Cheng Haijuan   Dong Miao   Tan Qinwen   Meng Linghai   Cai Yi   Jiang Jie   Yang Weisheng   Zhong Haizheng   Wang Lingxue  

      摘要 + 此论文可免费阅读 (可能需要登录)

A gradient-index Reuleaux-triangle-shaped hole array was fabricated on germanium by nanoimprint lithography and inductively coupled plasma processing as a broadband mid-IR antireflective surface. The interaction between the { 111} planes of cubic crystalline Ge and a circular mold successfully produced an orderly and periodically distributed Reuleaux-triangle-shaped hole array. As a result, the average transmittance increased 15.67% over the waveband at 3–12 μm and maintain stable at the incidence angle of up to 60°. The vertices of the Reuleaux triangle showed local enhancement of the electric field intensities due to interference of the incident and reflected radiation fields. It was also found that nonuniform hole depths acted to modulate the transmittance over the 3–12 μm waveband.

       PDF全文 (下载：3)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

Shen Yijiang   Peng Fei   Huang Xiaoyan   Zhang Zhenrong  

      摘要 + 此论文可免费阅读 (可能需要登录)

We develop a source mask co-optimization framework incorporating the minimization of edge placement error (EPE) and process variability band (PV Band) into the cost function to compensate simultaneously for the image distortion and the increasingly pronounced lithographic process conditions. Explicit differentiable functions of the EPE and the PV Band are presented and adaptive gradient methods are applied to break symmetry to escape suboptimial local minima. Dependence on the initial mask conditions is also investigated. Simulation results demonstrate the efficacy of the proposed SMO approach in pattern fidelity improvement, process robustness enhancement and almost unaffected performance with random initial masks.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

Huang Xuan   Yang Fang   Song Jian  

      摘要 + 此论文可免费阅读 (可能需要登录)

In this paper, the current research of underwater optical wireless communication (UWOC) network is reviewed first. Hybrid laser diode (LD) and light-emitting diode (LED) based UWOC system is then proposed and investigated, in which a hybrid cluster-based networking with mobility restricted nodes is utilized to improve both the life cycle and throughput of UWOC network. Moreover, the LEDs are utilized for the coarse alignment while the LDs are used for high precision positioning to reduce the difficulty of optical alignment. Finally, challenges and trends for UWOC are pointed out to provide some insight for the potential future work of researchers.

       PDF全文 (下载：3)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Zheng Qiaoyu   Li Yang   Wu Wenjuan   Zou Jun   Yang Bobo   Shi Mingming  

      摘要 + 此论文可免费阅读 (可能需要登录)

The phosphor in glass (PiG) employing Ce: YAG-doped boro-bismuthate glass via low-temperature co-sintering technology was successfully prepared, using Bi2O3- B2O3-ZnO glass as base material. The photoluminescence (PL) of PiG co-sintered at times ranging from 20 min to 60 min for 700 °C was investigated. As a result, the relative PL intensity of PiG under a reducing atmosphere of CO showed significantly enhanced about 7-14 times than that under air atmosphere sintering for 20-50 min. The photoluminescence intensity decreased gradually with the co-sintering time, which may be due to the corrosion of the YAG lattice structure.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Xu Jianxun   Jiang Ming   Chen Yufa  

      摘要 + 此论文可免费阅读 (可能需要登录)

High-rate techniques, such as optical orthogonal frequency division multiplexing (O-OFDM) and color shift keying (CSK), have been proposed for visible light communication (VLC). To fully exploit their advantages, in this letter we design a modulation scheme called rotated polarity-modulation (RPM) aided complex CSK (CCSK) for O-OFDM based VLC systems, and derive its theoretical bit error rate (BER) and an optimal scaling factor. Analytical and simulation results show that in comparison to the existing schemes, the new RPM-CCSK-OFDM system offers an improved link performance and data rate under a modest complexity. It can also be applied to VLC systems equipped with different types of LED devices, thus enabling flexible deployments.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Zhang Lu   Zhang Wendong   Zhang Shougang   Yan Shu-Bin  

