Showing papers in "Chinese Optics Letters in 2017"
TL;DR: This work reviews recent research progress in complex optical field modulation, multiplexing, and multicasting for data information transfer on different platforms of waveguides, free space, and fiber.
Abstract: Tailored complex optical fields, may find applications in optical manipulation, imaging, microscopy, quantum information processing, and optical communications. Here, we focus on data information transfer for optical communications using complex optical fields. We review recent research progress in complex optical field modulation, multiplexing, and multicasting for data information transfer on different platforms of waveguides, free space, and fiber. Challenges and perspectives are also discussed.
88 citations
TL;DR: In this article, the phase differences between the partially obstructed Gaussian light beam's constituent OAM modes are measured analogous to Stokes polarimetry, and it is shown that phase differences are directly proportional to the object's rotation orientation.
Abstract: Remotely sensing an object with light is essential for burgeoning
technologies, such as autonomous vehicles. Here, an object’s rotational
orientation is remotely sensed using light’s orbital angular momentum. An
object is illuminated by and partially obstructs a Gaussian light beam. Using
an SLM, the phase differences between the partially obstructed Gaussian light
beam’s constituent OAM modes are measured analogous to Stokes polarimetry. It
is shown that the phase differences are directly proportional to the object’s
rotational orientation. Comparison to the use of a pixelated camera and
implementation in the millimeter wave regime are discussed.
33 citations
TL;DR: In this article, a new type of fluoride glasses modified by Al(PO3)(3) with various Tm3+/Ho3+ doping concentrations were investigated, and it was shown that the introduced PO3- plays an effective role in improving the glass-forming ability and thermal stability.
Abstract: In this work, we investigate a new type of fluoride glasses modified by Al(PO3)(3) with various Tm3+/Ho3+ doping concentrations. The introduced PO3- plays an effective role in improving the glass-forming ability and thermal stability. Besides, 1.47, 1.8, and 2.0 mu m emissions originating from Tm3+ and Ho3+, respectively, are observed. The spectroscopic properties and energy transfer mechanisms between Tm3+ and Ho3+ are analyzed as well. It is noted that the higher predicted spontaneous transition probability (118.74 s(-1)) along with the larger product of measured decay lifetime and the emission cross section (sigma(emi) x tau) give evidence of intense 2.0 mu m fluorescence.
28 citations
TL;DR: Over a decade of technology evolution and advancement of intra-datacenter optical interconnect is reviewed, mainly driven by the explosive bandwidth growth of web and cloud-based services.
Abstract: We review over a decade of technology evolution and advancement of intra-datacenter optical interconnect, mainly driven by the explosive bandwidth growth of web and cloud-based services. Emerging trends and technology options to scale interface bandwidth beyond 400 Gb/s will also be discussed.
28 citations
TL;DR: An artificial neural-network-based visible light positioning algorithm is proposed in this Letter, and a trained neural network is used to achieve positioning with a diffuse channel.
Abstract: Visible light positioning becomes popular recently. However, its performance is degraded by the indoor diffuse optical channel. An artificial neural-network-based visible light positioning algorithm is proposed in this Letter, and a trained neural network is used to achieve positioning with a diffuse channel. Simulations are made to evaluate the proposed positioning algorithm. Results show that the average positioning error is reduced about 13 times, and the positioning time is reduced about two magnitudes. Moreover, the proposed algorithm is robust with a different field-of-view of the receiver and the reflectivity of the wall, which is suitable for various positioning applications.
24 citations
TL;DR: Results validate that the photonics-based radar is feasible in practical real-time and high-resolution ISAR imaging applications.
Abstract: Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar (ISAR). By photonic generation and de-chirping of broadband linear frequency modulation signals, the radar can achieve a high range resolution thanks to the large instantaneous bandwidth (8 GHz at the K band), as well as real-time ISAR imaging using low-speed analog-to-digital conversion (25 MSa/s). A small-size unmanned aerial vehicle is employed as the non-cooperative target, and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs. The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps. These results validate that the photonics-based radar is feasible in practical real-time and high-resolution ISAR imaging applications.
