Fig. 2
From: Highly sensitive ultrasound detection using nanofabricated polymer micro-ring resonators
(Reproduced with permission from [30])
Nanofabrication of polymer MRRs by maskless lithography. a A schematic illustration of fabrication procedures of maskless lithography such as EBL and MPL. b A top view SEM image of the SU-8 MRR by EBL. c A cross-sectional SEM image of the waveguide with a width of 800 nm and a height of 800 nm. d Close-up view of the gap of 150 nm between the ring and bus waveguides. e A schematic illustration of the packaged SU-8 MRR ultrasound detector coupled to two tapered optical fibers. f A schematic illustration of PAM setup with the SU-8 MRR ultrasound detector. g A spectral profile of the impulse response for the MRR based PAM system after a 10-point moving averaging. The 3-dB frequency bandwidth is 140 MHz. h The MAP image of the target along the x–y plane from the reconstructed volumetric image. i A cross-sectional image of the target at the position indicated by the arrows in the panel (h)