Optical Power Limiting Research Articles

Phenylene Vinylene Platinum(II) Acetylides with Prodigious Two-Photon Absorption

The linear and nonlinear optical properties of a series of linear and cross-conjugated platinum(II) acetylide complexes that contain extended p-(phenylene vinylene) chromophores are reported. The complexes exhibit very high femtosecond two-photon absorption (2PA) cross section values (σ(2) up to 10,000 GM), as measured by nonlinear transmission (NLT) and two-photon excited fluorescence (2PEF) methods. The large 2PA cross sections span a broad range of wavelengths, 570-810 nm, and they overlap with the triplet excited state absorption. Spectral coincidence of high cross section 2PA and triplet absorption is a key feature giving rise to efficient dual-mode optical power limiting (OPL).

Silica Hybrid Sol–Gel Materials with Unusually High Concentration of Pt–Organic Molecular Guests: Studies of Luminescence and Nonlinear Absorption of Light

The development of new photonic materials is a key step toward improvement of existing optical devices and for the preparation of a new generation of systems. Therefore synthesis of photonic hybrid materials with a thorough understanding and control of the microstructure-to-properties relationships is crucial. In this perspective, a new preparation method based on fast gelation reactions using simple dispersion of dyes without strong covalent bonding between dye and matrix has been developed. This new sol-gel method is demonstrated through synthesis of monolithic siloxane-based hybrid materials highly doped by various platinum(II) acetylide derivatives. Concentrations of the chromophores as high as 400 mM were obtained and resulted in unprecedented optical power limiting (OPL) performance at 532 nm of the surface-polished solids. Static and time-resolved photoluminescence of the prepared hybrid materials were consistent with both OPL data and previous studies of similar Pt(II) compounds in solution. The impacts of the microstructure and the chemical composition of the matrix on the spectroscopic properties, are discussed.

Syntheses, X-ray Crystal Structures, and Optical, Fluorescence, and Nonlinear Optical Characterizations of Diphenylphosphino-Substituted Bithiophenes

A series of bithiophene derivatives that are either symmetrically disubstituted with two Ph(2)(X)P groups (X = O, S, Se) or monosubstituted with one Ph(2)(X)P group (X = O, S, Se) and an organic functional group (H, CHO, CH(2)OH, CO(2)Me) have been synthesized. The X-ray crystal structures of Ph(2)(Se)P(C(4)H(2)S)(2)P(Se)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(S)P(C(4)H(2)S)(2)H, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH exhibit very different solid-state structures depending on the type of intermolecular π-π interactions that occur. The compounds have been characterized by electronic absorption and fluorescence studies. Of particular interest is that the quantum yields of Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(O)P(C(4)H(2)S)(2)P(O)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)CO(2)Me, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH are significantly larger than that of bithiophene (factors of 13, 14, 14, and 22, respectively). This behavior is quite different from that of analogously substituted terthiophenes in which substitution results in only modest increases in the quantum yields over that of terthiophene (factors of 0.94, 2.7, 1.3, and 1.5, respectively). DFT studies of the emission process suggest that modifying the Ph(2)(X)P group affects both the fluorescence and nonradiative rate constants while modifications of the organic substituents primarily affect the nonradiative rate constants. The higher quantum yields of the substituted bithiophenes make them promising for application in organic light-emitting devices (OLED). The optical power limiting (OPL) performances of these Ph(2)(X)P-substituted bithiophenes were evaluated by nonlinear transmission measurements in the violet-blue spectral region (430-480 nm) with picosecond laser pulses. The OPL performances are enhanced by heavier X groups and when by higher solubilities. Saturated chloroform solutions of Ph(2)(O)P(C(4)H(2)S)(2)H and Ph(2)(S)P(C(4)H(2)S)(2)H exhibit significantly stronger nonlinear absorption than any previously reported compounds and are promising candidates for use in broadband optical power limiters.

Optical Comb Sources for High Dynamic-Range Single-Span Long-Haul Analog Optical Links

We present a new technique for achieving high spurious-free dynamic range in long-haul analog optical links. Our technique utilizes an optical comb as the optical carrier in an externally intensity-modulated direct-detection link architecture. By distributing the optical carrier power over the comb (in contrast to concentrating it in a single continuous-wave laser, as in a conventional link), this technique circumvents the optical power limitations imposed by stimulated Brillouin scattering allowing a substantial increase in optical launch power. Increased launch power translates directly to decreased optical amplification requirements at the link terminus and results in a significantly lower noise floor than may be achieved in a conventional link architecture. To our knowledge, the dynamic range of SFDR=105.5 dB (1-Hz bandwidth, L=50 km link) is the highest reported to date for a single-span long-haul analog optical link.

