 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Acousto-Optic Modulators (AOM) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
By
virtue of having no moving parts our acousto-optic modulators (AOMs) are
able to amplitude modulate a laser beam at very high speed. For example
modulation bandwidths in excess of 50MHz are readily achievable. In
an AOM a laser beam is caused to interact with a high frequency
ultrasonic sound wave inside an optically polished block of crystal or
glass (the interaction medium). By carefully orientating the laser with
respect to the sound waves the beam can be made to reflect off the
acoustic wavefronts (Bragg diffraction). Therefore, when the sound field
is present the beam is deflected and when it is absent the beam passes
through undeviated. By switching the sound field on and off very rapidly
the deflected beam appears and disappears in response (digital
modulation). By varying the amplitude of the acoustic waves the
intensity of the deflected beam can similarly be modulated (analogue
modulation). It
is usual to choose the deflected beam as the one that is used in the
optical system because it can be switched on and off with high
extinction ratio (typically >40dB) and intensity can be varied from
zero to more that 85% of the incident beam. The rate at which the beam
can be modulated is governed by the time it takes the acoustic
wavefronts to traverse the laser beam, which depends on the beam
diameter and the acoustic velocity in the interaction medium. The
sound waves are generated by a transducer, usually a thin wafer of
lithium niobate, that is bonded onto the interaction medium using a
highly efficient cold-weld metallic bonding process. When a high
frequency electrical signal is applied to the transducer it vibrates,
generating the acoustic wave. The signal is derived from an RF driver,
which generates a high frequency carrier that is itself modulated by an
analogue or digital input signal. Principal
applications for AO modulators are pre-press (putting image and text
data onto films or plates as part of the printing process), laser
imaging and displays, switching in telecom fibres, instrumentation and
research.
1.
Free-space Acousto-optical Modulators
We
offer a wide range of standard AO Modulators, for digital or analogue
intensity modulation of laser beams.
Their main specifications are as follows:
An
RF
Driver provides
the electronic signal operating the AO Modulator. With a digital driver,
an external TTL signal enables rapid on and off switching of the optical
beam. Alternatively an anologue driver enables a variable intensity
output, typically from 0% to 85% of the input beam. The
maximum modulation bandwidth, or optical rise-time, is a function of the
acoustic transit time across the optical beam. Therefore, for the
highest speeds it is often necessary to focus the optical beam down to a
small spot inside the modulator. Our standard AOMs are listed below. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
2.
Fiber-coupled
Acousto-optical Modulators
(AOM)
Our
standard fibre-coupled AOMs are listed below. If you would like to see a
detailed technical data sheet just click on the relevant model number.
If you do not see a device that meets your requirements please contact
one of our engineers. We manufacture application-specific AOMs and would
be pleased to design one that meets your needs. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
We
offer a wide range of standard fibre-coupled AOMs with the following
characteristics: -
Options: Single mode, polarisation maintaining and multimode, with or without connectors. Available in two, three or four fibre package configurations. |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
More AOMs |
