Cai Hao   Yu Xingtao   Chu Qian   Jin Zhiqiang   Lin Bo   Wang Guanghui  

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A metal-lined hollow-core fiber based Raman probe extension kit is proposed in this paper for in Situ and sensitive ultramicro-analysis. Hollow-core fiber can confine light and fluid sample in its hollow core, with enhanced light-sample interaction. By using a homemade light coupling device with a glass window for liquid isolation, a 3.5 cm-long hollow-core fiber could mount on and connect to a Raman probe, with perfect light coupling efficient. After full filling the hollow-core fiber chamber with volume of 13 µL by using a syringe pump, it can act as an extension kit for ordinary Raman probe and could be used as ultramicro-analysis tool for the sample of microfluidic chips. In order to enhance its sensitivity, a gold film coated fiber tip is inserted into the capillary, which can double the Raman signal received by reflecting pump light and Raman light. Finally, a good sensitivity of detection limit of 5% for ethanol solution and an enhancement factor of 2 comparing with direct detection of bulk sample volume are demonstrated. Above all, our device can be utilized as a Raman probe extension kit, which is suitable for rapid, sensitive and in Situ measurements for few µL sample.

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

huang wei   cui yulong   Zhou Zhiyue   Li zhixian   Chen Yubin   Wang Zefeng  

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We report here a diode-pumped pulsed mid-infrared laser source based on gas-filled hollow-core fibers (HCFs) towards all-fiber structure by tapering method. The pump laser is coupled into an acetylene-filled HCF through a tapered single-mode fiber. By precisely tuning the wavelength of the diode to match different absorption lines of acetylene near 1.5 μm, mid-infrared emission around 3.1~3.2 μm is generated. With 2 m HCFs and 3 mbar acetylene gas, a maximum average power of 130 mW is obtained with a laser slope efficiency of ~24%. This work provides a potential scheme for all-fiber mid-infrared fiber gas lasers.

       PDF全文 (下载：3)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Lu Zhiyong   Lu Wei   Zhou Yu   Sun Jianfeng   Xu Qian   wang lijuan  

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A scanning three-dimensional coherent ladar based on the frequency modulated continuous wave (FMCW) is proposed and demonstrated, which can obtain many three-dimensional high-quality images. The system utilizes an electro-optic modulator and an optical filter to output a linear frequency modulated continuous waveform with a bandwidth of 2GHz. The flexible and variable rotating double prism is used for beam scanning. The images of flight demonstration are formed by attitude compensation correction. The experiment result validates the performance of our system for airborne three-dimensional scanning imaging.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Zhang Li   Lin Fei   qiu xiaodong   Chen Lixiang  

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We demonstrate the full vectorial feature of second-harmonic generation (SHG), i.e., from infrared full Poincaré beams to visible full Poincaré beams, based on two cascading type-I phase-matching BBO crystals of orthogonal optical axes. We visualize the structured features of vectorial SHG wave by using Stokes polarimetry and show the interesting doubling effect of polarization topological index, i.e., a low-order full Poincaré beam is converted to a high-order one. However, the polarization singularities of both C-points and L-lines are found to keep invariant during the SHG process. Our scheme could offer a deeper understanding on the interaction of vectorial light fields with media and can be generalized to other nonlinear optical effects

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

zhou xiong   Wang Hui   Xia Haiping   Song Hongwei   Chen Xu   Hu jianxu   chen baojiu  

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Yb³⁺/Er³⁺ co-doped Na₅Lu₉F₃₂ single crystals used as a spectral upconverter to improve the power conversion efficiency of perovskite solar cells are prepared via an improved Bridgman approach. Green and red upconversion (UC) emissions under the excitation of near-infrared (NIR) bands of 900-1000 nm and 1400-1600 nm can be observed. The effectiveness of the prepared materials as spectral converter is verified by the enhancement of power conversion efficiency of perovskite solar cells. Sample with UC layer is 15.5% more efficient to convert sunlight to electricity comparing to the UC layer-free sample due to the absorption of sunlight in the NIR range. The results suggest the synthesized Yb³⁺/Er³⁺ co-doped Na₅Lu₉F₃₂ single crystals are suitable for enhancing the performance of perovskite solar cells.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Zhang Xiaotong   Yang Shitai   Yuan Libo  

