title: Noncollinear third-harmonic generation with large angular acceptance by noncritical phase matching in KDP crystal.
abstract: The scheme of prefocusing to focus sum frequency generation (SFG) without a lens is proposed and experimentally verified in this study. Noncollinear type-I noncritical phase-matching SFG to generate a third-harmonic wave with large angular acceptance is presented. The principle of broad angular acceptance and the advantages of this PM configuration are also described in detail. External angular bandwidth of 7.33° for noncollinear SFG was measured in a 2 mm long KH2PO4 (KDP) crystal, which is in reasonably good agreement with the theoretical calculation. The mechanism of broadband SFG and the prefocusing scheme make it possible for the realization of convergent third-harmonic generation without involving a lens, which provides a promising way to avoid damage to optical components during the focusing of high-energy UV light in high-power laser facilities.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Yuanlin
authors.initials: Y
authors.lastname: Zheng
authors.forename: Ning
authors.initials: N
authors.lastname: An
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Chen