Single‐Shot Integrated Speckle Spectrometer With Ultrahigh Bandwidth‐to‐Resolution

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, it is demonstrated that an ultrahigh bandwidth‐to‐resolution reconstructive spectrometer can be easily implemented through a single‐shot image capture of the speckle pattern diffracted from a passive silicon photonic chip. By leveraging the high pixel count of an image sensor, a significant number of distinct spatial sampling channels can be instantly acquired. Those sampling channels are spatially decorrelated by using the passive optical network on chip including cascaded unbalanced Mach–Zehnder interferometers and wavelength‐dependent diffraction from an antenna array, where free‐space interference of fields from multiple antennas introduces an additional spatial degree of randomness, yielding highly decorrelated speckle patterns at the camera plane. 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.