Atomic and Molecular Optics
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The gravimeter based on atom interferometry has potential wide applications on building gravity networks and 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 65 μGal/Hz and a resolution of 1.1 μGal after 4000 s integration, being comparable to state-of-the-art atomic gravimeters. Our achievement paves the way for bringing the portable atomic gravimeter to field applications.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.090201
Fiber Optics and Optical Communications
Monette H. Khadr
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 communication (ACom) is introduced in this Letter as the first technique that aims to combine these two enhancements in visible light communications (VLCs). The dividends of the proposed concept are demonstrated via simulations and the performance is experimentally validated. Results show that ACom can simultaneously provide the high spectral efficiency and the resistance to eavesdropping, while introducing minimal signal-to-noise ratio penalties.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.090601
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 a digital look-up table is used. Considering the non-negligible loop delay, we optimize the loop natural frequency. Without error correction coding, a sensitivity of ?37 dBm/?35 dBm is achieved, while the bit error rate is below 10?9 at 2.5 Gbaud/5 Gbaud rate. For the QPSK communication system, the bit rate is twice the baud rate. The loop natural frequency is 0.647 Mrad/s, and the minimized steady-state phase-error standard deviation is 3.83°.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.090602
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 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   HTML全文 , 2020年第18卷第9期 pp.090001
A new architecture, naked-eye ghost imaging via photoelectric feedback, is developed that avoids computer algorithm processing. Instead, the proposed scheme uses a photoelectric feedback loop to first 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 feedback circuits, the digital circuit and the analog circuit, are presented that can achieve a feedback operation. Based on this design, 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   HTML全文 , 2020年第18卷第9期 pp.091101
Lasers and Laser Optics
Detailed power and spectral analysis of a diode-pumped c-cut Pbnm 3 at.% Tm-doped yttrium aluminum perovskite (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   HTML全文 , 2020年第18卷第9期 pp.091401
A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance could be on the order of 10?5 by matching the refractive index of Nd:glass, polymer, and cladding glass and eliminating defects in the adhesive layer. Residual reflection spatial distribution appears to be similar to Newton rings due to the edge surface flatness. The relationship between the residual reflectance and the edge surface flatness was discussed, and the results revealed that the edge surface flatness is very important during the cladding process.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.091402
The broadband photochromic effect on undoped and rare-earth-doped lead lanthanum zirconate titanate (PLZT) ceramics was studied under the illumination of ultraviolet light at 360 nm. The photocarriers’ trapping and detrapping processes of thermal disconnected traps played the vital role in both darkening and bleaching processes. The interaction between photocarrier traps and rare-earth ion energy levels was 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   HTML全文 , 2020年第18卷第9期 pp.091403
Y. F. Chen
C. C. Lee
C. H. Wang
M. X. Hsieh
The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring 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–LG (HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 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 an 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   HTML全文 , 2020年第18卷第9期 pp.091404
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 testing 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   HTML全文 , 2020年第18卷第9期 pp.092501
Other Areas of Optics
Optical edge detection, a part of image processing, plays an important role in extracting image information used in optical analog computation. In this Letter, 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 advantage of the convenience to use, simple fabrication process, and real-time tunable resolution. It may guide more significant applications in the optical field and other practical scenarios like machine vision in computers.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.093501
Plasmonics and Metamaterials
In a single nanoscale device, surface plasmon polaritons (SPPs) have potential to match the different length scales associated with photonics and electronics. In this Letter, we propose an accurate design of a plasmonic metasurface Luneburg lens (PMLL) accommodating SPPs. The simulations indicate that the full width at half-maximum 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 couples the SPPs to the 40 nm wide output waveguide. The couple efficiency is higher than that of a conventional taper coupler in a broad bandwidth. The design is compatible with standard lithography technology.
