High sensitivity of sensors based on two-dimensional photonic crystal

Abstract

Photonic crystals (PCs) have achieved a lot of research significance due to their projected applications. Their use as sensors is enabled due to their well-defined physical properties such as reflectance/ transmittance, superior levels of sensitivity resulting in precise detection limits. In this paper, we propose an ultracompact RI (refractive index) sensor based on single line photonic crystal waveguide structure. The properties of the sensor are simulated using the finite-difference time-domain (FDTD) method. The transmission spectrums of the sensor with different ambient refractive indices are calculated. The calculation results show that a change in ambient RI is apparent; the sensitivity of the sensor is achieved. The radius of the air holes localized at each side of the line defect is optimized to realize high sensitivity, wide measurement range and improved transmission. Development of sensor designs that enhance sensitivity is especially important because it allows detection of lower concentrations of analytes. For instance, refractive index (RI) sensing techniques detect an analyte by a local refractive index shift.

Enhancement of Refractive Index Sensitivity in Photonic Crystal Waveguide-Based Sensors by Selective Infiltration

“…The sensitivity of the PCW device, via 2D FDTD calculations, is recently reported to be four times improved by using larger holes in the rst rows adjacent to the line--defect than the background holes [18]. However, in our design the maximum sensitivity is obtained for smaller holes for the rst rows with a considerable enhancement in sensitivity.…”

“…By performing 2D FDTD calculations with an e ective index method for a PCW slab, it was found that substitution of all the PC air holes with water signi cantly enhances the sensing performance in comparison to substitution of the cladding layer [21]. Later, it was reported that in ltration of only the rst rows of holes adjacent to the line-defect with water enhances the sensitivity greater than the in ltration of all lattice holes [18]. These reported studies indicate that selective in ltration is more bene cial than cladding and all lattice hole in ltration methods.…”

“…In addition, rather than immersing the PC slab in a low-index uid (bulk-index sensing), the in ltration of selected holes, which interacts more with the eld, can be employed. The cut-o wavelength of a PCW is observed to be very sensitive to the changes in the surrounding environment [18]. Such a structure can be used as a sensor, whose principle of operation is based on the cut-o wavelength shift caused by the in ltration of the holes.…”

“…In some studies, the behavior of the cut-o or resonance wavelength shift under RI change is not evaluated [18,20,21]. However, to gain maximum performance from the sensor device, this characteristic should be revealed.…”

Photonic Crystals for Optical Sensing: A Review

“…An important parameter to be properly designed for increasing sensing performance in single line PhC waveguide sensor, is the radius of holes localized at both sides of the line defect (Bougriou et al, 2011). In this context, an integrated sensor based on a PhC waveguide has been proposed.…”