Microspectrometer uses donut-shaped resonators for higher resolution

An 81-channel microspectrometer with 2-μm-diameter singlemode microdonut resonators as its sensing elements is vastly shrunken in size compared to conventional spectrometers, but without sacrificing resolution. Fabricated on a silicon-on-insulator chip, the instrument was developed at the Georgia Institute of Technology (Atlanta, GA) for integrated lab-on-a-chip sensing applications.

Tunable-laser light in the 1550 nm range from an input-bus waveguide enters the microdonut array, with each microdonut resonator tapping only a small portion of the incoming light; each resonator is a unique channel and has a slightly different diameter. In a microdonut resonator, the fundamental radial mode interacts only with the donut’s outer wall; this is in contrast to a more conventional microring resonator, in which the light interacts with the inner and outer walls. Less interaction means a higher quality (Q) factor); the microdonuts have a loaded Q of 30,000 and an intrinsic Q of 80,000. The signal is collected by imaging from the top of the chip. The device achieved 0.6 nm resolution over a spectral range of more than 50 nm with a footprint less than 1 mm². The instrument can be integrated with devices including sensors, optoelectronics, and microfluidic channels for use in biological, chemical, medical, and pharmaceutical applications.

Contact Ali Adibi at [email protected].