Structured illumination microscopy using a photonic chip

Structured illumination microscopy (SIM) enables live-cell super-resolution imaging of subcellular structures at high speeds. At present, linear SIM uses free-space optics to illuminate the sample with the desired light patterns; however, such arrangements are prone to misalignment and add cost and complexity to the microscope. Here, we present an alternative photonic chip-based two-dimensional SIM approach (cSIM) in which the conventional glass sample slide in a microscope is replaced by a planar photonic chip that importantly both holds and illuminates the specimen. The photonic chip reduces the footprint of the light illumination path of SIM to around 4 x 4 cm(2). An array of optical waveguides on the chip creates standing wave interference patterns at different angles, which illuminate the sample via evanescent fields. High-refractive-index silicon nitride waveguides allow a 2.3 times enhancement in imaging spatial resolution, exceeding the usual 2 times limit of SIM. In summary, cSIM offers a simple, stable and affordable approach for performing two-dimensional super-resolution imaging over a large field of view. The use of a photonic integrated circuit to both hold a biological sample and generate the necessary light patterns for structured illumination microscopy promises convenient super-resolution imaging.