Long-Period Fiber Grating Sensor Based on a Conductive Polymer Functional Layer

A temperature sensor was fabricated with a functional conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) coating on a long-period fiber grating (LPFG). The LPFG was fabricated by laser-assisted wet-chemical etching for controlling the grating depth of the LPFG after the treated surface of an optical fiber was inscribed by laser light. The functional conductive polymer acts as a temperature sustained sensing layer and enhances the grating depth of the LPFG sensor as a strain buffer at various temperatures. The sensor was subjected to three cycles of temperature measurement to investigate the sensor’s wavelength shift and energy loss when exposed to temperatures between 30 and 100 °C. Results showed that the sensor’s average wavelength sensitivity and its linearity were 0.052 nm/°C and 99%, respectively; average transmission sensitivity and linearity were 0.048 (dB/°C) and 95%, respectively.

Systematic study of resonant transmission effects in visible band using variable depth gratings

The article focuses on depth-dependent visible band transmission effects in a symmetrical “insulator-metal-insulator” diffraction system based on a variable depth grating. These effects were studied both experimentally and theoretically in TM and TE polarizations. In particular, the existence of an optimized grating depth for plasmon-mediated resonant transmission was confirmed experimentally, and differences in TE and TM transmission behavior are discussed. We utilize a simple and flexible fabrication approach for rapid synthesis of apodized structures with adiabatically varying depth based on a beat pattern of two interferential lithography exposures. The present study can be useful in the fields of transmission-based optical security elements and biosensors.

Coupling Efficiency Analysis of Different Top Coupling Grating for Quantum Well Infrared Photo-Detector

The relative coupling efficiency of different top coupling grating for quantum well infrared photo-detector is calculated by finite difference time domain algorithms. The relative coupling efficiency respect to the grating parameters, such as, grating period and grating depth is analyzed for both square lattice and hexagonal lattice structure gratings. By comparison, it can be concluded that the optimization grating parameters is differential for different grating structure.

Optimization of Trapezoid Coupling Grating for Long-Wave Quantum Well Infrared Photodetector

The relative coupling efficiency of trapezoid coupling grating for long-wave quantum well infrared photodetector is calculated by finite difference time domain algorthms. By considering the lateral etching effects in grating fabrication, the relative coupling efficiency with respect to the grating parameters, such as, grating period, grating depth, grating top width and grating bottom width etc, is computed. The calculated results show that the relative coupling efficiency will reach the largest value for the 8.266µm incident infrared light when taking grating period asp=2.55 µm, grating depth as h=0.622 µm , grating top width as d1=1.253µm , grating bottom width as d2=0.626µm , duty ratio as q=0.5 and the ratio of bottom width and top width as α=0.5.

Surface Plasmon-Induced Band Gap in the Photocurrent Response of Organic Solar Cells

A 260 nm layer of organic bulk heterojunction blend of the polymer poly(3-hexylthiophene) (P3HT) and the fullerene [6,6]-phenyl C61-butyric (PCBM) was spin-coated in between aluminum and gold electrodes, respectively, on top of a laser inscribed azo polymer surface-relief diffraction grating. Angle-dependent surface plasmons (SPs) with a large band gap were observed in the normalized photocurrent by the P3HT-PCBM layer as a function of wavelength. The SP-induced photocurrents were also investigated as a function of the grating depth and spacing.

Characteristic Analysis of Anti-Reflective Subwavelength Cross Gratings Fabricated With Holographic Technique

The paper presents the investigation on anti-reflection property of subwavelength cross-gratings with relief profile close to pyramid or cone. Such gratings are polarization independent and have effective refractive index increasing gradually from the top to the substrate. Theoretical analysis indicates that, to obtain good anti-reflection effect, for normally incident lights in visible band (400 ∼ 700 nm) the grating period should not be larger than 266 nm. Cross gratings with different periods were fabricated using holographic double-exposure method on photoresist. Measurements show that the grating with 255 nm period has higher transmittance compared with the gratings with the periods larger than 266 nm. Measurements also show that larger grating depth results in higher transmittance. The experimental results are in good agreement with the theoretical analysis.