22 citations
TL;DR: In this article, a femtosecond laser transversal-scanning method was used to construct a high temperature-sensitive long period fiber grating (LPFG) sensor.
Abstract: We propose a high temperature-sensitive long period fiber grating (LPFG) sensor fabricated by using the femtosecond laser transversal-scanning method. The femtosecond pulses scan over the whole fiber core and some part of the cladding region; the modified regions are more extended. It is found that the LPFG-I fabricated by the transversal-scanning method shows higher temperature sensitivity and better temperature uniformity than that of LPFG-II written by the femtosecond laser point-by-point method. The LPFG-I with a temperature sensitivity of 75.96 pm/°C in the range of 25°C–400°C is measured. Moreover, in the range from 400°C to 800°C, a higher temperature sensitivity of 148.64 pm/°C and good linearity of 0.99 are achieved, while the temperature sensitivity of LPFG-II is only 95.55 pm/°C. LPFG-I exhibits better temperature characteristics, which, to the best of our knowledge, has the highest sensitivity in silica fiber temperature sensors.
22 citations
TL;DR: In this article, an optical sensor is designed to support the Fano effect based on a compound resonant waveguide grating (CRWG), and the transmission spectra of the CRWG are investigated by utilizing a theoretical method that combines the temporal coupled mode theory with the eigenmode information of the grating structure.
Abstract: An optical sensor is designed to support the Fano effect based on a compound resonant waveguide grating (CRWG). The transmission spectra of the CRWG are investigated by utilizing a theoretical method that combines the temporal coupled mode theory with the eigenmode information of the grating structure. The theoretical results, which are observed to agree closely with those acquired by rigorous coupled-wave analysis, show that the linewidth of the transmission spectrum decreases upon increasing the distance between the grating strips, and the central resonance frequency decreases as the refractive index of the analyte increases. Here, the proposed CRWG structures will find potential uses in optical sensing.
21 citations
TL;DR: In this article, the authors reported a continuous-wave Er:ZBLAN fiber laser with the operation wavelength reaching 3.68μm, which is the longest emission wavelength in free-running Er-ZBLan fiber lasers.
Abstract: We report a continuous-wave Er:ZBLAN fiber laser with the operation wavelength reaching 3.68 μm. The mid-infrared Er:ZBLAN fiber laser is pumped with the dual-wavelength sources consisting of a commercial laser diode at 970 nm and a homemade Tm-doped fiber laser at 1973 nm. By increasing the launched pump power at 1973 nm, the laser wavelength can be switched from 3.52 to 3.68 μm. The maximum output power of 0.85 W is obtained with a slope efficiency of 25.14% with respect to the 1973 nm pump power. In the experiment, the laser emission at 3.68 μm is obtained with a significant power of 0.62 W, which is the longest emission wavelength in free-running Er:ZBLAN fiber lasers.
21 citations
TL;DR: In this article, the transmission range of non-line-of-sight ultraviolet communication was extended to 500m in a real-time system experiment using a 200mW solid-state 266nm laser, where the data rate can reach 400kbps at a frame error rate lower than 10−5.
Abstract: We extend the transmission range of non-line-of-sight ultraviolet communication to 500 m in a real-time system experiment using a 200 mW solid-state 266 nm laser, where the data rate can reach 400 kbps at a frame error rate lower than 10−5 in the real-time system test. The results can beat the best record so far, in terms of both the data rate and transmission distance.
20 citations
TL;DR: In this article, the authors report the recent progress of their pulsed optically pumped (POP) vapor cell rubidium clock with dispersive detection, achieving a clock frequency stability of 3.53×10?13 at 1 s.
