Thick Optical‐Quality Films of Substituted Polyacetylenes with Large, Ultrafast Third‐Order Nonlinearities and Application to Image Correlation

Abstract

Processable organic materials with large, ultrafast thirdorder susceptibilities, x (3) , could enable all-optical signal processing (AOSP) applications through either fabrication of large-area thick films or integration into hybrid organic/ silicon photonic devices. [1][2][3][4] Conjugated polymers, such as polyacetylene, have been shown to exhibit large optical nonlinearities upon application of intense electromagnetic fields.[3] Despite these nonlinearities, many conjugated polymers are inadequate for photonic applications because they lack sufficient processability, or form films with significant crystallinity [5] or inhomogeneous morphologies [6] resulting in poor optical quality. For example, although films of unsubstituted polyacetylene have been found to possess large third-order susceptibilities, [7][8][9] they also exhibit extensive crystallinity, [10] resulting in poor optical quality and large scattering losses.[11] A more processable soluble diester polyacetylene derivative has been reported; [2] however, only thin films have been produced from this material and the bulky side groups can be anticipated to lead to a reduced nonlinear response through a dilution effect. The diester polyacetylene was successfully used in an image-correlation application performed using degenerate four-wave mixing (DFWM) in the visible region with resonant excitation, although the diffraction efficiency was relatively low, due mainly to the limited interaction length. Ring-opening metathesis polymerization (ROMP) provides for the facile synthesis of a great variety of unsaturated polymers.[12] The ROMP method (Scheme 1) utilizes an organometallic alkylidene-based initiator (e.g., rutheniumbased Grubbs initiators [13][14][15] or four-coordinate tungsten-and molybdenum-based Schrock initiators [16][17][18] ) to polymerize strained-ring olefin monomers. [6,19] The ROMP process allows for in situ polymerization of liquid-phase monomers, which allows facile processing of neat films [11] as well as potential integration of the resulting polymers into micro-or nanostructured photonic devices. Moreover, this method is amenable to independent optimization of monomers and initiators to improve processing conditions, optical quality of films, and the third-order susceptibility of the resulting conjugated polymers.Here we report on the synthesis, processing, and linear and nonlinear optical characterization of substituted polyacetylenes obtained using ROMP of mono-substituted cyclooctatetraene (R-COT) monomers. Polymerization and processing conditions have been developed that have led to thick (2-200 mm), large-area (>1 cm  1 cm) films possessing large third-order nonlinearities in the near-infrared (NIR) region including the telecommunications bands. The good optical quality of a 200 mm thick poly(n-butyl-COT) film allowed for DFWM image correlation under off-resonant excitation to be performed with improved diffraction efficiency relative to that obtained using the diester polyacetylene derivative mentioned above; the resulting di...

Polymethine materials with solid-state third-order optical susceptibilities suitable for all-optical signal-processing applications

“…12). Although comparable or even higher values of |Re(c (3) )| have been demonstrated in other organic materials at telecommunications wavelengths, including polyacetylene derivatives 18 and polymethines with dioxaborine 19 and tricyanofuran 20 termini, these have been accompanied by larger linear and/or nonlinear losses. Conversely, an arylethynyl-aryltetracyanobutadiene exhibits excellent loss parameters, but smaller |Re(c (3) )| than found for the present compounds.…”

Characterisation of a dipolar chromophore with third-harmonic generation applications in the near-IR

“…[6][7][8] We have previously reported a range of hydroxy-functionalised chromophores, including I ( Fig. 1), in which dicyanovinyl or tricyanovinyl acceptors are attached to the 5-position of thiophenes linked by a vinylene bridge in the 2 position to triarylamine donors.…”

“…Organic materials with large third-order optical susceptibilities, c (3) , 1 can be exploited for a wide variety of applications including all-optical switching (AOS) [2][3][4][5] and correlation for laser diagnostics and image recognition. [6][7][8] We have previously reported a range of hydroxy-functionalised chromophores, including I (Fig. 1), in which dicyanovinyl or tricyanovinyl acceptors are attached to the 5-position of thiophenes linked by a vinylene bridge in the 2 position to triarylamine donors.…”

Polyacetylenes containing BODIPY pendants with different connectivities: synthesis, characterization and opto-electronic properties

“…4,5 The incorporation of functional pendants into the polyacetylene structure not only overcomes its disadvantages of intractability and instability, but also endows new functional properties such as photo-and electroluminescence, [6][7][8][9][10][11][12][13][14][15][16] optical activity (chirality), [17][18][19][20][21][22][23][24][25][26][27][28] liquid crystallinity, [29][30][31][32][33][34][35][36] and nonlinear optics (NLO). [37][38][39][40][41][42][43][44][45] 4,4-Diuoro-4-bora-3a,4a-diaza-s-indacene (BODIPY), rst reported in 1968 by Treibs and Kreuzer, has garnered a great deal of attention in the past three decades. BODIPY has superior advantages over other dyes, such as the relatively high uorescence quantum yields and molar absorption coefficients, narrow absorption and emission bandwidths located in the visible spectral region ($500 nm), good solubility, and robustness against light and chemicals.…”