Direct Measurement of Optical Cross-talk in Silicon Photomultipliers - - PowerPoint PPT Presentation

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Direct Measurement of Optical Cross-talk in Silicon Photomultipliers - - PowerPoint PPT Presentation

Oct 25, 2023 299 likes •561 views

Direct Measurement of Optical Cross-talk in Silicon Photomultipliers Using Light Emission Microscopy Derek Strom, Razmik Mirzoyan, Jrgen Besenrieder Max-Planck-Institute for Physics, Munich, Germany 14 th Pisa Meeting, La Biodola, Isola dElba,

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Direct Measurement of Optical Cross-talk in Silicon Photomultipliers Using Light Emission Microscopy

Derek Strom, Razmik Mirzoyan, Jürgen Besenrieder Max-Planck-Institute for Physics, Munich, Germany 14th Pisa Meeting, La Biodola, Isola d’Elba, Italy Photo Detectors and PID May 28, 2018

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Outline

  • Motivation for Silicon Photomultiplier (SiPM)
  • Optical Cross-talk in SiPM
  • Light Emission Microscopy and Experimental Setup
  • Direct Measurement of Cross-talk in a sample SiPM
  • Summary and Outlook

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Silicon Photomultiplier (SiPM)

Solid-state single-photon-sensitive device based on single-photon avalanche diode (SPAD)

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Single element detector Multi-element arrays SPAD concept

Advantages Disadvantages Small cell sizes (10-100 um) High Dark Count Rates (wrt PMT) Nanosecond resolution Afterpulsing Low operating voltage Cross-talk B-field insensitive PDE greater than 40% Large dynamic range

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Optical Cross-talk in SiPMs

  • Optical cross-talk

– Probability for photons to trigger neighboring cells – Results in artificial increase in signal – Contributes to excess noise factor – Can be significant and problematic in applications

  • Objective: to learn about cross-talk probability from light emission in SiPMs

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2 neighboring SPADs

Strong energy dependence of photon absorption lengths in silicon

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  • How to measure cross-talk? By counting photons.
  • Light emission microscopy (LEM) is a precise and powerful visual tool for directly

measuring optical cross-talk.

  • Useful to also observe defects in cells, morphology of the avalanche process, etc.

γ γ

Avalanche Avalanche & cross-talk SiPM array

Optical Cross-talk in SiPMs

γ γ γ

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  • LEM is a powerful root cause failure analysis technique for detecting low

light levels otherwise not visible to an observer.

  • Utilizes resolving power of an objective lens and a low-noise camera to

detect weak light emission, e.g. from semiconductor devices such as SiPMs.

Light Emission Microscopy

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Dark Box

Integrated counts Magnification SiPM Light emission

γ

γ

γ

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  • Illuminate one SiPM cell with small laser spot (<< cell size).
  • Observe emission of photons from primary and secondary avalanche processes

using a microscope and record with a low-noise CCD.

  • Count photons emitted from the central cell where laser is fired and from neighboring

cells at distance 1 cell-unit away.

  • Assume the counts outside central cell

are all cross-talk counts since the laser is focused well within the central cell.

  • Measure cross-talk

Cross-talk = Counts (out) / Counts (in)

Direct Measurement of Cross-talk

Laser spot Counts (in) Counts (out) SiPM Array

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PC

CCD camera (Andor Clara) 1392 x 1040 sensor 2.5 e- readout noise 1 e-/hr thermal noise Tube lens Long pass filter (495 nm) Pellicle beam splitter Objective Lens (Olympus 10X, 0.25 NA) SiPM sample Function generator Laser (440 nm) ~10 ps pulse width Single mode fiber Collimating lens X-Y-Z translation stage Laser Light emission

Setup

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Setup

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SiPM Sample

  • Hamamatsu LCT4 single element
  • Device size = 3 mm x 3 mm
  • Cell size = 75 um x 75 um
  • Breakdown voltage = 51.10V
  • Cross-talk measured as function of
  • vervoltage
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SiPM under 10X Magnification

1392 px 1040 px 116 px

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Hamamatsu 75 um Ambient light conditions

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CCD Imaging Steps

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Step 1: Dark image Step 2: Background image with laser light only

  • To account for any reflections off surface of SiPM

Step 3: Background image with bias voltage only applied to SiPM

  • To account for light emission from powered device

Step 4: Signal image with laser light and bias voltage applied to SiPM Integration time for each step is 30 seconds

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Beam Profile

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X

FWHM: 11 um

Y

FWHM: 11 um

Measured with CMOS camera 1px = 3.8 um

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Observed Light Emission

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Overvoltage = 5V Integration time = 30s Laser fired here Cross-talk emission Hot spots?

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Observed Light Emission

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  • The laser light is focused on a single cell.
  • Light is observed from the fired cell and also neighboring cells.
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Direct Measurement of Cross-talk

COUNTS_IN = Σ☐ COUNTS_OUT = Σ☐ Cross-talk = COUNTS_OUT / COUNTS_IN

Overvoltage 5V Cross-talk = ~23%

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Optical Cross-talk vs. Overvoltage

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[NIM A 806 (2016), 383-394] LEM Method - Preliminary Standard Method (i.e. theshhold)

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Summary and Outlook

  • SiPMs are attractive photo-detectors for high-energy and astroparticle physics

experiments.

– Compact in size – Fast (few ns) response time – Low operating voltages compared to classical PMTs – Insensitive to magnetic fields – Photon detection efficiencies greater than 40%.

  • Crucial to reduce/eliminate cross-talk between neighboring cells.
  • Light emission microscopy is a powerful visual tool for measuring and

understanding the physics behind optical cross-talk, as well as for observing defects, avalanche morphology, etc.

  • LEM method is the most precise measurement of cross-talk.
  • Plans to measure cross-talk:

– in new batches of SiPMs. – in cells > 1 unit distance away from center. – at different regions of the cell. – near the borders of the device.

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sense-pro.org See us at the poster session Consortium Members UNIGE: A. Nagai, D. della Volpe, T. Montaruli KIT: A. Haungs, K. Link DESY: K. Henjes-Kunst MPI: R. Mirzoyan, D. Strom

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Backup

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Low Intensity Background Rejection

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Background region

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Low Intensity Background Rejection

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Signal region

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Hot Spot

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Bkg: Laser Only Bkg: Bias Only Signal Emission observed in signal image only

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SiPM under 10X Magnification

1392 px 1040 px 155 px

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Hamamatsu 100um Ambient light conditions

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Scope Trace

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Laser pulse 500 kHz SiPM output