Search

Quantum dot (QD) emitters on silicon platforms have been considered as a fascinating approach to building next-generation quantum light sources toward unbreakable secure communications. However, it has been challenging to integrate position-controlled QDs operating at the telecom band, which is a crucial requirement for practical applications. Here, we report monolithically integrated InAsP QDs embedded in InP nanowires on silicon. The positions of QD nanowires are predetermined by the lithography of gold catalysts, and the 3D geometry of nanowire heterostructures is precisely controlled. The InAsP QD forms atomically sharp interfaces with surrounding InP nanowires, which is in situ passivated by InP shells. The linewidths of the excitonic (X) and biexcitonic (XX) emissions from the QD and their power-dependent peak intensities reveal that the proposed QD-in-nanowire structure could be utilized as a non-classical light source that operates at silicon-transparent wavelengths, showing a great potential for diverse quantum optical and silicon photonic applications.

By integrating WSe 2 monolayers with a nanopatterned Si micro-cantilever, we create the quantum emitters at deterministic sites and control their frequency with voltages. Also, reduction of the fine-structure splitting is observed by engineering the strain.

Plasmonic nano-structures provides an efficient way to control and enhance the radiative properties of quantum emitters. Coupling these structures to single defects in low-dimensional materials provides a particularly promising material platform to study emitter-plasmon interactions because these emitters are not embedded in a surrounding dielectric. They can therefore approach a near-field plasmonic mode to nanoscale distances, potentially enabling strong light-matter interactions. However, this coupling requires precise alignment of the emitters to the plasmonic mode of the structures, which is particularly difficult to achieve in a site-controlled structure. We present a technique to generate quantum emitters in 2D tungsten diselenide (WSe2) coupled to site-controlled plasmonic nano-pillars. The plasmonic nano-pillars induce strain in the two dimensional material which generates quantum emitters near the high-field region of the plasmonic mode. The electric field of the nano-pillar mode lies close to parallel with the two-dimensional material, and is therefore in the correct orientation to couple to quantum emitters. Interactions between the emitter and plasmonic mode result in an enhanced spontaneous emission and increased brightness. This approach may enable bright site-controlled non-classical light sources for applications in quantum communication and optical quantum computing.

Future scalable photonic quantum information processing relies on the ability of integrating multiple interacting quantum emitters into a single chip. Quantum dots provide ideal on-chip quantum light sources. However, achieving quantum interaction between multiple quantum dots on-a-chip is a challenging task due to the randomness in their frequency and position, requiring local tuning technique and long-range quantum interaction. Here, we demonstrate quantum interactions between distant two quantum dots on a nanophotonic waveguide. We achieve a photon-mediated long-range interaction by integrating the quantum dots to the same optical mode of a nanophotonic waveguide and overcome spectral mismatch by incorporating on-chip thermal tuners. We observe their quantum interactions of the form of super-radiant emission, where the two dots collectively emit faster than each dot individually. Creating super-radiant emission from integrated quantum emitters could enable compact chip-integrated photonic structures that exhibit long-range quantum interactions. Therefore, these results represent a major step towards establishing photonic quantum information processors composed of multiple interacting quantum emitters on a semiconductor chip., Comment: 23 pages, 7 figures

Although the study of single quantum dot (QD) properties without the background noise and dephasing processes caused by surrounding carriers is a crucial issue, the spatial-selective excitation of a single QD is still challenging, due to the diffraction nature of light. Here, we demonstrate a deep subwavelength excitation of a single QD using two-photon plasmonic nanofocusing. Self-aligned plasmonic nanofocusing on a single QD was achieved using metal coated nanopyramid structures. The highly enhanced local electric field generated by the plasmonic nanofocusing gives rise to a large increase in the optical nonlinear effect (i.e., two-photon excitation). As a result of the enhanced field enhancement on the metal-pyramid hybrid structure, the two-photon luminescence intensity was enhanced by a factor of 5000, and the selective excitation of a single QD enabled us to observe InGaN QD emission at near room temperature, due to the large suppression of the background emission. Our approach opens promising persp...

Interactions between solid-state quantum emitters and cavities are important for a broad range of applications in quantum communication, linear optical quantum computing, nonlinear photonics, and photonic quantum simulation. These applications often require combining many devices on a single chip with identical emission wavelengths in order to generate two-photon interference, the primary mechanism for achieving effective photon-photon interactions. Such integration remains extremely challenging due to inhomogeneous broadening and fabrication errors that randomize the resonant frequencies of both the emitters and cavities. In this Letter, we demonstrate two-photon interference from independent cavity-coupled emitters on the same chip, providing a potential solution to this long-standing problem. We overcome spectral mismatch between different cavities due to fabrication errors by depositing and locally evaporating a thin layer of condensed nitrogen. We integrate optical heaters to tune individual dots within each cavity to the same resonance with better than 3 μeV of precision. Combining these tuning methods, we demonstrate two-photon interference between two devices spaced by less than 15 μm on the same chip with a postselected visibility of 33%, which is limited by timing resolution of the detectors and background. These results pave the way to integrate multiple quantum light sources on the same chip to develop quantum photonic devices.

We fabricated InGaN double-hetero structure (DHS) on the nanosized pyramid structure and successfully demonstrated efficient red color emission at 650 nm from this unique structure. The nanosized pyramid structure was fabricated by selective area growth method with nanoimprint. The different diffusion length of composite atoms and compositional pulling effect on the pyramid structure gave rise to not only compositional variation, but also high In-content InGaN of more than 40%. The InGaN DHS on nanopyramids shows high internal quantum efficiency, sub-ns fast recombination time (negligible built-in electric fields), and less efficiency droop even with the high In content. These results are important to realize efficient red emission based on InGaN material, providing possibilities for efficient photonic devices operating at the long wavelength visible region.

A dislocation-eliminating chemical control method for high-quality GaN nanostructures together with various types of InGaN quantum well structures are demonstrated using a chemical vapor-phase etching technique. Unlike chemical wet etching, chemical vapor-phase etching could efficiently control the GaN and form various shapes of dislocation-free and strain-relaxed GaN nanostructures. The chemically controlled GaN nanostructures showed improved crystal quality due to the selective etching of defects and revealed various facets with reduced residual strain via the facet-selective etching mechanism. These structural properties derived excellent optical performance of the GaN nanostructures. The chemical vapor-phase etching method also showed possibilities of the fascinating applications for high-efficiency InGaN quantum well structures, such as InGaN quantum well layer on void embedded GaN layer, InGaN quantum well embedded GaN nanostructure, and InGaN/GaN core/shell nanostructure.