Reply from Dave:
I was under the impression that laser beams could be modulated by
electro-mechanical mirrors which could possibly be useful at least up
to 100,000 Hz. Maybe taking different audio speaker system drivers and
glueing on some reflective materials like aluminum foil wrap on their
cones..even tweeters for the high end! Then drive the drivers with
signals! Titanium dome tweeters have a self resonance around 40khz, and
are already shiny, so I know they will go beyond that!
Remember, a laser listener system uses the subjects window to modulate
reflected steady state light back to the receiver!
I don't think that the beam of light sent to the mass under test has to
have a pin point of light on it. The light can be out of focus and
still serve the purpose?
Maybe if high output IR LED's driven by simple Class "B" pulsed driver
Bipolar or FET semiconductor stages fed with experimental frequencies
would be sufficient for results! Although the FET would only require
voltage drive, you may want to use a "source and sink" totem pole driver
stage. The "sink" side would slam off conduction by quickly discharging
the gates residual charge due to capacitance. This would insure that you
keep the poor LED from being stuck on a bit into class "AB" mode by a
partial D.C. current conduction flow and ending up being destroyed by
generated heat!
With such primitive tools like these, you can have Champagne taste on
a beer budget!
GO FOR IT!
<DAVE>