Gesine Steudle, Ingmar Müller, and Oliver Benson
Humboldt-Universität zu Berlin
Institut für Physik, AG Nano-Optik
http://www.physik.hu-berlin.de/nano
SFB 787 – Teilprojekt C2 19.06.2009
Superconducting Superconducting Single Photon Detectors Single Photon Detectors
OutlineOutline
MotivationMotivation
Working PrincipleWorking Principle
Experimental RealizationExperimental Realization
ResultsResults
Current Research / OutlookCurrent Research / Outlook
MotivationMotivation
Single photon detection is essential for any experiment with single photons.
MotivationMotivation
Single photon detection is essential for any experiment with single photons.
single photon detectors:
• avalanche photodiodes (APDs) - commercially available single photon detectors
MotivationMotivation
Single photon detection is essential for any experiment with single photons.
single photon detectors:
• avalanche photodiodes (APDs) - commercially available single photon detectors
• superconducting single photon detectors (SSPDs) - new kind of photodetectors - different types of SSPDs, in our case: meander-type SSPD
MotivationMotivation
Single Photon Detectors
APDs
Si-APDs
- high efficiencies in the visible (70 % at 700 nm)
- low dark count rates
- long dead times (40 ns)
- not working in the IR
MotivationMotivation
Single Photon Detectors
APDs
Si-APDs
- high efficiencies in the visible (70 % at 700 nm)
- low dark count rates
- long dead times (40 ns)
- not working in the IR InGaAs-APDs
- working in the IR
- high dark count rates
- long dead times (100ns)
MotivationMotivation
Single Photon Detectors
APDs
Si-APDs
- high efficiencies in the visible (70 % at 700 nm)
- low dark count rates
- long dead times (40 ns)
- not working in the IR InGaAs-APDs
- working in the IR
- high dark count rates
- long dead times (100ns)
SSPDs
meander-type SSPDs
- working in the IR
- low dark count rates
- short dead times (5 ns)
- working at 4.2 K
Working PrincipleWorking Principle
Absorption of light can distruct superconductivity.[L. Testardi, Phys. Rev. B 4, p. 2355 (1971)]
Working PrincipleWorking Principle
[G. N. Gol‘tsman et al., phys. stat. sol. c 2, p. 1480 (2005)]
Absorption of light can distruct superconductivity.[L. Testardi, Phys. Rev. B 4, p. 2355 (1971)]
a) absorption of a photon
superconducting wire biased close to critical current (I = 0.9 IC)
Working PrincipleWorking Principle
[G. N. Gol‘tsman et al., phys. stat. sol. c 2, p. 1480 (2005)]
Absorption of light can distruct superconductivity.[L. Testardi, Phys. Rev. B 4, p. 2355 (1971)]
a) absorption of a photon
b) absorbed photon causes “hot spot“
superconducting wire biased close to critical current (I = 0.9 IC)
Working PrincipleWorking Principle
[G. N. Gol‘tsman et al., phys. stat. sol. c 2, p. 1480 (2005)]
Absorption of light can distruct superconductivity.[L. Testardi, Phys. Rev. B 4, p. 2355 (1971)]
a) absorption of a photon
b) absorbed photon causes “hot spot“
c) current is repelled to the sidewalks - critical current density is exceeded
superconducting wire biased close to critical current (I = 0.9 IC)
Working PrincipleWorking Principle
[G. N. Gol‘tsman et al., phys. stat. sol. c 2, p. 1480 (2005)]
Absorption of light can distruct superconductivity.[L. Testardi, Phys. Rev. B 4, p. 2355 (1971)]
a) absorption of a photon
b) absorbed photon causes “hot spot“
c) current is repelled to the sidewalks - critical current density is exceeded
d) a resistive state appears across the whole strip
superconducting wire biased close to critical current (I = 0.9 IC)
Detector LayoutDetector Layout
Detectors are made at TU Delft by Sander Dorenbos and Val Zwiller.
[S. Dorenbos, Master Thesis, TU Delft (2007)]
• NbN on sapphire (TC, NbN =11K)• wire width: 100 nm• wire height: 4-6 nm• filling factor: 50%• wire length: ≈ 100 µm• active area: 10 x 10 µm2
Fiber CouplingFiber Coupling
scheme of the fiber coupling
• theoretical coupling factor: k = 0.87
• experimental coupling factor: k = 0.61 k = 0.333 in [W. Słysz et al., Appl. Phys. Lett. 88, 261113 (2006)]
backside view
frontside view
SetupSetup
SetupSetup
SetupSetup
SetupSetup
SetupSetup
Quantum EfficiencyQuantum Efficiency
• quantum efficiencies between 2% - 10%• quantum efficiency increases with bias current and photon energy
Dark CountsDark Counts
exponential increase of the dark counts with the bias current
Noise Equivalent Power (NEP)Noise Equivalent Power (NEP)
R dark count rate QE quantum efficiency
with
Noise Equivalent Power (NEP)Noise Equivalent Power (NEP)
R dark count rate QE quantum efficiency
with
NEP at 1550nm: ~10-15 W·Hz-1/2 (InGaAs-APDs: NEP = 10-13 W·Hz-1/2)
Single Photon DetectionSingle Photon Detection
• Hanburry-Brown and Twiss setup with APD and SSPD
• source: single N-V center in a diamond nanocrystal (emission around 637 nm)
Single Photon DetectionSingle Photon Detection
Outlook I Outlook I
Antibunching With One DetectorAntibunching With One Detector
• detector dead time: 5 ns
• life times of N-V defect centers in nano-diamonds: 40-60 ns
It is possible to see antibunching with one detector.
Outlook I Outlook I
Antibunching With One DetectorAntibunching With One Detector
• detector dead time: 5 ns
• life times of N-V defect centers in nano-diamonds: 40-60 ns
It is possible to see antibunching with one detector.
current problem:
more sophisticated electronics necessary
Outlook II Outlook II
Photon Number ResolutionPhoton Number Resolution
In principle SSPDs provide information about the energy absorbed by the detector.
This information is can be obtained e.g. by looking at the shape of the detector pulses. [A. D. Semenov et al., Physica C 351, p. 349 (2001)]
Outlook II Outlook II
Photon Number ResolutionPhoton Number Resolution
Our approach: Measurements at different bias currents
Idea: At low bias currents one single photon does not have enough energy to trigger the detector.
Reduction of the bias current makes the detector sensitive for multi-photon events (because single photon events are suppressed).
Outlook II Outlook II
excitation with attenuated lasers pulses (repetition rate: 82 MHz)
first test of muti-photon absorption:
Photon Number ResolutionPhoton Number Resolution
Thank you!Thank you!