Fig. 16
Adapted with permission from Ref [65], Copyright © 2020, IEEE
a The schematic of plasmonic slot waveguide with oblique illumination in free space. The red dashed line is perpendicular to the top surface of the waveguide. The green and the red arrows indicate the propagation directions of the pump beam and Stokes beam respectively. b The Raman plasmonic sensor (yellow) complemented by a Si3N4 mode converter between slot and strip waveguides, a strip waveguide and a taper for in/out coupling to free space. The red arrows for Input1 indicates the out-of-plane pumping beam mode of the excitation, while Input2 refers to the pump beam adopted in waveguide coupled mode for the comparison of noise suppression. In both cases the red and green colours refer to pump and Stokes beam respectively. Dashed arrows are the collected light.