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Emerging neuromorphic hardware promises to solve certain problems faster and with higher energy efficiency than traditional computing by using physical processes that take place at the device level as the computational primitives in neural networks. While initial results in photonic neuromorphic hardware are very promising, such hardware requires programming or “training” that is often power-hungry and time-consuming. In this article, we examine the online learning paradigm, where the machinery for training is built deeply into the hardware itself. We argue that some form of online learning will be necessary if photonic neuromorphic hardware is to achieve its true potential.

We fabricated and characterized record small microdisk resonators in thin (210 nm) 3C-SiC film grown on Si (100) substrate. It was found to support high quality factor whispering gallery modes at visible wavelengths. We demonstrated room temperature coupling of these modes to the intrinsic photoluminescence of 3C-SiC at room temperatures and identified their polarization. Finally, we discussed applications for quasi-phasematched second harmonic generation from infrared visible wavelengths.

For quantum applications, it is important to generate quantum states of light and detect them with extremely high efficiency. For future applications, it also important to do this at scale. This presents many engineering and metrology challenges. This paper discusses some of the open challenges and opportunities in single photon detector efficiency measurements, including the challenges ofmetrology for waveguide-integrated detectors on photonic circuits.

We demonstrate the design, fabrication, and characterization of nanobeam photonic crystal cavities in (111)-GaAs with multiple high-Q modes, with large frequency separations (up to 740 nm in experiment, i.e., a factor of 1.5 and up to an octave in theory). Such structures are crucial for efficient implementation of nonlinear frequency conversion. Here, we employ them to demonstrate sum-frequency generation from 1300 and 1950 nm to 780 nm. These wavelengths are particularly interesting for quantum frequency conversion between Si vacancy centers in diamond and the fiber-optic network.

We demonstrate photonic interfaces between infrared and visible wavelength ranges by employing enhanced nonlinear frequency conversion in photonic crystal cavities in GaP or GaAs. We first show resonantly enhanced second harmonic and sum frequency generation in GaP photonic crystal cavities. We then integrate these nonlinear frequency conversion elements with a single InAs quantum dot to produce a fast single photon source that is optically triggered at telecommunications wavelength. These frequency conversion techniques are critical for applications including light sources at wavelengths that are difficult to access with existing lasers, IR upconversion-based detectors, and photonic quantum interfaces between the fiber-optic networks and quantum emitters.

We use the third- and fourth-order autocorrelation functions g(3)(τ1,τ2) and g(4)(τ1,τ2,τ3) to detect the nonclassical character of the hght transmitted through a photonic-crystal nanocavity containing a strongly coupled quantum dot probed with a train of coherent hght pulses. We contrast the value of g(3)(0,0) with the conventionally used g(2)(0) and demonstrate that, in addition to being necessary for detecting two-photon states emitted by a low-intensity source, g(3) provides a more clear indication of the nonclassical character of a light source. We also present preliminary data that demonstrates bunching in the fourth-order autocorrelation function g(4)(τ1,τ2,τ3) as the first step toward detecting three-photon states. [ABSTRACT FROM AUTHOR]