Do Photocount Arrival Time Distributions Depend on Diode Current?
Measurements with the CLARA interferometer at ESB
Giulio Stancari and Alexander Shemyakin
January 19, 2023
Introduction
Measure the distributions of photocount arrival times as a function of current in the laser diode. We want to test whether we can use the time distributions to detect the transition of the diode from LED (chaotic) to laser (coherent) radiation states. This data will serve as test and calibration for the analysis of radiation from single electrons and electron bunches in IOTA.
Apparatus
MZI interferometer at ESB. Arm delay away from interference condition.
Interferometer configuration:
laser diode, Thorlabs LPS-635-FC, 637 nm, threshold 47 mA
neutral density filter OD=5, Thorlabs NE50A-B 650-1050 nm
band-pass filter (from Jonathan, mounted on Thorlabs SM1L03 tube), 635 nm, width 10 nm
Event timer configuration (Picoquant HydraHarp 400):
Removed IOTA channels (revolution marker, M2L PMT, M3L PMT, injection trigger)
Ch2 = SPAD1
Ch3 = SPAD2
Trigger = -400 mV, delays = 0 ps
T2 mode (all events recorded with absolute time stamp)
Collected time-tagged photocount events from SPAD1 and SPAD2 as a function of current in the diode.
E-log entry: https://www-bd.fnal.gov/Elog/?orEntryId=231813.
Data on the iota-fast.bd network drive.
Data Sets
| start_time | diode_voltage_V | diode_current_mA | arm_flipper | SPAD_shutter | avg_rate_Hz | acquisition_time_s | HH_filename |
|---|---|---|---|---|---|---|---|
| 2023-01-17 14:05:46 | 2.35 | 4.1600 | IN | OPEN | 1.74245(93)e5 | 10 | 1405_ID_4_mA_flipper_in |
| 2023-01-17 14:09:43 | 2.35 | 4.1600 | OUT | OPEN | 3.1027(23)e5 | 3 | 1409_ID_4_mA_flipper_out_1 |
| 2023-01-17 14:10:10 | 2.35 | 4.1600 | OUT | OPEN | 3.1525(23)e5 | 3 | 1409_ID_4_mA_flipper_out_2 |
| 2023-01-17 14:28:30 | 4.50 | 22.0000 | OUT | OPEN | 3.0534(12)e6 | 1 | 1428_ID_22_mA_flipper_out |
| 2023-01-17 14:30:57 | 4.50 | 22.0000 | IN | OPEN | 1.78925(95)e6 | 1 | 1430_ID_22_mA_flipper_in |
| 2023-01-17 14:34:42 | 1.90 | 0.8300 | IN | OPEN | 23541(11) | 100 | 1433_ID_083_mA_flipper_in |
| 2023-01-17 14:39:12 | 1.90 | 0.8300 | OUT | OPEN | 39219(20) | 50 | 1438_ID_083_mA_flipper_out |
| 2023-01-17 14:44:27 | 0.00 | 0.0000 | OUT | OPEN | 759.4(19) | 100 | 1444_ID_0_mA_flipper_out_shutters_open |
| 2023-01-17 14:48:15 | 0.00 | 0.0000 | IN | OPEN | 758.4(19) | 100 | 1447_ID_0_mA_flipper_in_shutters_open |
| 2023-01-17 15:15:35 | 6.50 | 0.0303 | IN | OPEN | 1.37495(83)e6 | 1 | 1513_ID_30_uA_flipper_in |
| 2023-01-17 15:44:07 | 6.50 | 0.0303 | IN | OPEN | 1.35193(82)e6 | 1 | 1541_ID_30_uA_flipper_in |
| 2023-01-17 15:49:43 | 2.30 | 0.0051 | IN | OPEN | 19035.4(98) | 100 | 1547_ID_5_uA_flipper_in |
| 2023-01-17 15:55:12 | 3.61 | 0.0128 | IN | OPEN | 1.30436(81)e5 | 10 | 1553_ID_13_uA_flipper_in |
| 2023-01-17 16:06:46 | 2.30 | 0.0051 | OUT | OPEN | 33304(18) | 50 | 1606_ID_5_uA_flipper_out |
| 2023-01-17 16:10:14 | 3.61 | 0.0128 | OUT | OPEN | 2.3820(15)e5 | 5 | 1609_ID_13_uA_flipper_out |
| 2023-01-17 16:13:18 | 6.50 | 0.0303 | OUT | OPEN | 2.3397(11)e6 | 1 | 1612_ID_30_uA_flipper_out |
| 2023-01-17 16:20:53 | 0.00 | 0.0000 | OUT | CLOSED | 197.30(99) | 100 | 1620_ID_0_uA_flipper_out_shutters_closed |
| 2023-01-17 16:24:41 | 0.00 | 0.0000 | OUT | OPEN | 751.5(19) | 100 | 1624_ID_0_uA_flipper_out_shutters_open |
Distribution of photocounts in a given time window
Limit cases:
Coherent light, Poissonian distribution: \[p_\mathrm{coh}(n, \mu) = \frac{\mu^n \cdot e^{-\mu}}{n!}\]
Chaotic light, geometrical distribution: \[p_\mathrm{cha}(n, \mu) = \frac{1}{1+\mu} \left(\frac{\mu}{1+\mu}\right)^n \]
(Need corrections for digital SPAD response? Pile-up?)
Histograms of number of counts in given time window
Interferometer in “beam-splitter” mode: arm 2 blocked.
Chosen time bins to keep the same average number of counts.
Fano factor vs. diode current
Distribution of intervals between photocount events
To do.
Conclusions
Does the distribution depend on diode current?