A new polarimeter based on optical non-reciprocity in gratings with two-dimensional chirality

We have studied the optical transmission properties of a number of different dielectric diffraction gratings that each exhibit two-dimensional chirality in their grating elements. We have found that the diffracted beams transmitted through these structures exhibit large anisotropic polarization changes and polarization-dependent intensity modulations even though the chiral elements are arranged in square grating arrays. The strength and functional form of both of these effects differ for each diffracted beam. They are also dependent on the chirality of the surface patterning and the thickness of the patterned dielectric film. We show how these properties could be exploited to provide a new and more versatile form of polarimeter, and how the operation of such a device is inherently dependent on the optical non-reciprocity of these chiral gratings.     

Improved output energy characteristic of optical limiting based on double stimulated Brillouin scattering

In order to improve the optical limiting performance based on stimulated Brillouin scattering (SBS), a method based on double SBS is proposed in this paper. The dependence of the output energy of optical limiting based on double SBS on the pump energy is numerically simulated, and experimentally validated with an Nd:YAG seed-injected laser. The results indicate that only the first SBS optical limiting works in the case of low pump energy. However, as the pump energy increases, the second SBS process can be activated if the transmitted power of the first SBS is still above the SBS threshold. Therefore, the output energy characteristic of optical limiting based on double SBS is much better than that based on single SBS. Owing to the sub-nanosecond response time and a high power threshold, the SBS optical limiting can provide protection in high power laser systems.     

A novel subwavelength plasmon-polariton optical filter based on tilted coupled structures

This work proposes a completely new approach for the design of resonant structures aiming at wavelength-filtering applications. The structure consists of a subwavelength metal-insulator-metal (MIM) waveguide presenting tilted coupled structures transversely arranged in the midpoint between the input and output ports. The cavity-like response of this device has shown that this concept can be particularly attractive for optical filter design for telecom applications. The extra degree of freedom provided by the tilting of the cavity has proved to be not only very effective on improving the quality factor of these structures, but also to be an elegant way of extending the range of applications for tuning multiple wavelengths, if necessary.     

Compact and widely tunable terahertz source based on a dual-wavelength intracavity optical parametric oscillation

In this paper, a continuously tunable terahertz (THz) source is obtained using a compact intracavity pumped dual-wavelength optical parametric oscillation operating around 2.1 μm as difference-frequency generation pump source. The tuning range of the THz-wave frequency covers from 0.147 THz to 3.651 THz. Based on the collinear difference-frequency generation in the GaSe crystal, the experiment result shows that our schematic is a good option to construct a compact and portable terahertz source with widely tunable range.     

A terabit capacity passive polymer optical backplane based on a novel meshed waveguide architecture

An optical backplane based on a meshed polymer waveguide architecture enabling high-speed board-to-board optical interconnection is presented. This planar array of multimode polymer waveguides can provide passive strictly non-blocking links between server line cards fitted with optical transmitter and receiver arrays. This architecture offers a scalable and low-cost solution to the bandwidth limitations faced by electrical backplanes and is suitable for PCB integration. The reported backplane demonstrator uses a matrix of 100 waveguides each capable of 10 Gb/s operation to interconnect 10 cards for a total capacity of a terabit per second aggregate data rate in multicast mode. Characterisation of the backplane demonstrator reveals low link losses of 2 to 8 dB for a multimode fibre input and crosstalk values below −35 dB. Error free data transmission at 10 Gb/s is achieved with a power penalty of only 0.2 dB at a bit-error-rate of 10⁻⁹. Additionally, lossless operation of a Gigabit Ethernet link over the backplane is achieved even when using the worst-case highest loss links.     

Measurements of cavitation bubble dynamics based on a beam-deflection probe

We present an optodynamic measurement of a laser-induced cavitation bubble and its oscillations based on a scanning technique using a laser beam-deflection probe. The deflection of the beam was detected with a fast quadrant photodiode which was built into the optical probe. The applied experimental setup enabled us to carry out one- or two-dimensional scanning of the cavitation bubble, automatic control of the experiment, data acquisition and data processing. Shadow photography was used as a comparative method during the experiments.     

