Fig1: A typical
GCLAD setup used for sensing
ultrasound in materials. The
shown is greatly exaggerated.
primary challenge is the
of the photodetector. The deflections,
as you can imagine, are quite
The Quarktet photodetector has been
optimized for sensitivity to beam
deflections at ultrasonic frequencies.
We have several prototypes and
ideas for further improvements.
We also have ideas
system sensitivity, such as multi-pass
detection, and multiple beam
that would dramatically improve the
sensitivity we have gained to date.
For further information, see our research
Fig2: Quarktet's Dulcian
Detector, built for a customer
who is using ultrasound to
interrogate skin tissues.
little difference between detecting
ultrasound and audible sound as far
as the concept is concerned.
Changes in the air's index
of refraction caused by the sound
waves deflect the beam of the light
from its original path. To
maximize sensitivity, a
photodetector is used, and we have
developed some simple
technique has been used to record such
acoustic waveforms as clapping,
human voice at normal, and musical
instruments. Shown in the
below is a sound wave produced by a
bassoon, played by the
| Fig 3:
notes played on a
bassoon and recorded by
|| Fig 4:
transform of the
tones. As evident
in the sound wave, the
easy to envision some applications
where this technology would be
useful, such as remote sound
recording, and directional
recording. However, this concept
has never fully taken root for
fear that the lasers involved would be
to expensive to justify.
This need not necessarily be the
case. Using improved
electronics, and multi-path detection,
the price tag can be reduced