need guidance in selection of photodiode for my project

It would be hard to think of a less suitable op-amp than the 741 to use with a fancy photo-diode. (I picked one of your selection at random and noticed that it costs £17.)

Why are you biasing the photo diode with an AC source ?

I suspect that you are not equipped to measure the reliability of the photo diode - just buy from a reputable source and operate it well within ratings for reverse bias etc.

Do some reading about photo diode trans impedance amplifiers (DuckDuckGo or Google it).

Here are some starters:

https://www.ti.com/lit/pdf/tidu535

www.ti.com/.../SSZTBC4

https://www.allaboutcircuits.com/technical-articles/design-tips-for-photodiode-amplifiers/

If possible you should start by measuring the photo current coming out of your test devices before you attempt to design an amplifier of your own.

Something like this would do:

https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1003

(There are other suppliers

https://www.aliexpress.com/item/1005005324917603.html

)

MK

Hi,

THnaks for your reply and sharing links..

I plan to use the OPA657 op-amp, as the 741 op-amp has higher noise and is not suitable for this application.

if you don't mind, I would appreciate your guidance on how to characterize different photodiodes to help me select the most suitable one for my project.

Hi,

THnaks for your reply and sharing links..

I plan to use the OPA657 op-amp, as the 741 op-amp has higher noise and is not suitable for this application.

if you don't mind, I would appreciate your guidance on how to characterize different photodiodes to help me select the most suitable one for my project.

You've already narrowed it down to the selection you listed, so maybe just try your top two or three selections, see which one meets your needs?

What I don't understand, is you've mentioned 0.8 mm3 volume, yet from the photos, each of the selected photo diodes look large (I have not looked at their datasheets). However much light are you expecting? Is it an extremely tiny amount? If so then maybe SPADs are a better choice than photodiode? See here:

 The Use of SiPMs in the Life Sciences 

I could be very wrong since I'm not knowledgeable in your subject area.

I think you need to explain exactly what your project is and where you are doing it and why.

The advice I would offer a student doing a thesis project is quite different to that I would offer to a professional engineer. 

There is plenty of published material about doing what you discuss. It took me  a couple of minutes to find this:

https://warwick.ac.uk/fac/sci/eng/research/grouplist/sensorsanddevices/mbl/database/ieeesensors09/PDFs/Papers/286_5764.pdf

There is a lot more on the web.

Have you done a comprehensive search of the published literature ?

MK

Hi,

Thanks for sharing article and yes, I am working on the same nature of project and in my project, I am using multichannel Fibre optic dosimeters.

I am looking to calculate the voltage obtained from the TIA output for estimating radiation flux. If I use BCF-60 as the scintillating material instead of a green LED, I would like to confirm which parameters are critical for accurate estimation.

In the clinical setup, the field size is 10×10 cm², the dose rate is 600 MU/min, the dose delivered is 100 MU, and the fibre is placed at the centre of the radiation field. The detector configuration consists of 1 mm of BCF-60 scintillating fibre and 4.9 cm of non-scintillating fibre.

Could you kindly guide me on which parameters I should consider to accurately estimate the signal generated from the BCF-60 fibre in this configuration?

Thank you in advance for your guidance.

Kind regards,

Hasham

You haven't answered my questions - 

"you need to explain exactly what your project is and where you are doing it and why"

You are asking for help and advice to be provided for free, which is fine, that's what E14 and other forums are for.

But you have to share, and that starts with being fully transparent about yourself and your project.

A second aspect to this is that you have to tell us about yourself - do you have a medical, physics or electronics background. Are you doing this work as a paid professional or a student. 

And the country you are doing the work in is important - the law in my country (and almost all others) forbids assistance to some other countries.

To start the ball rolling, I'm a professional electronics design engineer with approx 50 years experience, based in SW Scotland in the UK. 

MK

Hi MK,

Thanks for your reply,

Yes, this is my PhD project, which involves designing a dosimetry system using fibre-optic materials. I am currently pursuing a PhD in Medical Physics at the Centre for Medical and Radiation Physics (CMRP), University of Wollongong, Australia.

I have an electronics background and have also completed a two-year postgraduate diploma in Radiation Oncology Medical Physics.

One of the tasks in my project is to select the most suitable photodiode for use with BCF-60 scintillating fibre, and subsequently calculate the estimated output voltage from the transimpedance amplifier (TIA). I have to finish this task within two weeks, and I am struggling and need help and guidance.

Kind regards

Hasham

This is a tricky problem (and a long way from what I know much about which is gas detection with NDIR detectors)

You need to somehow work out how much power gets into the fibre, and then how well you can couple the PD into the fibre.

The first bit will be hard and the only hope is literature scouring or to talk to someone with direct experience.

This could help:

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://luxiumsolutions.com/sites/default/files/2021-11/Fiber-Product-Sheet.pdf&ved=2ahUKEwiIjNe_tqiPAxVsUkEAHXerDEYQFnoECBYQAQ&usg=AOvVaw3QOgYmhplIAWxlYq1r6OY2

It tells you how many photons per MeV you can expect.

I'm assuming that you need to be able to plug the end of the fibre into some kind of connector to the PD so you can use the same PD with lots of different fibres. This will mean less good coupling and you don't really want a big PD in a TO5 can.

The best I can suggest is that you reckon on spending the next two weeks on the internet, looking for information and following it up with trying to contact people directly.

For example email or better still phone Luxium (link above) and try and get to talk to someone who can help you with information or contacts.

It hard work and soul destroying (a lot of people won't be interested in helping you) but it can pay off.

The alternative is to get hold of some fibre, diodes and a radiation source and do some measuring, and extrapolate from there - this may not be easy - but people who make the coated fibre must have some kind of test rig they might talk about.

If you get a bit nearer to the amplifier bit (ie when you know the PD current and pulse width) I might be able to help a bit more.

MK

Hi, Thanks for your reply..

Yes, I am currently working on it, including the SMA connector and packaging to connect the photodiode to the fibre optic. I have also estimated the power by assuming a dose rate of LINAC is 600 MU/min, with 100 MU delivered. Based on my measurements, the pulse width is approximately 3 to 4 microseconds, with an elapsed time of 2.7 milliseconds.

The photodiode current sensitivity is around 0.2 A/W to 0.3 A/W for green light scintillator (BCF-60) with a wavelength of 530 nm.