Optical Power Limiting Research Articles

Click chemistry for photonic applications: triazole-functionalized platinum(ii) acetylides for optical power limiting

Three different triazole-containing platinum(II) acetylide compounds were synthesized by click chemistry and evaluated for their use in optical power limiting (OPL) applications. The triazole unit was incorporated at three different positions within, or at the end of, the conjugation path of the chromophore. The aim is to explore the possibilities of using click chemistry to prepare dendronized chromophores, and to evaluate how the triazole structure affects the photophysical properties and the optical power limiting abilities of these acetylide compounds. It is shown that the concept of click chemistry can be used to attach branched monomer units to ethynyl-phenyl arms by Huisgen 1,3-dipolar cycloaddition, forming triazole units within the chromophore. Photophysical characterization of these triazole-containing materials shows an absorption maximum within the UV-A region and emission through both fluorescence and phosphorescence. Bright phosphorescence was emitted from argon purged samples, and decay measurements thereof showed triplet lifetimes of up to 100 µs. The results from the photophysical characterization suggest that the triazole does break the conjugation path, and in order to gain maximum optical limiting the triazole needs to be placed at the end of the conjugation. All three investigated triazole-containing platinum(II) acetylides show good optical power limiting at 532 nm (10 ns pulse, f/5 set-up, 2 mm cells). The most efficient compound, with the triazole positioned at the end of the conjugation, reaches a defined clamping level of 2.5 µJ for a sample with a concentration of 50 mM in THF and a linear transmission above 80% at 532 nm. These data can be compared to the OPL properties of Zn-based porphyrins or derivatized thiophenes, reaching clamping levels of 6–15 µJ.

Negative refractivity assisted optical power limiting

We propose an approach for achieving optical power limiting (OPL) using planar multilayered media. The approach involves the use of multiple bilayer structures that consist of a negative index (NIM) layer followed by a nonlinear two-photon absorbing (TPA) layer. The NIM layers refocus light in the TPA layers to increase intensity and nonlinear absorption. We perform parametric two-dimensional finite difference time domain simulations and compute the power transmittance of the media as a function of the incident light intensity, the number of layers, the layer thickness, and the material properties. Our analysis demonstrates proof-of-concept and indicates that the TPA-based OPL can be enhanced and optimized using NIM focusing.

Synthesis, Structures and Optical Power Limiting of Some Transition Metal and Lanthanide Monoporphyrinate Complexes Containing Electron‐Rich Diphenylamino Substituents

AbstractTransition metal and lanthanide monoporphyrinate complexes based on 5,10,15,20‐tetrakis[p‐(diphenylamino)phenyl]‐21H,23H‐porphine (H2tdpapp) have been synthesized and characterized and the X‐ray crystal structures of the palladium and platinum analogues [M(tdpapp)] (M = Pd, Pt) determined. Experimental investigations of the nonlinear optical transmittance characteristics at 532 nm show that most of these new metalated porphyrinate complexes are excellent optical limiters with performances comparable or superior to those of the benchmark reverse saturable absorption dyes such as fullerene C60 and (phthalocyanine)metal complexes. The nonlinear optical measurements reveal that the optical‐limiting effects of porphyrins can be enhanced greatly by incorporation of lanthanide ions and covalent attachment of the electron‐donating diphenylamino moieties to the parent porphyrinate ring. The optical‐limiting thresholds for these lanthanide monoporphyrinate complexes range from 0.09 to 0.30 J cm–2 at 82 % linear transmittance, which makes them attractive candidates as optical‐limiting materials for the protection of various optical devices. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Axial Halogen Ligand Effect on Photophysics and Optical Power Limiting of Some Indium Naphthalocyanines

Three axially substituted complexes, 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium chloride (1a), 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium bromide (1b), and 2,3-octa(3,5-di-tert-butylphenoxy)-2,3-naphthalocyaninato indium iodide (1c) have been synthesized and their photophysical properties have been investigated. Optical power limiting of nanosecond (ns) and picosecond (ps) laser pulses at 532 nm using these complexes has been demonstrated. All complexes display strong Q(0,0) absorption and measurable emission in the near-infrared region and exhibit strong excited-state absorption in the range of 470-700 nm upon ns laser excitation. The different axial ligands show negligible effect on the linear absorption, emission, and transient difference absorption spectra. However, the excited-state lifetime, triplet excited-state quantum yield, and efficiency to generate singlet oxygen are affected significantly by the heavier axial ligand. Brominated and iodinated complexes 1b and 1c show higher triplet excited-state quantum yield, while chlorinated complex 1a has longer excited-state lifetime and is more efficient in generating singlet oxygen. The iodinated complex 1c displayed the best optical limiting due to the higher ratio of excited-state absorption cross section to ground state absorption cross section (sigma(eff)/sigma(0)).

