Browse Prior Art Database

Acoustic Light Deflector Chromatic Variation Compensation

IP.com Disclosure Number: IPCOM000073881D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Brown, BR: AUTHOR [+2]

Abstract

The wavelength emitted by a GaAs laser varies spasmodically over about a 100 Angstroms bandwidth, centered at 8500 Angstroms. When used with an acoustic deflector, this results in a chromatic variation in deflection position.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 77% of the total text.

Page 1 of 2

Acoustic Light Deflector Chromatic Variation Compensation

The wavelength emitted by a GaAs laser varies spasmodically over about a 100 Angstroms bandwidth, centered at 8500 Angstroms. When used with an acoustic deflector, this results in a chromatic variation in deflection position.

The deflection theta in a Bragg cell 1 is given by theta lambda where lambda is the light wavelength, f the driving frequency and v the velocity of sound. A change d lambda gives an increment in theta given by dtheta = d lambda over v (1).

Now let a small angle (<15degrees) prism 2 be placed after the acoustic deflector 1; its deflection delta is (n-1)a where a is the angle of the prism, and the increment dzeta due to a change delta n consequent to a d lambda is given by d delta = dn alpha (2).

The sum of (1) and (2) should clearly balance for the chromatic change in acoustic deflection to be nullified by the dispersive action of the prism, so that dn = - f over v alpha d (3).

Therefore, the chromatic difference is acoustic deflection is reduced to zero by passing the light, diffracted by the deflector, through a prism of suitable prism angle alpha and whose dispersive properties fulfill equation (3).

Generally, since the prism material would be different from that of the acousto-optic medium, prism and deflector would be separate entities as in A. However, for certain applications, prism and deflector may be made from one suitably cut piece of arsenic trisulphide 3, as shown in B.

As...