Filter-free single-photon quantum dot resonance fluorescence in an integrated cavity-waveguide device

Abstract

Semiconductor quantum dots embedded in micro-pillar cavities are excellent emitters of single photons when pumped resonantly. Often, the same spatial mode is used to both resonantly excite a quantum dot and to collect the emitted single photons, requiring cross-polarization to reduce the uncoupled scattered laser light. This inherently reduces the source brightness to 50 %. Critically, for some quantum applications the total efficiency from generation to detection must be over 50 %. Here, we demonstrate a resonant-excitation approach to creating single photons that is free of any cross-polarization, and in fact any filtering whatsoever. It potentially increases single-photon rates and collection efficiencies, and simplifies operation. This integrated device allows us to resonantly excite single quantum-dot states in several cavities in the plane of the device using connected waveguides, while the cavity-enhanced single-photon fluorescence is directed vertical (off-chip) in a Gaussian mode. We expect this design to be a prototype for larger chip-scale quantum photonics.In the on-going development of quantum optical technologies, devices will need to be easier to use, more compact, robust, and scalable, making them available to a broader community. These technologies include applications in quantum communication 1-4 , optical quantum metrology 5-8 , and optical quantum computation and simulation 9-12 . For example, a true single photon source on chip as a turnkey device would open quantum technologies to a unprecedented user group.Quantum dot (QD) excitonic states are excellent quantum emitters, showing bright emission of single photons 13-17 and excellent suppression of multi-photons states 16,18,19 . These properties are achieved due to the level structure and radiative efficiency of the optically allowed lowest level exciton states.While single QD exciton emission is inherently bright with low multi-photon contribution, the emitted light can be further enhanced and directed into a Gaussian mode by coupling the QD to an optical cavity. 14,20,21 In the weak coupling regime between emitter and cavity, this is known as the Purcell effect 22 . For a cavity with quality factor Q and mode volume V , the Purcell effect is characterized by F p = 3 4π 2 ( λ n ) 3 Q V for a dipole emitter in resonance with the cavity, placed at the maximum of the electric field, and with proper aligned polarization. λ is the wavelength of fundamental mode resonance and n is the material's index of refraction. With the emitter and cavity in resonance, this shortens the radiative lifetime. While various optical cavities can be used 17 , a particularly useful cavity is the pillar microcavity 23 because the single-photon emission is in a well defined Gaussian mode. Since weak cavity coupling reduces the radiative lifetime, decoherence contributions to the emission linewidth are reduced, leading to bandwidths that can approach the spontaneous-emission lifetime-limit, and near unity photon indistinguishability 17,24 .Because of the single mode n...

Optical Signals to Monitor the Dynamics of Phonon‐Modified Rabi Oscillations in a Quantum Dot

“…[ 34 ] The Mollow triplet has also been measured for QDs. [ 4,5,35,36 ] Driving with two laser pulses, the peaks split up even further resulting in a complex optical spectrum. [ 37 ] The resonance fluorescence signal is typically evaluated using the quantum regression theorem.…”

Sequential generation of linear cluster states from a single photon emitter

“…Further improved scaling ratios are thus expected to be within reach with QD sources in the near future. The QD source brightness can be increased by a factor of up to 2 by changing the excitation schemes following recent propositions 52 , 53 . The fibered brightness could also be increased by using a larger numerical aperture collection lens and engineering a better mode matching with the single mode fiber.…”

Nanoscale Positioning Approaches for Integrating Single Solid‐State Quantum Emitters with Photonic Nanostructures

“…The positioning technique may also play an essential role in filter‐free resonance fluorescence by pumping multiple QDs via an on‐chip waveguide and collecting single‐photons from the top. [ 71 ] With the positioning tools described in this review in hand, there is the opportunity to scale to multiple QD devices to build quantum networks with complexity and functionality far beyond single QDs devices based on probabilistic coupling. Along this line, Hong‐Ou‐Mandel interference from two remote QDs was demonstrated with both deterministically coupled micropillars [ 72 ] and microlenses.…”