      摘要 + 此论文可免费阅读 (可能需要登录)

Vapor cell provides a well-controlled and stable inner atmosphere for atomic sensors, such as atomic gyroscopes, atomic magnetometers and atomic clocks and its hermeticity affects the stability and aging of atomic sensors. We present the micro-fabrication of a MEMS wafer-level hermit vapor cell based on deep reactive ion etching and vacuum anodic-bonding technology. Anodic bonding process with the voltage increasing in steps of 200 V, had a critical influence on vapor cell hermeticity. Further, the silicon-glass bonding surface was experimentally investigated by SEM, which illustrated that there were no visual cracks and defects in the bonding surface. The leak rate was measured using helium leak detector. The result shows that the vapor cells with different optical cavity lengths comply with the MIL-STD-883E standard (5×10-8 mbar.l/s). Moreover, D2 absorption spectroscopy was characterized via optical-absorption. The bonding strength was determined to be 13 MPa, which further verified the quality of the vapor cells.

       PDF全文 (下载：5)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Li Yangliang   Shen Chao   Shao Li   Zhang Yujun  

      摘要 + 此论文可免费阅读 (可能需要登录)

Particle ejection is an important process during laser-induced exit surface damage in fused silica. Huge quantity of ejected particles, large ejection velocity and long ejection duration make this phenomenon difficult to be directly observed. An in situ two-frame shadowgraphy system combining with a digital particle recognition algorithm was employed to capture the transient ejecting images and obtain the particle parameters. The experimental system is based on the principle of polarization splitting and can capture two images at each damage event. By combing multiple similar damage events at different time delays, the timeline of ejecting evolution can be obtained. Particle recognition is achieved by an adaptively regularized kernel-based fuzzy C-means algorithm based on grey wolf optimizer. This algorithm overcomes the shortcoming of adaptively regularized kernel-based fuzzy C-means algorithm easily falling into local optimum and can resist strong image noises including diffraction pattern, laser speckle and motion artifact. This system is able to capture particles ejected after 600 ns with a time resolution of 6 ns and spatial resolution better than 5 μm under the particle recognition accuracy of 100%.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

He Qiang   Wang fan   Lin Zhiquan   Shao Chongyun   Wang Meng   Wang Shikai   Yu Chunlei   Hu Lili  

      摘要 + 此论文可免费阅读 (可能需要登录)

Using a heavily erbium doped aluminosilicate fiber prepared by sol-gel method combined with high temperature sintering, the temperature dependence of spectrum around 1.55nm band and single mode fiber laser properties were investigated respectively. The absorption cross section increases 29.2% at ~1558nm with temperature increasing from 20℃ to 140℃, while the emission cross section increase 4.3% slight. In addition, the laser slope of the EDF at 1558nm decreases 4.4% from 10.8% to 6.4 with the temperature increasing from 18℃ to 440℃. Meanwhile, an experiment lasting 3 hours proves that the fiber laser has excellent stability below 440℃.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Qian Jinwang   Zheng Zhennan   Lei Mingzheng   Song Chunqi   huang shanguo   Gao Xinlu  

      摘要 + 此论文可免费阅读 (可能需要登录)

A complex-coefficient microwave photonic filter with continuous tunability is proposed and demonstrated, which has a compact structure and stable performance without splitting the optical path and tuning the polarization state. By only controlling the DC biases of the modulator, the amplitudes and the phases of the filter taps can both be tuned. The phase difference between the two filter taps covers a full 360° range from 10 GHz to 32 GHz. Frequency responses of the proposed filter are measured within 10-20 GHz with different center frequency.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Srivastava Vibhu   Mishra Prateek   Sunny Sunny  

      摘要 + 此论文可免费阅读 (可能需要登录)

The impulse response for a phase-change material Ge2Sb2Te5 (GST) based photodetector integrated with SOI waveguide is simulated using finite difference time domain. The current is calculated by solving the drift-diffusion model for a short pulse (~10 fs) excitation for both of the stable phases. FWHM values of less than 1 ps are found in the investigation. The crystalline-GST has higher 3dB BW than the amorphous-GST at 1550 nm wavelength with responsivities of 21 A/W and 18.5 A/W, respectively, for 150nm thick GST layer biased at 2 V. Broad spectrum can be utilized by tuning the device using phase-change property of material in the near infra-red region.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第10期 pp.10      

