A New Design of Pressure Sensor Based on a GaAs-based Two Dimensional Photonic Crystal Slab on SiO2 Substrate

This paper reports the design and three dimensional (3D) simulation of a new photonic crystal (PC) pressure sensor. The device is constructed using a GaAs-based 2D PC slab on SiO2 substrate. The strain/stress simulations and also the spectral simulations are done using CST Studio Suite. In this investigation, the sensitivity of the proposed pressure sensor is calculated by considering the variation of the refractive index and also the deformation of the structure. The numerical results show that when pressure is applied, the refractive index variations cause an increment in the resonant wavelength of the transmission spectrum, but the deformation factor cause a decrease in the resonant wavelength. It has been shown that the relationship between the applied pressure and the resonant wavelength of the designed micro-cavity is linear. Based on the simulation results, the quality factor of the designed micro-cavity and the sensitivity of the pressure sensor are 2200 and 3.5 nm / GPa, respectively.

Shifting beams at normal incidence via controlling momentum-space geometric phases

When hitting interfaces between two different media, light beams may undergo small shifts. Such beam shifts cannot be described by the geometrical optics based on Snell’s law and their underlying physics has attracted much attention. Conventional beam shifts like Goos-Hänchen shifts and Imbert-Fedorov shifts not only require obliquely incident beams but also are mostly very small compared to the wavelength and waist size of the beams. Here we propose a method to realize large and controllable polarization-dependent lateral shifts for normally incident beams with photonic crystal slabs. As a proof of the concept, we engineer the momentum-space geometric phase distribution of a normally incident beam by controlling its interaction with a photonic crystal slab whose momentum-space polarization structure is designed on purpose. The engineered geometric phase distribution is designed to result in a large shift of the beam. We fabricate the designed photonic crystal slab and directly observe the beam shift, which is ~5 times the wavelength and approaches the waist radius. Based on periodic structures and only requiring simple manipulation of symmetry, our proposed method is an important step towards practical applications of beam shifting effects.

A Portable Micro-Gas Chromatography with Integrated Photonic Crystal Slab Sensors on Chip

The miniaturization of gas chromatography (GC) systems has made it possible to utilize the analytical technique in various on-site applications to rapidly analyze complex gas samples. Various types of miniaturized sensors have been developed for micro-gas chromatography (µGC). However, the integration of an appropriate detector in µGC systems still faces a significant challenge. We present a solution to the problem through integration of µGC with photonic crystal slab (PCS) sensors using transfer printing technology. This integration offers an opportunity to utilize the advantages of optical sensors, such as high sensitivity and rapid response time, and at the same time, compensate for the lack of detection specificity from which label-free optical sensors suffer. We transfer printed a 2D defect free PCS on a borofloat glass, bonded it to a silicon microfluidic gas cell or directly to a microfabricated GC column, and then coated it with a gas responsive polymer. Realtime spectral shift in Fano resonance of the PCS sensor was used to quantitatively detect analytes over a mass range of three orders. The integrated µGC–PCS system was used to demonstrate separation and detection of a complex mixture of 10 chemicals. Fast separation and detection (4 min) and a low detection limit (ng) was demonstrated.

Band Gap of Two-dimensional Layered Cylindrical Photonic Crystal Slab and Slow Light of W1 Waveguide

In this paper, we apply the scatterers of cylindrical rings to a two-dimensional photonic crystals (PCs) slab. The effects of the number of layers, the thickness, the index, and the height of the cylindrical layers on the photonic band gaps (PBGs) of such slab with different lattice arrangements are studied. It turns out that our new structure helps to obtain a large range of the PBGs. The maximum bandwidth is obtained with the value of 0.1497 (2πc/a). The PBGs are moved to the lower frequencies with the augment of thickness, refractive index, and height. The choice of height, refractive index, and thickness is a trade-off, and adding the number of dielectric layers is not always positively correlated with the area of PBGs. In addition, in the W1 waveguide with a triangular lattice layout, we obtain a slow light of 0.026×c. Compared with the square lattice, the triangular lattice is more suitable for slowing down the speed of light.