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Continuous Laser Deflection by Acoustic Bragg Diffraction Inside Degenerate Cavities

IP.com Disclosure Number: IPCOM000091878D
Original Publication Date: 1968-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Lean, EG: AUTHOR [+2]

Abstract

The techniques of acoustic Bragg diffraction at microwave frequencies can be used outside a laser cavity to deflect collimated laser teams. The angular bandwidth and the number of resolvable spots of the deflectors outside the laser cavity are related to the width of the acoustic column in the Bragg cell. In this device, an acousto-optic beam deflector is inside a degenerate laser cavity in which no limitation on the resolution is imposed by the acoustic beam width. The device consists of Bragg cell 1, either isotropic or anisotropic, in the middle of a degenerate cavity with half-mirrors 2 and 3 in both ends. Half of the degenerate modes are lasing in the cavity supported by the half mirrors in both ends.

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Continuous Laser Deflection by Acoustic Bragg Diffraction Inside Degenerate Cavities

The techniques of acoustic Bragg diffraction at microwave frequencies can be used outside a laser cavity to deflect collimated laser teams. The angular bandwidth and the number of resolvable spots of the deflectors outside the laser cavity are related to the width of the acoustic column in the Bragg cell. In this device, an acousto-optic beam deflector is inside a degenerate laser cavity in which no limitation on the resolution is imposed by the acoustic beam width. The device consists of Bragg cell 1, either isotropic or anisotropic, in the middle of a degenerate cavity with half-mirrors 2 and 3 in both ends. Half of the degenerate modes are lasing in the cavity supported by the half mirrors in both ends. The acoustic wave column in the Bragg cell 1 1 selects and couples out a set of transverse modes, which satisfy Bragg conditions.

For isotropic deflection the Bragg condition is given by sin theta = 1/2 lambda over v f where theta is the angle between the axis of the mode being selected and the acoustic wavefronts which are parallel to the axis of the cavity; v is the acoustic velocity, and f is the acoustic frequency. For the usual acousto-optic deflectors outside the cavity in which the incident beam is fixed at an incident angle theta with respect to the acoustic wave, the angular bandwidth is given by delta theta=lambda/Wsin theta where W is the width of the acoustic beam column. With the diameter D of the incident beam, the angular spread of the diffracted beam is delta alpha= lambda/D. The number of resolvable spots is N=(delta theta/delta alpha=D/Wsin theta which is inversely proportioned to the value of W.

In this device, the incident angle of the selected mode as well as that of t...