Ordered Carbon Nanotubes for Optical Power Limiting Devices

The electrospinning (ES) process was used to fabricate composite nanofibers (NFs) of poly(methyl methacrylate), PMMA, with embedded multiwalled carbon nanotubes (MWNTs) from a solution of PMMA in N,N-dimethylformamide (DMF) with homogenously dispersed MWNTs. Using both the sinklike and the elongation flows in the electrospinning process, we aligned the carbon nanotubes (CNTs) along the fiber axis. The NFs were subsequently deposited in an aligned manner on a glass surface using the electrostatic lens created by the edge of a rotating wheel collector. Semitransparent optical power limiter (OPL) films (~50% transmittance) were fabricated using an optically compatible polymeric resin infiltrated into the collected NFs. These comprised oriented NFs with different carbon nanotube loadings and film thicknesses. The OPLs exhibited high limiting abilities, with a limiting threshold of 1.5 J/cm(2) at about 50% linear transmittance. Some degree of polarization was also achieved, but significantly lower than expected because of the NF orientation.

ChemInform Abstract: Organometallic Acetylides of PtII, AuI and HgII as New Generation Optical Power Limiting Materials

AbstractReview: 106 refs.

Octupolar Polycyclic Aromatic Hydrocarbons as New Two-Photon Absorption Chromophores: Synthesis and Application for Optical Power Limiting

Octupolar Polycyclic Aromatic Hydrocarbons as New Two-Photon Absorption Chromophores: Synthesis and Application for Optical Power Limiting

Organometallic acetylides of PtII, AuI and HgII as new generation optical power limiting materials

Within the scope of nonlinear optics, optical power limiting (OPL) materials are commonly regarded as an important class of compounds which can protect the delicate optical sensors or human eyes from sudden exposure to damaging intense laser beams. Recent efforts have been devoted to developing organometallic acetylide complexes, dendrimers and polymers as high performance OPL materials of the next generation which can favorably optimize the optical limiting/transparency trade-off issue. These metallated materials offer a new avenue towards a new family of highly transparent homo- and heterometallic optical limiters with good solution processability which outperform those of current state-of-the-art visible-light-absorbing competitors such as fullerenes, metalloporphyrins and metallophthalocyanines. This critical review aims to provide a detailed account on the recent advances of these novel OPL chromophores. Their OPL activity was shown to depend strongly on the electronic characters of the aryleneethynylene ligand and transition metal moieties as well as the conjugation chain length of the compounds. Strategies including copolymerization with other transition metals, change of structural geometry, use of a dendritic platform and variation of the type and content of transition metal ions would strongly govern their photophysical behavior and improve the resulting OPL responses. Special emphasis is placed on the structure-OPL response relationships of these organometallic acetylide materials. The research endeavors for realizing practical OPL devices based on these materials have also been presented. This article concludes with perspectives on the current status of the field, as well as opportunities that lie just beyond its frontier (106 references).

Characterization and Optimization of Photonic Crystal Optical Power Limiters

In the work, there have been investigated the optical power limiting effects which occur in the nonlinear photonic crys-tals possessing saturable Kerr nonlinearity. The method is proposed which allows exact determination of the parame-ters of the structure as well as the radiation parameters which provide the limiting effect.

Effect of periodicity on optical forces between a one-dimensional periodic photonic crystal waveguide and an underlying substrate

We numerically investigate the attractive optical force between a suspended one-dimensional periodic photonic crystal waveguide and underlying substrate in a silicon-on-insulator platform. We show that the optical force is enhanced by designing the waveguide cross section to make the mode approach the band edge or substrate light line. We show that for periodic waveguides, the optical force is nonmonotonic with waveguide-substrate separation. This effect may enable the design of compact, integrated optical power limiters.

Design and Evaluation of Carbon Nanotube Based Optical Power Limiting Materials

Optical power limiters (OPLs) are "smart materials" that follow passive approaches to provide laser protection. They have the potential for protecting optical sensors and possibly even human eyes from laser-pulse damage. Optical power limiting has been a subject of increasing interest for more than two decades now. The interest is due to the increasingly large number of applications based on lasers that are currently available. Several research groups have been attempting to develop novel OPL materials based on nonlinear optical (NLO) chromophores. As a result, there are a large number of publications and patents on this subject. To date, however, there is not a single OPL material available which, taken individually, can provide ideal and smooth attenuation of an output beam. Therefore, the design and development of radically new types of materials for OPL is urgently required. During the last few years, materials containing carbon nanotubes (CNTs) have established themselves as some of the best-performing optical limiters; however, such materials are difficult to prepare and have issues with stability. In this review, the origin of OPL as well as the mechanisms of OPL are discussed. Ways to modify CNTs to make them suitable for OPL applications is also discussed.

