An efficient single photon source is indispensable for quantum information such as quantum communications and quantum computers. Single photon sources using single trapped atom or ion have been developed early, but their efficiency was not enough to use in practical. Here, we propose a new type of a single photon source comprised with GaAs quantum dot photonic crystal waveguides and a highly curved tapered fiber. It is very efficient to directly couple quantum dots embed in semiconductor material with high refractive index to the tapered fiber. However, the integration of them in a cryostat at low temperature is not trivial. To resolve this problem, a cryostat is remodeled and equipped with nano-stages for moving of photonic crystals and the tapered fiber. Photoluminescence of various photonic crystal cavities was measured with the integrated system in the remodeled cryostat through the tapered fiber. Also, we can collect single photons through the fiber from quantum dot photonic crystal waveguide, as the fiber contacts to the waveguide. To confirm single photon nature of collected signal, the second correlation was measured with Hanbury Brown-Twiss setup. $g^{(2)}(0)$ value is 0.15, and it shows truly single photon streams. Based on measured transmission of all optics and detection efficiency, coupling efficiency to the fiber is estimated up to 26%, which is much enhanced value compared with others.
고효율 단일광자원은 양자 통신과, 양자 컴퓨터 등의 양자정보 구현에 있어 반드시 필요하다. 단일원자 또는 단일이온을 포획하는 방법을 기반으로 한 단일광자원이 구현된 적이 있지만, 실용적으로 사용하기에는 효율이 매우 좋지 않은 형편이다. 본 연구에서는 GaAs 양자점 기반의 광결정 도파로와 휘어진 미세광섬유를 결합하여, 매우 높은 효율을 단일광자원을 구현하고자 한다. 이 둘을 결합하기 위해, 저온 냉동기 (~10K) 안에 nano-stage를 장착하였다. 이러한 실험 장치를 이용하여 다양한 광결정 공진기와 광결정 도파로의 발광특성을 미세광섬유를 통해 측정하였다. 단일광자임을 확인하기 위하여 HBT 셋업을 이용하여 $g^{(2)}(0)$ 값을 측정하였고, 단일광자임을 충분히 보여주는 0.15의 낮은 값을 얻었다. 사용된 모든 광학기기와 검출기의 검출 효율을 고려하여 효율을 계산한 결과, 26%의 높은 효율을 갖는 단일광자원임을 확인하였다.