Abstract: We report the recent progress of our pulsed optically pumped (POP) vapor cell rubidium clock with dispersive detection. A new compact physics package is made. A rubidium cell with a high precision buffer gases mixing ratio is obtained, and the temperature controlling system is renovated to reduce fractional frequency sensitivity to temperature variation. The resolution of the servo control voltage is also optimized. With these improvements, a clock frequency stability of 3.53×10?13 at 1 s is obtained, and a fractional frequency stability of 4.91×10?15 is achieved at an average time of τ=2000 s.
TL;DR: A femtosecond mode-locked erbium-doped fiber laser (EDFL) using a nickel oxide (NiO) as a saturable absorber (SA) was demonstrated in this article.
Abstract: We demonstrate a femtosecond mode-locked erbium-doped fiber laser (EDFL) using a nickel oxide (NiO) as a saturable absorber (SA). NiO nanoparticles are hosted into polyethylene oxide film and attached to fiber ferrule in the laser cavity. The NiO-SA shows a 39% modulation depth with a 0.04 MW/cm2 saturation intensity. Our ring laser cavity based on erbium-doped active fiber with managed intracavity dispersion has the ability to generate ultrashort pulses with a full width at half-maximum (FWHM) of around 2.85 nm centered at 1561.8 nm. The pulses repeat at a frequency of 0.96 MHz and duration of 950 fs.
TL;DR: In this paper, a full-band direct-conversion receiver using a microwave photonic in-phase and quadrature (I/Q) mixer is proposed and experimentally evaluated in terms of radio frequency (RF) range, port isolation, phase imbalance, conversion gain, noise figure, spurious-free dynamic range, and error vector magnitude.
Abstract: A full-band direct-conversion receiver using a microwave photonic in-phase and quadrature (I/Q) mixer is proposed and experimentally evaluated in terms of radio frequency (RF) range, port isolation, phase imbalance, conversion gain, noise figure, spurious-free dynamic range, and error vector magnitude. The proposed microwave photonic I/Q mixer shows significant advantages in local oscillator leakage and I/Q phase imbalance over entire RF bands, which are recognized as major drawbacks of conventional direct-conversion receivers.
TL;DR: In this article, a 360° light field 3D display system is presented, which consists of a liquid crystal display, a novel triplet lenses array, and a holographic functional screen.
Abstract: A 360° light field 3D display system is presented, which consists of a liquid crystal display, a novel triplet lenses array, and a holographic functional screen (HFS). The mapping relationship among pixels, 3D objects, and viewing positions are investigated. The aberration analysis of the single lens is carried out both in the simulation and the experiment, which shows that it cannot provide an excellent 3D image to the viewers. In order to suppress the aberrations, “the primary aberration theory” and “the damped least-squares method” are used for optical analysis and lens design. A 3D image with aberration correction can be viewed around the proposed display system.
TL;DR: Zhang et al. as mentioned in this paper proposed a new detection method, dark-field detection of adaptive smoothing and morphological differencing (DFD-ASMD), which can lay a foundation for quality control of defects on the high quality optical surface.
Abstract: There exist some shallow scratch defects on the super-smooth optical surface. Their detection has a low efficiency with the existing technologies. So a new detection method, dark-field detection of adaptive smoothing and morphological differencing (DFD-ASMD), is proposed. On one hand, the information of shallow scratches can be kept in dark-field images. On the other hand, their weak characteristics can be separated and protected from being overly reduced during the elimination of noise and background in the image. Experiments show the detection rate of shallow scratches is around 82%, and DFD-ASMD can lay a foundation for quality control of defects on the high-quality optical surface.
TL;DR: The results suggest that the cerebral veins rather than microvessels are sensitive components of the CBF related to the opening BBB, and the elevation of the BBB permeability is associated with the decrease of venous CBF and the increase of its complexity.