Wang Fang   Deng Xuewei   Liquan Wang   Li Fuquan   Han Wei   Zhou Wei   Huang Xiaoxia   Huaiwen Guo   Qihua Zhu  

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Fifth harmonic generation (5th HG) of Nd: glass laser is an effective way to acquire high-energy coherent deep-ultraviolet radiation near 200 nm. In this work, cascade generation of the fifth harmonic of Nd: glass laser in a 5mm ADP crystal was investigated, and maximum conversion efficiency of 14% and large angular acceptance of 45 mrad were demonstrated at non-critical phase-matching temperature of -75.1℃. However, as the results reveal, the temperature sensitivity and nonlinear absorption would hinder its high-energy application. As for it, based on the complementary relationship of angular and temperature in the phase-matching condition, an upgraded focusing 5thHG design coupled with cylindrical temperature distribution scheme was proposed. By this upgraded focusing design, more than the improving of the conversion efficiency, the output 5ω near-field intensity distribution turns to be insensitive to the temperature gradient. Potentially, this idea can be applied for many other frequency conversion schemes such as high-repetition frequency lasers which have similar temperature gradient problems.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

kang minqiang   Deng Ying   Yan xiongwei   Zeng Xiaoming   Guo Yangwu   Yao Jiyong   Zeng Fa   ZHENG Jiangang   Zhou Kainan   Qu Chongbing   Su Jingqin   Zhu Qihua  

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We report an efficient mid-infrared extracavity optical parametric oscillator (OPO) based on the nonlinear crystal BaGa4Se7 pumped by a diode-side-pumped Q-switched Nd:YAG laser. The maximum pulse energy of 1.03 mJ at 4.25 μm is obtained with the repetition rate of 10 Hz and pulse width of 12.6 ns when the pump energy was 13.5 mJ, corresponding to an optical-to-optical conversion efficiency of 7.6% from 1.064μm to 4.25 μm. And the idler wave slope convertion efficency was 12%. To our best knowledge, it is the highest reported conversion efficiency for the compact BaGa4Se7 OPO driven by the Nd:YAG laser.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

Wang Zhou-Xiang   Xie Yu-Chen   Huang Shuang-Yin   Zhou Han   Liu Rui   Liu Zhi-Feng   Wang Min   Qi Wen-Rong   Tian Qian-Qian   Kong Ling-Jun   Tu Chenghou   Li Yongnan   Wang Huitian  

      摘要 + 此论文可免费阅读 (可能需要登录)

In free-space or in optical fibers, the orbital angular momentum (OAM) multiplexing for information transmission has been greatly developed. The light sources used were well coherent communication bands and the fibers used were customized. Here we use an 810-nm femtosecond laser to generate optical vortices carrying OAM, and then feed them into two kinds of commercial step-index few-mode fibers to explore the transmission characteristics of OAM modes. We also propose a method without multiple-input multiple-output digital signal processing to identify the input OAMs. It is of great guiding significance for high-dimensional quantum information experiments via the OAMs as a degree of freedom, using the light generated by the spontaneous parametric down-conversion as source and the commercial fibers for information transmission.

       PDF全文 (下载：12)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

Gu Fuxing   ubaid saima   Liao Feng   Tao Guo   Qi Zhao   Linghu Shuangyi   Ma Yanna   Yu Jiaxin  

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We demonstrate an effective approach of mode suppression by simply using a tungsten probe to destroy the external neck surface of polymer microbottle resonators. The higher-order bottle modes with large axial orders, spatially located around the neck surface of the microresonator, will suffer large optical losses. Thus, excitation just with an ordinary free-space light beam will ensure direct generation of single fundamental bottle mode lasers. This method is very low cost and convenient, and can obtain high side mode suppression factors. Our work demonstrated here may have promising applications such as lasing and sensing devices.