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By using a specialty designed optical fiber, a series of powerful microparticle manipulation tools including optical tweezers, a micro-optical hand and an optical gun are developed and demonstrated. In this paper, a review of our research activities on the optical manipulation of microparticles will be presented. In particular, we will describe a kind of specialty optical fiber designed and fabricated for building optical trapping and manipulating tools. The performance of annular core fiber based optical tweezers, a multicore, fiber-based micro-optical hand and a coaxial dual waveguide fiber-based optical gun are demonstrated as examples of applications and discussed in detail. The fiber can be used in cell manipulation in life science and drug response in medicine.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Yang Xin   Wei Shibiao   Kou Shanshan   Yuan Fei   Cheng En  

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The misalignment of optical vortex (OV) beams, including transversal displacement and tilt, occurs in many situations, including on reflection or refraction at an interface between two different media and in propagation and tracking systems for optical communications. We propose a reliable method to determine and subsequently eliminate tilt and transversal displacement in an OV beam. An experimental setup was established to verify the proposed method and the experimental results showed good agreement with those of the numerical simulations. Using the measured misalignments, the initial orbital angular momentum spectrum can be recovered in free space.

       PDF全文 (下载：0)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Miao Shuaijie   Zhang Wentao   Song Ying  

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A new structure of short-cavity random fiber laser (RFL) with narrow linewidth lasing is proposed. A π-phase-shifted fiber Bragg grating (π-FBG) loop mirror was used in the RFL to spectral filtering and suppress multi-mode oscillation due to the narrow transmission window. The random feedback of the RFL was implemented by a randomly dispersed weak reflection FBG array. The high gain of the erbium-doped fiber and a half-open cavity design result in a low lasing threshold. The linewidth of the laser was 225 Hz with 58 dB side-mode-suppression-ratio. The laser threshold was 4.5 mW and the optical signal-to-noise ratio was up to 63 dB.

       PDF全文 (下载：5)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Liu Zhentao   Shen Xia   Liu Honglin   Yu Hong   Han Shensheng  

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The resolution of a conventional imaging system based on first-order field correlation can be directly obtained from the optical transfer function. However, it is challenging to determine the resolution of an imaging system through random media, including imaging through scattering media and imaging through randomly inhomogeneous media, since the point-to-point correspondence between the object and the image plane in these systems cannot be established by the first-order field correlation anymore. In this paper, from the perspective of ghost imaging, we demonstrate for the first time to our knowledge that the point-to-point correspondence in these imaging systems can be quantitatively recovered from the second-order correlation of light fields, and the imaging capability, such as resolution, of such imaging schemes can thus be derived by analyzing second-order correlation of the optical transfer function. Based on this theoretical analysis, we propose a lensless Wiener-Khinchin telescope based on second-order spatial autocorrelation of thermal light, which can acquire the image of an object by a snapshot via using a spatial random phase modulator. As an incoherent imaging approach illuminated by thermal light, lensless Wiener-Khinchin telescope can be applied in many fields such as X-ray astronomical observations.

       PDF全文 (下载：3)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Liu Xinyang   Li Xiaowen   Zhao Shengzhi   Yang Kejian   Guo Lei   Li Tao   Qiao Wenchao   Li Ming   Zhang Baitao   He Jingliang   Zheng Lihe   Su Liangbi   Xu Jun  

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A dual-wavelength synchronously mode-locked homogeneously broadened bulk laser operating at 1985.6 nm and 1989 nm is presented for the first time, to the best of our knowledge, which delivers a maximum output power of 166 mW and a repetition rate of 85 MHz. The pulse duration was measured to be 16.8 ps by assuming a Sech2 pulse shape. The recorded autocorrelation trace showed frequency beating signals with an interval of 3.8 ps and a FWHM duration of 2 ps, corresponding to an ultrahigh beating frequency of about 0.26 THz, which agrees well with the frequency difference of the emitted two spectral peaks. The results indicated that such a kind of dual-wavelength mode-locked Tm:YAP laser could be potentially used for generating terahertz radiations.

       PDF全文 (下载：12)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Chen Zhidong   Sang Xinzhu   Li Hui   Wang Yuan   Zhao Linmin  

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A novel see-through virtual retina display (VRD) system is proposed in this letter. An optical fiber projector is used as the thin-light-beam source, which is modified from a laser scan projector by separating the laser sources and the scan mechanical structure. A synthetic aperture method is proposed for simple, low-cost fabrication of a volume holographic lens with large numerical aperture. These two key performance-enhanced elements are integrated into a lightweight and ordinary-glasses-like optical see-through VRD system. The proposed VRD system achieves a weight of 30 grams and a diagonal field of view of 60.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Li Yuepeng   Cai Yawen   Li Runmin   Shi Haosen   Tian Haochen   He Mingzhao   Song Youjian   Hu Minglie  

