Transverse Inscription of Silicon Waveguides by Picosecond Laser Pulses

In this paper, picosecond laser inscription of segmented waveguides in crystalline silicon based on a deterministic single-pulse modification process is demonstrated.Pulses of 43 ps duration at 1.55 μm wavelength are used to transversely inscribe periodic structures with a pulse-to-pulse pitch of around 2 μm. Infrared shadowgraphy images and Raman spectroscopy measurements indicate that the modifications exhibit a spherical shape. Characterization of waveguide performance at 1.55 μm for various pulse energies and periods is carried out. Direct comparison with numerical simulations confirms the presence of graded index waveguides, encompassing a micrometer core size and a maximum refractive index change of around 7× 10^-3. This short-pulse inscription approach can pave the way for three-dimensional integrated photonic devices in the bulk of silicon.