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第12期 pp.12      

Cui Yuan   Zheng Guoxing   Chen Ming   Zhang Yilun   Yang Yan   Tao Jin   Li Zile  

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Design of a conventional zoom lens is always challengeable because it requires not only sophisticated optical design strategy, but also complex and precise mechanical structures for lens adjustment. Here, we propose a continuous-zoom lens consisting of two chiral geometric metasurfaces with dielectric nanobrick arrays sitting on a transparent substrate. The metalens can continuously vary the focal length by rotating either of the two metasurfaces along its optical axis without changing any other conditions. Because of the polarization dependence of the geometric metasurface, the positive and negative polarities are interchangeable in one identical metalens only by changing the handedness of the incident circularly polarized light, which can generate varying focal lengths ranging from −∞ to +∞ in principle.

       PDF全文 (下载：15)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Dong Jia-ning   Fan Jie   Mao Si-da   Lan Yun-ping   Zou Yonggang   Wang Hai-zhu   Zhang Jia-bin   Ma Xiaohui  

      摘要 + 此论文可免费阅读 (可能需要登录)

The effect of thermal annealing on the optical properties, microstructure and laser-induced damage threshold (LIDT) of HfO2/Ta2O5/SiO2 HR films have been investigated. The transmission spectra shift to short wavelength and the x-ray diffraction (XRD) diffraction peaks of monoclinic structure HfO2 are enhanced after thermal annealing. The calculated results of m(-111) diffraction peak show that HfO2 grain size is increased, which is conducive to increasing the thermal conductivity. The thermal annealing also reduces the laser absorption of HR films. The improvement of thermal conductivity and the decrease of laser absorption both contribute to the improvement of LIDT. The experimental results show that the highest LIDT of 22.4J/cm2 is obtained at 300℃ annealing temperature. With the further increase of annealing temperature, the damage mechanism of the film changes from thermal stress damage to thermal explosion damage, resulting in the decrease of LIDT

       PDF全文 (下载：6)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Li Xiang   wang xiaodan   Ma Hai   Chen Feifei   Zeng Xionghui  

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In this work, Er doped AlN, Pr doped AlN, and Er, Pr co-doped AlN thin films were prepared by ion implantation. After annealing, the luminescence properties were investigated by cathodoluminescence. Some new and interesting phenomena were observed. The peak at 480 nm was observed only for Er doped AlN. However, for Er, Pr co-doped AlN, it disappeared. At the same time, a new peak at 494 nm was observed, although it was not observed for Er-doped AlN or Pr-doped AlN before. Therefore, the energy transfer mechanism between Er3+ and Pr3+ in AlN thin films were investigated in detail. Through optimizing the dose ratio of Er3+ with respect to Pr3+, white light emission with CIE chromaticity coordinate (0.332, 0.332) was obtained. This work may provide a new strategy for realizing white light emission based on nitride semiconductors.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Fang Fang   Sun Bing   Zhang Zuxing   Xu Jing   Zhang Lin  

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The spectral characteristics and sensitivities of a tapered two-mode fiber (TTMF) sandwiched between two single-mode fibers (SMFs) are systematically proposed. Theoretical calculations reveal that a dispersion turning point (DTP) appears when the group effective refractive index (RI) difference between the fundamental mode and the higher-order mode equals zero, as a result, ultrahigh RI sensitivities can be achieved. Furthermore, the location of the DTP is strongly dependent on the tapering condition. Then we experimentally demonstrate high sensitivities of the RI sensor with the waist diameter of 2.4 μm by means of immersing it in a flow cell filled with glycerol solution. Further tracking the resonant wavelength shift around the DTP it is found that the proposed RI sensor exhibits a sensitivity of 1.81×104 nm/RIU and a limits of detection down up to 3.29×10-5 RIU in glycerol solution.

       PDF全文 (下载：7)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Wang Mingjun   Feng Shaodong   Wu Jigang  

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We propose a resolution enhancement method for lensless in-line holographic microscope (LIHM) by combining the hologram segmentation and pixel super-resolution (PSR) techniques. Our method is suitable for imaging specific target object in samples where the in-line hologram is disturbed by other objects in the samples. The resolution-enhancement capability of our method was proved by numerical simulations and imaging experiments while using a standard resolution target in a two-layer setup. We also applied our LIHM system to image the sample of living algae Euglena gracilis in water solution for further demonstration.

