In the context of correspondence ghost imaging, we utilize the correlation coefficients to separate the reference detector speckle patterns into positive and negative correlated parts. A positive image and a negative image of the object are obtained by averaging over corresponding speckle patterns. The visibility and contrast-to-noise ratio of the positive image are discussed, and it is found that the latter will reach a maximum by averaging over a little less than half of the total number of reference speckle patterns.

We propose a system of time-division multiplexing (TDM) and spatial frequency-division multiplexing (SFDM). Extrinsic Fabry–Perot interferometric sensors are applied to detect weak acoustic signals. The broadband source is employed, the light from it is modulated by a pulse signal sequence and is efficiently amplified by semiconductor optical amplifiers. Experimental results show that the equivalent noise pressure spectrum level is -97.2 dB re 1 rad/vHz below 1250 Hz, and the cross talk between two sensors in one TDM channel is -32.7 dB with a cavity length difference of 60 μm. The number of sensors in this multiplexing system can theoretically reach 160.

We experimentally demonstrate multichannel wavelength multicasting for two nonreturn-to-zero quadrature phase-shift keying (NRZ-QPSK) channels based on four-wave mixing (FWM) in semiconductor optical amplifier (SOA). Through the interaction with the two pumps in SOA, the input two 25 Gb/s NRZ-QPSK channels are successfully simultaneously multicast to five and two new wavelengths, respectively. All the multicast channels are with a power penalty less than 2.5 dB at a bit error rate (BER) of 10-3. A characterization of the system performance using conversion efficiency and BER as figures-of-merit in terms of pump and signal powers is also presented. The results indicate that the pump and signal powers can be optimized to eliminate the introduced deleterious nonlinear components. The wavelengths of the two NRZ-QPSK channels and the two pumps need to be specified to avoid the crosstalk induced by high-order FWM.

We present a new structure of nearly-zero flattened dispersion and highly nonlinear photonic crystal fiber (PCF) in the telecommunication window. This fiber design is comprised of a hybrid-core region with -bismuth-doped region in the center and three lower bismuth-doped regions in the first ring that enables dispersion control while maintaining a high nonlinear coefficient. Numerical analysis results show that the proposed PCF is achieved with a nonlinear coefficient of about 3301 W-1 km-1, a dispersion value of about 0.5537 ps/(nm·km) at 1550 nm, and nearly-zero flattened dispersion fluctuating within 2.5 ps/(nm·km) ranging from 1.496 to 1.596 μm.

We propose a security-enhanced double-random phase encryption (DRPE) scheme using orthogonally encoded image and electronically synthesized key data to cope with the security problem of DRPE technique caused by fixed double-random phase masks for encryption. In the proposed scheme, we adopt the electronically synthesized key to frequently update the phase mask using a spatial light modulator, and also employ the orthogonal encoding technique to encode the image and electronically synthesized key data, which can enhance the security of both data. We provide detailed procedures for encryption and decryption of the proposed scheme, and provide the simulation results to show the encryption effects of the proposed scheme.

We demonstrate the theory of chromatic dispersion (CD)-induced constellation rotation (CR) in a radio-over-fiber (ROF) link and a method for compensation. We also propose a 60 GHz full-duplex ROF system with vector signal transmission including no CD effect. The evaluation of 5 Gb/s 16 quadrature amplitude modulation signal transmission shows that the CD-induced CR can be entirely overcome due to the proposed method which is simply implemented through an optical phase shifter. The proposed ROF schedule is not only applicable for V-band (57–64 GHz) but also fits for W-band (75–110 GHz), or any other bandwidth.

We demonstrate a new scheme for generation of optical frequency comb (OFC) based on cascade modulators, 23 comb lines within 0.5 dB spectral power variation are obtained. An optical finite impulse response (FIR) filter is introduced for suppression of amplified spontaneous emission noise. It is shown that carrier-to-noise-ratio of the OFC generated by this scheme can be as high as 38.8 dB with 12 dB improvement by using a 16-tap FIR filter, and the error vector magnitude performances of loaded Nyquist-16 quadrature amplitude -modulation signal is improved from 14.20% to 7.44%.

In an optical performance monitoring system for high-speed optical communications, the ultra-short optical pulse from the laser is divided into two parts. One is to sample high-speed optical communication signal and the other as the sampling clock in an analog/digital converter (ADC) after detecting using a photon-detector. We propose a simple method based on variance calculation to align the phase of sampling clock in an ADC. The experiments demonstrate that, with the proposed method, the eye diagram or constellation diagram of high-speed optical communication signal can be reconstructed by the optical performance monitoring system.

With the development of the micro/nanolithography, the optic–optic or optic–electronic modulation devices with different pixel shapes and sizes can be used for three-dimensional (3D) dynamical holographic display. The influence of different parameters of the modulation devices on the image quality of the 3D reconstructed object is analyzed for two cases: the phase-only computer-generated holography (CGH) and the complex amplitude CGH. The results quantitatively show that the pixel shape of the modulation devices will affect the quality of the holographic image.

We present a high dense views auto-stereoscopic three-dimensional display method with the projectors array and lenticular lens array (LLA) screen. The principle and configuration are demonstrated. This display method utilizes lenticular screen to modulate the information of projectors. To increase the dense of views, we propose a novel arrangement way of projectors array. In the experiment, the viewer can obtain smooth motion parallax and evident stereo feeling at optimal distance. Through analyzing and observation, the maximum display depth is found to be more than 50 cm.

We demonstrate time-division-multiplexing (TDM) laser seeded optical amplification in a diode laser amplifier. With an acousto-optic modulator we combine two seeding beams of different frequencies and inject them alternately in the time domain into the tapered amplifier (TA) chip at a switching speed of 200 ns. The output high-power dual frequency components from the TA are time separated. The TDM seeded TA works safely and efficiently, which is useful for compact precision measurement instruments such as optical clocks and atom interferometers.

