Optical noise cancellation

"Laser noise cancellers"

Cheers,

Phil Hobbs

I really did not think that someone was going to write a reply. Thanks.

Most of us try to be helpful round here...provided that the person posting looks like he's willing to make some effort, and that it isn't an obvious homework problem.

Besides, laser noise cancellers are a bit of a hobby of mine.

Cheers,

Phil Hobbs

Hello again,

Mr Hobbs,

I built one of your circuits (Fig-3 in the paper "Ultrasensitive laser measurements without tears"). In principal it worked. However, I see lots of internal oscillations which can be considered as noise. For example whenever the signal beam becomes zero an oscillation around

Just saw this now...my news provider (supernews.com) is dropping a lot of posts.

Your feedback loop is oscillating. This could be due to inadequate bypassing, poor layout, or even hanging a coaxial cable on the output of an op amp with no isolation resistor.

If you can send me an actual schematic, I'll have a look at it, but that exact circuit works very well--the New Focus "Nirvana" detector is just that circuit in a nice box, for which they'll charge you $1500. (The email address above actually works, spam block and all.)

Cheers,

Phil Hobbs