Enhanced geometries of macroporous silicon photonic crystals for optical gas sensing applications

Abstract

A macroporous silicon photonic crystal is designed and optimized theoretically for its use in gas sensing applications and IR optical filters. Light impinges perpendicularly onto the sample surface (vertical propagation) so a three-dimensional (3d) structure is used. For gas sensing, a sharp resonance is desired in order to isolate an absorption line of the gas of interest. The high Q-factors needed mandate the use of a plane defect inside the PhC to give rise to a resonant mode inside the bandgap tuned to the gas absorption line. Furthermore to allow gas passage through the device, an open membrane is required. This can affect the mechanical resilience. To improve the strength of the photonic crystal the pores are extended after the “active” 3d part. The number of modulations, and the extension length have been optimized to obtain the largest Q-factor with reasonable transmitted power. These proposed structures have been experimentally performed, probing an enhancement of almost an order of magnitude in the Q-factor in respect with the basic case. Simulations considering CO2 have been performed showing that the proposed structures are promising as precise optical gas sensors.Peer ReviewedPostprint (author's final draft

Bandgap widening in macroporous silicon photonic crystals by multiperiodic structures

“…On the other hand, the peak transmission allows the detection of gases. This assertion is based on previous studies where it was found that in a macroporous silicon PhC structure with 18 modulations-similarly to the 20 modulations that we have-the peak amplitude diminished a 20% in a full CO 2 atmosphere [5].…”

“…In the proposed gas sensing application, the light comes from a broadband MIR light source and perpendicularly impinges on a PhC with an embedded resonant cavity whose resonant wavelength is centred at a fingerprint of a target gas. After them, a gas cell and a photodetector are used to obtain the gas absorption at that wavelength [5]. Further research has still to demonstrate whether placing the PhC inside the gas cell could help to increase the interaction pathlength between light and gas, similarly to the gas sensor reported by Wehrspohn et al [6].…”

Calculation of reflectance and transmittance of optical birefringent networks based on cholesteric liquid crystals

“…This is why, currently, a lot of attention is paid to the photonic crystals (PCs) having a three-dimensional (3D) ordered structure with a periodicity of the optical wavelength, whose optical properties, due to their periodic dielectric structures, are similar to the properties of LCs. In such materials, novel physical concepts have been predicted theoretically and different engineering applications of PCs have been proposed (Ozaki et al, 2007;Cardador et al, 2017;Escobar et al, 2018).…”

“…Due to the abovementioned advantages, PCs have attracted much attention from both fundamental studies and practical applications in optical circuits, devices and interconnects (Guo et al, 2010;Notomi, 2010;Prasmusinto et al, 2017). Among the most known new applications of PCs, one can mention light-emitting diodes (Wierer et al, 2009;Wiesmann et al, 2009), optical switches (Belotti et al, 2008;Nozaki et al, 2014), colour filters (Huang and Zhang, 2011;Lin et al, 2015), gas sensors (Hodgkinson and Tatam, 2013;Xu et al, 2013;Cardador et al, 2017) and lasers (Noda, 2010;Hirose et al, 2014;Ortega et al, 2018). Recently, photonic crystals find applications in building all-optical computers and communication systems, using photonic crystal logic gates for faster computers and mobile devices with high both speed processing of data and transmission rates.…”

Photoconductivity relaxation and electron transport in macroporous silicon structures

“…The effective carrier lifetime of surface-passivated macroporous silicon [2,3] and black silicon with cones and pyramids [4] is dependent on the surface morphology and passivation, bulk lifetime. Gas [5,6] and biological sensors [7] are developed on the porous silicon with CMOS-compatible manufacturing. Macroporous silicon [8,9] and black silicon nano-textured by cones and pyramids [4] are used as solar cells.…”