Third order nonlinear optical properties and two photon absorption in newly synthesized phenyl sydnone doped polymer

We have investigated third order nonlinear optical properties of three newly synthesized 3-phenyl sydnones, doped into PMMA and determined both real and imaginary part of χ (3). The measurements were performed using nanosecond laser pulses at 532 nm wavelength by employing Z-Scan technique. The nonlinear refractive index is found to be of the order of 10 −14 cm 2/W. The magnitude of third order susceptibility is of the order of 10 −13 esu. Their two photon absorption coefficient and absorption cross section have also been determined. The optical power limiting behavior of sydnone moieties doped PMMA was also investigated. The results suggest that among the three organic phenyl sydnone moieties, 2-benzylhydrazono-5-(3- p-tolylsydnone-4-yl)1,3,4,-thiadiazine doped PMMA is a promising class of nonlinear optical material due to its simple molecular structure with p-tolyl group. It also shows a very good optical limiting behaviour with a limiting threshold of 0.21 mJ/pulse. The nonlinear parameters obtained are comparable with the values obtained in stilbazolium like dye such as trans-4-[2-(pyrrl)vinyl]-1-methylpyridium iodide. Hence this material may be tailored suitably for applications such as optical power limiters, switches and modulators.

Optical Power Limiters Based on Colorless Di‐, Oligo‐, and Polymetallaynes: Highly Transparent Materials for Eye Protection Devices

AbstractThe synthesis, characterization, and photophysics of a series of solution‐processable and tractable di‐, oligo‐, and polymetallaynes of some group 10–12 transition metals are presented. Most of these materials are colorless with very good optical transparencies in the visible spectral region and exhibit excellent optical power limiting (OPL) for nanosecond laser pulse. Their OPL responses outweigh those of the state‐of‐the‐art reverse saturable absorption dyes such as C60, metalloporphyrins, and metallophthalocyanines that are all associated with very poor optical transparencies. On the basis of the results from photophysical studies and theoretical calculations, both the absorption of triplet and intramolecular charge‐transfer states can contribute to the enhancement of the OPL properties for these materials. Electronic influence of the type, spatial arrangement, and geometry of metal groups on the optical transparency/nonlinearity optimization is evaluated and discussed in detail. The positive contribution of transition metal ions to the OPL of these compounds generally follows the order: Pt > Au > Hg > Pd. The optical‐limiting thresholds for these polymetallaynes can be as low as 0.07 J cm–2 at 92 % linear transmittance and these highly transparent materials manifest very impressive figure of merit σex/σo values (up to 22.48), which are remarkably higher than those of the benchmark C60 and metal phthalocyanine complexes. The present work demonstrates an attractive approach to developing materials offering superior OPL/optical transparency trade‐offs and these metallopolyynes are thus very promising candidates for use in practical OPL devices for the protection of human eyes and other delicate optical sensors.

Luminescent organometallic poly(aryleneethynylene)s: functional properties towards implications in molecular optoelectronics

This article highlights recent progress in the development of rigid-rod metallopolyyne polymers of late transition metals which can exhibit easily tunable luminescent and electronic properties. Considerable focus is placed on the design strategies towards the tuning capability of phosphorescence emission color and optical bandgap of this class of luminescent metallopolymers, and the evaluation of their suitability as emitters in light-emitting applications, optical power limiters for sensor protection and semiconductors in organometallic photovoltaic cells. An effective approach based on structural modification of the spacer group can be devised to achieve the full-color phosphorescence emission spanning almost the whole visible spectrum and to tune the material properties of these functional organometallic polymers. The major advances, ongoing challenges and future perspectives of this research frontier are also discussed.

Packet clock recovery using a bismuth oxide fiber-based optical power limiter

We demonstrate an optical clock recovery circuit that extracts the line rate component on a per packet basis from short data packets at 40Gb/s. The circuit comprises a Fabry-Perot filter followed by a novel power limiting configuration, which in turn consists of a 5m highly nonlinear bismuth oxide fiber in cascade with an optical bandpass filter. Both experimental and simulation-based results are in close agreement and reveal that the proposed circuit acquires the timing information within only a small number of bits, yielding a packet clock for every respective data packet. Moreover, we investigate theoretically the scaling laws for the parameters of the circuit for operation beyond 40 Gb/s and present simulation results showing successful packet clock extraction for 160 Gb/s data packets. Finally, the circuit's potential for operation at 320 Gb/s is discussed, indicating that ultrafast packet clock recovery should be in principle feasible by exploiting the passive structure of the device and the fsec-scale nonlinear response of the optical fiber.

Clock Recovery at 160 Gb/s and Beyond, Using a Fiber-Based Optical Power Limiter

We propose a simple all-optical clock recovery technique for short data packets at 160 Gb/s, and beyond, which is based on the concept of using a Fabry-Peacuterot filter (FPF). The novel feature of the technique is the use of a highly nonlinear fiber followed by an optical bandpass filter, centered at the initial carrier wavelength, which acts as an ultrafast power limiter, removing drastically the amplitude modulation of the FPF's output and providing the clock signal

Theoretical Simulations of Clamping Levels in Optical Power Limiting

Multiphysics modeling, combining quantum mechanical and classical wave mechanical theories, of clamping levels has been performed for a platinum(II) organic compound in a sol-gel glass matrix. A clamping level of 2.5 microJ is found for a pulse duration of 10 ns. The excited-state absorption in the triplet manifold is shown to be crucial for clamping to occur.

