Suppression of self-focusing through low-pass spatial filtering and relay imaging

Abstract

Self-focusing effects in large, high power laser amplifiers become manifest as small-scale beam instabilities and as large-scale phase aberrations. Spatial filtering has been shown to control instabilities; spatial filters constitute appropriate lens pair elements for image relaying as well. In this paper, image relaying is presented as a technique for preserving the transverse intensity profile of a high power beam as it propagates long distances through nonlinear elements. As a consequence, amplifier apertures can be filled more effectively, leading to a doubling of fixed-aperture system performance. A rationale for optimal selection of spatial filter bandpass is also presented. This selection, as might be expected, depends upon details of the beam's spatial structure as it enters any filter. A geometrical optics approach is used throughout; nevertheless, derived results remain valid when diffraction is included.

Development of a two arm, high energy, high power laser for plasma research in India

“…The control circuit and the power supply are isolated from each other by an isolation amplifier and an opto-coupler. The laser is sequentially relayed and spatially filtered laser system to control the degradation of spatial beam quality of the laser [6] as can be seen from Figure 1, which shows the layout of the laser system. The laser beam has a net accumulated nonlinear phase (B integral) contribution of 2 Np or less.…”

270-W 15-kHz MOPA System Based on Side-pumped Rod-type Nd:YAG Gain Modules

“…The image relay with two positive lenses, as shown in Fig. 1, is a wellknown technique [10], but needs to be analyzed with ABCD-matrix for the understanding of its unique characteristics. The ABCD-matrix of the two-lens image relay can be calculated as follows.…”

“…If L=f 1 +f 2 , above equation becomes a well-known image relay formula in a confocal configuration [10] (m ㆍd 1 +d 2 /m=f 1 +f 2 , m=f 2 +f 1 ). One can see that the above equation is always satisfied regardless of L if d 1 =f 1 and d 2 =f 2 .…”

High-power pulsed lasers

“…[96][97][98]. The best fill factor that can presently be obtained by using image relaying 99 is T -0.8. Even with perfect relaying, diffraction from dirt, from inad vertent "edge clipping," or from self-focusing intensification, raises intensily peaks above the average mainbeam intensily.…”