Poor Boy Fabry–Pérot interferometer?

[AaronT]

I want to build a Fabry–Pérot interferometer in order to study and understand the equipment and technology.

Fabry–Pérot interferometer Wiki

It is also an excuse to buy my first "Lab Laser".

I intend to use this device to attempt to measure gravity. (proximity or even orientation to a large object "mountain, peak, valley" should produce different repeatable results)

So I think I have found a candidate HeNe for this project.

Fleaybay 20mW HeNe

 

[Rivem]

Sounds like a cool project idea!

I'm not an expert on interferometers (especially not for gravity), but I wouldn't expect your application to work out the way you suggest. If you're expecting the ambient gravity to alter the light and change fringes in a measurable way, it's not going to happen without a ridiculously precise instrument.

You're much more likely to see the change in air temperature/currents on a small DIY interferometer than anything else. You'd also need a very, very stable setup if you don't want to see the results of your optics shifting the tiny amounts that they tend to.

That said, it is still plenty feasible to build many different types of interferometer at home. You don't even need really a gas laser if you just want to observe fringes.

 

[WizardG]

"You don't even need really a gas laser if you just want to observe fringes."

No, but a single mode laser is a very good idea.

 

[Trendkilla254]

Gravity? Pshaw. It's just the flat earth disc moving vertically through space right? :tinfoil: :crackup::na::na:

 

[Rivem]

"You don't even need really a gas laser if you just want to observe fringes."

No, but a single mode laser is a very good idea.

Should have said that myself. A multimode laser won't give you good results at all, so highly recommend a good single mode diode or good TEM00 DPSS.

 

[ultimatekaiser]

If you want to build an interferometer you'll need a very small HeNe. that's much too big. most use a stabilized HeNe, which is big $$$$. generally they're a small 10" tube or so, about 1-2 mW. I have a few of them. Production ones are not cheap-but if you are good at making electronics you can make yourself one for pretty cheap if you know how.

 

[AaronT]

Here are a couple of setups from NASA I (eventually) want to emulate and even surpass.





I'm trying to learn the fundamentals before I put down big bucks on better equipment than NASA is using.

So far the obvious component that never changes is the use of a He-Ne laser. If it looks like a "buy once cry once" and will work for several types of devices and will work for my end product, then investing in the "right" one is key.

 

[ultimatekaiser]

That might be an IR tube in that setup, its hard to see though as the image is thumbnail size. but it is entirely possible with any tube under maybe 10". larger (red) tubes would require lots of advanced setup generally to get good results to my knowledge.

 

[AaronT]

Better?

What say you guys on the possibility of this being a usable HeNe?
Stabilized HeNe Laser Kit with Parts to build Arduino Compatible Controller



The next step up is in the expected 2K+ range but I assume is much closer to "NASA" quality.
SIOS SL02/1 Compact Self-Contained Stabilized HeNe Laser System

 

[lazeristasUVISIR]

Start looking for mirrors or flats for the interferometer. They can be really expensive.

 

[AaronT]

Start looking for mirrors or flats for the interferometer. They can be really expensive.

I could just buy very high quality equipment.
SA210-5B - 535-820 nm, Scanning Fabry-Perot Interferometer, 10 GHz FSR

But I would want to keep the Fabry–Pérot device on the same economic scale as this HeNe.

Stabilized HeNe Laser Kit with Parts to build Arduino Compatible Controller

 

[AaronT]

It looks like I can build what I'm after for under $500 and get the finesse over 500 and compete with $5000+ level equipment.

Stabilized HeNe Laser Kit with Parts to build Arduino Compatible Controller

Deluxe Scanning Fabry-Perot Interferometer KIT for Red Lasers

 

[ultimatekaiser]

Yes Sam has been selling stuff like that for a while now. Won't be very powerful but it still enough to get the job done for basic tasks. It is harder than it looks though.

 

[AaronT]

Yes Sam has been selling stuff like that for a while now. Won't be very powerful but it still enough to get the job done for basic tasks. It is harder than it looks though.

I didn't say it would be easy, and a single mw or 2 will be plenty, more laser won't give me a more accurate device.

I'm just a bit shocked that this indeed qualifies as a "Poor Boy" project considering the potential performance level advertised.

I have a 6 ft length of aluminum I beam. I'll use some of it to solidly mount the components to.

I see no reason I couldn't build a battery powered portable unit I can plug into a laptop. The whole setup would fit in a backpack, for say testing local gravity on a mountain top and such.

 

[ultimatekaiser]

Your power output will be heavily dependent on how you decide to do your set up. If the tube is well behaved, which I'm sure Sam will check for beforehand, you can choose to do either 1 or 2 mode stabilization. The two mode will be more accurate, with a little tiny tube like that I can't say how much power you'd get. How's little 6 inch tips are generally only rated for half a mW, but I really hot one to do as much as 1.5mW. I have a few of both types. Retail and home made. I'll post details if you'd like when I get time.

 

[AaronT]

Your power output will be heavily dependent on how you decide to do your set up. If the tube is well behaved, which I'm sure Sam will check for beforehand, you can choose to do either 1 or 2 mode stabilization. The two mode will be more accurate, with a little tiny tube like that I can't say how much power you'd get. How's little 6 inch tips are generally only rated for half a mW, but I really hot one to do as much as 1.5mW. I have a few of both types. Retail and home made. I'll post details if you'd like when I get time.

He advertises this one as a well behaved .8 to 1.2mw

Yes details on running HeNe lasers would be wonderful! Thanks muchly!