On Sun, 20 Apr 2014 10:35:08 -0700
cdelect@juno.com wrote:

I am not really sure about that.

(Disclaimer: my knowledge about solid state physics and piezo-electric
devices is at best rudimentary, so please correct me if i'm wrong)

The oscillations of the quartz crystal are deformations of the
crystal lattice. This deformation is induced by applying an electrical
field and coupled into the lattice over the piezo-electric effect.

The wavelength of the electromagnetic field is usually much much larger
than the dimensions of the crystal involved. As such, the field can be
seen as constant trough the crystal. I.e. the field induced strain on
the lattice is constant trough the whole length.

On the other hand, the wavelength of lasers is in the order of a couple
thousand times the lattice constant (approx 0.5nm). I.e. the field of
a laser within a quartz crystal wouldn't be constant if one would be
to use a crystal in the sweet spot region between 1MHz and 10MHz.
Using two lasers with a ~10MHz frequency difference and using two
photon absorbtion will probably yield to a very small energy coupling
to induce any measurable oscillation, if it is possible at all
(i don't know of any effect that would translate a two photon absorption
into lattice oscillations).

Thus, i don't think it would be possible to induce oscillations in a quartz
crystal using a laser based system.

On the other hand, there are currently experiments running to use lasers
to generate RF frequency refernces coupled to the interogation of atomic
clocks (see e.g. [1]) and the results are comparable to ultra low noise
crystal oscillators.

			Attila Kinali

[1] State-of-the-Art RF Signal Generation From Optical Frequency Division.
by Hati, Nelson, Barnes, Lirette, et. al., 2013

--
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In message AABKXJBN5AJ3WCZA@smtpout04.dca.untd.com, cdelect@juno.com writes:

I can see optical detection, but I have a hard time imagining how you
would excite it opticaly ?

You can obviously hammer it with a wavelength quartz absorbs, but that
turns into heat and I somewhat doubt you can get a heat/cooling cycle
to run at 10 MHz, even in perfect quartz ?

--
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Never attribute to malice what can adequately be explained by incompetence.

Hi Corby,

On 04/20/2014 07:35 PM, cdelect@juno.com wrote:

I only wonder if you can get sufficient drive-level that way. I haven't
heard about a way to drive quartz optically even if I can consider a few
different mechanisms. You have any papers on that?

Optically sensing the vibration I consider trivial.

Cheers,
Magnus

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.

Cheers,
Magnus

On 04/20/2014 11:03 PM, Bill Hawkins wrote:

It seems that it would be relatively easy to apply an electric field to a
quartz plate without actually making physical contact.  However, Star Trek's
force field hasn't been invented yet so there must be some way to support
the plate.  If you could arrange to support it on the nodes you could excite
it with a non contact electric field and then read it out with a laser.

Regards.

Max.  K 4 O DS.

Email: max@maxsmusicplace.com

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----- Original Message -----
From: "Attila Kinali" attila@kinali.ch
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, April 20, 2014 2:50 PM
Subject: Re: [time-nuts] optically excite a quartz crystal?

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Hi

The WWII era FT-243 is one example of a crystal that has the active portion of the electrodes separated from the resonator by an air gap. There are lots of similar holders from that era that do pretty much the same thing. Non-contacting electrodes are not very new.

Bob

On Apr 20, 2014, at 8:47 PM, Max Robinson max@maxsmusicplace.com wrote:

Ya, I remember those FT243s.  I used some when I was a novice KN4ODS.

Regards.

Max.  K 4 O DS.

Email: max@maxsmusicplace.com

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----- Original Message -----
From: "Bob Camp" lists@rtty.us
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, April 20, 2014 8:05 PM
Subject: Re: [time-nuts] optically excite a quartz crystal?

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On Mon, 21 Apr 2014 17:12:54 +1200
Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:

Thanks Bruce!

