Generation of lossy mode resonances in a broadband range with multilayer coated coverslips optimized for humidity sensing

Coverslips deposited with a metallic oxide can be employed for generating lossy mode resonances by lateral incidence of light on the coverslip. Here it is demonstrated that with copper oxide the fading observed with other materials in the near infrared (NIR) wavelength range is avoided and LMRs can be obtained in a broadband range from 400 to 1700 nm, which permitted to observe the better performance in the NIR region compared to the visible region: the sensitivity to humidity is improved by more than a factor of two. However, copper oxide is not adequate for sensing humidity. The sensitivity of the device was optimized initially with a tin oxide coating and later with an additional layer of agarose, specifically adequate for the detection of humidity. The best performance was obtained with an agarose concentration 1% w/v, which permitted to observe a 10-fold sensitivity increase compared to the same device without agarose. This opens the path towards the development of environmental, chemical or biological sensors with an optimized sensitivity to a specific parameter to detect.