Fig. 3 | Nature Communications

Fig. 3

From: On-chip single photon filtering and multiplexing in hybrid quantum photonic circuits

Fig. 3

On-chip filtering. a Experimental setup showing the hybrid integrated quantum circuit with electrical access to control the integrated filters. The setup allows for both in-plane (via the waveguide) and out-of-plane laser excitation. Details of out-of-chip coupling are included in the Methods section. The collected emission from the waveguide is either coupled to the APDs after filtering with a monochromator (case 1), or it can be directly coupled to the APDs with no external wavelength filtering (case 2). b Collected QD emission from the facet of the SiN waveguide in the forward direction. c By tuning the on-chip filter, a single QD transition is routed to the drop-port. d A close-up of the filtered trion (T) emission line. The QD emission wavelength is slightly different in b and c or d due to different biases applied to the ring resonator filter. Despite the presence of an intense laser for excitation and InP nanowire emission, the filtered spectrum shows only a single QD transition over a broad wavelength range (500–950 nm). e Second-order correlation measurement of the QD trion line using an off-chip commercial monochromator for filtering, resulting in a multi-photon probability of g (2)(0) = 0.13 ± 0.04 when taking into account the finite temporal resolution of the APDs. f Second-order correlation measurement of the QD trion line at the drop-port of the ring resonator after directly coupling it to the APDs. A single-stage ring filter is capable of delivering single photons on-chip with multi-photon probability g (2)(0) = 0.41 ± 0.05. The results show the excellent performance of the integrated ring resonator filter as compared to the bulky off-chip monochromator. g Second-order correlation measurement without any on-chip and off-chip filtering. The results show the expected Poissonian statistics of coherent (uncorrelated) emission. In e, f, the blue circles show the raw data, the green line represents a fit, and the red line represents the fit considering the finite detector response (see Supplementary Note 4 for more details)

Back to article page