A high peak-power mid-IR optical amplifier using a potassium titanyl arsenate (KTiOAsO 4) is also reported in. The mid-IR spectral regions up to ~4 µm could be readily accessible with the oxide NLO crystals such as lithium niobate (LiNbO 3), lithium tantalate (LiTaO 3), and potassium titanyl phosphate (KTiOPO 4). Nonlinear optic (NLO) crystals-particularly with second-order nonlinearities-have been spotlighted as a material platform for converting the wavelengths of existing lasers into the mid-IR spectral region or for realizing tunable lasers. The field of mid-infrared (IR) photonics is growing rapidly due to increasing demand for applications such as free space communications, remote sensing, environmental monitoring, thermal imaging, defense, IR countermeasure, medicine, gas sensing, and molecular fingerprint spectroscopy. Such broadband SHG using short pulse trains can potentially be applied to frequency up-conversion imaging in the mid-IR region, in information transmission, and in nonlinear optical signal processing. The corresponding SH spectral range spans from 1758.58 to 4737.18 nm in the non-oxide crystals considered in this study. The results will show that the spectral bandwidths of the fundamental wave allowed for broadband SHG to reach several hundreds of nm. We will describe broadband SHG characteristics in terms of beam propagation directions, spectral positions of resonance, effective nonlinearities, spatial walk-offs between interacting beams, and spectral bandwidths. The technique is based on group velocity matching between interacting waves in addition to birefringent phase matching. In this paper, we theoretically and numerically investigated the broadband SHG properties of non-oxide mid-IR crystals in three categories: chalcopyrite semiconductors, defect chalcopyrite, and orthorhombic ternary chalcogenides. In particular, the spectral coverage could be extended to ~19 µm with non-oxide NLO crystals. The second-order nonlinear optic (NLO) crystals have been spotlighted as a material platform for converting the wavelengths of existing lasers into the mid-IR spectral region or for realizing tunable lasers. Read more about how to correctly acknowledge RSC content.The mid-infrared (mid-IR) continuum generation based on broadband second harmonic generation (SHG) (or difference frequency generation) is of great interest in a wide range of applications such as free space communications, environmental monitoring, thermal imaging, high-sensitivity metrology, gas sensing, and molecular fingerprint spectroscopy. Permission is not required) please go to the Copyright If you want to reproduce the wholeĪrticle in a third-party commercial publication (excluding your thesis/dissertation for which If you are the author of this article, you do not need to request permission to reproduce figuresĪnd diagrams provided correct acknowledgement is given. Provided correct acknowledgement is given. If you are an author contributing to an RSC publication, you do not need to request permission Please go to the Copyright Clearance Center request page. To request permission to reproduce material from this article in a commercial publication, Provided that the correct acknowledgement is given and it is not used for commercial purposes. This article in other publications, without requesting further permission from the RSC, ![]() Lin,Ĭreative Commons Attribution-NonCommercial 3.0 Unported Licence. To improve the key properties of nonlinear optical crystals assembled with tetrahedral functional building units This work may afford some inspiration for enhancing the key performances of NLO crystals assembled with non-π-conjugated tetrahedra. It is interesting that ABAF shows vast structural similarities to the typical NLO crystals Sr 2Be 2B 2O 7 (SBBO) and KBe 2BO 3F 2 (KBBF), which might be the partial reason why it showed improvement in these vital properties. ![]() Notably, both SHG coefficient and birefringence of ABAF exceeded those of a great majority of phosphates, sulfates, or boron phosphates and achieved a preferable balance. Hence, we investigated for the first time the NLO-related properties of NH 4BAsO 4F (ABAF), which was constructed from tetrahedral and FBUs, and enhancements of these properties were observed in this material, that is large second-harmonic generation (SHG) response (2 × KDP) and improved birefringence (0.03 at 1064 nm). It is currently proposed that partially substituting oxygen atoms with fluoride atoms in these FBUs could enhance these crucial properties. Nonlinear optical (NLO) crystals assembled with conventional non-π-conjugated tetrahedral functional building units (FBUs), generally referring to and, usually exhibit weak nonlinearity and poor birefringence.
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