One-dimensional (1-D) chalcogenide polymeric compounds APSe6 (A = K, Rb) undergo a reversible crystal-glass phase transition and exhibit strong nonlinear optical (NLO) responses even in the amorphous phase, implying a preservation of local crystallographic order in the latter. We have investigated the second harmonic generation (SHG) and difference frequency generation (DFG) properties of these materials as a function of wavelength. APSe6 crystallize in the polar orthorhombic space group Pca21 with infinite 1-D chains of 1∞[PSe-6] that are separated by A+ cations. We find that the crystalline APSe6 compounds are type-I phase-matchable with a secondorder NLO coefficient X(2) ≃ 150 pm/V, which is the highest among known phasematchable NLO materials with bandgaps over 1.0 eV. The glassy APSe6 compounds exhibit SHG intensities comparable to those of AgGaSe2, which is a benchmark IR NLO material. We demonstrate that APSe6 can be engineered into various structural morphologies such as 1-D fibers and 2-D thin films with strong, intrinsic, and temporally stable NLO properties. The as-prepared glassy fibers and films exhibit SHG and DFG responses and optical transmission over a wide range of wavelengths. This implies that the APSe6 compounds could be utilized as active NLO media for mid-IR frequency conversion. Raman spectroscopy and pair distribution function (PDF) analysis provide further understanding of the local structure in glassy fibers and films. In addition we show that annealing glassy structures yields strongly enhanced NLO responses. We propose that our approach can be readily applied to prepare stablemid-IR NLO fibers and films for practical applications.
|Title of host publication
|New Developments in Photon and Materials Research
|Nova Science Publishers, Inc.
|Number of pages
|Published - Dec 1 2013
ASJC Scopus subject areas
- General Physics and Astronomy