Newport photodetector alternatives

[Arjun Krishnaswamy]

Hi,

I've read through the pycontrol paper and website and had some questions about the newport photodetector.

I have not purchased pycontrol board/optical parts yet, but wondered if the photodector can be switched: briefly, I have some spare R3896 hamamatsu pmts (sockets too) and thorlabs pmt amplifiers lying around from a 2photon build I did a while ago. It'd be great to give these parts new life in a pycontrol rig and we can build a housing to adapt these pmts to the optical components.

I do not know whether this swap will produce signals that are compatible with the pycontrol board. Any thoughts?

Arjun

[thoma...@neuro.fchampalimaud.org]

Hi Arjun,

Apologies for the delay getting back to you - your message ended up in my spam folder for some reason and I only saw it when visited the google group page.

I assume your talking about using the PMTs with pyPhotometry rather than pyControl.  The factors that will determine whether a photodetector is suitable for use with pyPhotometry are:

1. Sensitivity - can it detect the low light levels of photometry signals at the wavlengths you will be working with. I guess the answer is yes for the PMTs are they are normally very sensitive and the spec sheet says they work from 185-900nM wavelength.

2. Bandwidth - does the output signal respond fast enough to changes in light intensity to work with the time division illumination modes.  The bandwidth of the newport photodetectors in DC mode is ~0-750Hz so bandwith this wide or more will be fine.   The PMT and amplifier have much wider bandwidth (0-60MHz) so that is fine.

3.  Output voltage - the pyPhotometry board can acquire signals from 0-3.3V, and although they have protection diodes to protect from damage against overvoltage inputs,  a signal far outside this voltage range might risk damaging something.  The PMT amplifier looks fine here because although the default output voltage is -1.5-1.5V, there is a DC bias control that you can use to shift it to 0-3V which is idea.

Overall they look like they should work, though I have never tried this type of photodetector myself.

best,

Thomas