single-photon avalanche diodes (spads) demystified
TRANSCRIPT
1FABRIZIO GUERRIERI
SPAD DEMYSTIFIED
SINGLE-PHOTON AVALANCHE DIODE
DEMYSTIFIED
Fabrizio Guerrieri
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SPAD DEMYSTIFIED
LET’S CONSIDER THE TYPICAL PN JUNCTION I-V CHARACTERISTICS…
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SPAD DEMYSTIFIED
AVALANCHE CURRENT(JUNCTION BREAKDOWN)
DIRECT CURRENT
INVERSE CURRENT DUE TO THERMAL GENERATION IN THE DEPLETED ZONE
PN JUNCTION
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SPAD DEMYSTIFIED
AVALANCHE CURRENT(JUNCTION BREAKDOWN)
DIRECT CURRENT
INVERSE CURRENT DUE TO THERMAL GENERATION IN THE DEPLETED ZONE
PN JUNCTION
THE SPAD WORKS HERE
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SPAD DEMYSTIFIED
HOW DOES A SPAD WORK?
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SPAD DEMYSTIFIED
WITH A REVERSE VOLTAGE BELOWBREAKDOWN NO CURRENT FLOWS
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SPAD DEMYSTIFIED
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SPAD DEMYSTIFIED
AT THE BEGINNING,
NO CURRENT FLOWS EVEN WITH A REVERSE VOLTAGE ABOVE BREAKDOWN
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SPAD DEMYSTIFIED
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SPAD DEMYSTIFIED
AN AVALANCHE CURRENT IS TRIGGERED BY THEFIRST PHOTON GENERATING AN ELECTRON/HOLE
PAIR IN THE DEPLETED REGION
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SPAD DEMYSTIFIED
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SPAD DEMYSTIFIED
THE BRANCHED CHARACTERISTIC OF A SPAD
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SPAD DEMYSTIFIED
OBVIOUSLY A FRONT-END CIRCUIT (WE CALL ITQUENCHING CIRCUIT) IS NEEDED IN ORDER TO:
1. ENABLE THE SPAD RISING THE REVERSE VOLTAGE ABOVE BREAKDOWN
2. DETECT THE AVALANCHE CURRENT
3. QUENCH THE AVALANCHE CURRENT LOWERING THE REVERSE VOLTAGE BELOW BREAKDOWN
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SPAD DEMYSTIFIED
TWO MAIN ADVANTAGES
1. SINGLE-PHOTON LEVEL SENSITIVITY
2. ELECTRONIC PULSE’S RISING EDGE WITH VERY LOW TIME JITTER(30 ps OR BETTER)
HOW CAN I USE A SPAD?
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SPAD DEMYSTIFIED
1. TIME CORRELATED SINGLE-PHOTON COUNTING (TCSPC)(WE INFORMALLY CALL IT “PHOTON TIMING”)
2. TIME OF FLIGHT (TOF)
3. PHOTON-COUNTING
HOW CAN I USE A SPAD?
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SPAD DEMYSTIFIED
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
After somelaser pulses…
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
After somelaser pulses…
After morelaser pulses…
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
After somelaser pulses…
After morelaser pulses…
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
After somelaser pulses…
After morelaser pulses…
After MANYlaser pulses…
1 - PHOTON TIMING
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SPAD DEMYSTIFIED
2 – TIME-OF-FLIGHT
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SPAD DEMYSTIFIED
2 – TIME-OF-FLIGHT
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SPAD DEMYSTIFIED
2 – TIME-OF-FLIGHT
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SPAD DEMYSTIFIED
Laser pulse’s shapeEstimated TOF
2 – TIME-OF-FLIGHT
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SPAD DEMYSTIFIED
3 - PHOTON COUNTING
THE QUENCHING CIRCUIT DELIVERS AN OUTPUT PULSE EVERYTIME THE SPAD DETECTS A PHOTON
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SPAD DEMYSTIFIED
3 - PHOTON COUNTING
IN OUR ARRAYS EVERY PIXEL CONTAINS EVERYTHING TO DO PHOTON-COUNTING
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SPAD DEMYSTIFIED
# photo ns
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SPAD DEMYSTIFIED
# photo ns
FRAMESTART
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SPAD DEMYSTIFIED
# photo ns
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SPAD DEMYSTIFIED
# photo ns
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SPAD DEMYSTIFIED
# photo ns
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SPAD DEMYSTIFIED
# photo ns
FRAMESTARTFRAMESTOP