Fig. 6: Reconfigurable optical functions inside silicon by seeded writing.
From: In-chip critical plasma seeds for laser writing of reconfigurable silicon photonics systems
a Infrared microcopy images of a Fresnel plate written inside a silicon wafer (300-µm depth) and focusing performance characterization, followed by its erasure by scanned nanosecond laser irradiation (dark field images), and re-rewriting with design modifications for a change of the apparent focal length. b Infrared phase microscopy measurements of 2D phase plates at different phase levels obtained by seeded writing. The phase level can be varied by changing the picosecond pulse energy in the seeded writing procedure (first row) or by writing a given phase plate and progressively erasing it using nanosecond pulses of different energies (second row). The erasing leads to more uniform phase writing. The successive images of the second row reveal phase levels (and standard variation) measured at 0.81 ± 0.02, 0.74 ± 0.09, 0.61 ± 0.07, and 0.13 ± 0.03 radians. This shows the capacity to create phase elements which can be precisely reconfigured. c Measurements of the double-focus obtained by beam shaping with the step-phase plates produced by seeded writing. The ratio between the peak intensities of the spots compares well with those expected by simulation as a function of phase levels.