Bundling influence on ultrafast optical nonlinearities of single-walled carbon nanotubes in suspension and composite film

Nonlinear optical characteristics of single-walled carbon nanotubes (SWCNTs) dispersed in dichlorobenzene and imbedded in polymer were investigated at 800 nm using the time-resolved optical Kerr gate technique. For systematic study of the influence of SWCNT bundling on optical nonlinearities, SWCNT solutions with different concentrations and a series of SWCNT/polymer composites deposited on glass substrates with different concentrations and thicknesses were prepared. The nonlinear response was comparable to the pulse duration of the laser used (～90 fs) both in SWCNT solutions and SWCNT/polymer composites. Over three orders of magnitude enhancement was observed in the third-order nonlinear susceptibility of SWCNT/polymer composite film compared with that of SWCNT solution. An appreciable reduction of microscopic and macroscopic nonlinearities was observed with increasing SWCNT concentrations due to stronger bundling of SWCNTs.     

Realization of KaptonTM based optical interconnect by KMnO4 wet etching

In the paper, based on KMnO₄ wet-etching technology PDMS (polydimethylsiloxane) based flexible optical interconnect packaged with Kapton^TM (Dupont) foils was successfully realized through a stable and effective bonding technology. The optical and mechanical properties of the PDMS waveguide layer remained unchanged before and after packaging with KMnO₄ etched Kapton foils. The mechanical stability limit of the tested optical interconnects is determined only by the intrinsic mechanical stability of the used PDMS materials. The optical loss at 850 nm is <0.05 dB/cm even after temperature treatments up to lead-free soldering temperatures of 260°C. In addition, the main mechanism of forming a good bonding between PDMS and Kapton foil was identified and analyzed as well.     

A scalable quantum computer with ultranarrow optical transition of ultracold neutral atoms in an optical lattice

We propose a new quantum-computing scheme using ultracold neutral ytterbium atoms in an optical lattice, especially in a monolayer of three-dimensional optical lattice. The nuclear Zeeman sublevels define a qubit. This choice avoids the natural phase evolution due to the magnetic dipole interaction between qubits. The Zeeman sublevels with large magnetic moments in the long-lived metastable state are also exploited to address individual atoms and to construct a controlled-multiqubit gate. Estimated parameters required for this scheme show that this proposal is scalable and experimentally feasible.     

Quartz optical filter for wavelength selection of frequency-doubled laser based on optical rotatory dispersion effect

Based on the optical rotatory dispersion effect,an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers.The operating principle is analyzed by matrix formulation,and the result indicates that the second harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of(2n 1)π/2 (n=0,1,2,3,...)between the two polarizations of the second-harmonic laser and the fundamental laser.The spectrum of the output laser is taken by the AQ-6315A spectrometer,and the experimental results are in good agreement with the theoretical results.     

Cavity-enhanced optical frequency doubler based on transmission-mode Hänsch–Couillaud locking

A variant of the Hänsch–Couillaud technique for locking the pump laser frequency to a cavity-enhanced optical frequency doubler is presented. In contrast to the original scheme in which the pump laser light reflected by the enhancement cavity is monitored, the error signal for locking is obtained by polarization analysis of the light transmitted by the cavity. The cavity serves as a spectral and spatial filter for the pump beam, making the transmission-mode locking method particularly useful if the beam quality is poor. Experimental validation of the method is demonstrated by generating more than 190 mW of stable 461 nm light from a cavity-enhanced frequency doubler that is pumped by a diode laser system.     

