Second‐Order Nonlinear Optical Switch of a New Hydrogen‐Bonded Supramolecular Crystal with a High Laser‐Induced Damage Threshold

Abstract

advantages, such as large NLO effects, ultrafast responses, and high laser-induced damage thresholds. Several organic molecules and metal-organic compounds have displayed NLO switching in solution, by utilizing the chemical procedures of protonation, two-photon absorption, or oxidation/reduction. [ 2 ] However, the search for highly effi cient solid-state switches remains a challenge, particularly for second-harmonic generation (SHG) activities, because the macroscopic noncentrosymmetric (NCS) arrangement of NLO moieties must be reversibly controlled in a collective manner. [ 3 ] As far as we are aware, only a few solid-state SHG switches have been reported, including organometallic thin fi lms for redox switching, photochromic anil crystals and polymer fi lms, etc. [ 4 ] The switching-induced irreversible changes of the initial chromophore alignment severely limits the number of "on"/"off" cycles in these cases. Moreover, their inferior resistance to laser-induced damage also suppresses the NLO switching effi ciency, [ 5 ] since materials should suffer from high-power laser radiation and thus high laser-induced damage thresholds are essential.Crystalline materials with phase transitions (PTs) have attracted great interest, [ 6 ] since they display outstanding performances around the transition point ( T c ) and their bulk physical properties can be modulated. [ 7 ] In this context, thermally driven structural deformations during PTs afford a great possibility for high-performance SHG switches. Using this conceptually new scheme, simple organic salts and organic-inorganic hybrids have been reported to be potential NLO switches. [ 8 ] During our investigation of novel SHG modulators, H-bonded materials with long-range order of their dipolar arrangement provide us with promising SHG switch candidates. One of our strategies is to discover the hidden pseudo-symmetry induced by hydrogen bonds, [ 9 ] which may be destroyed during PTs and arouse macroscopic dipole moments, corresponding to the generation of SHG signals. [ 10 ] In the present work, a new supramolecular crystal, bis-(imidazolium hydrochlorate) dihydrate 18-crown-6 ( 1 ), is fi rstly reported as a solid-state SHG modulator with a superior switching contrast (∼12) and remarkable switching reversibility. Strikingly, its laser-induced damage threshold (up to ∼8.9 GW/cm 2 ) is much higher than other materials, which guarantees its conversion effi ciency under the high-power laser. As far as we Organic nonlinear optical (NLO) materials are anticipated as the competitive successors to inorganic compounds in the highly controllable photonic devices. Here, a new supramolecular crystal, bis(imidazolium hydrochlorate) dihydrate 18-crown-6 ( 1 ), behaves as a potential modulator of quadratic NLO responses. It is found that ( 1) possesses a superior NLO switchingcontrast of up to ∼12, a remarkable switching reversibility, and a quite high laser-induced damage threshold (up to ∼8.9 GW/cm 2 ), which may guarantee its device application. In addition, mechanism stu...

Growth and Property Investigations of Two Organic–Inorganic Hybrid Molecular Crystals with High Thermal Stability: 4-Iodoanilinium perchlorate 18-crown-6 and 4-Iodoanilinium Borofluorate 18-crown-6

“…[(2,6-diisopropylanilinium)([18]crown-6)]BF4 go through two phase transitions at T1 = 305 K and T2 = 120 K, and Ps and Pr reaching about 0.3 and 0.25 μC/cm 2 at 100K, with a large dielectric anomaly, significant pyroelectricity, and SHG response appeared [27]. Bis(imidazolium hydrochlorate) dehydrate 18-crown-6 displays attractive switching performances with a superior second-order nonlinear optical switching contrast (calculated by Landau theory) of 12 at about 0 K, and a phase transition occurred at 220 K [28]. (4-HNA)(18-crown-6)(HSO4) underwent phase transition at about 255 K with space group of P21/c in the high-temperature phase and P21/n in the low-temperature phase [29].…”

“…(2,6-diisopropylanilinium)([18]crown-6)](ClO4) [26] T1=278 T2=132 Ferroelectric Ps=0.35 μC/cm 2 (4-nitroanilinium)2(18-crown-6)2(PF6)2(CH3OH) [29] 265 -----(4-nitroanilinium)(18-crown-6)(HSO4 [29] 255 -----Bis(imidazolium hydrochlorate) dehydrate 18-crown-6 [28] 220…”

“…For example, the ferroelectric property was observed in 4-methoxyanilinium perrhenate 18-crown-6 [25] but was not detected in 4-ethoxyanilinium perchlorate 18-crown-6present [32], although the difference (methoxyl or ethyoxyl) of the two amine derivatives is very small. Ferroelectric P s = 0.35 µC/cm 2 (4-nitroanilinium) 2 (18-crown-6) 2 (PF6) 2 (CH3OH) [29] 265 -----(4-nitroanilinium)(18-crown-6)(HSO 4 [29] 255 -----Bis(imidazolium hydrochlorate) dehydrate 18-crown-6 [28] 220…”

“…A large number of crown type molecular materials have been synthesized in the recent decades [23][24][25][26][27][28][29][30][31][32][33][34]. For example, 4-methoxyanilinium tetrafluoroborate-18-crown-6 shows a second-order ferroelectric phase transition at 127 K, together with an abrupt dielectric anomaly, Debye-type relaxation behaviour [24].…”

UV-Induced Anisotropy In CdBr2-CdBr2: Cu Nanostructures

“…The optically operated devices like optical triggers [1][2][3][4] requires intensive search of materials possessing high sensitivity to laser light. Particular interest presents the UVoperated devices [5].…”