Seven-layer analysis model of an optical waveguide excitation fluorescence microscopy.

In this paper, an optical waveguide evanescent field fluorescence microscopy is studied. Based on Maxwell's equation, a seven-layer theoretical analysis model is developed for the evaluation of an optical waveguide excitation fluorescence microscopy. The optical waveguide excitation fluorescence microscopy structure is systematically and comprehensively analysed at the wavelengths of 488, 532 and 646 nm for fluorescent dyes. The analysis results provide some useful suggestions, which will be beneficial to the research of an optical waveguide evanescent field fluorescence microscopy.

Integrated opto-mechanical cantilever sensor with a rib waveguide.

An integrated opto-mechanical cantilever sensor with a rib waveguide is reported in this paper. The device consists of a rib waveguide cantilever with buried waveguides on silicon. The rib cantilever is introduced to match better with the buried waveguide, further for increasing the interface coupling efficiency. With this configuration, single-mode operating can be achieved in transverse direction without decreasing the width of optical waveguide cantilever. The system sensitivity is 1.1 µm-1 which is increased by about 21%, compared with the conventional structure.

An integrated optical waveguide micro-cantilever system for chip-based AFM.

An optical waveguide cantilever system with a tip is introduced as the displacement detection system of chip-based atomic force microscopy (AFM) system. A chip-based AFM on optical waveguide is demonstrated with sensitivity of up to 4.0 × 10-2 nm-1 , which is mainly constructed by a 210 nm thick optical waveguide cantilever with a nano-tip. The nano-tip is a height of 1.2 µm and diameter of 140 nm. This integrated on-chip system provides a displacement range of approximately ±0.4 µm, which makes it possible for the device to be used for AFM imaging and pays the way for further performance improvement.

Non-coplanar misalignment optical waveguide cantilever sensor with a monotonic response in a large operation range.

This paper reports a non-coplanar misalignment optical waveguide cantilever sensor realizing a monotonic response with a large operation range. A 1×2 Y-branch optical power splitter cantilever structure was designed, and one of the branches was reduced in thickness at the end, as a non-coplanar structure with respect to another. The misalignment coupling of the two branches due to the thickness of one branch leads to a monotonic response of an optical waveguide cantilever sensor. The simulation results showed a monotonic response with a sensitivity of 6×10-4 n m -1 in a large operation range of -1 to 1 µm.

Sensitivity-improved fiber optic current sensor based on an optoelectronic oscillator utilizing a dispersion induced microwave photonic filter.

An optoelectronic oscillator (OEO)-based fiber optic current sensor (FOCS) with greatly improved sensitivity is proposed and experimentally demonstrated. A microwave photonic filter (MPF) induced by the dispersion effect of a linearly chirped fiber Bragg grating (LCFBG) is used to select the frequency of the OEO oscillating signal. A two-tap MPF formed by a polarization multiplexed composite cavity is cascaded to achieve a stable single mode oscillation. When the current changes, the magneto-optic phase shift induced by Faraday effect will be introduced between the left and right circularly polarized lights transmitted in the reflective sensing unit. The magneto-optic phase shift is converted to the phase difference between the optical carrier and sidebands through a LiNbO3 Mach-Zehnder modulator. This phase difference is the decisive factor for the center frequency of the cascaded MPF as well as the oscillating frequency. Therefore, the current can be measured in the microwave frequency domain, which can improve the interrogation speed and accuracy to a large extent. The experimental results show that the oscillating frequency shifts up to 407.9 MHz as the current increases by 1 A.

Improved Optical Waveguide Microcantilever for Integrated Nanomechanical Sensor.

This paper reports on an improved optical waveguide microcantilever sensor with high sensitivity. To improve the sensitivity, a buffer was introduced into the connection of the input waveguide and optical waveguide cantilever by extending the input waveguide to reduce the coupling loss of the junction. The buffer-associated optical losses were examined for different cantilever thicknesses. The optimum length of the buffer was found to be 0.97 µm for a cantilever thickness of 300 nm. With this configuration, the optical loss was reduced to about 40%, and the maximum sensitivity was more than twice that of the conventional structure.

