Nonlinear Optical Properties Of Materials Research Articles

Study on the third-order nonlinear optical properties of four dmit complexes by Z-scan technique

Four novel dmit complexes: [(C2H5)4N][Ni (dmit)2], [(C3H7)4N][Ni(dmit)2], [(C2H5)4N][Au(dmit)2] and [(C3H7)4N][Au(dmit)2], abbreviated as EtNi, PrNi, EtAu, and PrAu, were synthesized. The third-order nonlinear optical properties of them in acetonitrile solutions were investigated by using the Z-scan technique with 20 ps pulses width at 1064 nm. When the on-axis irradiance at focus I0 was 5.025 GW/cm2, the nonlinear refraction coefficient n2, the third-order nonlinear susceptibility χ(3), the molecular second-order hyperpolarizability γ of the four types of material were obtained with subject to Z-scan curves, and these indexes were with the magnitudes of 10−18 m2/W, 10−13 esu, and 10−31 esu, respectively. The nonlinear absorption coefficient β of Ni samples had the 10−12 m/W scale. The impact of different metals and cations on the third-order nonlinear optical properties of materials was analyzed. Through the derivation, the result suggests that these dmit complexes are promising candidates for applications to nonlinear optical devices manufacture in the near-infrared waveband.

Third-order nonlinear optical materials: practical issues and theoretical challenges

The renewed interest in all-optical switching has led to more detailed experimental investigations of nonlinear optical properties of materials within wide wavelength ranges. The objectives of these studies are discussed here in the context of the availability of suitable computational data that might be compared with the results of the experimental research. It is concluded that the currently available data are insufficient and should be augmented to provide better guidance for experimental work.

Observation of second-harmonic generation induced by pure spin currents

Extensive efforts are currently being devoted to developing a new electronic technology, called spintronics, where the spin of electrons is explored to carry information. [1,2] Several techniques have been developed to generate pure spin currents in many materials and structures. [3-10] However, there is still no method available that can be used to directly detect pure spin currents, which carry no net charge current and no net magnetization. Currently, studies of pure spin currents rely on measuring the induced spin accumulation with optical techniques [5, 11-13] or spin-valve configurations. [14-17] However, the spin accumulation does not directly reflect the spatial distribution or temporal dynamics of the pure spin current, and therefore cannot monitor the pure spin current in a real-time and real-space fashion. This imposes severe constraints on research in this field. Here we demonstrate a second-order nonlinear optical effect of the pure spin current. We show that such a nonlinear optical effect, which has never been explored before, can be used for the non-invasive, non-destructive, and real-time imaging of pure spin currents. Since this detection scheme does not rely on optical resonances, it can be generally applied in a wide range of materials with different electronic bandstructures. Furthermore, the control of nonlinear optical properties of materials with pure spin currents may have potential applications in photonics integrated with spintronics.

Closed aperture z-scan technique using the Fresnel–Kirchhoff diffraction theory for materials with high nonlinear refractions

The close aperture z-scan experiment was carried out using Fresnel–Kirchhoff diffraction theory, and the special shape of close z-scan curves is determined based on the properties of the diffraction ring pattern. As an experimental case, the nonlinear refractive index of a dye (acid blue 9) is calculated using the mentioned method for the first time. Some new applications of the Fresnel–Kirchhoff diffraction theory are also explained which may be useful to characterize the nonlinear optical properties of materials. Finally, a numerical relation is evaluated to simply calculate the nonlinear refraction index in cases with high nonlinearity orders.

Optical nonlinearity in measurement of urea and uric acid in blood

The Z-scan technique is a simple and effective tool for determining nonlinear optical properties of materials. This technique is utilized in meas-urement of urea and uric acid in blood. The nonlinear refractive index of urea and uric acid are found to vary linearly with concentration. Hence by calculating the nonlinear refractive index it is possible to measure their concentra-tion in the sample. The results of this method are found to be in good agreement with the conventional colorimetric method.

