Third harmonic order imaging as a focal spot diagnostic for high intensity laser-solid interactions

摘要

As the state of the art for high power laser systems increases from terawatt to petawatt level and beyond, a crucial parameter for routinely monitoring high intensity performance is laser spot size on a solid target during an intense interaction in the tight focus regime (〈;10 )1m). Here we present a novel, simple technique for characterizing the spatial profile of such a laser focal spot by imaging the interaction region in third harmonic order (3___(laser)). Nearly linear intensity dependence aser of 3___(laser) generation for interactions 〉10~(19) Wcm~(-2) is demonstrated experimentally and shown to provide the basis for an effective focus diagnostic. Importantly, this technique is also shown to allow in-situ diagnosis of focal spot quality achieved after reflection from a double plasma mirror setup for very intense high contrast interactions (>10~(20) Wcm~(-2)) an important application for the field of high laser contrast interaction science.