Extracting light into free space is one of the challenges to face when dealing with solid-state emitters embedded within high-index materials. In particular, improving the extraction efficiency has been the object of intensive research when intrinsically dim light sources, like single-photon emitters, are implemented for fundamental science and quantum information technology applications.
Here, we show that metallic nano-rings, transferred on a gold-coated substrate, can be implemented to increase the extraction efficiency of single photons emitted by InAs quantum dots, thanks to the focusing effect of the plasmonic device. Furthermore, we show that such a device is scalable and gives broadband (over 60 nm) operation, as opposed to narrowband cavity-based geometries.
We introduce the traceable calibration of a cryogenic localization microscope, enabling accurate localization of quantum dots to improve subsequent integration into photonic cavities. We combine the calibration results with an assessment of fabrication accuracy by electron-beam lithography to introduce a comprehensive model of the effects of registration errors in the integration process on Purcell factor. Our theory shows the possibility of significantly improving the magnitude and distribution of Purcell factor across a wide field, enabling dramatic increases of process yield.
Single solid-state quantum emitters have demonstrated considerable potential for the implementation of important quantum photonic devices such as on-demand single-photon sources or deterministic quantum logic gates. Converting a bare quantum emitter into a device with sufficient performance for use in quantum photonic systems requires an efficient, high cooperativity interface to accessing optical fields. Such interfaces may in principle be implemented through nanophotonic geometries that leverage cavity quantum electrodynamics effects with strongly confined optical modes. A number of critical factors, however, such as preservation of the emitter coherence post-fabrication, and fabrication yield and scalability, must be simultaneously addressed, imposing significant challenges to device development. In this talk I will describe our past and current efforts to target such requirements through nanophotonic design, towards the development of scaled chip-integrated quantum photonic systems with functionality enabled by quantum emitters.
The deterministic integration of quantum emitters into on-chip photonic elements is crucial for the implementation of scalable on-chip quantum circuits. Here, we report on the deterministic integration of single quantum dots (QD) into tapered multimode interference beam splitters using in-situ electron beam lithography (EBL). We demonstrate the functionality of the deterministic QD-waveguide structures by µPL spectroscopy and by studying the photon cross-correlation between the two MMI output ports. The latter confirms single-photon emission and on-chip splitting associated with g(2)(0) << 0.5. Moreover, the deterministic integration of QDs enables the demonstration and controlled study of chiral light-matter effects and directional emission in QD-WGs, and the realization of low-loss heterogenous QD-WG systems with excellent quantum optical properties.
Semiconductor quantum dots are excellent emitters of single photons. Often, the same mode is used to resonantly excite a QD and to collect the emitted single-photons, requiring cross polarization to separate out scattered laser light. This reduces the source brightness to ≤50%, and potentially eliminates their use in some quantum applications. We demonstrate a resonant-excitation approach to creating single photons that is free of any filtering whatsoever. This integrated device allows us to resonantly excite single quantum-dot states in several cavities in the plane of the device using connected cavity-waveguides, while the cavity-enhanced single-photon fluorescence is directed vertically (off-chip) in a Gaussian mode.
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.
KEYWORDS: Sensors, Temperature metrology, Silicon, Resonators, Finite element methods, Transducers, Near field optics, Optical resonators, Near field, Neck
There exists a tradeoff between the mechanical resonant frequency (fm) and the mechanical quality factor (Qm) of a nanomechanical transducer, which resulted in a tradeoff between the band width and sensitivity. Here, we present monolithic silicon nitride (Si3N4) cavity optomechanical transducer, in which high fmand Qmare 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 fmand Qmby 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 Si3N4 film. A fundamental mechanical in-plane squeezing mode with fm ≈ 29 MHz and Qm ≈ 2.2×105 is experimentally achieved in a high-stress tuning fork device, corresponding to a fmQm product of 6.35×1012 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.
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