PDF全文   HTML全文 , 2020年第18卷第9期 pp.092401
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 numerical simulations, it can be deducted that the tuning process is attributed to the coupling between the dark mode existing in split-ring resonators and the bright mode existing in cut wire resonators. The transmission amplitude modulation is accompanied by 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   HTML全文 , 2020年第18卷第9期 pp.092402
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 direct femtosecond laser etching. The thickness of the middle dielectric layer is only 60 μm, which makes the absorber very transparent and flexible. The experimental results show that the THz resonant peaks have a 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   HTML全文 , 2020年第18卷第9期 pp.092403
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 a cylindrical lens. The interference period is adjusted to be an integer multiple of the wavelength of a surface plasmon polariton. Regular and uniform subwavelength nanogratings (RUSNGs) on a silicon wafer of a diameter of 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   HTML全文 , 2020年第18卷第9期 pp.093201
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In this letter, we experimentally investigate fast temporal intensity dynamics and statistical properties of the cladding-pumped Er/Yb co-doped random Rayleigh feedback fiber laser (EYRFL) for the first time, to the best of our knowledge. By using the optical spectral filtering method, strong and fast intensity fluctuations with the generation of extreme events are revealed at the output of EYRFL. The statistics of the intensity fluctuations strongly depends on the wavelength of the filtered radiation, and the intensity probability density function (PDF) with heavy tail is observed in the far wings of the spectrum. We also find the PDF of the intensity in the central part of the spectrum deviates from the exponential distribution, and has the dependence on the laser operating regimes, which indicates some correlations among different frequency components exist in the EYRFL radiation and may play an important role in the random lasing spectrum stabilization process.
PDF全文 (下载：6) ，2021年第19卷第2期 pp.02
The behavior of self-polarization emission in Nd:YAG/Cr4+:YAG lasers has been proved in some cases, however, the degree and direction of polarization were often sensitive and unstable. We experimentally observed different beam profiles versus the angle of polarizer relative to the polarization direction of laser. In order to explore the polarization mechanism, the dynamics of intracavity polarized eigenmodes were analyzed theoretically. Simulative results were well consistent with our experimental observations. It indicated that the linearly self-polarization emission was a composite state rather than intrinsic state. This study contributed to the improvement of the polarization stability in Nd:YAG/Cr4+:YAG passively Q-switched lasers.
PDF全文 (下载：0) ，2021年第19卷第2期 pp.02
We report a spatially modulated polarimetry scheme by using a zero-order vortex half-wave retarder (ZVHR) and spatial Fourier analysis method. A ZVHR is employed to analyze the input polarized light and convert it into a vectorial optical field, and an analyzer is set after the ZVHR to form an hourglass intensity pattern due to the spatial polarization modulation, and then the input light’s Stokes parameters can be calculated by spatial Fourier analysis of the hourglass pattern with a single shot. The working principle of the polarimeter has been analyzed by the Stokes-Mueller formalism, and some quantitative measuring experiments of different polarization states have been demonstrated, and the experimental results indicate that the proposed polarimeter is accurate, robust and simple to use.
PDF全文 (下载：5) ，2021年第19卷第2期 pp.02
A novel physical layer data encryption using two-level constellation masking in three-dimension carrier-less amplitude and phase modulation passive optical network (3D-CAP-PON) is proposed in this letter. The chaotic sequence generated by the Chua's circuit model realizes two-level encryption of displacement masking and constellation rotation for 3D constellation. We successfully conduct an experiment demonstrating 8.7 Gb/s 3D-CAP-8 data transmission over 25 km standard single-mode fiber (SSMF). With two-level constellation masking, a key space size of 2.1×10<sup>85 </sup>is achieved to bring about high security and good encryption performance, suggesting broad application prospects in future short-range secure communications.
PDF全文 (下载：3) ，2021年第19卷第1期 pp.01
Mohamed Zolkefl A.Y.
In this letter, we report on an Airy-like beam of magnetostatic surface spin wave (AiBMSSW) supported on the ferromagnetic film, which is transferred from optical field. The propagation properties of AiBMSSW were verified with micromagnetic simulation. From simulation results, the typical parabolic trajectory of Airy-type beam was observed by encoding 3/2 phase pattern into excitation sources. The simulation results are coincident well with design parameters. Furthermore, simulated results showed that the trajectories of AiBMSSW beam could be tuned readily with varied external magnetic field. This work can extend the application scenario of SWs.
We present the generation of the nanosecond cylindrical vector beams (CVBs) in two-mode fiber (TMF) and its applications of stimulated Raman scattering. The nanosecond (1064 nm, 10 ns, 10 Hz) CVBs has been directly produced with mode conversion efficiency of ~18 dB (98.4%) via an acoustically-induced fiber grating (AIFG), and then the stimulated Raman scattering signal is generated based on the transmission of the nanosecond CVBs in a 100-meters length TMF. The transverse mode intensity and polarization distributions of the 1st-order Stokes shift component (1116.8 nm) is consistent with the nanosecond CVBs pump pulse.
