[time-nuts] optically excite a quartz crystal?
magnus at rubidium.dyndns.org
Mon Apr 21 00:31:24 UTC 2014
Quartz is piezoelectric, so it deforms due to electrostatic fields and
vice versa. This is exactly what is being used in quartz oscillators.
For the BVA, the resonator is hanging in bridges of the same quartz
crystal it is being cut out from, and the orientation of the blank is
such that these bridges have minimal impact on the frequency. The other
aspect is that BVAs have the electrodes on concave quartz pieces just a
few micrometers from the surface of the resonator blank. These pieces is
really the expensive part of the BVA sandwich.
There are a couple of ways to monitor the crystal using optical measures.
The manipulation and sensing is done by electrostatic means, while the
crystal itself is resonant by means of acoustical waves.
So well, I guess you could be using another 10 MHz crystal as an
acoustical transmission source... but why is the big question. When
someone figures out why this is a super solution, I bet they won't tell
us until the patent has been accepted.
On 04/20/2014 11:03 PM, Bill Hawkins wrote:
> If laser excitation won't work, how about sound, as an opera singer
> breaking a glass?
> Use feedback control to bring the driven crystal to resonance with the
> "free" crystal. Might need to go down to 100 KHz to make this practical.
> Speaking of practical, how would you levitate the free crystal?
> Bill Hawkins
> -----Original Message-----
> From: cdelect at juno.com
> Sent: Sunday, April 20, 2014 12:35 PM
> After reading about how the BVA oscillators avoid the problems of "on
> crystal" electrodes I was wondering if anyone has tried to optically
> excite a quartz crystal in an oscillator?
> (Use a modulated laser to drive the bare crystal, and a photodetector
> setup to detect and provide feedback?)
> Seems like it might work. Any comments?
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