High Throughput High Sensitivity Depth Resolved Wide Field Microscopy

3D optical microscopies including confocal microscopy, two-photon excitation microscopy, and coherent anti-Stokes Raman scattering microscopy have optical sectioning capability, but their image acquisition is relatively slow due to the sequential nature of raster scanning. Recently, scanningless nonlinear microscopy based on temporal focusing was introduced as an alternative to using the diffraction-limited spot. However, comparable optical sectioning has not been proved without optimizing the optical design and high-throughput capability has not been achieved due to the optical power limitation. In this presentation, high-throughput high-sensitivity depth-resolved wide-field two-photon microscopy is proposed. To quantify depth discrimination capability, a comprehensive mathematical model for depth-resolved wide-field illumination is derived and experimentally validated. By optimizing optical design parameters through numerical simulation, the best 3D resolution is shown to be close to diffraction limit. In addition, single particle detection sensitivity and high-throughput imaging capability are demonstrated by incorporating quantum dots, which are known to have high two-photon cross section, as a contrast agent into the proposed system. Finally, depth-resolved single particle tracking is evaluated to study the transport process in the cells with the developed microscopy, which confirms that this microscopy holds the potential in the fields of biology and medicine where both sensitivity and throughput are required.

Tetrabrominated Lead Naphthalocyanine for Optical Power Limiting

The complex 2,(3)-tetrabromo-3,(2)-tetra[(3,5-di-tert-butyl)phenyloxy]-naphthalocyaninato lead [Br(4)(tBu(2)C(6)H(3)O)(4)NcPb, 1] has been prepared and its optical limiting properties for ns light pulses have been measured. Complex 1 behaves as a reverse saturable absorber within the spectral range 440-720 nm with a limiting threshold of 0.1 J cm(-2) at 532 nm. The lifetime of the absorbing triplet excited state has been evaluated as 3.8 x 10(-7) s and the quantum yield of triplet formation has been measured as 0.07 in toluene. The nonlinear optical transmission properties of complex 1 have also been determined in Plexiglas [naphthalocyanine content: 5.0 x 10(-4) M (0.1% by weight)]. A reversible nonlinear absorption was again observed for a fluence above 0.4 J cm(-2), but through different excited-state dynamics. This may be rationalized in terms of aggregation of the molecule in the polymer matrix.

Multifunctional composite materials for optical power limiting applications in space environments

A novel optical power limiter (OPL) has been designed and fabricated by synergistically combining the different optical power limiting mechanisms of various chromophores that include nanoparticulates such as fullerenes. The multi-mechanistic material, thus obtained, has been put together in a hyperbranched-polymer-based matrix system. Solid films and filters have been successfully fabricated using a solventless curing process, resulting in OPL filters of very high optical quality. These OPL filters have been subjected to gamma radiation and the effects on the OPL properties have been evaluated. The fabricated filters show potential for protecting optical sensors from laser-pulse damage in the space environment. Temperature- and space-radiation-induced effects in optical and electronic materials are well known and can cause disruption in OPL functions or, in the worst case, even failure of a sensor.

Violet blue laser mini‐bars

AbstractWe demonstrate the construction of violet blue multi‐quantum‐well (MQW) InGaN/GaN laser mini‐bars, a novel system in nitride‐based devices. It consists of three laser stripes, closely spaced with 40 μm pitch. The width of the stripe was 3 microns. Structures were fabricated on high pressure grown, low dislocation density substrates. Under cw operation the measured spectra demonstrate sharp, almost single line emission (FWHM ∼ 1.43 Å). Measurements of the optical far field pattern revealed that when operated under threshold the device was emitting light from all three stripes, whereas during lasing we observed the optical mode only in the area of the middle laser stripe. The behaviour of optical mode suggests the formation of the supermode (coherent emission from all three devices). The maximum optical output power was 270 mW at 402 nm and the slope efficiency was 0.7 W/A. This device offers the possibility to overcome the optical output power limit, characteristic for narrow stripe devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Symmetric Versus Unsymmetric Platinum(II) Bis(aryleneethynylene)s with Distinct Electronic Structures for Optical Power Limiting/Optical Transparency Trade‐off Optimization