Hartmann-Shack wavefront sensing for nonlinear materials characterization

We present two new techniques exploiting a Hartmann-Shack wavefront sensor to characterize the optical self-focusing effect of nonlinear materials. We demonstrate that the defocus Zernike coefficient (C5) can be used to quantify nonlinear optical properties of materials. In the first technique proposed, the wavefront of a collimated laser beam transmitted through a nonlinear sample is analyzed with different irradiance values. In the second technique,instead of conventional detectors, a Hartmann- Shack sensor is used in a Z-scan setup. The methods are demonstrated by measuring the nonlinear refractive indices of CS2 and Quartz, using femtosecond Ti:sapphire lasers at 76 MHz and 1 KHz repetition rate.

Determination of nonlinear optical characteristics of transparent materials using single laser pulses

A new method of express analysis of nonlinear optical properties of materials by determining their nonlinear refraction and nonlinear absorption upon irradiation by a single laser pulse is proposed. The nonlinear optical characteristics of media are determined based on an analysis of variations in the spatial distribution of radiation focused by a cylindrical lens and passed through the medium. The method proposed is tested by the example of optical nonlinearities of CS2.

Optical beam tracking and distortion compensation based on a nonlinear lens mechanism

Optical free-space communications involving moving parties require precise beam pointing and mutual tracking of communicating transceivers. The existing variety of tracking techniques is still the major limiting factor in free-space laser communications. Here we propose a technique for optical beam tracking that utilizes nonlinear optical properties of materials. In our proof-of-concept experiment, a thin layer of a nematic liquid crystal (NLC) with high thermal nonlinearity was used to produce a thermal lens induced by the incoming optical beam. That beam modulated the NLC refractive index. As the transmitted optical beam passed through the same layer, the beam intensity was modulated in the far field. A sharp intensity maximum was formed at the distant communicating party position. This tracking capability has been demonstrated for angular disturbances at a subkilohertz frequency. This tracking mechanism also offers adaptive capability of compensation of strong aberrations. Such compensation has been demonstrated experimentally; numerical modeling performed with the Fresnel integral technique showed very good agreement with the experiment.

MOLECULAR NONLINEAR OPTICS: FROM PARA-NITROANILINE TO ELECTROCHEMICAL SWITCHING OF THE HYPERPOLARIZABILITY

Molecular nonlinear optics describes the nonlinear optical properties of materials at the molecular level. At this most fundamental level, the nonlinear response can be described in terms of molecular parameters, such as number of polarizable electrons, non-centrosymmetric substitution by electron-donor or electron-accepting groups, molecular conformation, position of charge, or degree of charge transfer. We recount the shifts in molecular paradigms for second-order nonlinear optics, largely based on the instrumental possibilities offered to experimentally determine the nonlinear response. We start at the shift from the dipolar paradigm to the octopolar one, initiated by the possibilities of hyper-Rayleigh scattering, and end with the perspectives recently offered by electrochemical switching of the second-order nonlinear optical response at the molecular level.

N-State Interpretations of the First and Second Hyperpolarizabilities of Cyanobiphenyl-Based Liquid Crystal Molecules

Electronic structure calculations on the frequency-dependent hyperpolarizabilities of 5-alkyl cyanobiphenyl have been performed using the AM1 Hamiltonian and time dependent Hartree-Fock theory. Both the average first and second hyperpolarizabilities decrease with increasing twist angle, ø, between the two phenyl groups, and increase with increasing incident frequency. While the nonlinear optical properties of materials are frequently interpreted within the framework of two and three state models for the electronic spectrum, systems with a more complex electronic structure require an approach which can denote state importance. The linear optical properties of 5CB are dominated by two low-lying charge transfer transitions from the ground state, which would seem suitable to a three state model. However, large state dipole moments offset of low oscillator strengths for other transitions allowing them to also become significant contributors to the nonlinear optical properties.

