skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A Single-Lens Laser Beam Shaper for Uniform Flat-Top Profiles

Abstract

A novel design is presented for a simple laser beam shaping system. Unlike earlier reports and designs, we prove it is possible to convert a laser beam from a non-uniform profile to a uniform flat-top distribution with a single aspherical lens.

Authors:
; ;
Publication Date:
Research Org.:
Thomas Jefferson Lab National Accelerator Facility
Sponsoring Org.:
USDOE
OSTI Identifier:
955549
Report Number(s):
JLAB-ACC-03-04
Journal ID: ISSN 0003-6935; APOPAI; TRN: US1004694
DOE Contract Number:
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Optics
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BEAM SHAPING; DESIGN; DISTRIBUTION; LASERS; OPTICS

Citation Formats

Zhang, Shukui, Neil, George, and Michelle D. Shinn. A Single-Lens Laser Beam Shaper for Uniform Flat-Top Profiles. United States: N. p., 2006. Web.
Zhang, Shukui, Neil, George, & Michelle D. Shinn. A Single-Lens Laser Beam Shaper for Uniform Flat-Top Profiles. United States.
Zhang, Shukui, Neil, George, and Michelle D. Shinn. Sun . "A Single-Lens Laser Beam Shaper for Uniform Flat-Top Profiles". United States. doi:. https://www.osti.gov/servlets/purl/955549.
@article{osti_955549,
title = {A Single-Lens Laser Beam Shaper for Uniform Flat-Top Profiles},
author = {Zhang, Shukui and Neil, George and Michelle D. Shinn},
abstractNote = {A novel design is presented for a simple laser beam shaping system. Unlike earlier reports and designs, we prove it is possible to convert a laser beam from a non-uniform profile to a uniform flat-top distribution with a single aspherical lens.},
doi = {},
journal = {Applied Optics},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • We've generated high-quality flat-top spatial profiles from a modified Continuum Powerlite 9010 Nd:YAG laser using the Gaussian-to-flat-top refractive beam shaper available from Newport Corporation. The Powerlite is a flashlamp-pumped, Q-switched, injection-seeded Nd:YAG laser manufactured in 1993 that delivers 1.6 J at 10 Hz using an oscillator and two 9 mm diameter amplifier rods. While its pulse energy is impressive, its beam quality is typically poor, an all too common characteristic of research-grade Nd:YAG lasers manufactured in the late 1980's and early 1990's. Structure in its near-field spatial fluence profile is reminiscent of round-aperture diffraction that is superposed with additional hotmore » spots. These characteristics are largely due to poor beam quality from the oscillator coupled with over-filled amplifier rods, and reflect a design philosophy from the era of organic dye lasers. When these older laser systems are used for tasks like pumping optical parametric oscillators (OPO's), or for other applications demanding good beam quality, their designs are simply inadequate. To improve the 9010's beam quality we spatially filter the oscillator beam and remove the resulting Airy rings with an iris, then collimate and magnify the remaining central disk so its diameter is appropriate for input to the refractive shaper. The output of the beam shaper is then double-pass amplified through two amplifier rods with thermally induced focusing compensated by a negative lens before the first pass and by a convex mirror before the second pass. Using this approach we've obtained single-pass energy exceeding 250 mJ with little degradation of the flat-top profile and 950 mJ after double pass amplification. After double-passing the two amplifier rods the beam suffers some degradation in symmetry and uniformity, but is still much improved compared to the beam obtained using the 9010's original factory configuration. We find the modified 9010's flat-top profile improves conversion efficiency when used for our applications in crystal nonlinear optics.« less
  • A single lens bullet-shaped laser beam shaper capable of redistributing an arbitrary beam profile into any desired output profile comprising a unitary lens comprising: a convex front input surface defining a focal point and a flat output portion at the focal point; and b) a cylindrical core portion having a flat input surface coincident with the flat output portion of the first input portion at the focal point and a convex rear output surface remote from the convex front input surface.
  • Production of uniform (flat top) high energy laser beam profiles with relatively little beam energy loss is possible through the use of a modified kaleidoscope, multiple reflection beam scrambler.
  • A thermal lensing system using photodiode array detection is described for low-level molecular absorbance measurements. The beam profile is converted for use in the frequency (Fourier) domain rather than the spatial domain since this format seems to provide superior presentation. The effects of laser power and other design considerations are discussed.
  • The two-dimensional multi-lens array of 350 mm in diameter with spherical element lenses to improve the irradiation uniformity is tested. Circular and hexagonal shape of element lens aperture have been examined. The circular aperture is chosen for eliminating azimuthally asymmetric intensity distribution. An approximate flat-top intensity distribution is obtained with a lens array of 37 lenses. Beam patterns of coherent laser and partially coherent light (PCL) with the random phase plate (RPP) and the multi-lens array (MLA) are measured at GEKKO XII glass laser system. Spherical mode structure of the irradiation nonuniformity of MLA on a spherical target is calculatedmore » from the measured beam patterns. {copyright} {ital 1996 American Institute of Physics.}« less