AbstractA new series of symmetric and unsymmetric Pt(II) bis(acetylide) complexes of the type DC≡CPt(PBu3)2C≡CD (DPtD), AC≡CPt(PBu3)2C≡CA (APtA) and DC≡CPt(PBu3)2C≡CA (DPtA) (D, donor groups; A, acceptor groups) are synthesized, and show superior optical power limiting (OPL)/optical transparency trade‐offs. By tailoring the electronic properties of the aryleneethynylene group, distinct electronic structures for these metalated complexes can be obtained, which significantly affect their photophysical behavior and OPL properties for a nanosecond laser pulse at 532 nm. Electronic influence of the ligand type and the molecular symmetry of metal group on the optical transparency/nonlinearity optimization is thoroughly elucidated. Generally, aryleneethynylene ligands with π electron‐accepting nature will effectively enhance the harvesting efficiency of the triplet excited states. The ligand variation to the OPL strength of these Pt(II) compounds follows the order: DPtD > DPtA > APtA. These results could be attributed to the distinctive excited state character induced by their different electronic structures, on the basis of the data from both photophysical studies and theoretical calculations. All of the complexes show very good optical transparencies in the visible‐light region and exhibit excellent OPL responses with very impressive figure of merit σex/σo values (up to 17), which remarkably outweigh those of state‐of‐the‐art reverse saturable absorption dyes such as C60 and metallophthalocyanines with very poor transparencies. Their lower optical‐limiting thresholds (0.05 J cm−2 at 92% linear transmittance) compared with that of the best materials (ca. 0.07 J cm−2 for InPc and PbPc dyes) currently in use will render these highly transparent materials promising candidates for practical OPL devices for the protection of human eyes and other delicate electro‐optic sensors.

Optical Power Limiters: Symmetric Versus Unsymmetric Platinum(II) Bis(aryleneethynylene)s with Distinct Electronic Structures for Optical Power Limiting/Optical Transparency Trade‐off Optimization (Adv. Mater. 8/2009)

Optical Power Limiters: Symmetric Versus Unsymmetric Platinum(II) Bis(aryleneethynylene)s with Distinct Electronic Structures for Optical Power Limiting/Optical Transparency Trade‐off Optimization (Adv. Mater. 8/2009)

Stimulated Rayleigh–Bragg Scattering From a Two-Photon Absorbing CdSe–CdS–ZnS Quantum-Rods System: Optical Power Limiting and Phase-Conjugation

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This work reports the properties of stimulated Rayleigh–Bragg scattering (SRBS) from a two-photon absorbing CdSe–Cds–ZnS quantum-rods (QRs) solution in chloroform, excited by 1064-nm and <formula formulatype="inline"> <tex>$\sim$</tex></formula>13-ns laser pulses. The two-photon absorbing capability of the scattering medium, as well as the pump threshold, spectral structure, and pulse waveforms of the backward stimulated scattering were measured. Comparing to a pure solvent or an organic dye-solution, the semiconductor QR system has many advantages such as the lower pump threshold, higher energy transfer efficiency, and better photo-physical and photo-chemical stability. The measured output/input characteristic curve shows that the backward SRBS can enhance the optical power limiting performance that is based on two-photon absorption, backward stimulated scattering, and other nonlinear absorption mechanisms. In addition, the backward SRBS beam from our sample medium exhibits a fairly good optical phase-conjugation capability, so that the distortion influence from an inserted aberrator can be automatically removed. </para>

Efficient Nonlinear Absorbing Platinum(II) Acetylide Chromophores in Solid PMMA Matrices

AbstractPlatinum(II) acetylides were incorporated into poly(methyl methacrylate) (PMMA) glasses to obtain solid‐state nonlinear optical devices. We report on device fabrication, structural, chemical, and mechanical properties, as well as the optical limiting capabilities of the final solids. Two different guest‐host systems are presented: 1) Dye molecules functionalized to be readily dispersed in methyl methacrylate (MMA) and subsequent in situ polymerization of the MMA yielding solid PMMA host matrices. 2) Dye molecules functionalized to copolymerize with MMA forming covalent bonds between the guest and the PMMA host matrix. A range of doped organic solids were prepared, reaching concentrations up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices indicate that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photophysical properties observed for the same solute molecules in THF are maintained also in the solid state. Optical power limiting (OPL) characterization reveal clamping levels for the dyes nonbonded to the solid host being less than 4 µJ at pulse energies up to 110 µJ at 532 nm (f/5 arrangement and 5 ns pulses), which is comparable to the performance of similar dyes in THF solutions. In contrast, the highly crosslinked solid possesses a higher clamping level (8 µJ) at the same nominal concentration.

Photophysical Characterization, Two-Photon Absorption and Optical Power Limiting of Two Fluorenylperylene Diimides

Perylene diimides have unique optical and electronic properties and have attracted interest in fields ranging from nonlinear optics to photovoltaics. The steady-state linear photophysical properties, two-photon absorption (2PA) spectra, and optical limiting behavior of fluorenylperylene diimide-based derivatives were investigated in solution at room temperature. An efficient intramolecular energy transfer and specific strong dependences of fluorescence quantum yield on solvent properties were observed. The 2PA spectra were measured over a broad spectral region by two-photon induced fluorescence and open aperture Z-scan methods under femtosecond and picosecond excitation, respectively. The maximum values of pure 2PA cross sections, up to ∼3500 GM, were obtained for fluorenylperylene diimide-based derivatives under picosecond excitation, when excited-state absorption and stimulated emission processes were taken into account. These perylene derivatives exhibited efficient two-photon optical power limiting un...