[Laser] ULTRASONIC LIGHT MODULATION - new web page.

[wa4qal at ix.netcom.com]

> Message: 1
> Date: Mon, 11 Apr 2005 12:46:00 +0000
> From: "Chris L" <vocalion1928 at hotmail.com>
> Subject: [Laser] ULTRASONIC LIGHT MODULATION - new web page.
> To: laser at mailman.qth.net
> Message-ID: <BAY18-F3037B824632AE11429FE1DD2320 at phx.gbl>
> Content-Type: text/plain; format=flowed
> 
> Dear group,
> 
> Having seen a posting about how 'expensive and complex' ultrasound 
> modulation of light beams was (it's not true!) I've put up a web page on the 
> subject with details of a modulator that can reach about 500 kHz with ease, 
> and several mHz with modification.

I used to play with a bit of sonic modulation of light beams, but it was all
with electromechanical stuff (e.g., gluing a magnet onto a speaker).  Plus,
back in that era (30 years ago), I couldn't afford a laser (expensive), so
I used focused light beams.  It was all pretty marginal back then, but it 
was something interesting to keep a teenager out of trouble, mostly.  :*)

> Please visit:
> 
> http://www.bluehaze.com.au/modlight/UltrasoundMod.htm

Wow, VERY impressive.  Thanks.  

> Lots of constructional stuff - how to recover old ex-army 10 MHz crystals 
> and use them to generate ultrasound beams in a small liquid-filled glass 
> tank to make a diffraction cell.

I've been playing with crystal grinding last year:

http://pw1.netcom.com/~wa4qal/crystal.htm

It's not too hard to do if you have the right materials (Carborundum powder),
although Quartz is an exceedingly hard material, and it takes a lot of 
patience to grind it, even with the right material.

I have a supply of pre-cut crystal blanks, although I'm not exactly sure 
which cut they are [1], some of which going down to the 991 KHz range.
Most of them are in the 6.x MHz range, and are sized to fit FT-243 holders,
although I also have a rather extensive quantity of FT-241 crystals, too
(mostly 300-500 KHz).

[1] I could probably find out, based on the resonant frequency and the
thickness of the slab, since different cuts have different thickness/frequency
ratios.

> The ideal modulator if you're intent on using 632.8 um HeNe lasers...

Sounds VERY interesting.  I've been meaning to try some laser/crystal
experiments, but I just have way too many fun projects and not nearly
enough fun time.

> and please, any comments or corrections to the e-mail addy above will be 
> greatly appreciated.

No problem.  I also have lots of comments.  :*)
 
> All the best, folks!

Thanks again for a VERY interesting web page.
 
> Chris Long, Melbourne Australia.

Dave
WA4QAL