Photonic Needles for Light Delivery in Deep Tissue-like Media.

We demonstrate a new platform for minimally invasive, light delivery probes leveraging the maturing field of silicon photonics, enabling massively parallel fabrication of photonic structures. These Photonic Needles probes have sub-10 µm cross-sectional dimensions, lengths greater than 3 mm-surpassing 1000 to 1 aspect ratio, and are released completely into air without a substrate below. We show the Photonic Needles to be mechanically robust when inserted into 2% agarose. The propagation loss of these waveguides is low-on the order of 4 dB/cm.

Silicon-chip mid-infrared frequency comb generation.

Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2-20 µm) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers. However, material and dispersion engineering limitations have prevented the realization of an on-chip integrated mid-infrared microresonator comb source. Here we demonstrate a complementary metal-oxide-semiconductor compatible platform for on-chip comb generation using silicon microresonators, and realize a broadband frequency comb spanning from 2.1 to 3.5 µm. This platform is compact and robust and offers the potential to be versatile for use outside the laboratory environment for applications such as real-time monitoring of atmospheric gas conditions.