Surface Plasmon Enhancement on Infrared Photodetection

AbstractInAsSb based infrared photodetector is an alternative to the existing HgCdTe, PbSnTe, and InSb counterparts, but its room temperature performance is still relatively poor. One of the ways to improve its performance is through surface plasmon, which provides near field confinement that leads to enhancement in light matter interaction. In this work, the role of each parameter of two dimensional metallic hole arrays in plasmonic enhancement is studied in details, such as the periodicity of hole array, hole diameter and metal film thickness. The plasmonic resonances and their corresponding electric field distributions are comprehensively studied in finite difference time domain simulation, which also would serve as a guide for designing surface plasmon enhanced InAsSb infrared detector with high quantum efficiency and signal-to-noise ratio

Highly Sensitive Graphene/Polydimethylsiloxane Composite Films near the Threshold Concentration with Biaxial Stretching

Uniformly dispersed graphene effectively improves the strain-sensing capability of the composite film under a low graphene load in nanocomposites prepared with polydimethylsiloxane (PDMS) and graphene (GNP) monolayer powder. The threshold concentration of graphene was determined by loading nanocomposites at different temperatures. For different concentrations, when using traditional uniaxial stretching, the rate of resistance change of films near the threshold concentration is five times higher than the rate of films with a high concentration. Compared with traditional uniaxial stretching, the biaxial stretching we introduced can effectively improve the sensitivity of the film by an order of magnitude. The change in the resistance of the film near the threshold concentration is due to the change of the tunnel length and the cross-section of the tunnel, whereas the high concentration of the film is due to the change of the conductive path inside the film. Biaxial stretching has different effects on films with different concentrations, but the final effect of increasing sensitivity is the same. This study provides guidance for improving the strain-sensing sensitivity of GNP/PDMS composite films and the application of biaxial tension in detecting human motions

Flexible and Optical Fiber Sensors Composited by Graphene and PDMS for Motion Detection

A stretchable optical sensor can quantify the strain generated by human movement, which has been widely studied in the development of health monitoring systems, human–machine interfaces and wearable devices. This paper reports a graphene-added polydimethylsiloxane (PDMS) fiber, which has high tensile properties and good light transmittance suitable for detecting human movement. When the graphene-added PDMS fiber is stretched, the concentration of graphene per unit volume is constant, and the sensor uses the optical loss of the beam through the graphene PDMS fiber to detect the tensile strain. The fiber has excellent strain-sensing performance, outstanding sensitivity, a tensile property of 150%, and an excellent waterproofing performance. The linear response and repeated response in large dynamic range could reach 100% stability. The results show that the sensor can be used to detect human motion detection. These excellent properties indicate that the fiber has potential applications in wearable devices, soft robots and electronic skin

The new way of controlling aluminum-doped zinc oxide films properties : ion beam post-treatment with cooling system

AZO thin films with low surface roughness and low sheet resistance are required in the touch panels and display panels. In this work, we investigated the substrate cooling effect of the ion beam post-treatment on AZO films properties, and one new way to obtain low surface roughness and low sheet resistance at the same time was proposed. The more exciting find of this paper is that, compared to the samples without cooling during the process of the ion beam post-treatment, samples with proper cooling voltage show a sheet resistance decrease of 26 % (from 11.9 Ω/□ to 8.8 Ω/□) and a roughness decrease of 35.5 % (from 13.389 nm to 8.637 nm) without transparency losing. And the viewpoint that substrate cooling has the effect of weakening the crystallization, especially for the subface and internal parts of samples is deduced

Study of dual color infrared photodetection from n-GaSb/n-InAsSb heterostructures

We report detailed investigation of n-GaSb/n-InAsSb heterostructure photodetectors for infrared photodetection at different temperatures and biases. Our results show that the heterostructure photodetectors are capable of dual color photodetections at a fixed forward bias with its highest responsivity occurred at room temperature; With the decrease of the forward bias, a turning point, at which the photocurrent changes its direction, exist and the corresponding voltage values increases with the decrease of temperature; At all reverse biases, the photocurrents flow in the same direction but the maximum current occurs at about 205 K. A new model is proposed, which can well explain all the observations.ASTAR (Agency for Sci., Tech. and Research, S’pore)MOE (Min. of Education, S’pore)Published versio

The substrate cooling effect of ion beam post treatment on ZAO films properties

ZAO thin films with low surface roughness and low sheet resistance are required in the touch panels and display panels. In this work, we investigated the substrate cooling effect of ion beam post treatment on ZAO films properties, and one new way of obtain low surface roughness and low sheet resistance same time was proposed. The more exciting find of this paper is that, comparing to the samples without cooling during the process of ion beam post treatment, samples with proper cooling voltage show a sheet resistance decrease of 26% (from 11.9 Ω/□ to 8.8 Ω/□) and a roughness decrease of 35.5% (from 13.389 nm to 8.637 nm) without transparency losing. And the viewpoint that substrate cooling has the effect of weakening the crystallization, especially for the sub-face and internal parts of samples is deduced

Calculation of the diffraction efficiency on concave gratings based on Fresnel–Kirchhoff’s diffraction formula

Fraunhofer diffraction formula cannot be applied to calculate the diffraction wave energy distribution of concave gratings like plane gratings because their grooves are distributed on a concave spherical surface. In this paper, a method based on the Kirchhoff diffraction theory is proposed to calculate the diffraction efficiency on concave gratings by considering the curvature of the whole concave spherical surface. According to this approach, each groove surface is divided into several limited small planes, on which the Kirchhoff diffraction field distribution is calculated, and then the diffraction field of whole concave grating can be obtained by superimposition. Formulas to calculate the diffraction efficiency of Rowland-type and flat-field concave gratings are deduced from practical applications. Experimental results showed strong agreement with theoretical computations. With the proposed method, light energy can be optimized to the expected diffraction wave range while implementing aberration-corrected design of concave gratings, particularly for the concave blazed gratings.Published versio