We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.
Published online by Cambridge University Press: 18 January 2010
Scattering of light by acoustic waves was first investigated by Brillouin. The acoustic frequencies involved in Brillouin scattering fall in the ultrasonic and hypersonic regions. Hypersonic waves in a medium are caused by thermal excitation, whereas ultrasonic waves can be excited electronically using piezoelectric transducers. The acoustic waves used in acousto-optics are generally ultrasonic waves that have frequencies in the range between about 100 kHz and a few gigahertz. The basic principles of acousto-optic devices are based on the scattering of light by the periodic index variations generated by an acoustic wave in the supporting medium. These periodic index variations form a moving index grating, generated by a traveling acoustic wave, or a standing index grating, generated by a standing acousticwave. Because the speed of sound in dielectric media that are used for device applications typically falls in the range between 1 and 10 km s-1, the index gratings generated by ultrasonic acoustic waves have grating periods ranging from the order of 1 μm to a few centimeters. A unique property of the index grating created by an acoustic wave is that its period and modulation depth can be varied by varying the frequency and amplitude, respectively, of the acoustic wave through variation in the electronic signal applied to the transducer. Therefore, the operating parameters of an acousto-optic device can be controlled electronically. Practical acousto-optic devices include modulators, beam deflectors, frequency shifters, couplers, switches, and spectrum analyzers.
Elastic waves
An acoustic wave in a medium is an elastic wave of space- and time-dependent periodic deformation in the medium.
To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.