Abstract: The cerebral blood flow (CBF) alterations related to sound-induced opening of the blood–brain barrier (BBB) in adult mice are studied using laser speckle contrast imaging (LSCI) and wavelet analysis of vascular physiology. The results clearly show that the opening of the BBB is accompanied by the changes of venous but not microvessel circulation in the brain. The elevation of the BBB permeability is associated with the decrease of venous CBF and the increase of its complexity. These data suggest that the cerebral veins rather than microvessels are sensitive components of the CBF related to the opening BBB.
TL;DR: In this paper, the authors demonstrate the generation of sub-100-fs pulses from a diode-pumped passively mode-locked Yb:Y3ScAl4O12 (Yb-YSAG) ceramic laser.
Abstract: We experimentally demonstrate the generation of sub-100-fs pulses from a diode-pumped passively mode-locked Yb:Y3ScAl4O12 (Yb:YSAG) ceramic laser. Stable mode-locked pulses as short as 96 fs at the central wavelength of 1052 nm with a repetition rate of ∼102 MHz are obtained. The laser has a maximum average output power of 51 mW. To the best of our knowledge, these are so far the shortest pulses and the first demonstration of sub-100-fs pulses obtained from the mode-locked Yb:YSAG ceramic lasers.
TL;DR: In this article, a dual-wavelength fiber laser operating at the 1550nm region using a side-polished arc-shaped fiber with deposited ZnO nanoparticles is proposed and demonstrated.
Abstract: A dual-wavelength fiber laser operating at the 1550 nm region using a side-polished arc-shaped fiber with deposited ZnO nanoparticles is proposed and demonstrated. The arc-polished fiber is fabricated by using a simple but novel approach in which a silicon carbide paper polishes one side of a conventional single-mode fiber. An arc-polished fiber with a length of 2.25 mm and an insertion loss of 0.95 dB is obtained and deposited with ZnO nanoparticles by the drop-cast method. A stable dual-wavelength output is obtained at 1562.5 and 1563.4 nm at peak powers of −9.3 and −10.1 dBm, respectively, as well as a signal-to-noise ratio of 28.4 dB and a channel spacing of 0.9 nm. Both lasing wavelengths also have narrow linewidths of between 0.045 and 0.049 nm and show little to no wavelength or power fluctuations over continued testing.
TL;DR: Graphene-based split ring resonator (SRR) as discussed by the authors was proposed with the capacity for modulating transmitted terahertz (THz) waves under normal and oblique incidence.
Abstract: The plasmonic mode in graphene metamaterial provides a new approach to
manipulate terahertz (THz) waves. Graphene-based split ring resonator (SRR)
metamaterial is proposed with the capacity for modulating transmitted THz
waves under normal and oblique incidence. Here, we theoretically demonstrate
that the resonant strength of the dipolar mode can be significantly enhanced
by enlarging the arm-width of the SRR and by stacking graphene layers. The
principal mechanism of light–matter interaction in graphene metamaterial
provides a dynamical modulation based on the controllable graphene Fermi
level. This graphene-based design paves the way for a myriad of important THz
applications, such as optical modulators, absorbers, polarizers,
etc.
TL;DR: In this paper, a frequency-stabilized laser system at 1572nm for space-borne carbon dioxide (CO2) detection LIDAR to realize the precise measurement of the global atmospheric CO2 concentration is presented.
Abstract: A frequency-stabilized laser system at 1572 nm for space-borne carbon dioxide (CO2) detection LIDAR to realize the precise measurement of the global atmospheric CO2 concentration is presented in this Letter. A distributed-feedback laser diode serves as the master laser (ML) and is wavelength locked to the CO2 line center at 1572.0179 nm using the external frequency modulation technique. The root mean square frequency drift is suppressed to about 50 kHz at an average time of 0.1 s over 8 h. Based on optical phase-locked loops, an online seeder and an offline seeder are offset locked to the reference laser at 1572.024 and 1572.081 nm, respectively, retaining virtually the same frequency stability as the ML.