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We demonstrate a robust femtosecond LIDAR setup by using two free running environmentally stable all polarization-maintaining (PM) nonlinear amplified loop mirror mode-locked fiber lasers. Based on asynchronous optical sampling (ASOPS) method, a ranging accuracy of ±2 μm within 65m has been achieved, as tested in an 80-meter long underground optical tunnel. Through Kalman filter in the real-time data processing, the measurement accuracy can be maintained at a 200 Hz update rate. This setup provides a practical tool for various large scale industrial and astronomical ranging applications.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Gan Haiyong   He Yingwei   Liu Xiangliang   Xu Nan   Wu Houping   Feng Guojin   Liu Wende   Lin Yandong  

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An absolute cryogenic radiometer (ACR) with a detachable optical window was designed and built for high accuracy optical radiant power measurement and photodetector spectral responsivity calibration. The ACR receiver is an electroplated pure copper cavity with a 50-μm-thick wall and inner surface coated with a specular black polymer material mixed with highly dispersible carbon nanotubes. The absorptivity of the cavity receivers was evaluated to be ≥0.9999 in 250 nm ~16 μm wavelength range and ≥0.99995 in 500 nm ~16 μm. The cavity receiver works at the temperature of ~5.2 K with nW-level noise-equivalent-power. The relative standard uncertainty is 0.041% for the measurement of ~100 μW optical radiant power (250 nm ~ 16 μm) and 0.015% for ~1 mW (500 nm ~ 16 μm).

       PDF全文 (下载：6)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Deng Yuting   Jin Guofan   Zhu Jun  

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Freeform surfaces are difficult to manufacture due to their lack of rotational symmetry. To reduce the requirements for manufacturing precision, a design method is proposed for freeform reflective-imaging systems with low surface-figure-error sensitivity. The method considers both the surface-figure-error sensitivity and optical specifications, which can design initial systems insensitive to surface figure errors. Design starts with an initial planar system; the surface-figure-error sensitivity of the system is reduced during the construction. The proposed method and another which is irrelevant to figure-error sensitivity are used to design a freeform off-axis three-mirror imaging system. Comparison of the sensitivities of the two systems indicates the superiority of our proposed method.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Wang Xin   Yang Sihua  

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In this study, the feasibility of visualization of human joints using photoacoustic tomography (PAT) is investigated. To verify this idea, the system of integrated optical fiber bundles and custom-made flexible transducer is established, both of which give the advantage of morphological adaptation, therefore, the coupling section can be worn on human limbs. The imaging capacity of the flexible-transducer-based PAT system is validated by mapping the structures of the finger and the wrist joint. To our knowledge, it is the first time to achieve photoacoustic imaging of such a large human wrist joints. The cross-sectional photoacoustic images of a healthy joint clearly exhibit main internal structures including phalanx, tendons and blood vessels, which are comparable with the corresponding 3.0 T MRI images. The experimental results demonstrate that the proposed system holds promise for early diagnosis of joint disorders.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Zhou Xingye   Tan Xin   Wang Yuangang   Song Xubo   Han Tingting   Li Jia   Lu Weili   Gu Guodong   Liang Shixiong   Lv Yuanjie   Feng Zhihong  

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Ultroviolet (UV) detectors with large photosensitive area are more advantageous in low-level UV detection applications. In this letter, high-performance 4H-SiC p-i-n avalanche photodiodes (APDs) with large active area (800 µm diameter) are reported. With the optimized epitaxial structure and device fabrication process, a high multiplication gain of 1.4×10⁶ is obtained for the devices at room temperature, and the dark current is as low as ~10 pA at low reverse voltages. In addition, a record external quantum efficiency (QE) of 85.5% @ 274 nm is achieved, which is the highest value for the reported SiC APDs. Furthermore, the rejection ratio of UV to visible light reaches about 10⁴. The excellent performance of our devices indicates a tremendous improvement for large-area SiC APD-based UV detectors. Finally, the UV imaging performance of our fabricated 4H-SiC p-i-n APDs is also demonstrated for system-level applications.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Zhang Kui   Wang Zhengwei   Chen Guodong   Wang Yang   zeng Aijun   Zhu Jing   Avakaw Syarhei   Tsikhanchuk Heorgi  

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A Te-free binary phase change material SbBi is used as a new inorganic photoresist for laser heat-mode lithography. It shows good film-forming ability, low threshold power for crystallization, and enough etching selectivity. Line-type, dot-type, and complex pattern structures with the smallest feature size of 275 nm are fabricated on SbBi thin films using a laser direct writing system. In addition, the excellent grating structures with a period of 0.8 m demonstrate that thermal interference does not affect the adjacent microstructures obviously. These results indicate that SbBi is a promising laser heat-mode resist material for micro/nanostructure fabrication.

