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Browse Prior Art Database

Transducer for Dynamic Optical Cavity Length or Focus Control

IP.com Disclosure Number: IPCOM000104075D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 86K

Publishing Venue

IBM

Related People

Edelstein, DC: AUTHOR

Abstract

Figure - Top view (left) and cross-sectional view through segment A-A' of PZT optical transducer. Dotted lines on right show configuration during extension. BPZT=bimorphic PZT disc, AD=adaptor, M=laser mirror, S=spacer, G=glue, CF=copper foil, V=corrugated brass vane central to PZT disc, and V+, GND are electrical contacts to front+back, and center respectively.

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Transducer for Dynamic Optical Cavity Length or Focus Control

Figure - Top view (left) and cross-sectional view through segment
A-A' of PZT optical transducer.  Dotted lines on right show
configuration during extension.  BPZT=bimorphic PZT disc, AD=adaptor,
M=laser mirror, S=spacer, G=glue, CF=copper foil, V=corrugated brass
vane central to PZT disc, and V+, GND are electrical contacts to
front+back, and center respectively.

      A piezoelectric (PZT) transducer/laser mirror design is
disclosed for active length control of an optical cavity.  Compared
with conventional PZT actuators used for this purpose, it provides
superior amplitude and bandwidth performance, operates at low drive
voltages, provides optical access through a central bore hole, does
not sag during extension, and is very inexpensive.  This device may
be used for dynamic focussing systems, frequency and phase-locking of
multiple optical cavities, or length-stabilization of modelocked
lasers.

      The transducer is depicted in the Figure, which shows front and
cross-sectional views through points A-A'.  Dotted lines indicate the
configuration during extension.  A bimorphic PZT bilayer (BPZT) is
used, such as Vernitron "Bimorph"*, or for somewhat less extension
but lower cost, a Vernitron "Unimorph"*, which is a single PZT film
on a brass disc.  The bimorphic part is poled for parallel hookup,
with the outer two metallized surfaces shorted together by a strip of
copper foil (CF) and connected to the positive lead (V+), and the
brass strain-relief vane (V) connected to the negative lead (GND).
The disc is slightly less than 1" diameter, and is cemented into a
1"-diameter adapter (AD).  This allows easy implementation in
standard 1" optic mounts.  A central hole of 3-4 mm is easily bored
using a trepanning or ultrasonic tool, and a small metal spacer (S)
(a common flat washer) is cemented as shown.  A 1/2"-diameter laser
mirror (M) appropriate for the specific application is then cemented
to the spacer.  The spacer couples the central portion of the PZT
(which exhibits the most extension) to the mirror without fixing the
PZT at the larger diameter of the mirror.  Finally, wires are
soldered to the (metallized...