[time-nuts] Photodiodes for high frequency OPLL

[David Kirkby]

On 30 March 2013 19:50, Attila Kinali <attila at kinali.ch> wrote:
> On Sat, 30 Mar 2013 18:43:03 +0000
> David Kirkby <david.kirkby at onetel.net> wrote:
>
>> I would contact Hammamatsu Photonics
>>
>> http://www.hamamatsu.com

> This might be a good idea. Thanks!

>> I played tricks during my Ph.D. of gain-modulating an APD with a step
>> recovery diode.

> You mean pulsing the bias voltage at about 7GHz and see whether
> i can get a something out of that?

I did not really have anything in mind specifically. I was just
wondering if there was anything could do modulating the gain of a
detector so forming a non-linear detector.

I pulsed the voltage on an APD to buid a cross correlator. By doing
that I was able to get better temporal resolution than the basic APD.


Quick summary here:
http://www.medphys.ucl.ac.uk/research/borl/research/phd_projects/davek_phd.htm

Fulll thesis here
http://www.medphys.ucl.ac.uk/research/borl/docs/dkirkby.pdf

I have seen systems where one sinusoidally modulates the voltage of a
photomultipler tube. You could do the same with an APD. Then it acts a
a mixer. Essentially

1) Modulate laser at 100 MHz
2) Modlulate the APD bias voltage at 100.01 MHz
3) Detect light from laser on an APD.
4) Output of the APD is a sine wave at 10 kHz.

> There has been a similar idea around, using a third laser that
> is pulsed with the desired offset frequency.

I was wondering if it could be done in more than one stage. A bit like
a superhetrodyne receiver.

I've had quite a few beers tonight (OK, I am ****ed) so my mind is not
thinking too straight.

>> Have you considered using a photomultiplier tube? I think there are
>> some fast PMTs around, though perhaps not fast enough. 20 years I used
>> to know what was state of the art in this area, but not any more.
>
> Not really. I am mostly looking at stuff i can easily get my hands on.
> If possible without using ebay (other should be able to build the
> system as well).

PMTs are available new. Hamamatsu has almost 100 different types.

http://www.hamamatsu.com/eu/en/product/category/3100/3003/index.html

so there is no need to trawl ebay. Using PMTs you can easily get sub
ns temporal response.

Dave