Beyond Interferometers Based on Silicon-Air Bragg Reflectors: Toward On-Chip Optical Microinstruments—A Review

In this paper, we review recent advances in optical microinstruments based on distributed Bragg reflectors (DBR) focusing mainly on two application areas: spectrometry and profilometry. For spectrometry applications, we consider state-of-the-art architectures. Among these are novel architectures of high-Q Fabry-Perot resonators based on cylindrical surfaces. In addition, we consider a microelectromechanical Michelson interferometer based on a robust (silicon-air) beam splitting interface. Its measurement principle relies on recording the spatial interferogram using movable mirror followed by inverse Fast Fourier transform (iFFT) to deduce the spectral content of the tested sample. For profilometry applications instead, an elaborated Michelson interferometer based on planar DBR is deployed for profile measurements using the technique of wavelength sweep and FFT to extract the dimensional characteristics. In the last section, we revisit the applications of DBR structures in optofluidics wherein a curved FP cavity has been deployed for optical trapping and binding of microparticles. Besides, a Michelson-based optofluidic probe has been deployed for off-chip measurements of fluid refractive index and absorbance. Globally, DBR based microinstruments demonstrate a strong potential in the targeted application areas.