&lt;title&gt;Molecular structure and its relation to optical limiting&lt;/title&gt;

Hochbaum, A.; Hsu, Y. S.; Fergason, James L.

doi:10.1117/12.179593

Cited by 21 publications

(5 citation statements)

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“…UV/Vis absorption spectroscopy was used to investigate the stereoregularity of the TPB‐6 molecules (Figure a). The UV/Vis absorption spectrum of the template molecules (TPB‐6) in dilute water clearly exhibits two absorption bands (198 nm and 274 nm), which are ascribed to the π–π* transitions of the aromatic moieties . In the solid‐crystalline state in MMZ‐6, the template molecules are more densely packed, leading to obvious π–π stacking due to the overlap of the π molecular orbitals of the aromatic groups.…”

Section: Figurementioning

confidence: 99%

Single‐Crystalline MFI Zeolite with Sheet‐Like Mesopores Layered along the a Axis

Zhang

Shen

Gong

et al. 2018

Chemistry A European J

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Designing a templating strategy for directing mesopore growth along different crystallographic directions is essential for fabricating two‐ or three‐dimensional single‐crystalline mesoporous zeolites. However, so far, mesopores formed in MFI zeolites by soft templates have mostly been generated by disrupting growth along the b axis; generating mesopores by disrupting growth along the a axis is rare. Herein, a single‐crystalline mesoporous MFI zeolite (SCMMZ) with sheet‐like mesopores layered along the a and b axes was synthesized using a triply branched surfactant with diquaternary ammonium groups connected to 1,3,5‐triphenylbenzene by a six‐ and eight‐carbon alkyl chain (TPB‐6 and 8). The sheet‐like mesopores were embedded in the MFI framework and were retained even after calcination. Molecular mechanics calculations provided evidence of low binding energy configurations of the surfactant that directed the growth of straight and zigzag channels along the b and a axes, respectively. The formation of nanosheets was attributed to the geometric matching of the arrangement of the aromatic groups to the zeolite framework.

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Section: Figurementioning

confidence: 99%

Single‐Crystalline MFI Zeolite with Sheet‐Like Mesopores Layered along the a Axis

Zhang

Shen

Gong

et al. 2018

Chemistry A European J

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“…A variety of organic and organometallic materials have been found to fulfill these conditions. Materials known to possess a positive nonlinear absorption in the visible include phthalocyanines, ,− porphyrins, ,− organometallic cluster compounds, − and other materials. − …”

Section: Introductionmentioning

confidence: 99%

“…Materials known to possess a positive nonlinear absorption in the visible include phthalocyanines, 1,[8][9][10][11][12] porphyrins, 7,[13][14][15] organometallic cluster compounds, [16][17][18][19][20][21] and other materials. [22][23][24][25][26][27][28][29][30][31] The condition that σ ex is greater than σ 0 is necessary but it is not sufficient for a useful optical limiter material. A practical optical limiter must operate over the wide range of incident intensities that might be encountered.…”

Section: Introductionmentioning

confidence: 99%

Effect of Axial Substitution on the Optical Limiting Properties of Indium Phthalocyanines

et al. 2000

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Nonlinear absorption, refraction, and optical limiting by a series of monoaxially chloro- and aryl-substituted indium(III) phthalocyanines are described. The absorption cross sections and temporal evolution of the low-lying excited states are also reported. A large nonlinear absorption that increased with wavelength between 500 and 590 nm was observed in each material. The nanosecond nonlinear absorption and the optical limiting are shown to be dominated by a strong excited state absorption from an orientationally averaged triplet state. We derive and experimentally confirm the relation between the molecular absorption cross sections and the fluence-dependent nonlinear absorption coefficients. The effective nonlinear refraction on the nanosecond time scale was reduced because the electronic contribution to the nonlinear refractive index was of the opposite sign from the thermal contribution. An optical limiter using the new material, p-(trifluoromethyl)phenylindium(III) tetra-tert-butylphthalocyanine [(t-Bu)4PcIn(p-TMP)], showed a much lower threshold for optical limiting and a much lower transmission at high fluences than previously reported indium phthalocyanine limiters. This improved optical limiting was due both to the larger nonlinear absorption coefficient and to the design of the limiter device. The optical properties of the In phthalocyanine moiety were found to be surprisingly robust to structural changes in the axial position.

