis of the cross-section structure, phase and chemical composition combining optical coherence tomography (OCT) with spectroscopic methods such as X‐ray analytical microscope (μ-XRF) and micro-Raman spectroscopy (μ-RS), which allow us to effectively and conveniently identify the colorants used for each color region and the glass-making process of an ancient multicolored stratified glass eye bead. The results reveal that the sophisticated colors of the glass bead arise from the transition metals and chemical compound crystals deliberately added in the same base glass and carefully adjusted by the glass-maker to obtain four colors. We also propose and discuss the provenance of the glass bead. It was probably introduced to the mainland of China through the Northern Silk Road from Egypt or the Eastern Mediterranean areas about 1400 years ago. The combined multi-analytical technique is the promising approach for precious cultural heritage research.

       PDF全文 (下载：15)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Jia Tianqing   Cao Kaiqiang   Chen Long   Cheng Ke   Sun Zhenrong  

      摘要 + 此论文可免费阅读 (可能需要登录)

Inhomogeneity and low efficiency are two important factors that hinder the wide application of laser-induced periodic surface structures. Two-beam interference is commonly used to fabricate gratings with interference periods. This study reports regular and uniform periodic ripples fabricated efficiently by the interference of two femtosecond laser beams via cylindrical lens. The interference period is adjusted to be an integer multiple of the wavelength of surface plasmon polariton (SPP). Regular and uniform subwavelength nanogratings (RUSNGs) on a silicon wafer of diameter 100 mm are fabricated with a scanning velocity of 6–9 mm/s. Bright and pure colors (including purple, blue and red) are demonstrated on different patterns covered with RUSNGs.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Chen Bin   Long Jin-Bao   Xie Hong-Tai   Li Chen-Yang   Chen Luo-Kan   Jiang Bo-Nan   Chen Shuai  

      摘要 + 此论文可免费阅读 (可能需要登录)

The gravimeter based on atom interferometry has potentially wide applications on building the gravity networks, geophysics as well as gravity assisted navigation. Here, we demonstrate experimentally a portable atomic gravimeter operating in the noisy urban environment. Despite the influence of noisy external vibrations, our portable atomic gravimeter reaches a sensitivity as good as 65µGal/sqrt(Hz) and a resolution of 1.1µGal after 4000 s integration, being comparable to state-ofthe-art atomic gravimeters. Our achievement paves the way for bring the portable atomic gravimeter to field applications.

       PDF全文 (下载：6)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Khadr Monette   Elgala Hany  

      摘要 + 此论文可免费阅读 (可能需要登录)

A plethora of physical-layer techniques aim to enhance the performance of communication systems in several ways. Spectral efficiency and security are on the top of the list of enhancements; however, both are isolated and antagonistic islands of research. Augmented communications (ACom) is introduced in this letter as the first technique that aims to combine these two enhancements in visible light communications (VLC). The dividends of the proposed concept are demonstrated via simulations and the performance is experimentally validated. Results show that ACom can simultaneously provide both spectral efficiency and resistance to eavesdropping, while introducing minimal signal-to-noise ratio penalties.

       PDF全文 (下载：0)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Zhang Lei   Wang Lin   Wu Yanqing   Tai Renzhong  

      摘要 + 此论文可免费阅读 (可能需要登录)

In a single nanoscale device, surface-plasmon polaritons (SPPs) have potential to match the different length scales associated with photonics and electronics. In this work, we propose an accurate design of a plasmonic metasurface Luneburg lens (PMLL) accommodating SPPs. The simulations indicate that the fullwidth at half-maximum (FWHM) is 0.42 μm, and the focus efficiency is 78%. The characters of a PMLL have robustness to manufacturing errors. The PMLL is applied in a 10 μm long compact coupler model which couple the SPPs to the 40 nm-wide output waveguide. The couple efficiency is higher than a conventional taper coupler in a broad bandwidth. The design is compatible with standard lithography technology.

       PDF全文 (下载：0)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

y Yang   liu yang   wu yan   li ting   fan fan   Wen Shuangchun   Huang huihui  

      摘要 + 此论文可免费阅读 (可能需要登录)

Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this paper, we raise a new way to realize optical edge detection. This design is based on two liquid crystal polarization gratings with a period of 2.2 mm, which function as a spatial differentiator. We experimentally demonstrate broadband optical detection and real-time adjustable resolution. The proposed method takes advantages of convenient to use, simple fabrication process, and real-time tunable resolution. It may guide more significant applications in optical field, and other practical scenarios like machine vision in computer.

       PDF全文 (下载：2)        Chinese Optics Letters ，2020年第18卷第9期 pp.09      

Liang 方亮 Fang   Gan Xuetao   Zhao Jianlin  

      摘要 + 此论文可免费阅读 (可能需要登录)

Planar photonic crystal (PPC) cavities with high quality (Q) factors were currently designed by missing or moving air-holes. Here, we propose that cutting air-holes in PPC into semicircles could be considered as another strategy to realize and optimize cavities, presenting superiorities over cavities with missed or moved air-holes in higher Q factor and smaller mode volume (Vmode). Examples are demonstrated: (1) In a PPC lattice, cutting two adjacent air-holes promises cavity modes with Q exceeding 200,500 and ultrasmall mode volumes Vmode<0.329(λ/2n)3; (2) In a PPC waveguide, cutting two air-holes on opposite sides of the waveguide supports cavity modes with Q exceeding 104,600 and Vmode<1.22(λ/2n)3; (3) Cutting the two air-holes at the edges of a L3-type PPC cavity, the Q factor is optimized from 5,500 to 124,700 with almost constant Vmode. The concept of cutting air-holes to introduce defects in PPC promises the design of PPC waveguides with engineered transmission loss and dispersion.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第6期 pp.06      

