Real‐Time Dynamic Hologram of a 3D Object with Fast Photochromic Molecules

Abstract

wileyonlinelibrary.com COMMUNICATIONimage quickly disappears and reappears when the writing beams are blocked and unblocked. The effect of the thermal back reaction of the photochromism and the effect of the writing beam intensity on the fi rst-order diffraction intensity were also investigated to ascertain the required properties for the photochromic molecules to achieve effi cient holographic properties.Two photochromic compounds were used in this study, as shown in Scheme 1 . These compounds are labeled 1 and 2 for simplicity although they were previously abbreviated as pseudogem -DPI[2.2]PC [ 29 ] and pseudogem -TMDPI[2.2]PC, [ 30 ] respectively. These compounds generate imidazolyl radicals (colored form) upon UV-light irradiation and the generated colored forms revert to the initial colorless forms thermally with a timescale of tens to hundreds of milliseconds. A mixture of poly(methylmethacrylate) (PMMA) and tricrecylphosphate (TCP), PMMA:TCP = 1:9, was used as a polymer matrix. TCP acts as a plasticizer and a previous study revealed that the softer polymer matrix is better for effi cient photochromic reactions. [ 16 ] The photo chromic compounds and the host polymer were dispersed in CHCl 3 and the fi lm was prepared by casting the solution onto the glass substrate (27-37 wt %). Steady-state absorption spectra and transient absorption spectra of the fi lms of 1 and 2 excited with a 355-nm nanosecond laser pulse are shown and discussed in Section 1 of the Supporting Information. Figure 1 a shows the time profi les of the fi rst-order diffraction effi ciency, which corresponds to the brightness of the holographic image, of the fi lms of 1 and 2 when two writing beams were irradiated onto the fi lm. The details of the optical setup are shown in Section 2 of the Supporting Information ( Figure S3). The concentrations of the fi lms were 27 and 33 wt % for 1 and 2 , respectively, and the thickness of both fi lms was 1.2-1.3 µm. The solubility of 2 in the polymer matrix was slightly higher than that of 1 , probably because of the effect of the methoxy groups. Figure 1 a shows that the diffraction intensity of 2 is 26 times larger than that of 1 . Both the rise and decay kinetics of 1 are faster than those of 2 (Figure 1 b,c). The rise and decay kinetics were tentatively fi tted with a single exponential decay and rise functions, although they do not completely follow these functions ( Figure S5). The estimated half-lives ( τ 1/2 ) of the rise kinetics were 71 and 190 ms, and those of the decay kinetics were 57 and 190 ms, for 1 and 2 , respectively. The decay kinetics of the diffraction intensity are reported to follow the thermal back reaction from the colored to colorless forms of the photochromic compounds. [ 14 ] These half-lives of the decay kinetics of fi lms of 1 and 2 are qualitatively consistent with those of the thermal back reactions, as obtained from the transient absorption measurements. The slower thermal back reaction of 2 is probably due to the stabilization of the radical by the methoxy groups, ...

On-demand regulation of photochromic behavior through various counterions for high-level security printing

“…Photochromic molecules have emerged as critically notable mate rials for advanced photonic applications, including fluorescence imaging (1)(2)(3), smart lenses (4)(5)(6)(7)(8), optical data storage (9)(10)(11)(12)(13)(14), and anticounterfeiting (15). Current efforts in this field are focused on developing new photochromic molecules and controlling the photo chromic behavior of these materials to meet the criteria for different optoelectronic applications.…”

Effect of ketyl radical on the structure and performance of holographic polymer/liquid-crystal composites

“…Holography is a powerful technique that encodes information via the wave field interference [1]. Due to its unique capability of simultaneously reconstructing the whole information of coherent waves (e.g., amplitude, phase and polarization), holography has become a con-stant innovation source in ultrafast temporal imaging [2,3], optical shaping [4,5], particle assembly [6,7], threedimensional (3D) display [8,9], colored 3D image storage [10][11][12][13][14][15][16], and holographic polymer electrolyte construction [17]. On the other hand, polymer/liquid-crystal (LC) composites have attracted considerable attention due to their unique electro-optic response capability [18][19][20][21].…”

Picosecond Switchable Azo Dyes

“…In fact, the development of dye moleculest hat exhibit fast isomerizationk inetics undera mbient conditions is continuing at the forefront of new research in organic chemistry,b ecause they might open up potential applications not only within materials science but also in the biomedicalf ield. [12][13][14][15][16][17][18] Amongst the broad palette of molecular switches currently known, azobenzene and its substituted derivativesa re the chromophoreso fc ommon choice for switching applications because of their clean and highly reversible isomerization process and their abilityt ou ndergo the photoinduced trans-to-cis reactiono nt he subpicosecond timescale. [19,20] The reversei somerization reactionc an be initiated thermally or by light of an appropriate wavelength.T he thermal reverse reaction in unsubstituted azobenzenes, however,i s very slow and cannotb eu sed for applications in which af ast responsei ss ought-after.T oo vercome this issue, the design and study of novel switchable azobenzene-based molecular constructs that are able to tune their opticalp roperties within the subnanosecondt emporald omain is of the essence.…”