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“…61 Already first experiments on optical power limiting, acoustic grating generation and Z-scan measurements in LCs provided the experimental evidence for two-photon absorption dichroism. 34,54,63 Absolute values of nonlinear absorption coefficient β at several nanosecond pulse duration are found to be one-two orders of magnitude higher than under several tens of picosecond irradiation (see Table 2). 17,20,34,54,[65][66][67][68][69][70]72,73 In explanation of such a difference, there is some speculation in the literature about excited state absorption that strongly contributes to nonlinear absorption under nanosecond irradiation, and especially long-living-triplet-state absorption that can be significant over nanosecond time spans.…”

Section: Nonlinear Absorption Coefficients Of Nematic and Isotropic Lcsmentioning

confidence: 96%

“…Heating of cyanobiphenyl LCs by short-pulse laser radiation in the visible range that drives photoacoustical and thermooptical effects, is caused by two-photon absorption, 27,61 concurrent or subsequent excited-state absorption, 17,27,54 and the efficient decay of the excited states through radiationless-recombination channels. 17,27 Strong nonlinear absorption was observed in optical power limiting studies of LCs 12,13,20,45,[62][63][64][65] and Z-scan measurements. 34,[66][67][68][69][70] Linear absorption coefficients α of cyanobiphenyl LCs are incapable, however, to produce heating effects at low incident average powers.…”

Section: Nonlinear Absorption Mechanisms and Laser-induced Damagementioning

confidence: 97%

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

Lukishova

2000

J. Nonlinear Optic. Phys. Mat.

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Results from investigations are summarized into: (1) transient refractive and absorptive (two-photon) nonlinearities at 0.532 μm by the Z-scan method, and (2) reflective nonlinearity in the near-IR, of linearly nonabsorbing cyanobiphenyl liquid crystals under nanosecond laser irradiation. (1) For isotropic liquid crystals at the several-nanosecond time scale and several tens-micrometers beam-waist-diameter, transient molecular-reorientation and thermal/density refractive nonlinearities compete in changing the sign of the total transient refractive nonlinearity. For the different, given pulse durations, the influence of coupled thermal and density effects on nonlinear refraction depends, through buildup time, on the beam-waist diameter. Nonlinear absorption coefficients depend on the incident intensity. For planar nematic layers, cumulative effects in heating (and in refractive nonlinearity) were observed even at low, 2–10 Hz pulse repetition rate. These results are useful for optical power limiting applications, and for intensity and beam-quality sensors of pulsed, high-power lasers. (2) Reflective nonlinearity of chiral-nematic (cholesteric) mirrors near selective reflection conditions for circular polarized light at λ=1.064 μm was studied both under free space irradiation and inside a laser resonator. Specially chosen experimental irradiation conditions make it possible to attribute the observed changing of reflectivity to athermal helix unwinding by the optical field. The results can find applications in laser-resonator mirrors, Q-switches and soft apertures for beam-profile formation, and also in showing the limits of use cholesteric optical elements in high-power laser beams.

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<title>Molecular structure and its relation to optical limiting</title>

Cited by 21 publications

References 0 publications

Single‐Crystalline MFI Zeolite with Sheet‐Like Mesopores Layered along the a Axis

Single‐Crystalline MFI Zeolite with Sheet‐Like Mesopores Layered along the a Axis

Effect of Axial Substitution on the Optical Limiting Properties of Indium Phthalocyanines

Nonlinear Optical Response of Cyanobiphenyl Liquid Crystals to High-Power, Nanosecond Laser Radiation

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