Lasers beams with a specific intensity profile such as super–Gaussian, Airy or Dougnut-like are desirable in many applications such as laser materials processing, medicine and communications. We propose a new technique for laser beam shaping by amplifying a beam in an end-pumped bulk amplifier that is pumped with a beam that has a modified intensity profile. Advantages of this method are that it is relatively easy to implement, has the ability to reshape multimode beams and is naturally suited to high power/energy beams. Both three and four level gain materials can be used as amplifier media. However, a big advantage of using three level materials is their ability to attenuate of the seed beam, which enhances the contrast of the shaping.

We first developed a numerical method to obtain the required pump intensity for an arbitrary beam transformation. This method was subsequently experimentally verified using a three level system. The output of a 2.07 μm seed laser was amplified in a Ho:YLF bulk amplifier which was being pumped by a 1.89 μm Tm:YLF laser which had roughly a TEM10 Hermit Gaussian intensity profile. The seed beam was amplified from 0.3 W to 0.55 W at the full pump power of 35 W. More importantly, the beam profile in one transverse direction was significantly shaped from Gaussian to roughly flat-top, as the model predicted. The concept has therefore been shown to be viable and can be used to optimise the beam profile for a wide range of applications.

Date Published: 3 March 2015
PDF: 6 pages
Proc. SPIE 9343, Laser Resonators, Microresonators, and Beam Control XVII, 93430S (3 March 2015); doi: 10.1117/12.2077586

Published in SPIE Proceedings Vol. 9343:
Laser Resonators, Microresonators, and Beam Control XVII
Alexis V. Kudryashov; Alan H. Paxton; Vladimir S. Ilchenko; Lutz Aschke; Kunihiko Washio, Editor(s)