       PDF全文 (下载：11)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Ma Qungang   Cao Liangcai   He Zehao   Zhang Shengdong  

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In this paper, the principle and the optical methods for light-field display are introduced. The light-field display is divided into three categories, including layer-based method, projector-based method, and integral imaging method. The principle, characteristic, history and advanced research results of each method are also reviewed. The advantages of light-field display are discussed by comparing with other display technologies including binocular stereoscopic display, volumetric 3D display and holographic display.

       PDF全文 (下载：9)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Liu xin   Lei Ruoshan   Huang feifei   Deng Degang   Wang Huanping   Zhao shilong   Xu Shiqing  

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BaMoO4: Ho3+/Yb3+ phosphors with different concentrations were fabricated by a gel combustion method. The upconversion (UC) luminescence, intrinsic optical bistability (IOB) and the corresponding mechanisms were reported for the present system. The optical thermometric properties based on the red (5F5 →5I8) and green (5F4/5S2 →5I8) emissions were studied. The sensing sensitivities could be tuned by manipulating the cooperative energy transfer (CET) process. The highest absolute sensitivity was 99 ×10-4 K-1 at 573 K, which was larger than many previous UC materials.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Othman Nurulanati   Tay Kim Gaik   Mohd Shah Nor Shahida   Talib Rahmat   Pakarzadeh Hassan   Cholan Noran Azizan  

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The influence of the fourth-order dispersion coefficient on behavior of parametric gain and saturation power of one-pump fiber optical parametric amplifier over a signal wavelength span in presence of fiber random dispersion fluctuations was investigated. The output signal power for the parametric gain calculation was obtained by numerically solving the three-coupled amplitude equations. Based on the calculations of the parametric gain over a variation of the signal wavelength, it is found that the saturation power behavior is dependent on the behavior of parametric gain. The manipulations of signal wavelength and fourth-order dispersion coefficient changed the phase-matching condition, thereby affecting the resulting parametric gain and saturation power.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Guo Ying   Wang Kangshuai   Jiang Xueqin   Huang Duan  

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Seeking for good error correcting codes to improve the efficiency of continuous-variable quantum key distribution (CVQKD) reconciliation is a concerned issue. Due to the introduction of multidimensional reconciliation, the error correcting techniques in the classical binary-input additive white gaussian noise (BI)-AWGN channel is applicable to CVQKD. In this letter, we apply the quasi-cyclic low-density paritycheck (QC-LDPC) codes, which are specified in 5G protocol, to the reconciliation process. Simulation results show that the reconciliation efficiency can reach 92.6% when the code rate is 22/68 and the signal-to-noise ratio (SNR) is 0.623. Such a new error correcting code points out a new direction for the development of CVQKD.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Gao Qian   Zhang Hengli   Javed Fayyaz  

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A laser diode partially end-pumped, electro-optic Q-switched, Yb:YAG slab laser was reported. We obtained an output energy of 14.6 mJ/pulse with a pulse width of 30 ns at a repetition frequency of 2 kHz, and the corresponding peak power was 480 kW. The beam quality factors M2 in the unstable direction and the stable direction were 1.32 and 1.25, respectively.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Wang Qiangguo   Cui Na   Yao Yongping   Meng Lihua   Li Lei   Dong Lulu   Zhang Huiyun   Liu Shande   Li Dehua  

      摘要 + 此论文可免费阅读 (可能需要登录)

With a Nd:ScYSiO₅ crystal, a high peak power electro-optically Q-switched 1.0 μm laser and tri-wavelength laser operations at 1.3 μm band are both investigated. With RTP electro-optical switcher and a polarization beam splitter, a high signal-to-noise ratio 1.0 μm laser is obtained, generating the shortest pulse width of 30 ns, the highest pulse energy of 0.75 mJ, and the maximum peak power of 25.5 kW, respectively. The laser mode at the highest laser energy level is TEM₀₀ mode with the M² value in X and Y directions to be M_x²=1.52 and M_y²=1.54. Besides, a tri-wavelength Nd:ScYSiO₅ crystal laser at 1.3 μm is also investigated. A maximum tri-wavelength output power is 1.03 W under the absorbed pump power of 7 W, corresponding to a slope efficiency of 14.8%. The properties of the output wavelength are fully studied under different absorbed pump power.