White Metallopolyynes for Optical Limiting/Transparency Trade‐off Optimization

High-transparency optical limiters: A series of solution-processable white metallopolyynes are shown to be excellent optical power limiters (see picture) with optimized optical transparency/nonlinearity trade-off. They exhibit an optical-limiting performance superior to those of the common reverse saturable absorption dyes, such as C60 and metal phthalocyanine complexes. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z601651_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Optical limiting in defective quadratic nonlinear photonic crystals

By using a nonlinear transfer matrix method and an iteration method, we investigated an optical limiting in a defective quadratic nonlinear photonic crystal under strong pump-depletion conditions. Due to a giant enhancement of the second harmonic (SH) generation induced by the strong localization of light near the defective band, the progress of the energy exchange from the forward fundamental frequency (FF) channel to the SH channels (both forward and backward) and the backward FF channel is speeded up. The structure can therefore be used as a high-efficient compact optical power limiter. We have also studied the effects of two important parameters of the defective nonlinear periodic structure, the number of the periods and the nonlinear efficiency of the composite material, on the optical limiting.

Analysis of stable all-optical limiting in nonlinear periodic structures

We have studied the propagation of coherent light through a passive optical power limiter (OPL) consisting of two alternating layers with different linear and nonlinear refractive indices. We have obtained general formulas for the transmittance and the optical limiting output power.

Dendron Decorated Platinum(II) Acetylides for Optical Power Limiting

The effect of dendritic substituents on a nonlinear optical chromophore for optical power limiting (OPL) has been investigated. Synthesis and characterization of bis((4-(phenylethynyl)phenyl)ethyny ...

Synthesis of, Light Emission from, and Optical Power Limiting in Soluble Single-Walled Carbon Nanotubes Functionalized by Disubstituted Polyacetylenes

Single-walled carbon nanotubes are covalently functionalized by conjugated polyacetylenes through their cyclization reactions with poly(1-phenyl-1-alkyne) and poly(diphenylacetylene) derivatives carrying azido functional groups at the ends of their alkyl pendants. The resultant polyene nanotube addends are soluble in common solvents, emit intense visible lights and strongly attenuate the power of harsh laser pulses.

Non‐linear absorption of 2,5‐dialkynyl thiophenes

AbstractThree diarylalkynyl‐substituted thiophenes were synthesized and the optical power limiting (OPL) effect at 532 nm was investigated for solutions of these compounds. The relationship between the OPL and parameters obtained from molecular‐orbital‐based calculations is discussed. Semi‐empirical calculations indicate that the compounds can have a broad distribution of conformations due to inter‐ring twisting, but that the second hyperpolarizability (γ) can be significant despite a ring twist. The calculations imply that substitution by alkyl groups can lead to enhanced γ values. The measurements and calculations show a greater increase of the OPL and γ effects from compound 5 to 6 than from 6 to 7. For these compounds, which differ mainly by the length of the π‐electron system, the magnitude of non‐linear absorption seems to be well correlated with several properties of the electronic ground state estimated by standard ab initio molecular orbital calculations, as well as with γ values from the semi‐empirical calculations. Copyright © 2004 John Wiley & Sons, Ltd.

Optical Power Limiter Using a Saturated SOA-Based Interferometric Switch

We demonstrate an optical power limiter using a semiconductor optical amplifier (SOA)-based interferometric gate powered by a strong continuous-wave input signal. We present a detailed theoretical and experimental investigation of the power limiting characteristics of saturated SOA-based switches, showing good agreement between theory and experiment.

Optical bistability, instabilities and power limiting behaviour from a dual nonlinear optical fibre loop mirror resonator

A resonator composed of two connected nonlinear optical fibre loop mirrors was investigated numerically. Results show optical bistability and instabilities in the reflected and transmitted output. The input power to induce the bistable behaviour was lower than for a similar arrangement of a single nonlinear optical loop mirror with feedback. For certain parameter values the transmitted output can be clamped to a relatively steady value, offering potential as an optical power limiter.

Optical power management using second harmonic generation in periodic segmented waveguides

A combination of loss properties of Periodic Segmented Waveguides and second-order wavelength conversion processes is shown to exhibit features which allow to realize an adjustable optical power limiter using classical integrated optics technologies. Results of numerical simulations are presented to confirm the viability of the proposed approach using input and output power levels in the range involved in standard optical telecommunication systems.

Optical limiting in the red–NIR range with soluble two-photon absorbing molecules

Two-photon absorbing chromophores were designed and investigated for optical power limitation based on multiphoton absorption processes. These molecules combine very large two-photon absorption cross-sections (with typical σ 2p maximum values of 3 × 10 −20 cm 4 GW −1 at 735 nm) and large excited-state cross-sections (with typical maximum σ e values of 5 × 10 −16 cm 2) in the red–NIR region, as shown by two-photon-excited fluorescence and pump–probe Kerr ellipsometry experiments. Numerical simulations demonstrate that these chromophores show a strongly nonlinear absorption behavior suitable for optical limiting of ns pulses (with threshold values down to 1.5 × 10 −2 J cm −2 for 0.55 ns pulses).