Ultrahigh-resolution on-chip spectrometer with silicon photonic resonators

Abstract

A compact spectrometer on silicon is proposed and demonstrated with an ultrahigh resolution. It consists of a thermallytunable ultra-high-Q resonator aiming at ultrahigh resolution and an array of wideband resonators for achieving a broadened working window. The present on-chip spectrometer has a footprint as compact as 0.35 mm 2 , and is realized with standard multi-project-wafer foundry processes. The measurement results show that the on-chip spectrometer has an ultra-high resolution ∆λ of 5 pm and a wide working window of 10 nm. The dynamic range defined as the ratio of the working window and the wavelength resolution is as large as 1940, which is the largest for on-chip dispersive spectrometers to the best of our knowledge. The present high-performance on-chip spectrometer has great potential for highresolution spectrum measurement in the applications of gas sensing, food monitoring, health analysis, etc.

Integrated Single-Resonator Spectrometer beyond the Free-Spectral-Range Limit

“…Due to the inherent trade-off between linewidths and free spectral ranges (FSRs), however, it is challenging to simultaneously attain high resolutions and broad bandwidths in filter-based spectrometers. This issue can be resolved to a limited extent by sorting FSRs with extra demultiplexers − or paralleling multiple FSR-free photonic-crystal (PhC) nanobeam cavities. − Nevertheless, these approaches will eventually raise the device footprint and layout complexity. Also, the FSR broadening of nanobeam cavities is typically accompanied by the tightly confined mode volume, resulting in a narrow tuning range and an increase in aggregate power consumption. , For FTSs, the unknown spectrum is retrieved in the Fourier domain from a modulated interferogram.…”

“…For instance, frequency-domain optical coherence tomography (OCT) requires a <85 pm spectral resolution and a >75 nm bandwidth (around the 1300 nm wavelength) to accomplish a <10 μm depth resolution and a >5 mm imaging depth . It is feasible to circumvent the FSR limit by exploiting tandem filters or parallel nanocavities, − in which temporal and spatial decorrelations are combined. In spite of this, the scalability of these schemes is basically compromised by larger footprints and higher power arising from a greater number of cascaded resonators.…”

Multiscale Optical Field Manipulation via Planar Digital Optics

“…In addition to topology optimization, deep learning, a data-driven artificial intelligence optimization algorithm, is an alternative approach for the intelligent design of metasurfaces. − By learning the relationship between the structural morphology of a large number of meta-devices and their optical response, the performance of large-scale devices could be improved . This design method may achieve a breakthrough in the field of metasurface design, making metasurface design fast, efficient, and automatic …”

“…Conventional grating couplers face the challenge of low coupling efficiency and high polarization sensitivity. By introducing subwavelength microstructures in the grating couplers, the above problems can be effectively avoided. ,− Metasurface-assisted broadband and multifunctional directional couplers have been proposed based on geometric phase − and propagation phase . These waveguide-integrated metasurfaces have shown the potential to be used as ultracompact polarization-demultiplexing on-chip devices for high–bit rate telecommunication applications …”

Planar photonic chips with tailored dispersion relations for high-efficient spectrographic devices

“…Thus, much attention is focused on improving the signal-to-noise ratio, while the spectral resolution is always been ignored 31,35,36 . To improve the spectral resolution, many state-of-the-art techniques have employed tunable narrowband filters 37,38,39,40 . However, the challenge lies in inevitable fabrication imperfections for the large-scale complex devices.…”