PHONON "LASER"?
910...@darwin.ntu.edu.au
phonons just like phonons in lasers? Maybe someone out there who
is working in this area or has read about it can fill me with details.
Thanks.
Ms Thila
NT University
Australia.
Matthew P Wiener
>I am wondering whether anybody has designed a coherent source of
>phonons just like phonons in lasers? Maybe someone out there who is
>working in this area or has read about it can fill me with details.
I haven't heard of anyone building such, but H Froehlich first described
them in the sixties and speculated that they exist in biological systems.
Here are a few references:
H Froehlich INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 2,p641 (1968)
S Webb Laser-Raman Spectroscopy of Living Cells PHYSICS REPORTS 60,p201 (1980)
H Froehlich INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 23,p1589 (1983)
G L Sewell QUANTUM THEORY OF COLLECTIVE PHENOMENA, Section 7.4 (1986)
--
-Matthew P Wiener (wee...@libra.wistar.upenn.edu)
John Whitmore
>I am wondering whether anybody has designed a coherent source of
>phonons just like phonons in lasers? Maybe someone out there who
>is working in this area or has read about it can fill me with details.
Yes, coherent phonon sources are available. One uses
an airflow as the excitation source (there must be some sort of
blockage, of course, to create phonons from the moving air),
and a resonator with partially-reflecting end conditions.
The result is a pure tone with (regrettably) poor directionality
in its output. Diffraction effects do not allow COLLIMATED
phonons in the relevant frequency range without awkwardly
large apparatus.
The device is called a 'whistle'.
John Whitmore
Masahiro Kitagawa
>I am wondering whether anybody has designed a coherent source of
>phonons just like phonons in lasers?
If two strong optical waves with frequency difference equal to the
phonon frequency are propagating in a crystal, the phase of phonon
tends to become well-defined due to Raman coupling. The two optical
waves can be generated from a single laser beam by acoust-optical or
electro-optical modulator. Therefore you can make a phonon replica of
the RF signal. This can be regarded as a coherent phonon generation.
Please check the textbooks of Nonlinear Optics since this is not my
recent working field.
masa *--- **** ***-- *--* *-* *-*
Masahiro Kitagawa
NTT Research Labs. Tokyo Japan
kita...@will.NTT.JP
Anthony E. Siegman
materials will cause the appearance of a coherent phonon beam and a
second coherent optical signal at a slightly lower frequency, the
latter traveling back in the opposite direction to the primary laser
beam.
This is essentially a "parametric oscillator" rather than a laser
effect, with the phonon beam and the second optical beam playing the
role of signal and idler waves for the parametric oscillator, and the
primary laser beam being the "pump", and is referred to as stimulated
Brilluoin scattering. The phonon frequency is typically in the high
microwave range, and the coupling mechanism is the acoustooptic
coupling between sound waves and light. The phonon beam can be very
intense.
2) In addition, if one prepares a microwave solid-state maser material
such as ruby, pumped with microwaves to produce a population inversion
on the Zeeman-split ground-state levels of the maser material, one can
then send in either (microwave) photons or (microwave) phonons at the
microwave transition frequency corresponding to the inverted
transition in the solid-state maser material, and one can thereby
amplify *either* the microwave photons or the microwave phonons. This
is referred to as a "phonon maser", and devices of this type were
built in the 60's or 70's. So far as I know they have no practical
use.
--AES