Title: Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof

Abstract

In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temporal oscillations which average out rapidly in timemore » thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation. 16 figs. « less

Inventors:

Skupsky, S; Craxton, R S; Soures, J

Issue Date:

Tue Oct 02 00:00:00 EDT 1990

Research Org.:

The University of Rochester (Rochester, NY)

Sponsoring Org.:

USDOE

OSTI Identifier:

7159875

Patent Number(s):

4961195

Application Number:

PPN: US 7-228131

Assignee:

The University of Rochester (Rochester, NY)

DOE Contract Number:  

FC08-85DP40200

Resource Type:

Patent

Resource Relation:

Patent File Date: 3 Aug 1988

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; LASER RADIATION; BEAM SHAPING; LASER TARGETS; ILLUMINANCE; BEAM OPTICS; BEAM PROFILES; COLLIMATORS; DIFFRACTION GRATINGS; EMISSION SPECTRA; FREQUENCY CONVERTERS; INERTIAL CONFINEMENT; CONFINEMENT; ELECTROMAGNETIC RADIATION; GRATINGS; PLASMA CONFINEMENT; RADIATIONS; SPECTRA; TARGETS; 700411* - Inertial Confinement Devices- (1992-)