Fig. 4: Characterizing the refractive index as a function of the writing laser power.
From: Direct laser writing of volumetric gradient index lenses and waveguides
a Schematic of an interference pattern produced by a subsurface Fresnel biprism. b The xz-plane cross section of the simulated and measured interference patterns at 633 nm produced by a Fresnel biprism with an effective refractive index of 1.82. c Overlaid intensity profiles of the simulated and measured interference patterns at the cut line shown in b. d, e Plots of the refractive index versus average laser power of prisms written inside PSi (d) and PSiO2 (e) for blue (488 nm), green (543 nm), and red (633 nm) light. All biprisms were printed with a scan speed of 10 mm s−1
