An integrated method based on optical and digital image processing is presented to suppress speckle in digital holography. A spatial light modulator is adopted to introduce random phases to the illuminating beam. Multiple holograms are reconstructed and superimposed, and the intensity is averaged to smooth the noise. The adaptive algorithm based on the nonlocal means is designed to further suppress the speckle. The presented method is compared with other methods. The experimental results show that speckle reduction is improved, and the proposed method is effective and feasible.

A new polarization gating is demonstrated by our principle-of-proof experiment, which is theoretically proposed to generate the isolated or double attosecond pulses with the multi-cycle driving laser pulse in the previous work [Optics Express. 20, 5196 (2012)]. In the experiment, the polarization gating is formed by two orthogonally-polarized linearly chirped multi-cycle laser pulses, and the spectral bandwidths of the harmonics are broadened by more than two times, which agree with the previous theoretical work.

Transmission and reflection of an electromagnetic pulse through a dielectric slab doped with the quantum dot molecules are investigated. It is shown that the transmission and reflection coefficients depend on the inter-dot tunneling effect and can be simply controlled by applying a gate voltage without any changing in the refractive index or thickness of the slab. Such simple controlling prepares an active beam splitter which can be used in all optical switching, optical limiting, and other optical systems.

We report a line-narrowed electro-optic periodically-poled-lithium-niobate (PPLN) Q-switched laser with intra-cavity optical parametric oscillation using a grazing-incidence grating, producing 8-ns, 5-\mu J pulses at 10-kHz repetition rate when pumped with a 10-W diode laser at 808 nm. The output wavelength is centered at 1554.3 nm with a 0.03-nm spectral width. Wavelength tuning is achieved by rotating a mirror and changing the crystal temperature.

Fe-Mn-Si-Cr-Ni composite powders are utilized to form a functional shape memory alloy cladding layer (SMACL) using a laser cladding method. The microstructure, microhardness, and phase composition of the SMACL are measured, and the extent of deformation of the laser cladding samples is determined. The SMACL is composed of planar, cellular, and dendritic crystals, equiaxed grains, and oxides with increasing distance from the substrate surface. The SMACL is further composed of \varepsilon -martensite and \gamma -austenite phases, while the tempered SMACL consists mainly of \gamma -austenite. Extensive deformation occurs in AISI 304 stainless steel laser cladding samples. By contrast, limited deformation is observed in the SMACL samples.

By using PDM-OFDM-16QAM modulation, all-Raman amplification, coherent detection, and 7% forward error correction (FEC) threshold, we successfully demonstrate 63-Tb/s (368×183.3-Gb/s) signal over 160-km standard single mode fiber (SSMF) transmission in the C- and L-bands with 25-GHz channel spacing. 368 optical channels with bandwidth spacing of 25 GHz are generated from 16 external cavity laser sources. After 160-km SSMF transmission, all tested bit error rate (BER) are under 3.8×10-3, which can be recovered by 7% FEC threshold. Within each channel, we achieve the spectral efficiency of 6.85 bit/s/Hz in C/L band.

This letter reports a study of a hybrid burst assembly and a hybrid burst loss recovery scheme (delay-based burst assembly and hybrid loss recovery (DBAHLR)) which selectively employs proactive or reactive loss recovery techniques depending on the classification of traffic into short term and long term, respectively. Traffic prediction and segregation of optical burst switching network flows into the long term and short term are conducted based on predicted link holding times using the hidden Markov model (HMM). The hybrid burst assembly implemented in DBAHLR uses a consecutive average-based burst assembly to handle jitter reduction necessary in real-time applications, with variations in burst sizes due to the non-monotonic nature of the average delay handled by additional burst length thresholding. This dynamic hybrid approach based on HMM prediction provides overall a lower blocking probability and delay and more throughput when compared with forward segment redundancy mechanism or purely HMM prediction-based adaptive burst sizing and wavelength allocation (HMM-TP).

This letter presents a low cost solution for wavelength division multiplexed orthogonal frequency division multiplexed passive optical network (WDM-OFDM-PON) with widely tunable optical filter and linear small form-factor pluggable (SFP) module. With 9-nm tunable range from 1551 to 1560 nm, the tunable filter can support up to 10-channel 100-GHz spacing WDM PON system. A linear avalanche photodiode (APD) based SFP+ module is designed for optical OFDM signal demodulation, which can provide better receiver performance compared with limiting APD module. Experimental results show that ~34 dB power budget can be achieved in 4×5-Gbps WDM-OFDM-PON system, which can satisfy the transmission requirements of next generation PON system.

We demonstrate a digital optical communication system based on minimum shift keying (MSK) signal transmission with coherent detection. 5-Gb/s MSK signal can transmit over a 160-km standard single mode fiber (SSMF) without phase compensation. At the receiver, we use data-aided channel estimation and frequency domain equalization (FDE) techniques in the digital signal processing (DSP) algorithm, then analyze its performance characteristics compared with quadrature phase shift keying (QPSK) format. The simulation results show that the MSK format will be a potential candidate for next-generation access network.

