Single quantum emitters are an important resource for quantum photonics, constituting building blocks for single-photon sources, qubits, and deterministic quantum gates. Robust implementation of such functions, however, can only be achieved through systems that provide both strong light–matter interactions and a low-loss interface between emitter and probing optical fields.
This presentation will discuss the development of quantum photonic integration platforms that allow the creation of photonic circuits incorporating single-emitter based functionality. The single emitter of choice is the self-assembled InAs quantum dot, which can be embedded inside a GaAs nanophotonic device. Such quantum dot containing nanophotonic structures can be designed to provide highly efficient coupling to an underlying waveguide-based photonic device based on transparent or nonlinear optical materials, such as Si3N4 and SiO2.
The introduction of single quantum dot based devices as functional elements in quantum photonic circuits may enable significant scaling of on-chip photonic quantum information systems, in two complementary ways. First, by acting as chip-integrated on-demand, bright single-photon sources, these devices can significantly boost the photonic flux available for non-deterministic, linear-optics based quantum computation. Furthermore, single-emitters strongly coupled to on-chip cavities provide a path towards single-photon nonlinearities, which would enable deterministic quantum operations through cavity quantum electrodynamics within a quantum network formed by a photonic integrated circuit.
New developments in heterogenous integration and hybrid, pick-and-place fabrication methods will be discussed in the talk.
Photonic integration is an enabling technology for photonic quantum science, offering greater
scalability, stability, and functionality than traditional bulk optics. Here, we describe a scalable,
heterogeneous III-V/silicon integration platform to produce Si3N4 photonic circuits incorporating
GaAs-based nanophotonic devices containing self-assembled InAs/GaAs quantum dots. We
demonstrate pure single-photon emission from individual quantum dots in GaAs waveguides
and cavities - where strong control of spontaneous emission rate is observed - directly launched
into Si3N4 waveguides with > 90 % efficiency through evanescent coupling. To date, InAs/GaAs
quantum dots constitute the most promising solid state triggered single-photon sources, offering
bright, pure and indistinguishable emission that can be electrically and optically controlled.
Si3N4 waveguides offer low-loss propagation, tailorable dispersion and high Kerr nonlinearities,
desirable for linear and nonlinear optical signal processing down to the quantum level. We
combine these two in an integration platform that will enable a new class of scalable, efficient
and versatile integrated quantum photonic devices.
There exists a tradeoff between the mechanical resonant frequency (<i>f<sub>m</sub></i>) and the mechanical quality factor (<i>Q<sub>m</sub></i>) of a nanomechanical transducer, which resulted in a tradeoff between the band width and sensitivity. Here, we present monolithic silicon nitride (Si<sub>3</sub>N<sub>4</sub>) cavity optomechanical transducer, in which high <i>f<sub>m</sub> </i>and <i>Q<sub>m</sub> </i>are achieved simultaneously. A nanoscale tuning fork mechanical resonator is near-field coupled with a microdisk optical resonator, allowing the displacement of mechanical resonator to be optically read out. Compared with a single beam with same length, width, and thickness, the tuning fork simultaneously increases <i>f<sub>m</sub> </i>and <i>Q<sub>m</sub> </i>by up to 1.4 and 12 times, respectively. A design enabled, on-chip stress tuning method is also demonstrated. By engineering the clamp design, we increased the stress in the tuning fork by 3 times that of the Si<sub>3</sub>N<sub>4</sub> film. A fundamental mechanical in-plane squeezing mode with <i>f<sub>m</sub></i> ≈ 29 MHz and <i>Q<sub>m</sub> </i> ≈ 2.2×10<sup>5</sup> is experimentally achieved in a high-stress tuning fork device, corresponding to a <i>f<sub>m</sub>Q<sub>m</sub></i> product of 6.35×10<sup>12</sup> Hz. The tuning fork cavity optomechanical sensors may find applications where both temporal resolution and sensitivity are important such as atomic force microscopy.
Photonic crystal waveguides have long attracted much attention in
the integrated photonics community due to their high confinement properties and potential for the achievement of photonic circuits with a very high level of integration. While high propagation losses still impair most of the practical applications of such waveguides, predicted and demonstrated slow and dispersive propagation within compact lengths remain very attractive for optical signal processing. In this talk, results will be presented from an investigation on slow and dispersive propagation in two different types of InP-based photonic crystal waveguides fabricated at UCSB. Waveguides of the membrane type, with very strong vertical confinement, were fabricated and characterized, as well as guides with weak vertical confinement and deeply-etched holes. Those of the latter kind were successfully integrated with structures found in standard photonic circuits produced in our group. Detailed measurements of transmission will be presented showing slow and dispersive propagation close to band edges.
Reasonable group delay enhancement is found, which is clearly dependent on propagation losses; on the other hand, extremely large GVD is found over reasonably wide bandwidths, even when considerable losses are present. This suggests that, by proper tuning of coupling coefficients, very compact dispersion-compensating elements can be designed. A discussion on the advantages and disadvantages, as well as different possibilities of using this class of waveguides for the implementation of delay lines and dispersion compensation will be presented.