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Photons 1 Photon/S Single-Photon Detector & Metrology Efforts at NIST Alan Migdall Sergey Polyakov Sae Woo Nam Jay Fan Rich Mirin Josh Bienfang John Lehman Allesandro Restelli NIST, Boulder Single Photon Workshop, Nov, 2009 Boulder, CO phho ton. jq i.umd .ed u/ spw2009 Keck Institute, CalTech, Pasedena, CA Jan. 26, 2010 Single-Photon Detector Efforts • Detectors – Deadtime reduction by • space multiplexing • avalanche photodiode- advanced electronics • smart processing • Metrology – Correlated Photon Method – Transfer Standard Method – High-gain low-noise transfer standard to disseminate calibrations – Bridging the gap between cryogenic radiometry & photon counting • Coincidence counting – Simple FPGA-based multi-coincidence analyzer Detectors: The problem (good news & bad news) • Single photon & entangled photon History of Entangled Photon Pair Production sources are getting brighter ~5 MHz • Detector count rates are limited Kwiat, et al QCMC 2004 – absolute max rates ~5-15 MHz – practical max rates ~1 MHz Overloading the system • Deadtime ~50 ns(vis) 10 μs(NIR) • Afterpul si ng ~ 1 – 10-3 Ways to reduce effective deadtime: Detector Tree: a detection apparatus based on a set of detectors used in “tree” configuration Improved Single Detector with Reduced Deadtime: technological efforts to reduce the deadtime of the single detector Multiplexed Detector Array: a detection apparatus based on an active optical switch and an array of dtdetec tors Deadtime Model of Multiplexed Detector Array 1 50 ns deadtime Acceptable count rate 0.8is such that DTF < 10% Single Detector 0.6 raction FF N detector systems 0.4 dtime N=1N = 1 Dea 2 3 0.2 4 5 6 10% deadtime reached at ~35x higher rate for 6 detector system 0 106 107 108 109 Mean Incident Photon Rate (Hz) zero switch transition time DTF and detection count rates •ItIn most cases an accept tblttihthtDTF<10%able count rate is such that DTF < 10% Hypothetical single detector (5ns deadtime) zero switch transition time Benefits Beyond Deadtime: dark counts & afterpulsing N −2 i P(nN≥−=− 1) 1 exp( −λ Td )∑ (λ T ) / i ! Beamsplitter tree i=0 10 tree 1 one 8 active sw. detector or a ity, a.u. a.u. ll ,, detector tree 080.8 3 detector active switching 6 0.6 2 detector active switching 4 detector active 4 0.4 switching ark count rate count ark lsing probabi lsing dd 2 Active switching uu 020.2 0 0 afterp 0 0.2 0.4 0.6 0.8 1 13579 mean incident photon rate, a.u. # of detectors IR InGaAs Int Experimental setup detectors Si SPAD optical switch photons @ 810nm photon @ 1550nm Si SPAD heralding SMF 810 nm 1 trigger start L1 F1 stop L PPLN OD λ/2 p L2 CW DM SMF2 532 nm InGaAs SPAD FC heralded assembly 1550 nm Realism • Switch transition time ≠ 0 includes: – Switch latency time – Switch propagation time – Tswitch ∼ 100 ns is practical for Tdddead ∼ 1 μs • Gate deadtime , – deadtime ≠ 0 for no detection – Tgate ∼ 200 ns in our setup Latest Result Trigger Electronics Deadtime: deadtime when it does not fire Deadtime 0.5 single detector Fraction 0.4 0.3 multiplexed schemes 0.2 detection deadtime reduction 0.1 5x improvement with just 2 detectors trigger deadtime reduction 0.0 0.5 1.0 1.5 Heralding Count Rate (MHz) Scalable multiplexed detector system for high-rate telecom-band single-photon detection Rev. Sci. Instr. 80, 116103 (2009) APD- Advanced Electronics Getting the most out of existing detectors JhJoshua BifBienfang Allesandro Restelli Active gating and quenching Si APDs Typical thick‐Si‐APD anode All use fu l in forma tion is acqu ire d a t onse t o f ava lanc he •Combination of passive & active quenching Æ latencyyy in recovery time •Any means to shorten recovery benefits count rate Sub‐nanosecond control of Si APD bias can enable 50 ns nanosecond gating , and reduce charge flow and after‐ pulsing. Requires switching >20 V in less than a nanosecond 10x reduction in charge with q quench 500 ps after avalanche • GHz logic can provide <200ps propagation delay • next issue: APD package high frequency compatibility Front-end electronics for Geiger-mode InGaAs/InP detectors (requires gated operation) VBias τ SbSub-nanosecondtid gating + (with self differencing scheme*) Power Period τ = 1.6ns Balun Short gates & splitter Out Lbi07Low overbias 0.7 v _ Avalanche signal Before τ 100x reduction After (*) Z.L.Yuan, B.E.Kardynal, A.W.Sharpe, and A.J.Shields “High speed single photon detection in the near infrared” Applied Phys. Letters, 2007. Front-end electronics for Geiger-mode InGaAs/InP detectors. Detection efficiency is limited by afterpulsing! In addaddition…ition… 1. Avalanche current flow in adjacent gates can be masked / 1.6ns 1.6ns Undetected avalanche 2. The gate has to be periodic: •No ppyossibility to introduce a dead-time longggper than the gate period to reduce the afterpulsing. 