Single-Shot Integrated Speckle Spectrometer with Ultrahigh Bandwidth-to-Resolution

TL;DR

This paper introduces a single-shot, integrated speckle spectrometer on a silicon chip that achieves ultrahigh bandwidth-to-resolution, enabling precise spectral measurements with a simple image capture.

Contribution

The authors demonstrate a novel spectrometer design that combines high pixel count sampling with passive optical networks to significantly improve bandwidth-to-resolution ratio.

Findings

Spectral resolution of 10 pm achieved

Operational bandwidth of 200 nm demonstrated

Sampling channels up to 2730 used for spectral reconstruction

Abstract

Miniaturized spectrometers employing chip solutions are essential for a wide range of applications, such as wearable health monitoring, biochemical sensing, and portable optical coherence tomography. However, the development of integrated spectrometers is hampered by the inherent trade-off between bandwidth-to-resolution, footprint, sampling channels, and operation speed. Here, we demonstrate that an ultrahigh bandwidth-to-resolution reconstructive spectrometer can be easily implemented through a single image capture of the speckle pattern diffracted from a passive silicon photonic chip. By leveraging the high pixel count of an image sensor, we can instantly acquire a significant number of distinct spatial sampling channels. Those sampling channels are spatially decorrelated by using our passive optical network on chip including cascaded unbalanced Mach-Zehnder interferometers, random diffraction by an antenna array, and mutual interference in free space before being captured. Hence, each speckle pattern contains wavelength-specific information across its spatial distribution to enhance the effectiveness of the global sampling strategy. Experimentally, we achieve a spectral resolution of 10 pm and an operational bandwidth of 200 nm, with sampling channels up to 2730. Multiple unknown narrowband and broadband spectra can also be precisely obtained.