Strongly suppressed multi‐photon generation from a single quantum dot in a metal‐embedded structure

Abstract

Received ZZZ, revised ZZZ, accepted ZZZ Published online ZZZ (Dates will be provided by the publisher.)Keywords (quantum dot, single photon, g (2) (0), photon extraction efficiency) We introduce novel metal-embedded semiconductor pillar structure including quantum dots as highly efficient single-photon sources for quantum information applications. We have developed related processes for fabricating the proposed structure, and have demonstrated strongly suppressed multi-photon generation and improved photon extraction efficiency. As a result, under non-resonant excitation, which is highly preferable for the practical use, single-photon purity with g (2) (0) as low as 0.015 has been measured. Extremely small semiconductor volume in the metal embedded structure is a crucial factor for this observation. Moreover, single-photon generation rate from a single quantum dot up to 6.4 million per second has been achieved.Copyright line will be provided by the publisher IntroductionFor quantum information applications, realization of efficient single-photon sources is one of the key issues. Semiconductor quantum dots (QDs) are a good candidate for realizing single-photon sources, entangled-photon-pair sources [1][2][3], and quantum gates [4] etc. Especially, in view of the single-photon sources based on QDs, high-bitrate on-demand generation is expected.However, for the practical use, two main issues are remaining. First, multi-photon generation evaluated by a second-order photon correlation function at zero time delay g (2) (0) should be minimized. For long-distance quantum key distribution, lower g (2) (0) is crucial for practical applications with high bit rate operation [5]. So far, many groups have reported single photon emission from QDs [6][7][8][9], and relatively low g (2) (0) values of 0.02-0.03 were reported in ref. 6, 7. However, these values have been obtained under p-shell resonant excitation which requires strict energy tuning. For practical devices driven by electrical pumping, further suppression of multi-photon generation without strict energy tuning is much preferable. Another issue is to approach the on-demand operation. Generally, photon extraction efficiency from QDs is less than 1% in the case of a planar surface due to large difference

Bright single-photon source based on an InAs quantum dot in a silver-embedded nanocone structure

“…14,15 This structure is completely embedded in metal and is fundamentally flat and mechanically stable. Direct contact of this kind of photon sources to a single-mode fiber will provide a fiberbased photon source with long-term stability.…”

Enhanced Photon Extraction from a Quantum Dot Induced by a Silver Microcolumnar Photon Reflector

“…However, hard metals are known to have low optical reflectivity, and the photon extraction efficiency was limited to 8%. 19) In this paper, we newly introduce a removal layer for separating the metal reflector layer from the substrate, and a much improved fabrication yield as high as 70% is achieved. Furthermore a redesigned pillar structure with higher aspect ratio enables us to adopt highly reflective silver (Ag) as the microcolumnar photon reflector, leading to the high photon extraction efficiency up to 18%.…”

“…After the growth, pillar structures were fabricated by electron-beam (EB) lithography and inductively coupled plasma reactive ion etching (ICP-RIE). Instead of the previously employed pillars of 300 nm height, 19) we prepared pillar structures of 750 nm height for the following cleavage process. Then, a 5 nm SiO 2 layer was deposited by plasma-enhanced chemical-vapor deposition (PECVD) and a 5-nm-thick silane coupling agent (Siliconize L-25) was coated as a removal layer [ Fig.…”

Anomalous dip observed in intensity autocorrelation function as an inherent nature of single-photon emitters

“…a) Electronic mail: nakajima@es.hokudai.ac.jp 1 A variety of single-photon emitters (SPEs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been widely investigated for applications in quantum key distribution (QKD) 21 , quantum information processing 22 , and quantum metrology 23 .…”

“…Optical properties of the QDs were examined by a standard micro-photoluminescence (µ-PL) setup equipped with a modelocked Ti:sapphire laser (photon energy of 1.3920 eV, pulse repetition period of 13.2 ns, pulse duration of ∼ 5 ps) and a Si charge-coupled-device detector. Figure 1 Here, we analyze the measured intensity autocorrelation function with a commonly accepted formula under nonresonant pulsed excitation 6,7,10,18,19 …”