Study on loss and crosstalk in WDM passive optical network based on spectral slicing

A model for calculating loss and crosstalk in WDM passive optical network based on spectral slicing is proposed in this paper. Through theoretical analysis and numerical calculation, the relationship between loss or crosstalk and the parameters of the system, such as the bandwidth of the light-source, the parameters of the multiplexer, the number of channels and the fraction of channel misalignment, was demonstrated.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG), and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Function-lock strategy in OR/NOR optical logic gates based on cross-polarization modulation effect in semiconductor optical amplifier

We have studied a function-lock strategy for all-optical logic gate (AOLG) utilizing the cross-polarization modulation (CPM) effect in a semiconductor optical amplifier (SOA).By monitoring the power of logic light,the strategy realized controllable methods to capture OR and NOR functions and switch between them.The strategy has been successfully applied in experiment with 10-Gb/s not-return-to-zero (NRZ) signals,which has a high success-rate above 95% and ensures the high extinction ratio of result light above 11.4 dB.Every step in the strategy has definite numeric evaluation,which provides the potential of automatic implementation.     

The moire topography based on optical logic operation

The optical logic-operated moire,which is proposed on the basis of optical logicoperation,is a new method to obtain specific moire beat pattern.Its advantages lie in the ca-pability to select carrier-free,sharpened fringes with high contrast.The experimental methodand results of the application of the optical logic-operared moire in moire topography are pre-sented in this paper.     

Subpicosecond pulse compression in nonlinear photonic crystal waveguides based on the formation of high-order optical solitons

We investigate by numerical simulation the compression of subpicosecond pulses in two-dimensional nonlinear photonic crystal (PC) waveguides. The compression originates from the generation of high-order optical solitons through the interplay of the huge group-velocity dispersion and the enhanced self-phase modulation in nonlinear PC waveguides.Both the formation of Bragg grating solitons and gap solitons can lead to efficient pulse compression. The compression factors under different excitation power densities and the optimum length for subpicosecond pulse compression have been determined. As a compressor, the total length of the nonlinear PC waveguide is only ten micrometres and therefore can be easily incorporated into PC integrated circuits.     

Application of PWM dimming based on Grassmann optical model北大核心CSCD

针对发光二极管（light-emitting diode,LED）光源颜色和光通量精准调控难度高,在生产应用中,调控操作需在电脑等设备上进行的问题,基于格拉斯曼颜色混合定律,结合脉宽调制(pulse width modulation,PWM)调控LED的特性,建立表示PWM与LED照度关系的数学模型,以STM 32微控制器为核心设计了三基色LED调光调色系统。对系统分别进行单色、双色和3色的混光照度实验,数字照度计的测量值与光照数学模型的理论值对比结果表明,该系统在0~370 lx区间内系统的光源照度误差≤4%,合成光色共16 777 216种,且对光源颜色和光通量的调控操作可直接在系统上完成,无需接入其他设备,减少了操作流程,满足工业视觉检测、农作物补光照明和文化旅游对光源颜色和照度的需求。     

Compact optical filter for dual-wavelength fluorescence-spectrometry based on enhanced transmission through metallic nano-slit array

A novel optical filter based on enhanced transmission through metallic nano-slit is proposed for dual-wavelength fluorescence-spectrometry. A special structure, sampled-period slit array, is utilized to meet the requirement of dual-wavelength transmission in this system. Structure parameters on the transmission property are analyzed by means of Fourier transformation. With the features both to enhance the fluorescence generation and to enhance light transmission, in addition with the feasibility for miniaturization, integration on one chip, and mass production, the proposed filters are promising for the realization of dual-wavelength fluorescence-spectrometry in micro-total-analysis-system.     

Interpretation of the change in optical constants of different compositions of Ge–Se–In in terms of cohesive energy

Compositional dependencies of the optical and physical properties of as-deposited amorphous Ge_xSe_90?xIn₅ films (with 5≤x≤30 at%), prepared by thermal evaporation have been studied. The optical energy gap $E_g^{opt}$ is derived from Tauc's extrapolation in the strong absorption region in terms of transmission and reflection spectra. The relationship between the optical gap and chemical composition of the Ge_xSe_90?xIn₅ (with 5≤x≤30 at%) amorphous system is discussed in terms of the chemical bond approach. The refractive index, n and film thickness, d have been determined by an envelope method using transmission spectra. It is observed that the refractive index, n of Ge_xSe_90?xIn₅ thin films increases with increasing x, over the entire spectral range, which is related to both the increased density and average coordination number.