TL;DR: In this paper, a polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional (2D) scanning with high efficiency, where the core components are two polarization-dependent devices, which are called liquid crystal optical phased arrays (LC-OPAs).
Abstract: A polarization-independent nonmechanical laser beam steering scheme is proposed to realize continuous two-dimensional (2D) scanning with high efficiency, where the core components are two polarization-dependent devices, which are called liquid crystal optical phased arrays (LC-OPAs). These two one-dimensional (1D) devices are orthogonally cascaded to work on the state of azimuthal and elevation steering, respectively. Properties of polarization independence as well as 2D beam steering are mathematically and experimentally verified with a good agreement. Based on the experimental setup, linearly polarized beams with different polarization angles are steered with high accuracy. The measured angular deviations are less than 5 μrad, which is on the same order of the accuracy of the measurement system. This polarization-independent 2D laser beam steering scheme has potential application for nonmechanical laser communication, lidar, and other LC-based systems.
TL;DR: In this article, the authors reported a Golay3 sparse-aperture telescope with 3.33μrad with respect to the diffraction limit of 6.07μrad using the Rayleigh criteria at 632nm.
Abstract: In this Letter, we report a Golay3 sparse-aperture telescope newly built in the Key Laboratory of Optical Engineering, Chinese Academy of Sciences and present the experimental results of enhanced resolution. The telescope consisting of 3 collector telescopes of 127 mm diameter can achieve a theoretical resolution corresponding to a monolithic aperture of 245 mm diameter. It is shown by the experimental results that the resolution is improved to 3.33 μrad with respect to the diffraction limit of 6.07 μrad for a single aperture using the Rayleigh criteria at 632 nm. The compact optical configuration and cophasing approach are also described.
TL;DR: In this article, the authors proposed a method for measuring the double correlation function (DCF) of a partially coherent vortex beam and demonstrated the determination of the mode orders of the beam.
Abstract: It is known that one can determine the mode orders (i.e., the azimuthal order and radial order) of a partially coherent LGpl beam (i.e., a partially coherent vortex beam) based on the measurement of the cross-correlation function (CCF) and the double correlation function (DCF) together. The technique for measuring the CCF is known. In this Letter, we propose a method for measuring the DCF. Based on the proposed method, the determination of the mode orders of a partially coherent LGpl beam is demonstrated experimentally.
TL;DR: In this paper, a temperature-insensitive refractive index (RI) fiber sensor based on a Mach-Zehnder interferometer was proposed, where two microcavities were formed at both junctions because of the collapse of the photonic crystal fiber air holes.
Abstract: We propose a temperature-insensitive refractive index (RI) fiber sensor based on a Mach–Zehnder interferometer. The sensor with high sensitivity and a robust structure is fabricated by splicing a short photonic crystal fiber (PCF) between two single-mode fibers, where two microcavities are formed at both junctions because of the collapse of the PCF air holes. The microcavity with a larger equatorial dimension can excite higher-order cladding modes, so the sensor presents a high RI sensitivity, which can reach 244.16 nm/RIU in the RI range of 1.333–1.3778. Meanwhile it has a low temperature sensitivity of 0.005 nm/°C in the range of 33°C–360°C.
TL;DR: In this article, a femtosecond laser pulse train is used to improve the success probability of chemical etchings in a fused silica glass micro-channel, and the optimum pulse energy distribution ratio to the etching is also investigated.
Abstract: A fused silica glass micro-channel can be formed by chemical etching after femtosecond laser irradiation, and the successful etching probability is only 48%. In order to improve the micro-channel fabrication success probability, the method of processing a high-temperature lattice by a femtosecond laser pulse train is provided. With the same pulse energy and scanning speed, the success probability can be increased to 98% by optimizing pulse delay. The enhancement is mainly caused by the nanostructure, which changes from a periodic slabs structure to some intensive and loose pore structures. In this Letter, the optimum pulse energy distribution ratio to the etching is also investigated. OCIS codes: 140.0140, 230.7380, 260.0260. doi: 10.3788/COL201715.071403.