       PDF全文 (下载：1)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Luo Xiaoqing   Tan Zhi-Yong   Wang Chang   Cao Juncheng  

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We propose and experimentally demonstrate a wideband linear polarization converter in reflection mode operating from 2.4 to 4.2 THz with conversion efficiency more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation was performed for this metamaterial converter, which showed a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry-Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of meta-structure and multiple reflections within the Fabry-Pérot cavity.

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Yang Baodong   Zhang Jinfang   Wang Junmin  

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An experimental investigation of two-color polarization spectroscopy (TCPS) is presented based on the cesium 6S1/2 - 6P3/2 - 8S1/2 (852.3 nm + 794.6 nm) ladder-type system in a room-temperature vapor cell. The dependency of lineshapes of TCPS on the power of 852.3 nm pump and 794.6 nm probe laser are measured in detail, and we confirm that the linewidth of TCPS in counter-propagating configuration between the pump and probe laser beams is obviously narrower than that of co-propagating configuration due to atomic coherence effect. It is helpful for laser stabilization to excited state transition using TCPS without frequency modulation.

       PDF全文 (下载：6)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Xie Youpeng   Lei Ting   Yang Chuanwu   Du Luping   Yuan Xiao-Cong (Larry)  

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Digital micro-mirror device (DMD)-based optical switch has the advantages of high-speed channels reallocation, miniaturization, stability and large capacity for short reach optical communication in Datacenter. However, the thermal turbulent atmosphere in Datacenter would cause perturbations and channel crosstalk for the optical switch. The self-healing optical beams such as the Bessel beams have the non-diffraction property to mitigate the turbulence issue. Here, we propose and demonstrate Bessel beams enabled DMD-based optical switch to improve the stability and performance of the optical communication in turbulent atmosphere. We statistically characterize the beam wanders of the Gaussian beams and Bessel beams in turbulent atmosphere at the temperatures of 60oC and 80oC. We built the two channels optical switch communication system and measure the bit error rate of the 15Gbit/s OOK signals transmitted by the Gaussian beams and Bessel beams at the temperatures of 60℃ and 80℃, respectively. The optical switch using the Bessel beams shows lower bit error rates with weaker fluctuations compared with the Gaussian beams. The DMD-based optical switch using the Bessel beams has the potential for practical optical communication applications in Datacenter.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Wang Xin-wen   Liu Kangkang   Cheng He-nan   ren wei   xiang jingfeng   Ji Jing-wei   Peng Xiang-kai   Zhang Zhen   zhao jianbo   ye meifeng   Li Lin   Li Tang   wang bin   qu qiuzhi   Liu Liang   lü desheng  

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A high-performance transportable fountain clock is attractive for use in laboratories with high-precision time-frequency measurement requirements. This letter reports the improvement on stability of a transportable rubidium-87 fountain clock because of an optimization of temperature characteristic. This clock integrates its physical packaging, optical benches, microwave frequency synthesizers and electronic controls onto an easily movable wheeled plate. Two optical benches with high vibration resistance is realized in this work. No additional adjustment is required after several times movement of them. The Allan deviation of the fountain clock frequency was measured by comparing it with that of the hydrogen maser. The fountain clock got a short-term stability of 2.3×10⁻¹³@1s and long-term stability to the order of 10⁻¹⁶@100000s

       PDF全文 (下载：3)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Kong Qian   Zhan Yafeng   Wan Peng  

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We report on a DCN architecture based on hybrid Optical Circuit Switching (OCS) and Optical Burst Switching (OBS) interconnect for dynamic DCN connectivity provisioning. With the combination of the centralized and distributed control of the Software Defined Optical Networks (SDON), the proposed interconnect can achieve unprecedented flexibility in dealing with both mice and elephant flow in the DCN. Numerical simulation is employed to investigate the performance of the proposed architecture. The results show that OBS module has preferable performance in dealing with larger burst packet, and the throughput is constrained by the capacity of the server Random Access Memory (RAM) module.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Cen Yuan   Xie Jianlan   Liu Jianjun  

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In this Letter, a photonic crystal (PC) flat lens with scatterer-size-gradient is proposed, which simultaneously achieve imaging of point source and sub-wavelength focusing of plane wave in the first, the second and the fifth bands. The imaging of point source breaks through the diffraction limit in the second and the fifth bands. The PC flat lens with scatterer-size-gradient is expected to be used to new multifunctional optical imaging and focusing device, which improves the application potential of PC flat lens.