We investigate the influence of environmental media on ablation rate of AISI 443 stainless steel under femtosecond (fs) laser single raster scan and multiple raster scans in air, water, and methanol. Meanwhile, the development of ablation rate with the change of fs laser-induced surface morphology in the three environmental media is comparatively studied. The results show that environmental media as well as fs laser-induced morphology control the ablation rate with the increasing number of raster scans (N). Under single raster scanning (N = 1), the ablation rate is higher in liquid than in air due to the confinement of plasma, laser-induced shockwaves, and bubble-related mechanical forces. However, under multiple raster scans, the variation in ablation rate with the increase in N in these three environmental media is complicated and is largely determined by the surface morphology induced by previous fs laser ablation. When N > 20, the ablation rate is much higher in air than in liquids due to preferential ablation caused by the formation of nanostructures-textured mound-shaped microstructures in air. Besides, the redeposition of ejected ablated materials is also an important factor that affects the ablation depth.

We demonstrate a diode-pumped picosecond Yb-doped silicate Yb3+:Sc2SiO5 (Yb:SSO) chirped pulse amplifier. The seed source with a pulse width of 220 fs is a diode-pumped Yb:KGW femtosecond oscillator. A single chirped volume Bragg grating is employed both as a pulse stretcher and as a compressor to improve the compactness of the system. Stretched pulse is amplified using a diode-pumped Yb:SSO regenerative amplifier. The maximum amplified pulse energy obtained at a pump power of 13.5 W is 450 μJ. The amplified pulse is centered at 1033.3 nm before compression at a frequency of 1 kHz. After compression, the pulse energy is 315 μJ with a pulse duration of approximately 1 ps.

We experimentally demonstrate a femtosecond optical parametric oscillator (OPO) synchronously pumped by a home-made solid-state mode-locking Yb:YCOB laser, which is capable of laser pulse as short as 102 fs and average power of 620 mW at the central wavelength of 1052 nm. By using a periodically poled lithium niobate with tuning of the grating periods from 28.5 to 31.5 μm as the nonlinear gain crystal, tunable femtosecond pulses from 1444 to 1683 nm are realized by conveniently adjusting the OPO cavity length with 76.8 MHz repetition rate. The maximum average output power is 152 mW at 1568 nm, corresponding to an idler power of 75 mW at 3197 nm as well as 36.6% total extraction efficiency.

We investigate terahertz radiation (T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature.

We present the single-slit diffraction of the arbitrary vector fields with different parameters m, n, and f0 theoretically and experimentally. The single slit covers the polarization singularity in the center and therefore the influence of the polarization singularity on the diffraction fringes is analyzed. The experimental results which agree well with the simulation results show that the total intensity of the diffraction field is related only to the topological charge m, but the polarization distribution of the diffraction field is related to all the parameters m, n, and f0. Therefore, the diffraction patterns allow to determine all the parameters of the arbitrary vector fields.

A terahertz (THz) broadband polarizer using bilayer subwavelength metal wire-grid structure on both sides of polyimide film is simulated by the finite-difference time-domain method. We analyze the effect of film -thickness, material loss, and lateral shift between two metallic gratings on the performance of the THz -polarizer. Bilayer wire-grid polarizers are fabricated by a simple way of laser induced and non-electrolytic plating with copper. The THz time-domain spectroscopy measurements show that in 0.2–1.6 THz frequency range, the extinction ratio is better than 45 dB, the average extinction ratio reaches 53 dB, and the -transmittance exceeds 67%, which shows great advantage over conventional single wire-grid THz polarizer.

We present a technique and algorithm for measuring the phase retardation of a wave plate based on spectral transmission curve. Through accurately extracting the intersection points' wavelengths from the spectral transmission curve, the effective phase retardation, absolute phase retardation, order, and physical thickness of the wave plate can be measured simultaneously in a wide spectral range. Experimental results show that the proposed technique has many advantages, such as higher data utilization, simpler extraction algorithm, and no strict requirement for the directions of transmission axes of the polarizer and analyzer, and the fast axis of the wave plate.

Quantum key distribution (QKD) is a major research topic because it provides unconditional security. Unfortunately, many imperfections remain in QKD's experimental realization. The Faraday–Michelson (FM) QKD system is proposed to eliminate these imperfections using polarization. However, the long arm's phase modulator (PM) has an unexpected insertion loss, meaning that the state sent is no longer perfect. In this letter, we propose an alternative FM-QKD system structure, and analyze the security and key generation rate in comparison with the original system via diffeerent analysis methods. We find an obvious key rate improvement when the PM insertion loss is not extremely small.

Squeezed state of light explores a new era in noiseless communication and data processing recently breaking the quantum limit of noise. We propose a new mechanism of modulating an amplitude-squeezed signal with the instantaneous intensity variation of a coherent signal. The modulating signal is a coherent light where the amplitude-squeezed light takes the role of a carrier signal.

We present a Herriott-type multipass laser absorption spectrometer enhanced by optical heterodyne detection. The proposal is demonstrated by measuring the spectra of water vapor molecule in the region from 12247.6873 to 12249.6954 cm-1. Compared with direct absorption spectroscopy, the signal-to-noise ratio is improved nearly one magnitude of factor by combining with the optical heterodyne spectroscopy and extra weak absorption lines are observed. The minimum detectable absorption is estimated at 4.36×10-8 cm-1and the measured line shape dominated by Doppler broadening can be precisely recovered by direct transformation of experimental optical heterodyne spectral profile.