A compact optofluidic refractometer is demonstrated. Consisting of a grating structure with rectangular grooves integrated into a microfluidic network, its working principle is based on the modulation of the zeroth-order diffraction intensity of the transmission induced by the refractive index (RI) of a sample fluid that fills the groove space. The performance of the device is dependent on the grating structure parameters such as thickness. Theoretical analysis and experimental measurements agree well with each other and both demonstrate that having a thicker grating results in higher sensitivity but a smaller measurement range, and vice versa. It can also be expected that smaller changes in the RI can be resolved by using a detector with a lower detection limit.
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