• 한국광학회지
• /
• 제14권6호
• /
• pp.573-577
• /
• 2003

Hong-Ou-Handel 간섭계를 이용한 광자쌍의 4차 간섭실험에서 두 광자의 뭉침이 단일계수에 미치는 영향을 조사하였다. 검출기의 단일광자 시간 분해능보다 짧은 시간간격으로 두 광자가 검출기에 입사할 때 하나의 검출기에서 측정되는 단일계수가 현저하게 줄어드는 변화를 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제14권6호
• /
• pp.789-796
• /
• 2014

A CMOS photo detection bias quenching circuit is developed to be used with single photon avalanche photodiodes (SPADs) operating in Geiger mode for the detection of weak optical signals. The proposed bias quenching circuits for the performance improvement reduce the circuit size as well as improve the performance of the quenching operation. They are fabricated in a $0.18-{\mu}m$ standard CMOS technology to verify the effectiveness of this technique with the chip area of only $300{\mu}m^2$, which is about 60 % of the previous reported circuit. Two types of proposed circuits with resistive and capacitive load demonstrated improved performance of reduced quenching time. With a commercial APD by HAMAMATSU, the dead time can be adjusted as small as 50 ns.

• Progress in Superconductivity
• /
• 제14권2호
• /
• pp.96-98
• /
• 2012

Bias current dependence of a superconducting strip photon detector is studied in the wavelength range of 405 to 1310 nm. The detector is made of an $MgB_2$ meander pattern with the line width of 135 nm and thickness of 10 nm. At 1310 nm, the detection efficiency exponentially decreases as the bias current decreases. While at 405 nm, the detection efficiency almost saturates in the high bias current region. These features suggest that the intrinsic detection efficiency of the $MgB_2$ detector is high at 405 nm.

• Current Optics and Photonics
• /
• 제5권4호
• /
• pp.375-383
• /
• 2021

We present a simulation method to design antireflection coating (ARCs) for fiber-coupled superconducting nanowire single-photon detectors. Using a finite-element method, the absorptance of the nanowire is calculated for a defined unit-cell structure consisting of a fiber, ARC layer, nanowire absorber, distributed Bragg reflector (DBR) mirror, and air gap. We develop a method to evaluate the uncertainty in absorptance due to the uncontrollable parameter of air-gap distance. The validity of the simulation method is tested by comparison to an experimental realization for a case of single-layer ARC, which results in good agreement. We show finally a double-layer ARC design optimized for a system detection efficiency of higher than 95%, with a reduced uncertainty due to the air-gap distance.

• 한국초전도ㆍ저온공학회논문지
• /
• 제19권4호
• /
• pp.22-25
• /
• 2017

Superconducting nanowire single photon detectors (SNSPD) have become the most competent photon-counting devices in wide range of wavelengths. Especially in the communication wavelength (infrared), SNSPD has shown unbeatable superior performance compared to the state-of-art semiconductor single photon detectors. The technology has matured enough for the last decade so that several commercial systems are now almost ready for routine use in general optics experiments. Here we summarize briefly the recent progress in this research field, and hope to motivate further research on the improvement of the device and the system. We cover the basic key concepts, device and system performances, remaining issues and possible further research directions of SNSPD.

• Nuclear Engineering and Technology
• /
• 제56권8호
• /
• pp.3076-3083
• /
• 2024

In this work, single photon avalanche diodes (SPADs) were fabricated using the standard 180 nm complementary metal-oxide semiconductor process. Their small size of 15-16 µ m and low operating voltage made it possible to easily integrate them with readout circuits for compact on-chip sensors, particularly those used in the radiation sensor network of a nuclear plant. Four architectures were proposed for the SPADs, with a shallow trench isolation (STI) guard ring and different depletion regions designed to demonstrate the main performance parameters in each experimental configuration. The wide absorption region structure with PSD and a deep N-well could achieve a uniform electric field, resulting in a stable dark count rate (DCR). Additionally, the STI guard ring was implanted to mitigate the premature edge breakdown. A breakdown voltage was achieved for a low operating voltage of 10.75 V. The DCR results showed 286.3 Hz per ㎛² at an excess voltage of 0.04 V. A photon detection probability of 21.48% was obtained at 405 nm.

• 한국광학회지
• /
• 제8권4호
• /
• pp.353-355
• /
• 1997

공초점 형광 현미경과 단일 광자 계수기로 구성되어 있는 단일 분자 검출장치를 사용하여, 색소 농도에 따른 광자 계수율의 변화를 관측하였다. 농도가 증가함에 따라 계수율이 포화하는 경향을 보였으며, 광검출기의 죽은 시간을 고려하여 측정 결과를 설명하였다. 계수율과 검출 부피, 광검출기의 양자효율, 입사 광량 사이의 관계를 나타내는 관계식을 제시하였다. 또한 신호대 잡음비에 대해서도 간략하게 논하였다.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2001년도 하계학술발표회
• /
• pp.202-203
• /
• 2001

• 한국광학회지
• /
• 제22권5호
• /
• pp.223-229
• /
• 2011

1.5 ${\mu}m$ 통신파장 대역 단일광자의 효율적인 측정을 위해서 PPLN WG(periodically poled $LiNbO_3$ waveguide)에서 준위상정합을 이용한 합주파수 생성에 의한 주파수 상향변환 검출기를 구성하고 검출 효율, 잡음 계수 및 타이밍 지터를 측정하였다. 974 nm에서 발진하는 펌프광의 세기가 300 mW일 때 최대 검출효율이 약 7%, 잡음 계수율은 약 480 kHz로 측정되었다. 피코초펄스 레이저를 이용한 자발적 매개하향변환에서 발생한 펄스형 단일광자 신호를 이용하여 측정된 주파수 상향변환 검출기의 최소 타이밍 지터는 약 39.1 ps였다. 또한 아주 좁은 동시계수 시간 폭으로 펄스형의 주파수 상향변환된 단일광자를 측정하면 잡음의 효과를 최소화할 수 있고, 신호대 잡음비의 특성을 최대로 높일 수 있다.

• 대한핵의학회지
• /
• 제32권3호
• /
• pp.211-224
• /
• 1998

The role of scintigraphic imaging has moved from the detection of lesions to the tissue-specific characterization of lesions over the past 2 decades. Major advances in nuclear medicine imaging include: 1) positron imaging, 2) improved instrumentation, such as the use of multidetector (dual or triple head) gamma cameras for single photon emission computed tomography, and 3) development of numerous new radiopharmaceuticals for positron or single photon imaging (labeled glucose analogue, amino acids, fatty acids, hormones, drugs, receptor ligands, monoclonal antibodies, etc). These advances have resulted in a significantly improved efficacy of radionuclide techniques for the evaluation of various tumors, including those within the liver. The current role of nuclear medicine in the evaluation of focal hepatic tumors is reviewed in this article with an emphasis on the clinical applications of various tracer studies and imaging findings.