For those who dont want to buy the paper, here a short summary:

They used a 10mW HeNe laser, modulated with 1kHz to 1MHz on
various quartz cuts (X+5°, DT, AT) and could measure oscillations
of the quartz using metal electrodes.
The mechanism of exitation was photothermal

		Attila Kinali

--
I pity people who can't find laughter or at least some bit of amusement in
the little doings of the day. I believe I could find something ridiculous
even in the saddest moment, if necessary. It has nothing to do with being
superficial. It's a matter of joy in life.
-- Sophie Scholl

On 04/21/2014 11:40 AM, Attila Kinali wrote:

10 mW laser is reasonable.

What levels of signal where they getting?

Cheers,
Magnus

I'm puzzling over this statement.  The FT-243's I have seen have a spring
that squishes the quartz blank between the electrodes.  They aren't plated
onto the quartz, but they are still in intimate mechanical and electrical
contact.

-Chuck Harris

Bob Camp wrote:

Hi

If you look closely at most of them, the plates are not flat. They are higher on the edges than in the center. There’s a gap in the middle. If you don’t have the gap, the blank is constrained by the big heavy plate. That damps the resonance and lowers the Q.

Bob

On Apr 21, 2014, at 9:00 AM, Chuck Harris cfharris@erols.com wrote:

On Mon, 21 Apr 2014 14:54:12 +0200
Magnus Danielson magnus@rubidium.dyndns.org wrote:

6.2mV, with an real laser incident power of 5mW (the AOM "ate" half of the power)

		Attila Kinali

--
I pity people who can't find laughter or at least some bit of amusement in
the little doings of the day. I believe I could find something ridiculous
even in the saddest moment, if necessary. It has nothing to do with being
superficial. It's a matter of joy in life.
-- Sophie Scholl

Agree there are some like that, but, only a few. A large spring loaded plate
is not going to dampen a piece of quartz vibrating in the MHz range at all.
Granted, the sealed, and metalized construction is a better one, but it is
mostly done to minimize shock and impurities. - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Bob Camp
Sent: Monday, April 21, 2014 9:17 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] optically excite a quartz crystal?

Hi

If you look closely at most of them, the plates are not flat. They are
higher on the edges than in the center. There's a gap in the middle. If you
don't have the gap, the blank is constrained by the big heavy plate. That
damps the resonance and lowers the Q.

Bob

On Apr 21, 2014, at 9:00 AM, Chuck Harris cfharris@erols.com wrote:

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Hi

One of the reasons for going to plated electrodes was to control the damping on the resonator. You control plating thickness fairly tightly for this reason. A great big lump of iron on your vibrating area does indeed damp it.

Bob

On Apr 21, 2014, at 9:29 AM, Mike Feher mfeher@eozinc.com wrote:

On 04/21/2014 03:18 PM, Attila Kinali wrote:

Cool. Today we use semiconductor lasers that we can modulate directly,
so no need for the AOM on the NeHe laser.

Cheers,
Magnus

Hi

If you are going to thermally excite the resonator, and measure the resonance optically, there’s no reason at all to use quartz. There are other materials with much higher acoustic Q than quartz.

Bob

On Apr 21, 2014, at 9:47 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

No. There is just a little rectangular quartz wafer. No plating.

In fact, post WWII, when many ham transmitters were 'rock bound' (ie:
crystal conteolled) it was common pratice to regrind mil surplus rystals
to move them into the ham banda.

Apparently, some were also etched using a cleanser called Whink, which
contains a flourine compound.

Also, some advocated applying graphite from a pencil lead was used to
decrease the frequency.

If the crystal ativity was low, they were taken appart and cleaned.

-John

==============

Hi

Early in the WWII era, quartz blanks were not commonly etched after begin ground / polished to frequency. This left debris on the surface of the blank. The net result was that the resonators failed after a period of time in the field, especially under damp conditions. The problem got so bad that it actually threatened the ability to communicate in 1942. A fairly high level team looked into the issue and etching of blanks (and a few other mods) were made a mandatory part of all crystals suppled to the government. Ammonium bi-flouride and water was the most common etchant in that era. There are a number of papers about the whole deal in the FCS, and many stories told by those who were part of the changes.