Laser system for investigation of nonlinear properties of optical materials

An Nd:glass laser system is described that enables smoothly varying the pulse duration of single-frequency laser radiation in the range from 0.2 to 30 ns and focusing the beam to spot sizes from 0.4 ?m at high reproducibility of spectral and spatial-temporal parameters of radiation. This laser system is used to examine the nonlinear photoinduced processes and laser-induced damage in chalcogenide glasses under high-power laser radiation in the near-IR spectral range. It is found that photoinduced losses (absorption and scattering) are produced in chalcogenide glasses by high-power laser radiation with photon energy hv < Eg . The exposure results in both reversible and irreversible structural transformation of these glasses in the exposed region. The reversible darkening is similar to the known effect of photostructural transformations in thin films exposed to photons with energy higher than the glass bandgap. The irreversible contribution is connected with the photoinduced localized destruction of bulk material. It is believed that the process of local destruction is connected with the nonlinear excitation of the structural irregularities randomly distributed in the glass.

Simple Life Satisfies This Grad Student

OSAKA, JAPAN— The life of a Ph.D. student isn't easy. A dearth of government and industry fellowships forces most students to survive on parental handouts and meager earnings from moonlighting jobs while putting in long hours in the lab for no pay. That description fits Kenji Kintaka, 26, a third-year Ph.D. student at Osaka University, to a T. Each weekday morning, Kintaka arrives in the lab by nine o'clock, gulps his breakfast—a cup of coffee—and sits down at a lab bench covered with lasers and lenses, where he investigates the properties of nonlinear optical materials. Most days he doesn't leave the lab until midnight, and he usually returns to work on weekends as well. Home is an aging, ground-floor flat only six tatami mats in area (about 3 by 4 meters) that costs $300 a month. “Most students now live in better apartments,” he says. By eating his two meals a day in the school cafeteria he has been able to scrape by on what his parents send him, which is less than $1000 a month. But Kintaka says his simple life suits him fine. “I'm a student, after all,” he says with a shrug. Indeed, his behavior seems as much a matter of choice as of economic necessity. Although he recently received an $1800-a-month fellowship from the Japan Society for the Promotion of Science—finally relieving his parents of having to support him—“my lifestyle hasn't changed,” he says. “I just save up the extra money.” ![Figure][1] Prudent passion. Kenji Kintaka hopes an optoelectronics Ph.D. will lead to a “fun” career at a national institute. Photo credit: Eiji Miyazawa/Black Star Such prudence is a way of life for Kintaka. He applied to Osaka, for example, after calculating that his high-school test scores were good enough to get him into the country's third-ranked national university. In his fourth year, he did a similar calculation about his job prospects before seeking a laboratory position with Hiroshi Nishihara, an expert in optoelectronics: “This is a field that will become big, for sure.” In typical Japanese fashion, Kintaka stayed in the lab to pursue his master's and doctoral degrees, forging an all-important link with a mentor who can help him find a job. “I think he is a typical student,” says Nishihara. “He is very serious and devoted to his work.” But Nishihara says Kintaka has a lighter side, too. He enjoys tennis and “goes often to the drinking and Karaoke parties with his fellow students,” says his mentor. As for Kintaka's long hours in the lab, Nishihara says, “it seems that research is almost his hobby.” Kintaka says he is not bothered by the fact that companies rarely hire engineers with doctorates. “I'm not very interested in an industry job,” Kintaka says, “and I don't think I'm cut out for academics.” His goal is a research post at a national institute, and he is not deterred by the stiff competition. “This looked like fun,” he says about his decision to pursue a research career. Fortunately, a life of parsimony is a price he is happy to pay to indulge his passion for science. [1]: pending:yes

Third Order Non-linear Optical Properties of Side Chain Liquid Crystalline Polymers Studied by Third Harmonic Generation from Thin Films