TL;DR: In this article, the authors provide an overview of the recent work on subwavelength grating (SWG) waveguide devices as an enabling technology for integrated microwave photonics, including ring resonators, Bragg gratings, and contradirectional couplers.
Abstract: We provide an overview of our recent work on developing subwavelength grating (SWG) waveguide devices as an enabling technology for integrated microwave photonics. First, we describe wavelength-selective SWG waveguide filters, including ring resonators, Bragg gratings, and contradirectional couplers. Second, we discuss the development of an index variable optical true time delay line that exploits spatial diversity in an equal-length waveguide array. These SWG waveguide components are fundamental building blocks for realizing more complex structures for advanced microwave photonic signal processing.
TL;DR: Comparisons with the currently employed element-based algorithms, stepwise sequential algorithm (SSA), and continuous sequential algorithms (CSA) show that FEDA only takes one third of the measurement time to find the optimized solution, which means that it is promising in practical applications, such as for deep tissue imaging.
Abstract: Aiming to overcome the low converging rate and susceptibility to the environment in focusing the coherent light through the turbid medium, four-element division algorithm (FEDA) optimization is proposed. Full levels of comparisons with the currently employed element-based algorithms, stepwise sequential algorithm (SSA), and continuous sequential algorithm (CSA) show that FEDA only takes one third of the measurement time to find the optimized solution, which means that FEDA is promising in practical applications, such as for deep tissue imaging.
TL;DR: In this paper, the influence of chirped parameter C on the propagation of the CAiV beams through slabs of left-handed materials (LHMs) and right-handed material (RHMs) is discussed.
Abstract: We present an investigation on the propagation properties of the chirped Airy vortex (CAiV) beams through slabs of left-handed materials (LHMs) and right-handed materials (RHMs). We discuss the influence of chirped parameter C on the propagation of the CAiV beams through LHM and RHM slabs. Our simulation results show that a maximum accelerated velocity appears during the propagation process. The intensity concentration of the CAiV beams increases with the absolute value of the chirped parameter. The peak intensity of the CAiV beams changes abruptly, and the chirped parameter plays an active role on the difference of the maximum and the minimum. In the energy flow, we find that the effects of the chirped parameter on the strength of the vortex are different at different propagation distances.
TL;DR: In this article, a molybdenum sulfide selenide (MoSSe)-based saturable absorber (SA) was used to measure the modulation depth and saturation intensity of the SA.
Abstract: Passively Q-switched ytterbium-doped fiber lasers (YDFLs) incorporating a molybdenum sulfide selenide (MoSSe)-based saturable absorber (SA) are demonstrated. The modulation depth and saturation intensity of the MoSSe-based SA are measured to be approximately 25.0% and 0.002 MW/cm2, respectively, using the twin detector technique. The YDFL’s output has a center wavelength of 1038.5 nm with a top pulse width and energy of 1.2 μs and 18.9 nJ, respectively, at a pump power of 333 mW. The MoSSe-based SA has a good linear optical response, providing significant opportunity for use in applications over an ultra-broadband spectrum, particularly spectroscopy and biomedical diagnostics.
TL;DR: A lamp-pumped Nd: phosphate glass laser amplifier delivering up to 1 J of pulse energy at 1053 nm with a repetition rate of 1 Hz and an injected pulse energy of 2.5 mJ is presented in this article.
Abstract: We present a lamp-pumped Nd: phosphate glass laser amplifier delivering up to 1 J of pulse energy at 1053 nm with a repetition rate of 1 Hz and an injected pulse energy of 2.5 mJ. The amplifier system employs a beam-shaping module and a four-pass, lamp-pumped amplifier. The thermally induced wavefront distortion is mitigated and a uniform gain distribution is obtained by a four-lamp-pumped laser head in the amplifier. Thus, an excellent beam quality is obtained.