Glucose concentration sensor based on a mid-infrared O⁵⁺ ion-irradiated ZnSe optical waveguide

Sensing technology relying on mid-infrared (MIR) waveguides has garnered considerable attention as it contains abundant molecular vibrational absorption bands and provides valuable spectroscopic information for biochemical sensing. In this paper, we show a simple ZnSe ridge waveguide platform for glucose detection achieved by a combination of O⁵⁺ ion irradiation and precision diamond-blade dicing. This results in a waveguide that supports single-mode propagation with a propagation loss of 1.0 dB/cm at the wavelength of 4 µm. Glucose concentration can be quantitatively determined by monitoring the concentration-dependent propagation loss arising from the interaction between the evanescent field and the surrounding glucose solution. The experimental results show that the sensor has a good linear response in the glucose concentration range of 0-35 mM, and it has a high concentration sensitivity up to 0.0479dB⋅cm^-1⋅mM^-1. The suggested platform will bring together low loss, compact integration, and enhanced light-matter interaction, paving the way to various applications such as biochemical sensing in the MIR and miniaturized lab-on-a-chip systems.