Orbital angular momentum (OAM), as a fundamental parameter of photon, has attracted great attention in recent years. Although various properties and applications have been developed by modulating the OAM of photons, there is rare research about the non-uniform OAM. We propose and generate a new kind of continuously tunable azimuthally non-uniform OAM for the first time, which is carried by hybridly polarized vector optical field with cylindrically symmetric intensity profile and a complex polarization singularity. We also present the perfect vector optical field carrying non-uniform OAM with fixed radius independent of topological charges, which can propagate steadily without radial separation, solving the problem of the unsteady propagation due to the broaden OAM spectrum of the non-uniform OAM. This new kind of tunable non-uniform OAM with cylindrical symmetric intensity profile, complex polarization singularity and propagation stability enriches the family of OAM, and can be widely used in many regions such as optical manipulation, quantum optics, optical communications and so on.
PDF全文 (下载：1) ，2020年第18卷第12期 pp.12
We propose a concept of wavelength synchronization to ensure the stability of ultra-dense channels in ultra dense wavelength division multiplexing passive optical network (UDWDM-PON) transmitter. A mode-locked laser (MLL) is used to provide wavelength references for users. By injection locking semiconductor laser, the separation of wavelength reference is realized in optical line terminal (OLT). The downlink and uplink wavelength references are interlaced distributed to facilitate the synchronization of uplink carriers. In optical network unit (ONU), the uplink optical carriers are filtered by injection locking semiconductor lasers, which achieve wavelength synchronization for the uplink users. In this paper, an adaptive wavelength synchronization transmitter for UDWDM-PON is realized with a channel spacing of 5 GHz.
PDF全文 (下载：0) ，2021年第19卷第1期 pp.01
Nanogap plasmonic structures with strong coupling between separated components have different responses to orthogonal polarized light, giving rise to giant optical chirality. Here, we proposed a 3D nanostructure consists of two vertically and twistedly aligned nanogaps, showing the hybridized charge distribution within 3D structures. It is discovered that the structure twisted with 60<sup>o</sup> performs plasmonic coupling behaviour with/without gap mode for different circular-polarized plane waves, showing giant chiral response (ΔT) of 60% at the wavelength of 1550 nm. By controlling the disk radius and the insulator layer, the CD signal can be further tuned between 1538~1626 nm.
PDF全文 (下载：1) ，2021年第19卷第1期 pp.01
A novel and simple scheme of photonic aided vector millimeter-wave (mm-wave) signal generation without a digital to analog converter (DAC) is proposed. Based on our scheme, 20Gb/s 4-ary quadrature amplitude modulation (4-QAM) mm-wave signal is generated without using a DAC. The experiment results demonstrate that the bit error rate (BER) of 20Gb/s 4-QAM mm-wave signal can reach below hard-decision forward-error-correction (HD-FEC) threshold of 3.8x10-3 after a delivery over 1-m wireless distance. Because the DAC is not required, it can reduce the system cost. Besides, by using photonic technology, the system is easily integrated to create large-scale production and application in high- speed optical communication
We propose a photonics-assisted equivalent frequency sampling (EFS) method to analyze the instantaneous frequency of broadband linearly frequency modulated (LFM) microwave signals. The proposed EFS method is implemented by a photonic scanning receiver which is operated with a frequency scanning rate slightly different from the repetition rate of the LFM signals. Compared with the broadband LFM signal analysis based on temporal sampling, the proposed method avoids the use of high-speed analog to digital converters and the instantaneous frequency acquisition realized by frequency-to-time mapping is also simplified since real-time Fourier transformation is not required. Feasibility of the proposed method is verified through an experiment, in which frequency analysis of Ka-band LFM signals with a bandwidth up to 3 GHz is demonstrated with a moderate sampling rate of 100 MSa/s. The proposed method is highly demanded for analyzing the instantaneous frequency of broadband LFM signals used in radar and electronic warfare systems.
PDF全文 (下载：4) ，2021年第19卷第1期 pp.01
Recently reported plasmon-induced transparency (PIT) in metamaterials endows the optical structures in classical system with quantum optical effects. In particular, nonreconfigurable nature in metamaterials makes multifunctional applications of PIT effect in terahertz communications and optical networks remain a great challenge. Here we present an ultrafast process-selectable modulation of PIT effect. By incorporating silicon islands into diatomic metamaterials, the PIT effect is modulated reversely, depending on the vertical and horizontal configurations, with giant modulation depth as high as 129% and 109%. Accompanied by the enormous switching of transparent window, remarkable slow light effect occurs.
