Fig. 1: Waveguide-based excitation scheme.
a Illustration of the mode filtering operation. The resonant pump laser in the first-order waveguide mode excites the emitter and is subsequently squeezed out of the waveguide in the taper section. The QD emission into the fundamental mode of the waveguide is collected efficiently and guided. The photonic crystal acts a mirror for the fundamental mode, thereby enabling the directional out-coupling of the QD signal. b Scanning electron microscope image of the fabricated device (length of scale bar is 10 μm). The excitation and collection spots are highlighted with red and green spots. The Y-splitter is used to excite the fundamental and first-order modes of the waveguide. The photonic crystal (zoomed in the inset to highlight the lattice of air holes) selectively transmits only the first-order mode into the emitter section. The pump laser filter section is composed of a waveguide taper and two 90∘ bends to suppress the pump laser. The bottom-left grating is used to align the in-coupling of the laser beam by monitoring the reflected signal from the photonic crystal. c The measured and calculated transmission Tp spectrum of the device for a laser coupled in at the excitation grating and collected at the detection grating.