       PDF全文 (下载：21)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

刘 贺言   Yu yongji   sun dehui   Liu Hong   Wang yuheng   Zheng hao   Li dan   Jin Guangyong  

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We report on a 1514nm eye-safe passively Q-switched self-optical parametric oscillator (SOPO). The nonlinear crystal is a a-cut Nd:MgO:PPLN crystal and the size of the crystal was 6 mm × 2 mm ×30 mm with 0.4at.% Nd3+ doped, grating period was 29.8μm.When the crystal absorbed 12.8W, the output maximum single pulse energy reached 39μJ and the pulse width of 6.1ns at a 5.4 kHz repetition rate was obtained, peak power is 6kw and giving a slope efficiency of 42%.

       PDF全文 (下载：11)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Wei Wei   Huang Lihua   zhu Xinran   ling liqing   Guo Kai   Huang Huijie  

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In our paper two kinds of handwriting traces, colored and colorless, are studied by means of Reflectance Transformation Imaging (RTI).The illumination direction and rendering mode can be changed alternatively to obtain two-dimensional and three-dimensional details of the traces that are not viewed easily by the naked eye. Furthemore, an objective evaluation method without reference is applied to evaluate the reconstructed images, which provides a basis for setting the illumination direction and rendering mode. Therefore, the information of handwriting traces including the written content, the writing features, and the stroke order features can be obtained objectively and accurately.

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Wang Xiaoyan   Yan Xiaona   Jin Kailong   Dai Ye   Jin Zuanming   Yang Xihua   Ma Guohong  

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Based on Kogelnik’s coupled-wave theory, it is found that when a femtosecond pulse incidents on transmitted volume holographic grating, two transverse standing waves along grating vector direction will be generated inside the VHG. Due to field localization of two standing waves, they have two different velocities along propagation depth. On the output plane of the VHG, femtosecond dual pulses are generated on both the diffracted and transmitted directions. Results show that the pulse interval is determined by the refractive index modulation and thickness of the grating, while the waveform of the dual pulses is independent of grating parameters.

       PDF全文 (下载：8)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Cai Yuancheng   Gao Xiang   Ling Yun   Xu Bo   Qiu Kun  

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A pre-coding-assisted power detection scheme for radio over fiber downlink is presented. This scheme can eliminate laser phase noise, while avoiding high energy-consuming electrical carrier required in conventional power and/or envelope detection scheme. Theoretical analysis and experimental verification are performed. 0.625 Gbaud pre-coded quadrature phase shift keying or 16 quadrature amplitude modulation signals can both be recovered by power detec-tion without electrical carrier assistance at the receiver after 75 km fiber transmission. Not only robust against the laser phase noise, an improvement of about 5 dB in receiver sensitivity can also be achieved, as compared with the conventional power detection scheme.

       PDF全文 (下载：6)        Chinese Optics Letters ，2019年第17卷第11期 pp.11      

Xiong Ling   Qi Erhui   Luo Xiao   Zhang Feng   Xue Donglin   Zhang Xuejun  

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We implemented a stitching swing arm profilometer (SSAP) test for inner and outer region of a large aspheric surface with a short arm. The SSAP was more capable of improving sampling density of surface, and was less sensitive to system error, like vibration noise, air-table noise. Firstly, a calculation model was built to evaluate the sampling density of the SSAP test. Then sensitivity to system noise was tested when different length of arm was used. At the end, an experiment on a 3m diameter aspheric was implemented, where test efficiency was promoted and high sampling density was achieved.

       PDF全文 (下载：5)        Chinese Optics Letters ，2019年第17卷第11期 pp.11