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Frequency conversion and beam shaping of high energy beams by transverse quasi phase matching

Laser frequency can be converted very efficiently nowadays using electrically field poled ferroelectric crystals, such as LiNbO3 or KTiOPO4. Unfortunately, these crystals are readily available only with relatively small aperture – up to 1 mm in the critical Z axis of the crystal – thereby severely limiting the ability of these crystals to convert high energy lasers, with pulse energies exceeding a few milli-Joules, or high peak powers lasers, exceeding several Mega-Watts.

Here we present a new configuration that removes this limitation. This is achieved by tilting the crystal, so that a much larger aperture can be achieved. Up until recently this configuration was considered useless due to the relatively low conversion efficiency. We have now found a way to overcome this limitation and reach high efficiencies for high energy pulses. Moreover, this configuration also enables spatially shaping the generated beam. In addition, the operating wavelengths can be tuned by slight change of the tilt angle.

This concept has already been demonstrated to work in the lab with low peak power sources. In this project, we are working to show the full potential of this method by 1) operating with high energy/peak power pump sources, 2) to study parametric amplification processes that are relevant to some of the potential industrial partners, and 3) to demonstrate the ability of replacing external bulk optical and mechanical elements such as lenses, beam shapers and pinholes with suitably designed nonlinear crystals.

• Conversion of high power solid state and fiber infrared lasers to the visible (potential interest to fiber laser manufacturers or nonlinear optical crystal manufacturers).
• Generation of mid-infrared coherent light by optical parametric oscillator or amplifier for infrared counter measures used in civilian applications. Medical applications may also exist where high energy radiation in the 2-3micron regime is required.
• The technology may also be relevant to companies that need high power ultraviolet lasers, or to Pharma companies that need infrared sources for monitoring their production. 

• Can handle high energy/high power sources.
• Enables compact manipulation of the generated beam.
• Can be tuned to operate at different wavelengths.