Large optical third-order nonlinearities in a switchable Prussian blue analogue

Abstract

We report on the observation of an efficient coherent up-conversion via third harmonic generation (THG) in Rb 0.94 Mn[Fe(CN) 6 ] 0.98 .0.3H 2 O material. Our THG measurements at fundamental wavelengths ranging from 1200 to 2400 nm show that, in this spectral range, the THG signal overcomes the signal generated by frequency doubling. This demonstrates that this material possesses significant third-order nonlinear optical (NLO) responses. Its effective χ (3) value is at least two orders of magnitude greater than α-Quartz. We also demonstrate that this material exhibits a broad thermal hysteresis loop around room temperature, which makes it possible to simultaneously photo-commute its linear and thirdorder nonlinear optical properties.

Second‐Harmonic and Terahertz Generation in a Prussian‐Blue Analogue

“…These two irises fix precisely the position of the sample. [7] Then the sample is removed and the ZnSe window is installed in such a way that the excitation reflected by its front surface passes through the center of these two irises. Moreover, to ensure we detect only the SHG generated at the surface of the ZnSe window, a razor blade placed on the top surface of the ZnSe window was used to block the SHG signal reflected by the back surface of the latter.…”

“…The latter expression is slightly different from the one we previously derived. [7] It now takes into account the multiple reflections of the SHG signal by the different interfaces. Equations (1), (2), and (3) stress that the SHG signal strongly depends on the indices and absorption of the studied material at the second-harmonic wavelength (λ/2).…”

“…This value is very close to the one previously published for this sample and it indicates that two-photon absorption, which has been considered by previous authors in second-and third-harmonic generation experiments, is likely negligible in our sample. [7,19,20] However, in the LT phase, xvz (2) presents clear dispersion. Below 1.2 μm, it rapidly increases, and at 1.1 μm, it is ca.…”

“…We have recently shown that this makes it possible to optically photoswitch its third-order nonlinear optical properties. [7] Since the second-order nonlinear properties of these compounds are different in the LT and HT phases, it should be also possible to record the modulation of their second-order nonlinear properties as the sample is switched from the LT phase to the HT phase. To demonstrate this phenomenon, we performed an experiment very similar to the one we realized to demonstrate the photoswitching of the third-order nonlinear optical properties of Rb 0.94 Mn[Fe(CN) 6 ] 0.98 ·0.3H 2 O.…”

“…[1][2][3] Among these compounds, it has been shown that Prussian-blue analogues offer many prospects in nonlinear optics. [4][5][6][7][8] For instance, the cyano-bridged coordination polymer of Rb x Mn[Fe(CN) 6 ] (x+2)/3 ·zH 2 O switches from a centrosymmetric to a non-centrosymmetric and piezoelectric structure when one increases the Rb content above x = 0.7. [6] The non-centrosymmetric structure of the compound gives rise to second-order nonlinear optical properties that are revealed by second-harmonic generation (SHG) experiments.…”