Shu Qin   He Xiuli   Wang Chang   Yang Yunxiu  

      摘要 + 此论文可免费阅读 (可能需要登录)

This Point clouds scanned by 3D laser scanner may be affine transformed when the size and posture of the objects being scanned are different. This type of problem is common, but few algorithms can solve it. Therefore, this paper proposes a parallel registration algorithm. The algorithm eliminates the effects of the affine matrix in the point cloud, based on a simple whitening operation. Moreover, it also has strong anti-noise performance. The algorithm proposed in this paper is not only simple in structure, but also shows excellent effects in practical applications and simulations.

       PDF全文 (下载：0)        Chinese Optics Letters ，2020年第18卷第7期 pp.07      

Wang Shuang   Zhou Jie   JIANG J.F.   Liu Kun   Han Qun   Duan Yanan   Wang Rundong   Liu Tiegen  

      摘要 + 此论文可免费阅读 (可能需要登录)

A multi-channel synchronous demodulation system of polarized low-coherence interferometer (PLCI) based on a matrix charge-coupled-device (CCD) is proposed and demonstrated. By using special designs, the system allows the signals from different channels to be received and demodulated synchronously. Multi-channel air pressure experiments were implemented to verify the effectiveness of the proposed system. The experiment results showed that the Fabry-Perot (F-P) sensors could be demodulated synchronously with high tolerance for light sources and sensors which indicated any sensor and light source that can be demodulated by PLCI were allowed to be employed, leading to a wide application in the field of multi-channel synchronous measurement.

       PDF全文 (下载：3)        Chinese Optics Letters ，2020年第18卷第7期 pp.07      

Dai Pan   Zhou Yu   Wang Leilei   Liu Shangjing   Zhang Xuping   Chen Xiangfei  

      摘要 + 此论文可免费阅读 (可能需要登录)

Until now, a high-efficiency demodulation method for fiber Bragg grating (FBG) sensors is still a challenge. In this paper, by employing multi-peak FBGs, a FBG sensor with partial wavelength scan is proposed and initially demonstrated. By demodulating a near-symmetrical multi-peak FBG and an asymmetrical multi-peak FBG in the strain experiment, the sensor sensitivity of 1.02 pm/με and 1.01 pm/με are measured for the interrogation system, respectively. The average demodulation deviations for the two sensors are 1.81% and 0.4%, respectively. The proposed method is expected to realize high-efficiency and low-cost FBG interrogators.

       PDF全文 (下载：4)        Chinese Optics Letters ，2020年第18卷第7期 pp.07      

Hua Shijia   Du Kang   Wang Heng   Zhang Wending   Mei Ting   Dogheche Elhadj  

      摘要 + 此论文可免费阅读 (可能需要登录)

Goodness of fit is demonstrated for theoretical calculation of z-scan data based on beam propagating in the nonlinear medium and Fresnel-Kirchhoff diffraction integral in experiments with high nonlinear refraction and absorption. The constancy of nonlinear optical parameters is achieved regardless of sample thickness and laser intensity, which clarifies the physical significance of optical parameters. We have obtained γ = 2.0 × 10-19 m2/W and β = 5.0 × 10-13 m/W for carbon disulfide excited by pulsed laser at 800nm with pulse duration 35 femtoseconds, which are independent of sample thickness and laser intensity. Affirming constancy of the extracted parameters to the incident light intensity may become a practice to verify the goodness of the z-scan experiment.

       PDF全文 (下载：0)        Chinese Optics Letters ，2020年第18卷第7期 pp.07      

Shi Weiyi   Deng Weimin   Liu Weinan   Zhuang Zepeng   Fan Zhibin   Dong Jianwen  

      摘要 + 此论文可免费阅读 (可能需要登录)

In this Letter, we propose a metagrating consisting of simple rectangle bars for nearly-unity anomalous diffraction with large deflection angle. The analysis by the scattering-matrix method shows that such exceptional beam steering derives from the couplings of the two lowest propagation waveguide-array-modes and their constructive interferences. Besides, the tolerance of the incident angle for high diffraction efficiency (e.g. > 90%) is within the range of 33°. We also discuss that such advantage can survive after considering the reasonable loss and dispersion. We envision that the proposed strategy may have wide use in the field of high-performance wavefront shaping applications.

       PDF全文 (下载：8)        Chinese Optics Letters ，2020年第18卷第7期 pp.07      

Huang Aiwang   Chen Danni   Li Heng   Tang Dexiang   Yu Bin   Li Jia   Qu Junle  

      摘要 + 此论文可免费阅读 (可能需要登录)

Tracking moving particles in cells by single particle tracking (SPT) is an important optical approach widely used in biological research. In order to track multiple particles within a whole cell simultaneously, a parallel tracking approach with large depth of field was put forward. It was based on distorted grating and dual-objective bifocal imaging, making use of distorted grating to expand depth of field, dual-objective to gather as many photons as possible, and bifocal plane imaging to realize three-dimensional localization. Simulation of parallel tracking of two particles moving along z axis demonstrated that even when the two are axially separated by 10 μm, they can both be localized simultaneously with transversal precision better than 5nm and axial precision better than 20nm.

       PDF全文 (下载：4)        Chinese Optics Letters ，2020年第18卷第7期 pp.07