Generation of Lossy Mode Resonances in Planar Waveguides Toward Development of Humidity Sensors

Abstract

Lossy mode resonances (LMRs) are typically obtained with optical fibre. The Kretschmann configuration is an alternative but LMRs are generated with angles approaching grazing incidence. In this work, a new setup is explored, based on the lateral incidence of light on conventional planar waveguides such as glass slides or coverslips. Indium tin oxide was deposited onto both types of waveguides generating LMRs. The results of the simulations carried out agree well with the experimental results. As an example of the potential of this new and simple optical configuration, a humidity sensor with a sensitivity of 0.212 nm/%RH in the range from 65 to 90% of RH was developed, which expedites the development of other types of sensors already explored with LMR based optical fibre sensors.

Generation of lossy mode resonances with different nanocoatings deposited on coverslips

“…The LMR depth increases as a function of wavelength for CuO coated coverslips while decreases for ITO and SnO 2 . This fading effect has also been observed in [23] for the first LMR, the most sensitive one, and CuO is the first material that solves this issue, which is also shown in this article as a new material that can be used for generating LMRs. In view of these results, CuO has a great potential in sensors based on this type of phenomenon.…”

“…The setup without the polarizer was placed in a DC sputtering machine (K675XD from Quorum Technologies, Ltd.) in order to observe the evolution of the optical spectrum during the deposition (to this purpose the pigtails connected to the light source and the detector enter the sputtering machine via a feedthrough). The reason why the polarizer is not introduced is because it can be damaged due to the deposition, while it is possible to observe the generation of the LMRs with unpolarized light [23].…”

“…More recently, it has been demonstrated that it is possible to generate lossy mode resonances by lateral light incidence in nanocoated planar waveguides [23,24]. There are several advantages in using a planar structure compared to optical fiber.…”

A Comprehensive Review: Materials for the Fabrication of Optical Fiber Refractometers Based on Lossy Mode Resonance

“…Recently, microscope coverslips coated with an ITO layer have been used as planar waveguides in a fiber setup to induce LMR [25], obtaining high sensitivity values (1405 and 920 nm/RIU for TE and TM modes, respectively). A similar setup using either a microscope glass slide or a coverslip coated with ITO and located in a poly(methyl methacrylate) (PMMA) block was used for the fabrication of a relative humidity sensor based on LMR [26].…”

Dually nanocoated planar waveguides towards multi-parameter sensing

“…As a result of the different excitation conditions for LMRs compared to SPRs, the best angles of incidence for LMR generation are those approaching 90°1 1 , whereas SPRs are typically obtained with angles ranging from 40 to 75°1 2,13 . This is what makes possible the lateral incidence of light on the edge of the coverslip 5,14 (see Fig. 1a).…”