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Matching the Electron Beam and Light Beam Velocities to Obtain Greater Power from Longitudinally Pumped Gas Lasers

IP.com Disclosure Number: IPCOM000080886D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Dreyfus, RW: AUTHOR [+3]

Abstract

A system is provided for improving the efficiency of an ultraviolet laser, when pumped by an electron beam traveling a path that is along the axis of the laser.

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Matching the Electron Beam and Light Beam Velocities to Obtain Greater Power from Longitudinally Pumped Gas Lasers

A system is provided for improving the efficiency of an ultraviolet laser, when pumped by an electron beam traveling a path that is along the axis of the laser.

When radiation is produced in an ultraviolet emitting laser, employing H(2) or N(2) gas as the active medium, by sending a pumping beam of electrons along the longitudinal axis of the laser, the maximum laser power is limited in that the electron beam (E-beam) transfers its energy slowly to the gas,because the speed of an electron beam traveling longitudinally through the laser tube is only 85% that of the speed of laser light traveling through the same laser tube. By effectively slowing down the speed of the light beam in the laser cavity so that the speed matches that of the electron beam, greater power is transferred from the electron beam to the light beam.

It has been determined that the group velocity upsilon(g) of light in a laser cavity is equal to c/1 + beta, where c is the velocity of light and beta = alpha(1n2)/1/2// pi/3/2/ delta approx. upsilon(D) with alpha = gain/cm, and delta upsilon(D) = Doppler linewidth (in cm/-1/). Assuming the following operating conditions: a 10 kA/cm/2/ Febetron electron beam, deuterium gas at 15 degrees K, one obtains delta approx. upsilon(D) = 0.090 cm/-1/ and alpha = 0.3 cm/-1/. The value of beta is then 0.64, hence upsilon(g) approx. c/1.64 = 0.61 c. At 296 degrees K, beta = 0.0336 and upsilon(g) = 0.966 c.

The above relationship indicates that changing the temperature of the H(2) or N(2) in the laser cavity would be sufficient to slow down upsilon(g), to equal that of the electron-beam velocity and achieve improved coupling between the pumping electron beam and the laser light.

It is noted that beta will actually be a function of time when the laser is operating near...