Modeling of photonic chips for two-photon fluorescence microscopy

Two-photon microscopy is a well-established bio-medical imaging method which offers elevated penetration depths with high resolution¹. This method relies on two-photon excitation of fluorescent dyes by a high-power pulsed laser. Additionally, recent microscopy techniques which rely on the control of scattered light^2,3, often called scattering-compensation microscopy, show that imaging depth can be further increased if the wavefront of the laser excitation can be controlled. Combining the two methods, two-photon and scattering-compensation microscopy, has a promising potential for in-vivo imaging at elevated depths. However, there are several challenges. The main one is the compatibility of the photonic integrated circuit (PIC), which offer dynamic wavefront control, with high-power pulsed lasers. Therefore, the first step in this research direction is the analysis of the PIC power handling capabilities and dispersion performance.    

This master thesis will investigate femtosecond pulse propagation in photonic integrated circuits using analytical approaches and numerical Maxwell solvers such as Lumerical FDTD. Based on the findings, dispersion-engineered PIC components, compatible with pulsed laser sources, will be designed. Finally, experiments to characterize the components will have to be designed.

This master thesis builds upon existing work on bio-medical imaging and scattering-compensation microscopy at imec.

References:

1. Helmchen, F., Denk, W. Deep tissue two-photon microscopy. Nat Methods 2, 932–940 (2005). https://doi.org/10.1038/nmeth818
2. May, M.A., Barré, N., Kummer, K.K. et al. Fast holographic scattering compensation for deep tissue biological imaging. Nat Commun 12, 4340 (2021). https://doi.org/10.1038/s41467-021-24666-9
3. Yang, J., He, Q., Liu, L. et al. Anti-scattering light focusing by fast wavefront shaping based on multi-pixel encoded digital-micromirror device. Light Sci Appl 10, 149 (2021). https://doi.org/10.1038/s41377-021-00591-w