Systems for controlling the intensity variations in a laser beam and for frequency conversion thereof
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 time 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.
- Research Organization:
- The University of Rochester (Rochester, NY)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC08-85DP40200
- Assignee:
- The University of Rochester (Rochester, NY)
- Patent Number(s):
- US 4961195; A
- Application Number:
- PPN: US 7-228131
- OSTI ID:
- 7159875
- Resource Relation:
- Patent File Date: 3 Aug 1988
- Country of Publication:
- United States
- Language:
- English
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System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)
System for obtaining smooth laser beams where intensity variations are reduced by spectral dispersion of the laser light (SSD)
Related Subjects
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-)