Black Phosphorus Nano-Polarizer with High Extinction Ratio in Visible and Near-Infrared Regime.

We study computationally the design of a high extinction ratio nano polarizer based on black phosphorus (BP). A scattering-matrix calculation method is applied to compute the overall polarization extinction ratio along two orthogonal directions. The results reveal that, with a resonance cavity of SiO2, both BP/ SiO 2 /Si and h-BN/BP/ SiO 2 /Si configurations can build a linear polarizer with extinction ratio higher than 16 dB at a polarized wavelength in the range of 400 nm⁻900 nm. The polarization wavelength is tunable by adjusting the thickness of the BP layer while the thicknesses of the isotrocpic layers are in charge of extinction ratios. The additional top layer of h-BN was used to prevent BP degradation from oxidation and strengthens the practical applications of BP polarizer. The study shows that the BP/ SiO 2 /Si structure, with a silicon compatible and easy-to-realize method, is a valuable solution when designing polarization functional module in integrated photonics and optical communications circuits.

Explanation of the distorted spectrum in a spectral hole burning RF spectrum analyzer using Bloch equations.

A readout using a frequency-chirped laser is investigated in a spectrum analyzer with spectral-hole-burning (SHB). An analysis based on the Bloch equations is presented for the spectral distortion due to a fast readout, and a recovery algorithm is developed for the distortion. The experiment of a SHB spectrum analyzer is executed to demonstrate the optical spectral distortion due to fast readout. The experimental spectral distortion is recovered by the recovery algorithm developed from the Bloch equations.

8 x 8 wavelength router of optical network on chip.

An integrated 8 x 8 wavelength router based on the micro-ring resonators using 2 x 2 multi-interference (MMI) crossing is demonstrated on silicon-on-insulator (SOI) technology, which is manufactured with microelectronics equipment. Experimental results show a free spectral range (FSR) about ~37 nm, an on/off contrast larger than 20 dB, an imbalance among the channels less than 2 dB, a crosstalk of channels smaller than -10 dB, a spacing between close channels about 3.6 ± 0.7 nm and an output efficiency of every channel smaller than 20 dB.

A process to control light in a micro resonator through a coupling modulation by surface acoustic waves.

A novel process to control light through the coupling modulation by surface acoustic wave (SAW) is presented in an optical micro resonator. An optical waveguide modulator of a racetrack resonator on silicon-on-insulator (SOI) technology is took as an example to explore the mechanism. A finite-difference time-domain (FDTD) is developed to simulate the acousto-optical (AO) modulator using the mechanism. An analytical method is presented to verify our proposal. The results show that the process can work well as an optical modulator by SAW.

Dependence of integrated acousto-optical devices with one and two modulated arms on the static phase difference.

In this paper, we develop an analytical model of an integrated acousto-optical (AO) device with arms modulated by a single surface acoustic wave beam. A comparison between one-arm and two-arm modulation is presented, which shows that two-arm modulation can significantly enhance modulation efficiency by an optimized design. A detailed analysis of the influence of static phase difference on the behavior of the AO devices has been provided, and some interesting results have been obtained. These will be helpful for an optimized design of AO devices for different functionalities.

Improved coupling technique of ultracompact ring resonators in silicon-on-insulator technology.

In order to improve the coupling coefficient between a bus waveguide and a bent waveguide of an ultracompact microring to obtain the critical coupling, a design using a bent bus waveguide with reduced width is provided to maintain a better phase matching and increase the coupling. A full vectorial finite difference model, specifically suited for high index contrast and smaller size waveguides, for example, a waveguide in the silicon-on-insulator (SOI) technology, is developed. As a validation, the straight and bent waveguides are simulated using this model, whose results are compared with the results deduced from the measurement results of the ultracompact ring resonators in SOI technology. Also, the model solver is performed to simulate the design, and an experiment is implemented to testify the design.