Quantum Light Generation Based on GaN Microring toward Fully On-Chip Source

An integrated quantum light source is increasingly desirable in large-scale quantum information processing. Despite recent remarkable advances, a new material platform is constantly being explored for the fully on-chip integration of quantum light generation, active and passive manipulation, and detection. Here, for the first time, we demonstrate a gallium nitride (GaN) microring based quantum light generation in the telecom C-band, which has potential toward the monolithic integration of quantum light source. In our demonstration, the GaN microring has a free spectral range of 330 GHz and a near-zero anomalous dispersion region of over 100 nm. The generation of energy-time entangled photon pair is demonstrated with a typical raw two-photon interference visibility of $95.5\pm 6.5\%$, which is further configured to generate a heralded single photon with a typical heralded second-order autocorrelation $g_H^{(2)}(0)$ of $0.045\pm 0.001$. Our results pave the way for developing a chip-scale quantum photonic circuit.

Figure 1

(a) Scanning electron microscopy image of the GaN MRR pulley with a $60\text{−}\mathrm{\mu }\mathrm{m}$ radius. (b) Measured transmission spectrum near 1550 nm with a free spectral range of 330 GHz. (c) Resonance dip around 1550.1 nm, indicating a loaded quality factor of $4.3\times {10}^5$. (d) Measured and fitted results of the integrated dispersion of the TE00 mode.

Figure 2

Schematic diagram of experimental setups. (a) Generation of correlated photon pairs. (b) Correlation properties. (c) Photon spectrum. (d) Energy-time entanglement with two-photon interference. (e) Heralded single-photon with HBT experimental setup. The SNSPDs are operated at a temperature of 2.2 K.

Figure 3

Experimental results of generated correlated photon pairs. (a) Single side count rate of the idler photon at 1566.23 nm versus pump power. (b) Coincidence count rate and the calculated CAR versus pump power. The inset is the measured coincidence histogram of the signal and idler photons at 1534.30 and 1566.23 nm. (c) Spectra of the correlated photons and noise photons in the on-resonance case from 1480 to 1620 nm. (d) Coincidence count rate of different combinations of the wavelength of correlated photon pairs. (e) CAR of different combinations of wavelength of correlated photon pairs.

Figure 4

Experimental results of two-photon interference. (a) and (b) correspond to constructive and destructive two-photon interference within 15 s, respectively. (c) Photon count rate of the signal and idler photons. (d) Interference fringe of energy-time entangled photons with a visibility of $95.5\pm 6.5\%$ (blue dots and lines). The single-photon interference is given by the right vertical axis with red dots and line.

Figure 5

Characterization of single-photon purity. (a) Unheralded second-order autocorrelation coincidence histogram of photon at 1566.23 nm. (b) Heralded second-order autocorrelation $g_H^{(2)}(\tau )$ of heralded photon at 1566.23 nm and heralding photons at 1534.30 nm. (c) Heralded second-order autocorrelation $g_H^{(2)}(0)$ versus heralding count rate.