       PDF全文 (下载：6)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Gao Xin-Xia   Cui Jin-Ming   Huang Yunfeng   Li Chuanfeng   Guo Guangcan  

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We have demonstrated a mode matching method between two different fibers by a hybrid thermal expanded core (TEC) technique, which can be applied to match the modes of fiber-based Fabry-P\'erot cavities (FFPCs). Experimentally, this method has achieved an expansion of the ultraviolet fiber core by 3.5 times while keeping fundamental mode propagation. With the experiment parameters, the fundamental mode coupling efficiency between the fiber and micro-cavity can reach 95% for a plano-concave cavity with a length of 400 \mum. This method can not only have potential in quantum photonics research, but also can be applied in classical optical fields.

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第9期 pp.09      

Xia Renjie   Wang Changshun   Chen Tianyu   Pan Yujia   Lyu Ziyao   Sun Lili  

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In this paper, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals: 1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been recorded and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Xue Jinxing   Liu Candong   Zeng Zhinan   Li Ruxin   Xu ZhiZhan  

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We theoretically investigate delay-dependent attosecond transient absorption spectra in the helium atom dressed by an infrared laser pulse in the wavelength range of 800–2400 nm. By numerically solving the three-dimensional time-dependent Schrödinger equation, we find that the absorption spectrogram exhibits a multiple-fringe structure for using the longer-wavelength dressing pulse. The quantitative calculation of the transition matrix between different Floquet states provides direct evidence on the origin of the multiple-fringe structure. Our result shows that the wavelength of the dressing pulse is an important parameter and the unique feature of attosecond transient absorption spectroscopy can be induced in the mid-infrared regime.

       PDF全文 (下载：5)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Wang Guoyan   Jiang Lan   Sun Jingya   Hu Jie   Wang Qingsong   Li Ming   Lu Yongfeng  

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Cylindrical shockwave inside PMMA generated simultaneously with two hemispherical shockwaves induced by femtosecond Gaussian beam laser was investigated using ultrafast pump-probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by degraded nonlinear effect due to pre-ablated structure in multi-pulses irradiation.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Li Yingyi   Yang Ke   Liu Gaoyou   Yao Baoquan   Ju Youlun  

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We demonstrate a Fe:ZnSe laser gain-switched by a ZnGeP₂ (ZGP) optical parametric oscillator (OPO) under the pulse repetition frequency (PRF) of 1 kHz at room temperature. The 2.9 μm signal light of the OPO is employed as the pump for the Fe:ZnSe laser. The maximum output power of the Fe:ZnSe laser is 58 mW with the pulse duration of 2.7 ns under the incident pump power of 280 mW, corresponding to a peak pulse power of 21.5 kW and an optical-to-optical efficiency of 20.7%. The spectrum of the Fe:ZnSe laser has a range of 4030.2-4593.6 nm with a dip in 4187.1-4340.4 nm due to the absorption of CO₂.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

Ji Jianhua   Zhang Jianjia   Wu Bing   Wang Ke   Xu Ming  

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We experimentally demonstrate a 10 Gb/s FSO wiretap channel based on spatial diversity scheme and optical code division multiple access (OCDMA). In weak and middle turbulence cases, bit error rate of legitimate user can be decreased and physical layer security can be enhanced simultaneously.

       PDF全文 (下载：2)        Chinese Optics Letters ，2019年第17卷第8期 pp.08      

He Xiaopeng   Huang Panhui   Yang Xiaoyu   Jin Zuanming   Lou shitao   Zhang Xiaolei   Jin Qingyuan  

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The ultrafast spin dynamic of in-plane magnetized Fe/Pt films was investigated by terahertz emission spectroscopy. The amplitude of emitted terahertz wave is proportional to the intensity of the exciting laser beams. Both the amplitude and polarity of the terahertz wave can be adjusted by modifying the external magnetic field. The dependency of the amplitude on external magnetic fields is coincidence to the hysteresis loops of the sample. Also the polarity of terahertz wave is reversed as the magnetization orientation is reversed. The superdiffusive transient spin current with inverse spin Hall effect (ISHE) is attributed to main mechanism of the terahertz emission.

       PDF全文 (下载：4)        Chinese Optics Letters ，2019年第17卷第8期 pp.08