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One of the most fascinating predictions of the theory of general relativity is the effect of gravitational lensing, the bending of light in close proximity to massive stellar objects. Recently, artificial optical materials have been proposed to study the various aspects of curved spacetimes, including light trapping and Hawking radiation. However, the development of experimental ‘toy’ models that simulate gravitational lensing in curved spacetimes remains a challenge, especially for visible light. Here, by utilizing a microstructured optical waveguide around a microsphere, we propose to mimic curved spacetimes caused by gravity, with high precision. We experimentally demonstrate both far-field gravitational lensing effects and the critical phenomenon in close proximity to the photon sphere of astrophysical objects under hydrostatic equilibrium. The proposed microstructured waveguide can be used as an omnidirectional absorber, with potential light harvesting and microcavity applications. By utilizing a microstructured optical waveguide around a microsphere, an optical anlogue of the effects of gravity on the motion of light rays is demonstrated. Both far-field gravitational-lensing effects and the critical phenomenon that occurs close to the photon sphere of astrophysical objects under hydrostatic equilibrium are experimentally demonstrated.

Harmonic-assisted phase amplification was investigated in a 300-µm-thick Nd:GdVO4 laser with coated end mirrors in the self-mixing interference scheme. The key event is the self-induced hybrid skew cosh Gaussian (abbreviated as skew ch-G)-type transverse mode oscillation in a thin-slice solid-state laser with wide-aperture laser-diode pumping. The present hybrid skew-chG mode was proved to be formed by the locking of nearly frequency-degenerate TEM00 and annular fields. The resultant modal-interference-induced gain modulation at the beat frequency between the two modal fields, which is far above the relaxation oscillation frequency, increased the experimental self-mixing modulation bandwidth accordingly. Fifty-fold phase amplification was achieved in a strong optical feedback regime.

It is shown how time-modulating the refractive index of two coupled microcavities with a 90 degree phase shift between them leads to non-reciprocal wave propagation. The cavities are implemented as defects in a one-dimensional photonic crystal. The ratio of forward to backward power transmission can be as high as 25 dB with experimentally realizable modulation frequencies and amplitudes. Further, it is demonstrated how a simple passive filter can remove modulation sidebands.

In this paper we present a novel approach for the analysis and design of inhomogeneous lenses. The standard method of Geometrical Optics for inhomogeneous media is augmented by introducing a novel wavefront-curvature transport equation, which allows the implementation of a full electromagnetic ray tracing (i.e., vector problem including polarization) in a real 1-D fashion, namely along the ray. This opens the possibility of easy parallelization and ultra-fast analysis of inhomogeneous lenses. The design of the lens is then accomplished by resorting to a novel direct synthesis method which, by inverting the analysis problem, directly provides the refractive index spatial distribution capable to drive the rays along prescribed paths which are defined to transform the impinging field on the input surface into the target aperture distribution on the output surface of the lens.

Design and simulation of novel all-optical fundamental X-NOR and NAND logic gates based on two dimensional photonic crystals are reported in this paper. In a photonic crystal self collimated beams are partially transmitted and partially reflected with a phase lag at a line defect in Gamma-X direction. The phase shifter is employed, the reflected and transmitted input beams are interfered constructively or destructively to obtain the required logic outputs. The operations of the logic gates are simulated using two dimensional Finite Difference Time Domain (FDTD) method.

We observed the near field for a refractive index grating fabricated on a planar light waveguide circuit (PLC) by scanning an optically-trapped 100 nm diameter gold particle. We demonstrate that stable trapping and scanning occur with a Gaussian laser beam at the scan velocity of 1.6 μm/s and Nd:YAG laser power of 25mW. The scattered Ar† laser light from the gold particle is strong at high refractive indexes of the grating with periods of 1.06 μm and 0.53 μm both by s and p polarized illumination. In addition, we observed the surface profile of the optical disk tracking groove with and without the gold particle. © 2004 The Optical Society of Japan

When driving the paralleled LED strings, the large forward tolerance across the LED will result in the current nonuniformly distributed between each string, which causes LEDs to be overdriven and influence the lifespan. This paper presents a single inductor multiple outputs parallel string LED driver with time multiplexing control schemes. Two kinds of pulse-width modulation schemes are presented and compared. The system architecture, operation principle, simulation and hardware implementation results are demonstrated. The efficiency of the LED driver based on PWM scheme II approaches 88.9% with less than 5% current mismatch between each parallel LED strings, an improvement over PWM scheme I.

Intelligent building automation systems require a large number of sensors to increase spatial resolution in order to achieve fine-grained sensing and control. However, traditional building automation systems are wired networks that require a tremendous cabling cost. In addition, cables themselves are unwelcome in many living environments. ZigBee has become an emerging wireless networking technology in recent years, which meets easy installation and flexible deployment requirements. Also, ZigBee technology satisfies the market's need for a cost-effective, standardsbased wireless network that provides a low power consumption, reliability and security. Therefore, ZigBee technology is very suitable for the networking of a building automation system. The goal of this paper was to develop a robust ZigBee wireless sensor network for building lighting control and to integrate the network into an existing building automation system. A Modbus-ZigBee gateway was developed to integrate these two different protocol systems. We tested our system in our testbed to verify the correctness of the gateway function and the network communication performance. The test results showed that ZigBee technology is feasible for use in building automation systems.

A novel high-precision LED driving system based on LLC resonant converter is presented in this paper. Dual control loops are embedded in this system. One is used as the main loop of the whole system, which can regulate the output signal, and realize analog dimming. The other loop is an assistant loop, which is used to achieve high-precision PWM dimming. Analog dimming loop achieves constant current through the error amplifier (EA) and the voltage-controlled oscillator (VCO). Intelligent duty-cycle builder (IDCB) is realized with the external PWM signal and the difference between the actual output current and the pre-set current. The actual PWM control signal in the system can be dynamically adjusted by the IDCB, which can greatly improve the accuracy of PWM dimming. Besides, the transformer-isolated driver is adopted in this system to reduce the operating voltage of the control chip. The proposed LED driving system has been validated with 0.35μm BCD technology. The accuracy of PWM dimming can be improved by 17% with the assistant loop and reaches up to 95%. The current consumption of the LLC resonant controller IC is 5mA for a 100 kHz operation frequency using a 400V supply voltage. In addition, the power switching MOSFETs can achieve zero-voltage switching (ZVS) and the rectifier diodes can achieve zero-current switching (ZCS).

Focusing on the increasingly large energy loss of lighting power, this paper introduces a kind of practical auto-control system of classroom lights. This system will adopt the combination of MC-S20T180NO opposite type photoelectric switch, DC Solid Relay and middle and small scale integration 74LS47, CD40192, etc. It will take Multisim10 simulation software as the design platform. Through the circuit design and simulative experiment, the system can automatically control the lights according to the variations of environment illumination and the amount of people in the classroom. Each performance index has reached the design requirements. It has quite strong adaptability to all kinds of classrooms in universities, middle schools and primary schools. It has got actual promotion values.