Oscillations, Waves, and Interactions - GWDG

Applied physics at the “Dritte” 11
nomena using ultrasound were immediately developed in Göttingen [87]. A cinematograph
was constructed that allowed for picture sequences of oscillating bubbles at a
picture repetition rate up to 65 000 per second [88]. Soon interest was directed towards
nonlinear vibration characteristics of bubbles in water [89] and, in a series of
papers [90–92], the occurrence of sonoluminescence in the sonically induced bubbles
was reported.
Lauterborn generated cavitation bubbles by focusing giant pulses from a ruby laser
into liquids [93]. He investigated the bubble dynamics by high-speed cinematography
with picture repetition rates up to 900 000 per second [94]. For his fundamental contributions
to the field he was awarded the Physikpreis of the Deutsche Physikalische
Gesellschaft (German Physical Society) in 1976.
Since then many aspects of cavitation are being investigated by Lauterborn and
his group. Bubble dynamics was studied experimentally and theoretically [60,61,
95]. Much emphasis was placed on the spatial distribution of bubbles in cavitation
structures and on the collective phenomena of bubble clusters. The chaotic behaviour
of bubbles as reflected in the properties of sound waves radiated from cavitation
structures opened new vistas in nonlinear acoustics of fluids [96] and added a new
experimental branch to nonlinear physics [97,98]. It had a considerable influence on
various of the institute’s areas of research [99] (see section 9 of this article). The
fascinating features of sonoluminescence have been an enduring topic of interest [100,
101]. Also neutrons in close temporal proximity to cavitation luminescence were
searched for [102].
An appealing characteristic of the field is the combination of basic research with a
multitude of applications. Biologically and medically related applications are briefly
mentioned in section 13 on “Biophysics”. Some are described in greater detail in
other contributions to this book [103,104]. Use of high power ultrasound in chemical
processing and cleaning is also based on energy concentration by bubble collapse [105,
106].
8 Optics and Holography
Common photographic techniques and high-speed cinematography are rather limited
when three-dimensional bubble clusters are to be recorded. Superior images of cavitation
structures were obtained using holography [107]. Shortly after the invention
of the laser, this method to store three-dimensional images became very popular
worldwide. At the institute holography was not just used for imaging but also for
generation of cavitation bubble systems [108].
Werner Lauterborn and Karl Joachim Ebeling took a big step forward by conceiving
high-speed holocinematography [109,110]. Spatial and spatial-frequency multiplexing
techniques were applied to achieve image separation during the reconstruction
process. Acousto-optic modulators [110,111] were employed as beam splitters
and deflectors. Up to eight holograms were successively recorded at a maximum
frame rate 20 000 s −1 to show the interactions of laser-produced bubbles. Combining
rotation of the holographic plate and acousto-optic beam deflection, the capability
of high-speed holocinematography was extended to record up to 4,000 holograms