Ultra-high resolution and broadband chip-scale speckle enhanced Fourier-transform spectrometer

Abstract

Recent advancements in silicon photonics are enabling the development of chip-scale photonics devices for sensing and signal processing applications. Here we report on a novel passive, chip-scale, hybrid speckle-enhanced discrete Fourier transform device that exhibits a two order-of-magnitude improvement in finesse (bandwidth/resolution) over the current state-of-the art chip-scale waveguide speckle and Fourier transform spectrometers reported in the literature. In our proof-of-principle device, we demonstrated a spectral resolution of 140 MHz with 12-nm bandwidth for a finesse of 10 4 that can operate over a range of 1500-1600 nm. This chip-scale spectrometer structure implements a typical spatial heterodyne discrete Fourier transform waveguide interferometer network that is enhanced by speckle generated from the wafer substrate. This latter effect, which is extremely simple to invoke, superimposes the high wavelength resolution intrinsic to speckle generated from high NA waveguide with a more broadband but lower resolution DFT modality of the overarching waveguide structure. This hybrid approach signifies a new pathway for realizing chip-scale spectrometers capable of ultra-high resolution and broadband performance.

Using multidimensional speckle dynamics for high-speed, large-scale, parallel photonic computing

“…Figure 8 shows an example of the entire photonic architecture for reservoir computing. The multimode waveguide with a spiral geometry or interferometer structure fabricated on a silicon chip can provide a long optical path length and high NA to generate speckles sensitive to the wavelength [34,35,36]; further, it can be used to induce speckle dynamics with a shorter latency in a small footprint. Each signal from the multimode waveguide can be split by a splitter and wavelength demultiplexer and detected by the photodetector array.…”

Research Progress on On‐Chip Fourier Transform Spectrometer

“…[ 91 ] In the same year, Paudel et al proposed a speckle enhanced SHS with a spectral resolution of 140 MHz and 12 nm bandwidth for a finesse of 104 that can operate over a range of 1500–1600 nm. [ 92 ] Xia et al used an artificial neural networks to analyze the output stationary interferogram, and the resolution could be improved without increasing the maximum path length difference and the number of MZIs, thus reducing the burden of adding more power budget. [ 93 ] In 2021, Dinh et al proposed and experimentally demonstrated the Jacquinot's advantage for the first time with 13 dB étendue increase, compared with a device with a conventional grating coupler input.…”

Optical-domain spectral super-resolution via a quantum-memory-based time-frequency processor

“…Optical spectroscopy is an indispensable tool in the studies of matter and light, including chemistry 1 , 2 , astronomy 3 , biology and medicine 4 , metrology, and more. Yet, the resolution of all state-of-the-art methods, such as grating-based 5 , 6 and Fourier spectrometers 7 – 9 , is subject to the Fourier limit. Methods of beating analogous Rayleigh limit are widely known in the context of imaging and include modifying or exploiting very specific properties of the source or illumination 10 – 13 , which is often impossible to implement.…”