Wednesday, April 27, 2022

90-min Tutorial on Single Photon Detectors

Krister Shalm of National Institute of Standards and Technologies presented a tutorial: Single-photon detectors at the 2013 QCrypt Conference in August. http://2013.qcrypt.net

This is from a while back but an excellent educational resource nevertheless!

The video is roughly 90-minutes long but has several gaps that can be skipped ahead. Or play it at >1x speed!




13 comments:

  1. A lot of progress in single photon detection has occurred since almost 10 years ago. Megapixel SPADs and QIS devices (in fact SPAD-QIS and CIS-QIS) are now products. They operate at room temperature and in principle can be mass produced.

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    1. Totally agree. 10 years ago, single photon detectors such as SPAD or QIS are very specialized devices. Now they are mainstream devices, almost in everybody's pocket. You can see tremendous progress made in last four years, performance and cost have been scaling like Moore's Law. For example, SPAD performance in NIR 900nm range improves from ~5% to >25% and size shrinks from 20-30um to 6um. Most CIS foundries or OEMS have some SPAD activities. Believe that SPAD or QIS will be readily available from most major CIS or analog foundries in few years.

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  2. Who created these weird names? SPAD-QIS and CIS-QIS? Is CIS-QIS an abbreviation of "CMOS image sensor quanta image sensor"? Such a bad taste in naming.

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  3. QIS can be implemented with SPAD-type pixels (impact ionization gain) or CIS-type pixels (intra-pixel charge transfer with CDS). If you have a better way of naming these two types of image sensors be my guest.

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  4. SPAD-QIS and C-QIS; in the latter at least "image sensor" is not repeated implicitly.

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  5. What's the difference between the SPAD and SPAD-QIS?

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    1. SPAD refers to the diode itself regardless of the bigger structure in which it is utilised. For example, a SPAD can be used to make SiPMs etc.
      Moreover, a SPAD array can be used for timing purposes and not necessarily for imaging (i.e. standard photon counting), nor for imaging based on the principle of QIS.

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    2. Thanks. We do talk about imaging here, though.

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    3. QIS is a name that Eric Fossum came up with. There is no real QIS even close to prototype, let alone production. Based on Fossum, QIS concept takes advantage of shrinking pixel sizes (sub-diffraction limit pixels). It means for most of the imaging (specially consumers) applications, pixel pitch (jot pitch) should be far less than 1um for example less than 0.5um and it has to be sensitive to single photon. Today, you can't make any SPAD pixel with 0.5um (not even 2um) and the Gigajot's imagers are more like improved CIS than anything close to the QIS concept. Fossum is trying to categorize these non-QIS devices as QIS so he can claim the QIS came to reality. Not a good idea.

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    4. This comment has been removed by the author.

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    5. We also talk about time-resolved imaging here and its operating principle is different from the standard photon counting. I think the SPAD is mostly used in the time-resolved imaging although I'm excited to see the SPAD image sensor (or SPAD-QIS) being commercialized now.

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  6. Albert Theuwissen - Harvest ImagingApril 29, 2022 at 9:32 AM

    Check out the explanation of avalanching at the time 48:00. Quite funny but very instructive !

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