On Wednesday, April 11, 2018 at 3:19:41 PM UTC-4, John Larkin wrote:
> On Wed, 11 Apr 2018 11:19:52 -0700 (PDT), George Herold
> <gherold@teachspin.com> wrote:
>
> >On Wednesday, April 11, 2018 at 11:19:53 AM UTC-4, John Larkin wrote:
> >> On Wed, 11 Apr 2018 06:35:11 -0700 (PDT), George Herold
> >> <gherold@teachspin.com> wrote:
> >>
> >> >On Tuesday, April 10, 2018 at 8:13:31 PM UTC-4, Phil Hobbs wrote:
> >> >> On 04/10/18 19:03, George Herold wrote:
> >> >> > On Tuesday, April 10, 2018 at 6:39:24 PM UTC-4, Uwe Bonnes wrote:
> >> >> >> George Herold <gherold@teachspin.com> wrote:
> >> >> >>> This is a bit of a shot in the dark, but I wonder if anyone has used
> >> >> >>> 'garden variety' APD (Avalanche Photodiodes) in the photon counting
> >> >> >>> mode where they are biased above their breakdown voltage?
> >> >> >>>
> >> >> >>> I just got a quote on some of these,
> >> >> >>> https://www.lasercomponents.com/fileadmin/user_upload/home/Datasheets/lcd/sar-series.pdf
> >> >> >>>
> >> >> >>> The difference between the SAR and SARP looks mostly to be the noise
> >> >> >>> and dark current. (see figs 6,7,8)
> >> >> >>>
> >> >> >>> Oh the SAR500 is $60 for one the SARP500 is $150
> >> >> >>> and with TEC they are $375 and $670... that is some serious scratch.
> >> >> >>>
> >> >> >>> George H.
> >> >> >>
> >> >> >> Why APD's and not MPPC(Silicon Photo Multipliers)?
> >> >> >>
> >> >> >> --
> >> >> >> Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de
> >> >> >>
> >> >> >> Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
> >> >> >> --------- Tel. 06151 1623569 ------- Fax. 06151 1623305 ---------
> >> >> >
> >> >> > I need to count photons with some decent efficiency at ~800nm.
> >> >> > longer wavelength might work too, but low dark count and
> >> >> > high QE is what I need. I should probably get fiber coupling
> >> >> > too. It's an entangled photon, exp. You start with a UV laser
> >> >> > (~400nm.) with a magic x-tal to phase entangle the down converted
> >> >> > 800 nm photons. (I need to read a lot more about it.)
> >> >> >
> >> >> > George H.
> >> >> >
> >> >> >
> >> >> > I'm going to order
> >> >> >
> >> >> Well, "low dark count" and APDs only go together for very permissive
> >> >> values of "low". On a per-area basis, APDs have six orders of magnitude
> >> >> worse dark counts than PMTs, and that's an apples-to-apples comparison:
> >> >> Si APDs and visible-sensitive bialkali PMTs--a 100-um APD has about the
> >> >> same dark count rate as a *FOUR INCH* PMT.
> >> >
> >> >Right, If you know of a small pmt with quantum efficiency (QE) greater than
> >> >(?) ~50% at 800 nm I could try that. :^)
> >>
> >> You might consider using a microchannel plate, like from a
> >> night-vision gadget. Since they are area amplifiers, one could
> >> possibly be used as two (or more!) detectors.
> >
> >Hmm I don't know about those. (guessing) There is some
> >photocathode, that emits electrons when a photon hits it.
>
> Yes. And the electrons get amplified, by a microchannel plate or, in
> the cheap ones, just by being accelerated by a lot of voltage.
>
> The dark emission should be like a PMT which, as Phil notes, is
> zillions of times better than an APD.
Right, this experiment is all about two correlated photons, down
converted with a x-tal from a 405 nm laser diode. The correlation
goes as the product of the detector eff. So at 10% QE only 1% of the
'good' events are detected. I guess anything above 50% should be good
enough, but you always want as much as you can get... signal wise.
You can buy these detectors for ~$2-5k*, the price depends on the
dark count. I've seen numbers from 10 Hz to 10 kHz.
(. at some point it's a reversed biased diode
above the avalanche point and it breaks down continuously...
it only stops conducting at lower bias 'cause the avalanche is
a little random. (or someone shuts it down.) at least that's
my limited understanding.) There's after-pulsing too,
charges stuck in the channel, or something.
George H.
*laser-components makes packages too, I asked for prices today...
I hate when there is no price list.
It's a complicated physics package.
>
>
> In which case
> >it will have the same problem as PMT's. The photocathodes are not that
> >efficient at 800nm. The APD's I'm looking at have a QE of 90%!! at
> >800nm (For correlations with two detectors it's the square of the QE that I care about, so 10% is the pits.)
> >
> >
> >>
> >> Even a gen-1 night vision thing (they are cheap) could be used as a
> >> photon amplifier maybe.
> >>
> >> Hamamatsu has a tiny MEMS PMT that they don't want to sell.
> >
> >They have some Silicon PM (MPPC) which are arrays of APD's, but the
> >ones I know about are all in the visible... response peaks ~500 nm.
> >
> >https://www.hamamatsu.com/us/en/community/optical_sensors/articles/physics_and_operation_of_mppc/index.html
> >
> >Trolling Hamamatsu, these might be OK.
> >http://www.hamamatsu.com/resources/pdf/ssd/s10341_series_kapd1030e.pdf
> >
> >But no data on operation above the breakdown voltage.
> >George H.
> >>
> >>
> >> --
> >>
> >> John Larkin Highland Technology, Inc
> >>
> >> lunatic fringe electronics
>
> The night-vision gadgets usually include a near-IR illuminator, just
> barely visible, so it's around 800 nm. The classic sniperscopes worked
> with invisible IR, so the bad guys wouldn't see the immuminator.
>
> I have a cheap russian night-vision scope that's great for spying on
> critters in the back yard at night. Skunks, raccoons, cats, possom,
> now occasionally coyotes, plus deer and wildcats in Truckee.
>
>
>
>
> --
>
> John Larkin Highland Technology, Inc
> picosecond timing precision measurement
>
> jlarkin att highlandtechnology dott com
> http://www.highlandtechnology.com