Bob

On Apr 21, 2014, at 10:10 AM, J. Forster jfor@quikus.com wrote:

In message A5032606-D7D7-4231-B1BD-434670274532@rtty.us, Bob Camp writes:

The story is slightly more interesting than that:

Blileys crystals were almost totally without these problems, but
they wouldn't tell why that might be.

In the end the government put a lot of pressure on Bliley to squeeze
out the manufacturing secret.

The secret was etching.

To keep it secret, Bliley had called it something along the lines
of "X-Grind" and not applied for a patent.

The Government forced Bliley to share the etching secret without
giving any compensation, and the Blileys were bitter about that for
the rest of their lifes.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Who said they were plated?

-Chuck Harris

J. Forster wrote:

The etching referred to was by post-war hams,

-John

===============

Hi

As with all “good stories” there are many versions told by many people. I’ve heard far to many mutually contradictory versions to have any real idea what’s true. You are correct that etching was a known process in the 1930’s and that it had been used by various people at various times. Since it added time (and complexity) to the process, it got dropped by most people to speed up production …

Bob

On Apr 21, 2014, at 10:51 AM, Poul-Henning Kamp phk@phk.freebsd.dk wrote:

Hi

Well I can name at least one post war ham (me at age 14) who did not understand the need for etch after grinding…

Bob

On Apr 21, 2014, at 11:21 AM, J. Forster jfor@quikus.com wrote:

When this question was first posed, AOM's first jumped to my mind. An AOM (sometimes AOD) is an Acousto-Optic Modulator that works by setting up an acoustic wave in a crystal. When a laser is directed through (or reflected by) an AOM, it is deflected.

One way to think about this is the crystal lattice deforms with the period of the acoustic wave. The lattice deformations form a grating of regions of varying indices of refraction which produce varying phase delay. This steers the beam just as a grating would.

Another way of thinking about it is the 'phonon's' momentum and the photon's momentum add producing a deflection (like two billiard balls colliding). This might seem impossible, but the math works out exactly..

Another nice thing is, if you recall, the EM field produced in the far-field of a coherent EM wave impinging on a grating is the Fourier Transform of the grating itself. In something like a CD, the grating has hard edges, producing lots of harmonic content. AOMs look like sine waves, most of the energy ends up in the deflected beam.

AOMs are often constructed using quartz crystals because they are fairly broadband (optically) and piezoelectric. The piezoelectric properties make it easy to set up the acoustic wave in the crystal.

The key difference is, AOMs are typically designed to absorb as little power as possible (power absorption is their primary failure mechanism). Depending on your laser, you might want to find an AOM that is less transparent in your excitation regime.

That said, you can get a lot of energy out of lasers these days. Megawatt pulses are not impossible with something like a Kerr-lens mode locked laser. This results in extremely high electric fields (MW pulse in 0.1 mm^2).

Andy Bardagjy
bardagjy.com

On Apr 21, 2014, at 6:47 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:

I'll have to check (dig it out from under a pile of gear.....) but if I remember correctly the HRO receiver (at least the early, pre-war, ones) had a 'non-contact' crystal holder for the IF notch filter. The crystal was a block about 1/2" square and a bit less thick (-ish) and fitted loosely between two support plates which incorporated the electrodes. It was certainly not a tight fit and the crystal could be easily removed.

Paul Reeves        G8GJA

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Chuck Harris
Sent: 21 April 2014 14:01
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] optically excite a quartz crystal?

I'm puzzling over this statement.  The FT-243's I have seen have a spring
that squishes the quartz blank between the electrodes.  They aren't plated
onto the quartz, but they are still in intimate mechanical and electrical
contact.

-Chuck Harris

Bob Camp wrote:

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