Simulation of mode deflection and reshaping in lithium niobate planar waveguide with serrated array electrodes
In this paper, we establish a lithium niobate (LN) thin film planar waveguide model with serrated array electrode configuration to reshape the optical mode. The refractive index profile of the waveguide can be slightly electro-optically manipulated, so the optical beam can be deflected and reshaped in the transmitted direction of waveguide. When the beam deflection can be modulated via the high speed electro-optic effect of LN, the temporally and spatially beam smoothing can be potentially achieved for the application of inertial confinement fusion system.
Improved laser‐beam uniformity using the angular dispersion of frequency‐modulated light
A new technique is presented for obtaining highly smooth focused laser beams. This approach is consistent with the constraints on frequency tripling the light, and it will not produce any significant high‐intensity spikes within the laser chain, making the technique attractive for the high‐power glass lasers used in current fusion experiments. Smoothing is obtained by imposing a frequency‐modulated bandwidth on the laser beam using an electro‐optic crystal. A pair of gratings is used to disperse the frequencies across the beam, without distorting the temporal pulse shape. The beam is broken up into beamlets, using a phase plate, such that the beamlet diffraction‐limited focal spot is the size of the target. The time‐averaged interference between beamlets is greatly reduced because of the frequency differences between the beamlets, and the result is a relatively smooth diffraction‐limited intensity pattern on target.
The Invariance of the Vacuum is the Invariance of the World
The following theorem is demonstrated: If the vacuum is invariant under the group generated by the space integral of the time component of a local vector current, then the Hamiltonian is invariant also. A similar theorem holds for the group generated by the space integral of a space component of a local axial-vector current.