Abstract Highly-conjugated main chain polymers have been studied extensively in recent years as third order non-linear optical materials. However, in a non-centrosyinmetric system such as a polyene which has been substituted with an electron donor and acceptor group, the relaxation of certain selection rules results in an increase in the static third order hyperpolarisibility. Consequently, there has been recent interest in the third order non-linear optical properties of materials more typically studied for their quardratic non-linear response. One of the driving forces for this work has been the possibility of producing single device substrates possessing significant second and third order non-linearitics which could lead to highly integrated optical devices. We present the third order non-linear susceptibilities of some asymmetrically-substituted, side-chain liquid crystalline polymers, measured in amorphous thin films by third harmonic generation at 1064 nm and 1579 nm. The highest χ(3) value of 1.02 ...

Materials for all-optical devices

We briefly review the present status of work on all-optical photonic devices and discuss the properties of nonlinear optical materials that control and limit device performance. We then describe some recent work that indicates that As-rich GaAs is a promising material for ultrafast all-optical devices, and conclude with some projections for future progress in this field.

Linear and Nonlinear Optical Properties of New Organic Materials

Abstract Single crystals of new organic nonlinear optical materials, N-(2,4-dinitrophenyl)-1-chloro-3-phenyl-2-propanamine(DNCPA) and N-(5-nitro-2-pyridyl)leucinol(NPLO) have been grown by a seeded solution growth technique. Linear and nonlinear optical properties of these materials have been investigated. Angle-tuned type I and type II phase matching for frequency doubling of 1064 nm radiation at room temperature were achieved for DNCPA and NPLO crystals. The effective nonlinear coefficients were d eff = 0.13 pm/V (type I), d eff = 1.1 pm/V (type II) for DNCPA and d eff = 40 pm/V (type I), d eff = 3.0 pm/V (type II) for NPLO, respectively.

Picosecond Integrated Optical Logic

The concept of all-optical computing usually implies two-dimensional arrays of optical bistable logic elements interconnected by a lens imaging between them. The approach discussed here uses all-optical nonbistable devices with integrated optical wiring instead of bulk optics. It should provide most of the architectural flexibility of current electronic IC-based computers and be much faster. This article discusses first the advantages of its wiring over that of a lens-based system, then shows a method for achieving this integrated optical wiring. Next, it examines the properties of nonlinear optical materials and shows that a particular effect, the quantum well envelope state transition (QWEST), has the required properties. Finally, it outlines a method for creating an all-optical computer with 5- to 10-picosecond logic gates and gigabit memories.

Synthesis and structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene], an organotransition metal compound with a large second-order optical nonlinearity

There is considerable interest in materials with nonlinear optical properties. Two important manifestations of light interacting with a nonlinear optical material are, the process of second-harmonic generation (SHG) which is relevant to new laser technology, and the electro-optic effect which has applications in telecommunications and in integrated optics1. Several inorganic and organic materials with unusually large second-order nonlinearities are known1. However, reports of organometallic compounds with second-order nonlinear optical properties are few2–4 and they have relatively small values for SHG efficiencies. Here we describe a new compound (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] (compound 2) exhibits solvatochromic behaviour. A Kurtz-powder measurement, using 1.907 µm light from a Raman shifted Nd-YAG laser operating at 1.064 µm, shows the compound provides highly efficient second harmonic generation, with a signal some 62 times that from a urea reference sample. The single crystal X-ray structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] has been determined. The large nonlinear optical property of this compound demonstrates that organotransition metal compounds can play an important role in the development of the nonlinear optical properties of materials.

Correction to "Evaluation of the phase-matching properties of nonlinear optical materials in the powder form"

Correction to "Evaluation of the phase-matching properties of nonlinear optical materials in the powder form"

Evaluation of the phase-matching properties of nonlinear optical materials in the powder form

We describe an experimental technique for evaluating the phase-matching properties of nonlinear optical materials in powder form. The short wavelength phase-matching cutoff can be measured for new materials in a form readily available. We also selected, through this technique, three materials useful for device applications.