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Low Loss Double Pass System for Laser Amplifiers

IP.com Disclosure Number: IPCOM000076796D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Grischkowsky, DR: AUTHOR

Abstract

An arrangement of standard optical components is used to allow a beam of light to make two passes through a laser amplifier, yet suffer very little insertion loss due to these components.

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Low Loss Double Pass System for Laser Amplifiers

An arrangement of standard optical components is used to allow a beam of light to make two passes through a laser amplifier, yet suffer very little insertion loss due to these components.

The low-loss double-pass system can be of two types; type I uses a Faraday rotator (Fig. 1), and type II uses a quarter-wave plate (Fig. 2). In the following discussion it is assumed that all surfaces are antireflection coated, consequently only the unavoidable reflective losses will be considered.

For type I, the incident linearly polarized beam with intensity I(o) enters the system and is incident upon the Glan polarizer oriented for maximum transmission. In passing through the polarizer the beam suffers unavoidable reflective losses, of the order of 5%, at surfaces 1 and 2 of the Glan prisms. The beam emerges with intensity (1-R(1))(1-R(2)) I(o) and passes through the Faraday rotator, which rotates the polarization vector by 45 degrees by the Faraday effect. The beam then goes through the amplifier and emerges with intensity (1-R(1))(1-R(2)) g I(o), where g is the gain of the amplifier. After a 100% reflection at the reflectivity mirror, the beam goes through the amplifier the second time and emerges with intensity (1-R(1))(1-R(2)) g/2/ I(o). The beam passes through the Faraday rotator for the second time and the polarization is again rotated by 45 degrees, causing the polarization vector of the output beam to be perpendicular to the polarization vector of the input beam. Because of the 90 degrees rotation of the polarization vector, the output beam is entirely reflected by the polarizer, as shown in Fig. 1, and emerges with intensity (1-R(1)) (1-R(2)) g/2/ I(o). The only insertion loss for the system is given by [1-(1-R(1))(1- R(2))], which is typicall...