Fast photodiode recommendations

[norty303]

I was reviewing this thread last night, after returning from my laser safety training.
http://www.photonlexicon.com/forums/...here-any-point

I think I'd like to get a fast photodiode and scope, maybe one of the handheld ones with screen if suitable.

I realise that thread is a few years old now, and time and technology move on.

Can anyone advise/link to suitable photodiodes (bare and finished units) and suitable scopes?

Cheers muchly!

[andythemechanic]

Hi,

I use BPX65 Photodiodes and wire a 1kOhm Resistor in parallel to convert the current to a voltage. This is a very easy and fast setup which can be used to measure risetimes <1µs on any scope with >20Mhz analog bandwith. a full hit of a laserbeam with some mW will saturate it already so when measuring direct beams you have to use some attenuation filters. It has a small area of 1mm^2

Best
Andreas

[LaNeK779]

Thanks for this andy, itis really usefull
would any of the $100 -$150 handheld "mini" scopes be up to the task?

how crusial is osciloscope quality for this use? i guess we are looking for some relatively cheap alternative to a proper bench scope

[norty303]

Also, one of the big issues for me is evaluating a combined rgb beam for safety (not necessarily a scanning beam). Are there any reasonably affordable thermal heads in the mW ranges that anyone can recommend?

[Jem]

I have one of these...

http://search.newport.com/?q=*&x2=sku&q2=818-SL

This fits on my Newport power meter. However, very conveniently it also fits directly on to my Oscilloscope and seems to do the job for measuring pulse duration etc.

Probably a little expensive though.

Jem

[norty303]

Well, there's the thermal one, but *ouch* on the price, and thats just the head...
http://thorlabs.com/thorProduct.cfm?partNumber=S302C

[-bart-]

Keep in mind that photodiodes like bpx65 are wavelength sensitive.
Twice as sensitive for 650 as for 450.

[norty303]

Yep, thats why I'm thinking thermal, like the Ophir 3A heads.

Can you get 'broadband' photodiodes?

[LaNeK779]

Well, there's the thermal one, but *ouch* on the price, and thats just the head...
http://thorlabs.com/thorProduct.cfm?partNumber=S302C

ophir heads, laserbee, tec diy not up to the task?

[norty303]

Well I was just thinking about that.

I need to be able to measure 6.4mW or below on my Laserbee for it to be 10mW/cm2 or less.
I guess I could find someone with a meter accurate and calibrated in this range, and then test my laserbee in the same range. I could then apply a conversion factor.
I guess it just depends on if its stable and repeatable in that range.
I think Doc reported laserbee to be quite linear in response in the low range, just over reading (which is obviously safer)

I think the graph he did is in the thread I linked up top (can't check now, work blocks images...)