DNA tetrahedral nanostructures are considered to be new nanocarriers because they can be precisely controlled and hold excellent penetration ability to the cellular membrane. Although the DNA tetrahedral nanostructure is extensively studied in biology and medicine, its behavior in the cells with nanoscale resolution is not understood clearly. In this letter, we demonstrate superresolution fluorescence imaging of the distribution of DNA tetrahedral nanostructures in the cell with a simulated emission depletion (STED) microscope, which is built based on a conventional confocal microscope and can provide a resolution of 70 nm.

Transmission and negative refractive index (NRI) of metal-dielectric-metal (MDM) metamaterials perforated with different thickness of dielectric layer are studied. It can be found that transmission peaks of rectangular hole are sensitive to the thickness of the dielectric layer. NRI and the bandwidth of NRI are increased with the increasing of the thickness of dielectric layer. NRI of rectangular hole with the thickness of dielectric layer almost follows a linear law when the thickness of dielectric layer in 2–5 μm. A high NRI of metamateriral can be obtained by adjusting the thickness of the dielectric layer of the rectangular hole on MDM metamateriral arrays.

Two-dimensional metallic photonic crystal slabs with square lattice are proposed to be used for the design of waveguide bandpass filters operating in millimeter to terahertz region. Filter characteristics are studied when rod radii and lattice constants are changed. Based on the frequency scaling technique, a series of higher frequency filters has been designed. By using laser drilling and welding processing techniques, a compact waveguide filter embedded in an EIA-WR10 waveguide with central frequency 145.5 GHz and 3-dB bandwidth of 5.26 GHz is fabricated and measured. The measurement data agree well with the simulation prediction.

A series of Alx-(Alq3)1-x granular films is prepared on Si wafer with native oxide layer using co-evaporation technique. Large lateral photovoltaic effect (LPE) is observed, with an optimal LPV sensitivity of 75 mV/mm in x = 0.35 sample. The dependence of LPE on temperature and Al composition is investigated, and the possible mechanism is discussed.

We describe a surface plasmon resonance-based fiber sensor based on a side-polished graded-index multimode fiber, in which an Al-doped zinc oxide/gold (AZO/Au) bilayer is deposited on the side-polished surface of the fiber core to improve the detection sensitivity of the device. The AZO/Au layer is used as the active sensing member of the device with a combination of a 75-nm-thick AZO layer and a 40-nm-thick Au layer. Such a device is then applied to the concentration measurement of CH3COONa solutions, as an example showing a good response to concentration variation. The results indicate that the additional AZO layer in the active sensing member may lead to higher detection sensitivity and greater measurement stability in the measurements of solution concentration.

This paper proposes the post-integration technology based on sub-pixel image registration and image fusion to improve the signal-to-noise ratio (SNR) of remote sensing images without motion degradation caused by satellite vibration. A two-dimensional vibration system is set up to simulate satellite disturbance. Image sequences with different exposure times are captured using a high-speed CMOS camera. The displacement plots are compared with the motion data measured by the grating linear encoder. These plots indicate that the accuracy of the registration algorithm is better than 0.1 pixels. The sub-pixel image fusion shows an improvement in image quality, thus indicating that this technology is powerful for staring imaging systems in geostationary orbit.

A novel high-throughput spectrometer with a wide-slit is presented. In conventional spectrometers, the slit limited the light throughput. Here, the slit is replaced with a much wider one (200 μm) to increase throughput. A beam splitter is utilized to construct a dual-path optics to measure both non-dispersed and dispersed light intensity which comes from the wide-slit. While the dispersed light intensity is result of the non-dispersed light convoluted spectrum of the source, the spectrum can be acquired by solving the inverse problem of deconvolution. Experiments show that the reconstructed spectra achieved almost the same resolution measured by traditional spectrometer, while throughput and peak signal-to-noise ratio (PSNR) are improved dramatically.

A polymethyl-methacrylate (PMMA) acrylic sample cell using flow injection is developed in this research for the determination of nitrite in an aqueous media. The research focuses on exhibiting direct absorbance spectrophotometry of nitrite using concentration of samples ranging from 0.1078 to 1.725 ppm. Nitrite determination is done colorimetrically using the Greiss reagent method. This method is based on the reaction of nitrite with sulphanilamide acid and N-1-napthylamine (NED) utilizing diazo coupling, and a syringe is used to administer the nitrite solution. The sample cell being used possesses a diameter of 1 mm with an overall size of 7.35×22 mm2. To gauge the direct absorbance, a wavelength range from 400 to 650 nm has been selected for the testing, and the maximum absorbance is found to be at 545 nm. The validity of the proposed cell is explained in this letter.

Different from the cases discussed preciously, nonlinear changes of refractive index in the photorefractive materials are influenced by both the linear and quadratic electro-optic effect simultaneously now. Here we present the evolution equations of one-dimension incoherently coupled spatial soliton families due to two-photon effect in biased photorefractive crystals with both the linear and quadratic electro-optic effect and discuss their existence conditions and properties in detail. Our analysis indicates that these soliton families can exist in all three possible realizations: dark-dark, bright-bright and dark-bright provided that the incident beams have the same polarization, wavelength and are mutually incoherent. Finally, the stabilities of these soliton families have been discussed by means of beam propagation methods.