Recently the nested Mach-Zehnder interferometer [Phys. Rev. Lett.111, 240402 (2013)] was modified by adding Dove prisms in a paper [Quantum Stud.: Math. Found. 2, 255 (2015)], and an interesting result is that, after the Dove prisms being inserted, a signal at the first mirror of the nested interferometer was obtained. But according to the former original paper, the photons have never been present near that mirror. In this work we interpret this result naturally by resorting to the three path interference method. Moreover, we find that even the photons have been somewhere, they can hide the trace of being there.
In order to solve the shortcomings of the traditional contact and non-contact rotational speed measurement methods, and further improve the accuracy and universality of the rotational speed measurement, an instantaneous rotational speed measurement method based on laser Doppler technology is proposed. The principle of laser Doppler velocimeter is expounded, and the composition and working principle of the new system are discussed in detail. Theoretical and experimental results show that: the new rotational speed measurement system belongs to the non-contact measurement method, which greatly improves the applicability and accuracy. Compared to the commonly used speed measurement method, the measurement accuracy of the new speed measurement system will not be affected by the system’s installation angle deviation, and it does not need to measure the radius of the rotating body, so the influence of the radius fluctuation of the rotating body on the measurement accuracy can be avoided while outputting the rotational speed in real time. The relative error of the rotational speed measurement is less than 0.06% (1σ).
PDF全文 (下载：2) ，2021年第19卷第1期 pp.01
One-step precipitation of Ag nanoparticles in Ag+-doped silicate glasses was achieved through a focused picosecond laser with a high-repetition rate. Absorption spectra and transmission electron microscopy (TEM) confirmed that metallic Ag nanoparticles were precipitated within glass samples in the laser-written domain. The surface plasmon absorbance fits well with the experimental absorption spectrum. The nonlinear absorption coefficient β is determined to be 2.47 × 10−14 m/W by fitting the open aperture Z-scan curve, which originating from the intraband transition in the s-p Ag band. The formation mechanism of Ag-glass nanocomposites is discussed as well.
The research on nanophotonic devices has made great progress during the past decades. It is the unremitting pursuit of researchers that realize various device functions to meet practical applications. However, most of the traditional methods rely on human experience and physical inspiration for structural design and parameter optimization, which usually require a lot of resources, and the performance of the designed device is limited. Intelligent algorithms, which are composed of rich optimized algorithms, show a vigorous development trend in the field of nanophotonic devices in recent years. The design of nanophotonic devices by intelligent algorithms can break the restrictions of traditional methods and predict novel configurations, which is universal and efficient for different materials, different structures, different modes and different wavelengths, etc. In this review, intelligent algorithms for designing nanophotonic devices are introduced from their concepts to their applications, including deep learning methods, the gradient-based inverse design method, swarm intelligence algorithms, individual inspired algorithms and some other algorithms. The design principle based on intelligent algorithms and the design of typical new nanophotonic devices are reviewed. Intelligent algorithms can play an important role in designing complex functions and improving the performances of nanophotonic devices, which provide new avenues for the realization of photonic chip.
In this letter, a single scattering turbulence model in a narrow beam case for ultraviolet (UV) communication is proposed based on the division of the effective scattering volume. This model takes the variation of atmospheric scattering, absorption, and turbulence in different paths into account. Meanwhile, the applicable transceiver configurations of this model are provided by analyzing path loss error caused by the single scattering assumption in the UV channel. Furthermore, we investigate the effect of turbulence on the probability density function of the arriving power in both coplanar and non-coplanar scenarios. The averaging effect of multipath propagation on the arriving power’s fluctuations is presented. Then the bit-error-rate performance is also studied. This work provides an efficient way for the UV turbulence channel estimation.
PDF全文 (下载：0) ，2020年第18卷第12期 pp.12
We report on a simultaneous generation of double white light lasers through filamentation by focusing a femtosecond laser pulse. The appearance of the two white light lasers can be controlled by tilting the focusing lens and spectral bandwidth, pulse energy of the double white light lasers were controlled by tuning laser filamenting pulse energy and polarization. Two white light lasers with pulse energies of 1.54 mJ and 1.84 mJ, respectively, were generated with the pump laser energy of 7.43 mJ. Besides being beneficial in understanding the multiple white light lasers generation process through multiple filamentation and its control, the results are also valuable for white light laser-based applications.
