Photonic integrated circuits for life sciences

TL;DR

This paper discusses the use of silicon nitride photonic integrated circuits in high-precision biophotonic instruments, enabling multi-wavelength excitation, modulation, and switching for advanced microscopy and cellular analysis.

Contribution

It introduces silicon nitride PICs as versatile platforms for multi-color laser sources with integrated modulation and switching functionalities in life sciences applications.

Findings

Demonstrated multi-wavelength laser excitation capabilities

Integrated modulation for optical trapping and imaging

Switching functionalities for microscopy modes

Abstract

We report on the use of silicon nitride (SiN) photonic integrated circuits (PICs) in high-value instrumentation, namely multi-color laser engines (MLEs), a core element of cutting-edge biophotonic systems applied to confocal microscopy, fluorescent microscopy - including super-resolution stimulated emission depletion (STED) microscopy - flow cytometry, optogenetics, genetic analysis and DNA sequencing, to name just a few. These have in common the selective optical excitation of molecules - fluorophores, or, in the case of optogenetics, light-gated ion channels - with laser radiation falling within their absorption spectrum. Unambiguous identification of molecules or cellular subsets often requires jointly analyzing fluorescent signals from several fluorescent markers, so that MLEs are required to provide excitation wavelengths for several commercially available biocompatible fluorophores. A number of functionalities are required from MLEs in addition to sourcing the required wavelengths: Variable attenuation and/or digital intensity modulation in the Hz to kHz range are required for a number of applications such as optical trapping, lifetime imaging, or fluorescence recovery after photobleaching (FRAP). Moreover, switching of the laser between two fiber outputs can be utilized for example to switch between scanning confocal microscopy and widefield illumination modes, for instance, for conventional fluorescence imaging.