Abstract
An optical filter array consisting of vertical narrow-band Fabry-Pérot (FP) resonators formed by two highly reflective high contrast subwavelength grating mirrors is reported. The filters are designed to cover a wide range of operation wavelengths (Δλ/λ = 5%) just by changing the in-plane grating parameters while the device thickness is maintained constant. Operation in the telecom band with transmission efficiencies greater than 40% and quality factors greater than 1,000 are measured experimentally for filters fabricated on the same substrate.
Highlights
The spectrometer is one of the most important instruments in the field of optics
Such a narrowband optical filter array is conventionally implemented by using FP resonators formed by two highly reflective distributed Bragg reflectors (DBRs) with spatially varied cavity length such that each of the resonators has a different resonance wavelength [6]
We propose and demonstrate a method to design a set of narrowband filters that covers a wide range of wavelengths, based on a vertical FP resonators formed by two-layers of highly reflective subwavelength grating (SWG) reflectors [8, 9]
Summary
The spectrometer is one of the most important instruments in the field of optics. Miniaturized spectrometers have been the subject of considerable recent interest due to their applications in a wide range of applications in sensing and various test and measurement equipment [1]. By the narrowband wavelength filters with different central wavelengths, and the corresponding underlying photodetectors are used to detect the optical power of the filtered spectra, allowing to reconstruct the spectral information for the incident light Such a narrowband optical filter array is conventionally implemented by using FP resonators formed by two highly reflective distributed Bragg reflectors (DBRs) with spatially varied cavity length such that each of the resonators has a different resonance wavelength [6]. Each of the narrowband optical filters is made of two identical SWG reflectors separated by a distance on the order of a wavelength of interest, to satisfy the symmetric FP condition Such symmetric FP resonators are critically coupled, have theoretical transmission of 100% at their resonance wavelength, and reflect back off-resonance portion of the incident light
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