Mid-infrared T-shaped photonic crystal waveguide for optical refractive index sensing

Abstract

In this paper, we propose and design a new type of an integrated optical sensor that performs sensing in a wide wavelength range corresponding to mid-infrared (mid-IR) spectrum. By engineering the structural parameters of square-lattice photonic crystal (PC) slab incorporated with a T-shaped air-slot, strong light confinement and interaction with the analytes are assured. Numerical analyses in the time and frequency domain are conducted to determine the structural parameters of the design. The direct interaction between the slot waveguide mode and the analyte infiltrated into the slot gives rise to highly sensitive refractive index sensors. The highest sensitivity of the proposed T-slotted PC sensor is 1040 nm/RIU within the range of analytes’ refractive indices n = 1.05-1.10, and the overall sensitivity corresponding to the higher refractive index range of n = 1.10-1.30 is around 500 nm/RIU. Moreover, for a realistic PC slab structure, we determined an average refractive index sensitivity of 530 nm/RIU within the range of n = 1.10-1.25 and an average sensitivity of 390 nm/RIU within the range of n = 1.00-1.30. Furthermore, we speculate on the possible approach for the fabrication and the optical characterization of the device. The assets of the device include being compact, having a feasible measurement and fabrication technique, and possessing label-free sensing characteristic. We expect that the presented work may lead to the further development of the mid-IR label-free biochemical sensor devices for detection of various materials and gases in the near future.Peer ReviewedPostprint (published version

Electrical Double Layer-Induced Ion Surface Accumulation for Ultrasensitive Refractive Index Sensing with Nanostructured Porous Silicon Interferometers

“…Refractive index optical sensors based on plasmonic , and photonic micro and nanostructures − have recently attracted increased attention for the realization of ultrasensitive and ultracompact refractometers. Either evanescent field (e.g., surface plasmon resonance, − long period grating fibers ,, ) or resonant (e.g., localized SPR, − ring resonators , ) and interference (e.g., interferometers, − photonic crystals , ) effects between electromagnetic field and matter of interest have been exploited to quantify refractive index variations by increasing the light–matter interaction at the micro and/or nanoscale. An increased light–matter interaction leads, indeed, to an augmented sensitivity ( S ) and, in turn, to a higher resolution ( R ) that ultimately gives the minimum variation of refractive index that can be resolved above the noise floor (σ), also known as detection limit (DL = 3σ/ S ) .…”

A Controllable Plasmonic Resonance in a SiC-Loaded Single-Polarization Single-Mode Photonic Crystal Fiber Enables Its Application as a Compact LWIR Environmental Sensor

“…The proposed ENG-loaded SPSM PCF spectrometer was compared with comparable state-of-the-art sensors based on measuring the refractive index change of the material being sensed. Table 2 summarizes these comparisons; they show that the sensitivity value of the proposed spectrometer is better than those reported in [ 42 , 43 , 44 , 45 , 46 , 47 ] and it is comparable to the highest ones in [ 48 , 49 , 50 ]. Its sensitivity per linewidth value is average in comparison.…”

Self‐Collimation and Slow Light‐Based Refractive Index Sensor with a Large Detection Range

“…Recently, Mid‐IR applications have attracted lots of attention, due to the low cost and accessible lasers and detectors for this range of wavelength, especially in spectroscopy. [ 36–38 ] Also according to the previous reports, using high dielectric material provides SC property in lower normalized frequencies which results not only in compact devices but also facilitates achieving the all‐angle and PISC characteristic. [ 34 ] Hence in this study, PbTe is used as the background substrate for the proposed PC sensor with high refractive index of n ∼ 6 at Mid‐IR range.…”