Realization of ultra-efficient single photon source using nano-photonics and nano manipulation technologies

We will realize the world’s first ultra-highly efficient single photon source utilizing microfabricated nano optical fiber and lattice defect in a diamond crystal. To achieve this objective, we will collaborate with professor Benson at Humboldt University (Berlin) and combine these two group’s technologies: 300nm diameter optical nano filber development (our group), evaluation scheme under ultra-low temperature (our group), nano manipulation and assembly techniques (professor Benson’s group). Motivation and Objectives: Nowadays, the largest bottleneck for photonic quantum information technology is the efficiency of single photon source. Down-converted photon pair hitherto used is reaching a limit due to its low efficiency for the multiple photon generation. To surmount this problem, solid-state single photon source has been actively investigated from the end of the nineties. While the multi-photon emission has been sufficiently suppressed, it has been difficult to achieve a highly efficient coupling to a single-mode fiber. Even in the latest result with solid immersion Lens (SIM), the coupling efficiency was only a few percent. The objective of this research is to realize a single-mode single photon source connecting to a nano-fiber with drastically improving the efficiency (>50%) by the collaborative work between us and professor Benson at Humboldt University (Germany). Research methods: Recently, we realized “nano optical fiber” manufactured by stretching a single mode fiber to 300nm diameter (OptExp2011). Furthermore, we were able to couple a percentage (7.4 %) of total emitted light from a single quantum dot directly to a single-mode optical fiber through the nano fiber (NanoLett2011). The high coupling efficiency is achieved by the large evanescent field of waveguide mode at the nano fiber region with 300nm diameter. A master course student (Mr. Schröder) studying under Prof. Benson stayed at our laboratory for 3 months for a collaborative work and succeeded in realizing a single photon source embedded in a single mode fiber by coupling of a nano-optical fiber and a diamond nano crystal (OptExp2012). We achieved the world record of photon number coupled to a single mode fiber (689Kcps). However, the achieved coupling efficiency was several times as small as that of the theoretical prediction because of the problem of the attachment method of diamond nano crystal. By this application, the collaborative work between these two countries will be progressed further and the efficiency will be drastically improved (>50%). Concretely speaking, we will investigate the following two things; ① Improvement of the coupling efficiency using a manufactured nano optical fiber which we are now developing. ② Optimization of the positioning of a diamond nano crystal using the nano manipulation system developed originally by Prof. Benson’s group.

Principal Investigators
Benson, Oliver Prof. Dr. rer. nat. (Details) (Experimental Physics / Nanooptics)

Duration of Project
Start date: 01/2014
End date: 12/2015

Last updated on 2020-22-03 at 23:05