Photodiode / Laser pulse measuring test set up.

[TCWilliamson]

Under advice from Steve(mixedgas) I am making a small experimental set up to familiarize myself with Laser mechanics.

I intend to buy a photodiode (https://www.thorlabs.de/_sd.cfm?path...tnumber=FDS100)

and this laser diode (https://www.thorlabs.com/thorproduct...umber=L980P010)

I would like to know if this is advisable, is it safe to aim the diode at the photodiode (I don't wish to damage it...) and how should I work such a thing out in future?
I am aware this might be a rather 'newbie' question, however I feel it would be more embarrassing to be expected to know in the futre and, not to know then to ask now.

I will get a little diode laser mount machined next to my work probibly, else order one next day from Ebay (probibly cheaper)

Any advice would be appreciated.

[VDX]

... I've done some simple/fast laserpulse measuring with the phototransistor of a light barrier (simply broke it apart) - pretty cheap and easy to source

Viktor

[TCWilliamson]

I also want to work out the laser's power from using it too. I'm trying to get a good understanding of optical technology.

[VDX]

... the laser-power can be measured with a small black coated Peltier cooler ... or you can read about "Ulbricht sphere" or "integrating sphere": https://en.wikipedia.org/wiki/Integrating_sphere

I have some of this Ulbricht spheres and a "Coblentz sphere" (which is reflecting, instead of diffusing) for laser power measuring.

But I too have a "normal" Silizium sensor power meter with measuring capacity of up to 3MW laserpower, so didn't try with the other methodes ...

Viktor

[TCWilliamson]

Thanks for your replies. While I see that this can be done a multitude of ways (many of which I intend to have a look at)
I'm more interested in familiarizing myself with photodiodes first. If anyone has any useful references beyond the thorlabs tutorial it would be greatly appreciated.

[danielbriggs]

If you're building your own DET10 (a great biased photodiode!) they use the FDS010 inside.
(Smaller active area, faster rise time) but for the Q-switch frequencies you'll be measuring... either should be fine.

Why the 980nm laser diode?
If you're just using it to test the photodiode circuit... <5mW red diodes would do; hookup the modulation line of the diode driver to a signal gen, and monitor commanded + observed signal. The diode driver will be the "slowest" link in the chain.

I know you said it was problematic in transport... but should you ever be able to bring your YAG to the office, you can use all those tools to measure yours [DET10 / Coherent Labmax-TOP / Spectrometers etc.)
(or bring yourself + have a go with one of the units there)

What do you want to achieve? Just learning? Or a specific task for the bigger laser?
Photodiodes saturate with a few µW's-mW's; so either position it "near" a high powered beam, or use ND filters (not advisable for your Q-switched laser!)

Dan

[TCWilliamson]

If you're building your own DET10 (a great biased photodiode!) they use the FDS010 inside.
(Smaller active area, faster rise time) but for the Q-switch frequencies you'll be measuring... either should be fine.

Why the 980nm laser diode?
If you're just using it to test the photodiode circuit... <5mW red diodes would do; hookup the modulation line of the diode driver to a signal gen, and monitor commanded + observed signal. The diode driver will be the "slowest" link in the chain.

I know you said it was problematic in transport... but should you ever be able to bring your YAG to the office, you can use all those tools to measure yours [DET10 / Coherent Labmax-TOP / Spectrometers etc.)
(or bring yourself + have a go with one of the units there)

What do you want to achieve? Just learning? Or a specific task for the bigger laser?
Photodiodes saturate with a few µW's-mW's; so either position it "near" a high powered beam, or use ND filters (not advisable for your Q-switched laser!)

Dan

Hello Dan,

That's good to hear I'm barking up roughly the right tree. I'm building this little jig to experiment and just learn about lasers in general until I get that YAG running.

From the other thread I have been highly discouraged to even touch that laser until I am much more familier with lasers and have someone to guide me through safe operation and the right equipment.

I don't actually have any red laser diodes laying around. I thought that diode might be good as it also has an internal photodiode inside it which would be interesting to play around with.

Unless I get a bigger motorbike that can take me to nottingham, rather then my current 50cc, it seems unlikely and the cost of going up there by train, booking accomidation and local transport oughtweighs everything until I can get a full car driving license. I wouldn't want to put myself near any fancy laser gear until I am much more read up and have 'earned it'

I'll stick with the current planned photodiode as it is half the price (so I can get two) giving me less risk of money loss from component damages. I'm still pretty rusty with analog, digital is my area of expertese.

On the bigger laser, I'm actually just waiting on yours and some of the other 'pros' to advise me on it and tell me when I should begin to operate it and start fixing it up / what to do with it.
I need to get the book on solid state laser engineering first, should arrive next week as it's ordered on amazon.

I'm sure we can discuss this tomorrow morning (well, this morning at the time I'm writing this post...) via phone or alternativly skype.

[danielbriggs]

I'm sure I have a few spare brand new 5mW 635nm'/660nm's lying around I am never going to use + can send you?

Personally, I'd stick with visible laser diodes for now [especially if you've never focused lasers + have no IR viewing aids].

Dan

[TCWilliamson]

I'm sure I have a few spare brand new 5mW 635nm'/660nm's lying around I am never going to use + can send you?

Personally, I'd stick with visible laser diodes for now [especially if you've never focused lasers + have no IR viewing aids].

Dan

I'd really appreciate that Dan, I'll send you a PM with my address in exchange for a paypal to cover postage costs.

You have an excellent point there.


Also, on a side note, reading into IR viewing aids... an occulus rift / HTC vive with a suitable camera or two would be great for such a thing I'd imagine.

[lasersbee]

Under advice from Steve(mixedgas) I am making a small experimental set up to familiarize myself with Laser mechanics.

I intend to buy a photodiode (https://www.thorlabs.de/_sd.cfm?path...tnumber=FDS100)

and this laser diode (https://www.thorlabs.com/thorproduct...umber=L980P010)

I would like to know if this is advisable, is it safe to aim the diode at the photodiode (I don't wish to damage it...) and how should I work such a thing out in future?
I am aware this might be a rather 'newbie' question, however I feel it would be more embarrassing to be expected to know in the futre and, not to know then to ask now.

I will get a little diode laser mount machined next to my work probibly, else order one next day from Ebay (probibly cheaper)

Any advice would be appreciated.

The IR Laser Diode that you linked to only outputs 10mW.
You should not have any problems with damaging the photo
diode that you linked to.

As Dan has mentioned it would be a lot easier to align a
Laser beam or dot if you could see it.
Don't forget that the Photo diode output is not linear and
outputs different voltages/currents at different wavelength
even if those input wavelengths are the same identical
power.

Not sure what part of the Globe you are on but if Canada
is closer than the UK I can sent you a couple of 650nm
red Lasers for your experiments.


Jerry