MIT Develops Low-Cost On-Chip Optical Spectrometers With High Channel Count And Signal-To-Noise Ratio

Researchers are working on miniature chip-based spectrometers that are as accurate and powerful as conventional large devices, costing six figures. Standard chipmaking processes could be used to mass-produce the new spectrometers. This approach may enable spectrometry to be used in previously physically and financially impossible ways.

The device, known as the digital Fourier-transform (dFT) spectrometer, includes a reconfigurable Mach-Zehnder interferometer (MZI) with optical switches on each arm that direct light to waveguides with different and unique path lengths scaled in powers of 2. As a result, the number of optical switches scales exponentially with the number of channels. In comparison, other chip-based approaches add one device per channel, resulting in linear scaling.

Other groups have attempted to develop chip-based spectrometers. Still, there is an inherent difficulty: The ability of a device to disperse light spectrally using any conventional optical system is highly dependent on its size.

Another type of spectrometer employs the Fourier-transform method; however, these devices are still constrained by the same size constraint: long optical paths are required for high performance.

Electro-optical switches eliminate the need for movable mirrors in the new MIT system and can be easily fabricated using standard chipmaking technology. The elimination of moving parts has a significant impact on robustness. It would not be damaged if you dropped it off the table.

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