PDF全文 (下载：11) ，2020年第18卷第12期 pp.12
A novel tiled Ti: sapphire (Ti:S) amplifier was experimentally demonstrated with >1 J amplified chirped pulse output. Two Ti:S crystals having a dimension of 14 × 14 × 25 mm were tiled as the gain medium in a four-pass amplifier. A maximum output energy of 1.18 J was obtained with 2.75 J pump energy. The energy conversion efficiency of the tiled Ti:S amplifier was comparable with a single Ti:S amplifier. The laser pulse having the maximum peak power of 28 TW was obtained after the compressor. Moreover, the influence of the beam gap on the far field was discussed. This novel tiled Ti:S amplifier technique can provide a potential way for 100 PW or EW lasers in the future.
In this study the effects of purification, dehydration and coagulation processes on the absorption and reduced scattering coefficients of chicken liver tissues have been investigated by using single integrating sphere system. The purification process performed on the tissue samples to remove blood residues has been found to cause a slight change in the optical parameters. Although the dehydration process brings about an increase in the absorption coefficient due to the water loss, no direct relationship has been observed between the reduced scattering coefficient and the dehydration level of the tissue. In addition, it has been observed that there was a relatively small increase in absorption coefficient and a significant increase in reduced scattering coefficient after the coagulation process. Therefore, it can be said that the optical penetration depth decreased significantly after dehydration and coagulation processes unlike blood purification. Moreover, fluence rate distributions inside the fresh, blood purified, dehydrated and coagulated tissue models have been investigated by using MCML simulation code.
In this Letter, we present a display system based on curved screen and parallax barrier, which provides stereo images with a horizontal field of view of 360° without wearing any eyewear, to achieve an immersive autostereoscopic effect. The display principle and characteristics of this display system are studied theoretically in detail. Three consecutive pixels on curved screen and parallax barrier form a display unit, which can generate separate viewing zones for the left and right eyes, respectively. Simulation and experimental results show that non-crosstalk effect can be obtained in the viewing zones, which proves the effectiveness of this display system. This study provides some new ideas for the improvement of the autostereoscopic display and to enable envisioned applications in virtual reality technology.
This paper proposes a novel method for enhancing terahertz (THz) radiation from microstructure photoconductive antennas (MSPCA). We present two types of MSPCA, which contain split-ring resonators (SRR) and dipole photoconductive antennas (D-PCA). The experimental results reveal that when the femtosecond laser is pumping onto the split position of the SRR, the maximum THz radiation power is enhanced by 92 times compared to pumping at the electrode edge of the D-PCA. Two π phase shifts occur as the pumping laser propagates from the negative electrode to the positive electrode. Analysis show that photoinduced carrier charges move within the split position of the SRR.
A rotating Nd:YAG disk laser resonator for efficiently generating vector beam with azimuthal and radial polarization is demonstrated. In the study, the laser crystal is rotary for the thermal alleviation and the polarization discrimination uses a c-cut ytterbium vanadate (YVO4). The laser output could be switched between azimuthal and radial polarizations by simply adjusting the cavity length. The laser power reached 4.38 W azimuthally and 4.64 W radially polarized beams at the slope efficiencies of 45.3% and 48.5%, respectively. Our study proved that an efficient, high-power vector rotary disk lase would be realistic.
PDF全文 (下载：10) ，2020年第18卷第12期 pp.12
In this work, we demonstrated the Bi/Al-codoped silica glass prepared by the laser additive manufacturing technology for the first time. The bismuth was uniformly doped into the silica matrix. The hydroxyl content of the glass sample was measured to be 29.36 ppm. Using 808 nm LD as the excitation source, a broadband NIR emission from 1000 to 1600 nm was obtained. The emission peak was centered at 1249 nm and the corresponding FWHM was more than 400 nm. The results show that the laser additive manufacturing technology is promising to fabricate Bi-doped core materials with high homogeneity and broader emission band, which is beneficial to solve the communication capacity crunch and promotes the development of fiber communication in the upcoming 5th and 6th generation systems.