3. We are working on alternative setups to measure afterpulsing in the ns regime. VBias A B Waveform Synthesis Smart TES signal processing No inherent deadtime: Deadtime-free processing: Simple, cheap, high throughput signal processor physics.nist.gov/Divisions/Div844/ FPGA/fpga.html Photon-Counting Metrology Based on creating light two photons at a time Optical Parametric Downconversion One in - two out O K1 PT IC AX PARAMETRIC ω IS 1 CRYSTAL θ ω 0 1 θ K0 2 ω 2 K2 = + K0 K1 K2 ω 0 = ω1+ ω 2 Optical Parametric Downconversion Crystal Pump Beam Correlated Pair Two-Photon Detector Efficiency Metrology No External Standards Needed! Detector to be Calibrated Absolute ω COUNTER Quantum 1 Efficiency COINC N COUNTER ω 0 PARAMETRIC CRYSTAL ω2 COUNTER Trigger or “Herald” Detector N1=η1N N2=η2N NC=η1η2N η1=NC/ N2 Verifyyging the Method Absolute Calibrated Quantum Si Detector Efficiency Comparison Absolute COUNTER Quantum Efficiency DUT COINC N COUNTER ω 0 PARAMETRIC CRYSTAL ω 2 COUNTER Trigger Turning Two-Photon Method into Metrology Sources of uncertainty: DUT Collection Efficiencies absorption StilSpatial Coinc. Angular Trigger DUT Spectral reflection … Coinc. Trigger geometric DUT Coinc. Trigger Trigger counting Coincidence determination Histogram and its Details stop COUNTER ω1 # COINC N COUNTER ω0 Main correlation peak start stop-start PARAMETRIC CRYSTAL ω2 COUNTER 6 10 TiTrigger arm-idinduce d corre ltilations: -Fiber back reflection -Trigger afterpulsing ounts ounts 5 ??? CC CC 10 Afterpulse peak Ideal histogram 4 Real world 10 Deadtime 0 50 100 150 200 StartDelay (ns) – Stop (ns) Signal and Background (we can model it) 15000 HCB()τ iii= ()ττ+ () 12500 H(τ) 10000 nts uu Co 7500 B (τ) ⎡ i−1 ⎤ Bm B0 BNH()τ ij=−⎢ trig ∑ (τ )⎥ NBdtrig− 0 jid= − 5000 ⎣⎦ 2500 0 50 100 150 200 Delay (ns) Correlated photon calibration method uncertainty budget Relative Relative uncertainty uncertainty of value of DE Physical property Value (%) Sensitivity (%) Crystal reflectance 0.09249 0.2% 0.1 0.02% Crystal transmittance 0.99996 0.009% 1 0.009% Optical lo Lens transmittance 0.97544 0.0027% 1 0.0027% Geometric collection (raster scan) 0.9995 0.05% 1 0.05% s DUT filter transmittance 0.9136 0.1% 1 0.10% ses Trigger bandpass to virtual bandpass/wavelength 0.07% Histogram background subtraction 0.03% H istogram Coincidence circuit correction 0.0083 10.0% 0.008 0.084% Counting statistics 0.08% Deadtime (due to rate changes with time) 0.02% Trigger afterpulsing 0.0025 25.0% 0.003 0.06% Trigger Trigger background, & statistics 175000 0.3% 0.035 0.01% Trigger signal due to uncorrelated photons 0 0.07% 1 0.07% Trigger signal due to fiber back reflection 0.00202 1.60% 0.002 0.003% Total 0.18% Verifyyging the Method Absolute Calibrated Quantum Si Detector Efficiency Comparison Absolute COUNTER Quantum Efficiency DUT COINC N COUNTER ω 0 Another detail: the two methods PARAMETRIC measure different CRYSTAL ω 2 COUNTER physical quantities! Trigger Comparison/Results • NIST implementation of High Accuracy SPD Calibration methods Method Absolute uncertainty Two-photon 0.18% Substitution 0.17% • Uncertainty of each individual comparison: 0.25% • OlldiffbtthtthdOverall mean difference between the two methods: 0.15%±0.14% (η sub. > η 2-photon) Highest accuracy verification of the 2-photon method yet achieved 2-Photon Metrology Pro gress Uncertainty of Year 1st author Method Verification External Comparison 1970 Burnham ~35% Calibrated lamp 1981 Malygin - 1986 Bowman ~10% 1987 Rarity ~10% HeNe + attenuation 1991 Penin >3%> 3% 1993 Ginzburg ~10% Published values 1994 Kwiat ~3% 1995 Migdall < 2% 1% Calibrated Si Detector 2000 Brida ~0.5% 2% Calibrated Si Detector 2005 Ghazi-Bellouati 1.1, 0.62% 6.8% French cryoradiometer 2006 Wu 2.1% 2007 Polyakov 0.18% 0.15% Calibrated Si Detector Metrology Progress 10 %) (( tainty tainty rr 1 Unce This wor k Uncertainty Verification 010.1 1985 1995 2005 Year Single Photon Metrology Goal: 0.5% photon counting calibration to the masses •Metrology – Correlated Photon Method – Transfer Standard Method • Compared the two • Lessons Learned • Dissem ina tion Effort – High-gain low-noise transfer standard Transfer standard design Goal: 0.5% uncertainty disseminated to users Desires: Bridging photon-counting to analog levels •Detector: •Visible •Stable response vs temperature •Spatially uniform response •Low No ise fo r p ho to n cou nting leve ls •Amplifier •High gain for photon-counting levels •Lower gain for analog calibration levels •Thermal stability •Gain stability & precision for calibration ease Transfer standard design Goal: 0.5% uncertainty Si detector/amplifier disseminated to users •Detector: Si 5.8x5.8 mm Sapphire window (Hamamatsu S2592-04) •Spa tia l response unif ormit y: 0 .1% •Cooled detector for high shunt resistance: ~ 5 GΩ high gain:
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