PDF全文 (下载：9) ，2020年第18卷第12期 pp.12
In this work, a neural network (NN) method is developed for the pulse duration inferring for an erbium-doped fiber laser at 1550 nm. Experimentally, the interferometric autocorrelation trace is observed clearly with the use of the TPA effect in a GaAs photodiode. The intensity autocorrelation function is curve-fitted by the NN with an appropriate performance, and the measuring accuracy is consistent with a commercial autocorrelator. Compared with the Levenberg–Marquardt curve-fitting method, the NN can retrieve the intensity autocorrelation function more stably and has a certain noise reduction ability, simplifying the signal processing for a TPA photodiode-based autocorrelator.
PDF全文 (下载：8) ，2020年第18卷第12期 pp.12
Squeezed vacuum, as a nonclassical field, has many interesting properties and results in many potential applications for quantum measurement and information processing. Here, we investigate a single atom cavity QED system driven by a broadband squeezed vacuum. In the presence of the atom, we show that both the mean photon number and the quantum fluctuations of photons in the cavity undergo a significant depletion due to the additional transition pathways generated by the atom-cavity interaction. We also show that two-photon excitation can be significantly suppressed by the quantum destructive interference when the squeezing strength is very weak. Theses results presented here is helpful to understand the quantum nature of the broadband squeezed vacuum.
PDF全文 (下载：3) ，2020年第18卷第12期 pp.12
In spectral diagnostic physics experiments of inertial confinement fusion, the spectral signal is weak due to the low diffraction efficiency when using the bent crystals. A spectral diagnostic instrument with high efficiency and wide spectral range is urgently needed. A multi-curvature bent crystal with multi-energy focusing ability is proposed based on the traditional conical crystal geometry. It has advantages of wide spectral range, strong focusing ability and A high spectral resolution. It also can eliminate the imaging aberration in principle due to rotational symmetry for the incoming X rays. A spectrum diagnostic experiment based on a fabricated multi-curvature α-quartz crystal was accomplished using a Titanium X-ray tube, of the bend crystal and the corresponding experimental data using a plane α-quartz crystal was also acquired to demonstrate the strong focusing ability. The result shows that the Kα intensity of the multi-curvature α-quartz crystal is 157 times greater than that of the plane crystal, and the corresponding energy range is about 4.51~5.14 keV. This diagnostic instrument could be combined with a streak camera at a vertical direction so as to intensify the diffracted X-ray signal with wide spectral range.
PDF全文 (下载：5) ，2020年第18卷第11期 pp.11
Tian Qing hua
A modulation classification method in combination with Partition-Fractal and SVM learning method is proposed to realize no prior recognition of modulation mode in satellite laser communication system. The effectiveness and accuracy of this method are verified under nine modulation modes and compared with other learning algorithms. The simulation results show when signal-to-noise ratio (SNR) of the modulated signal is more than 8dB, the classifier accuracy based on the proposed method can achieve more than 98%, especially when in BPSK and QASK modes, the classifier achieve 100% identifiable whatever SNR change. In addition, the proposed method has strong scalability to achieve more modulation mode identification in future.
PDF全文 (下载：4) ，2020年第18卷第11期 pp.11
We report on two strategies to design and implement the galvanometer-based laser-scanning mechanisms for the realization of reflection confocal microscopy (RCM) and stimulated Raman scattering (SRS) microscopy systems. The RCM system uses a resonant galvanometer scanner driven by a home-built FPGA circuit with a novel dual-trigger mode and a home-built high-speed data acquisition card. The SRS system uses linear galvanometers with commercially available modules. We demonstrate video-rate high-resolution imaging at 11 frames per second (fps) of in vivo human skin with the RCM system and label-free biomolecular imaging of cancer cells with the SRS system. A comparison of the two strategies for controlling galvanometer scanners provides scientific and technical reference for future design and commercialization of various laser scanning microscopes using galvanometers.
PDF全文 (下载：4) ，2020年第18卷第12期 pp.12
We demonstrate a photonic architecture to enable the separation of ultra-wideband signals. The architecture consists of a channel-interleaved photonic analog-to-digital converter (PADC) and a dilated fully convolutional network (DFCN). The aim of the PADC is to perform ultra-wideband signal acquisition, which introduces the mixing of signals between different frequency bands. To alleviate the interference among wideband signals, the DFCN is applied to reconstruct the waveform of the target signal from the ultra-wideband mixed signals in the time domain. The channel-interleaved PADC provides a wide spectrum reception capability. Relying on the DFCN reconstruction algorithm, the ultra-wideband signals which are originally mixed up are effectively separated. Additionally, experimental results show that the DFCN reconstruction algorithm improves the average bit error rate (BER) by nearly three orders compared with that without the algorithm.