ABSTRACT We demonstrate phase-matched frequency-doubling in Langmuir-Blodgett film waveguides of 2-docosylamino-5-nitropyridine (DCANP). The largest nonlinear optical coefficient d33 could be used by exciting TE modes propagating in the... more
ABSTRACT We demonstrate phase-matched frequency-doubling in Langmuir-Blodgett film waveguides of 2-docosylamino-5-nitropyridine (DCANP). The largest nonlinear optical coefficient d33 could be used by exciting TE modes propagating in the film. Using the Cerenkov-type configuration we can generate light in the absorption region of DCANP (at least down to λ = 410 nm where d33 = 27 pm/V, longest wavelength absorption maximum at λ = 380 nm). Conversion efficiencies of up to η meas conv = P2ω/Pω = 2·10−3 were measured (power Pω inside of the film) which is in agreement with the theory. Conditions for further optimization of the frequency-doubling efficiency are evaluated. Using a substrate material with optimized dispersion of the refractive index and a strip-waveguide geometry (width Wstrip = 2 µm) a conversion efficiency of η meas conv ∼ 10%W−1cm−1 could be obtained at a fundamental wavelength of λ = 795 nm.
Research Interests:
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
The incommensurate-commensurate phase transition in Rb2ZnCl4 has been investigated by means of refractive index measurements and second-harmonic generation experiments. The anomalies of the refractive indices n1, and n3 at the phase... more
The incommensurate-commensurate phase transition in Rb2ZnCl4 has been investigated by means of refractive index measurements and second-harmonic generation experiments. The anomalies of the refractive indices n1, and n3 at the phase transition temperature T c can be explained by assuming Bloch type light waves propagating in the incommensurate structure, vanishing gradient terms in the Landau expansion of the free energy density and a discontinuity of the amplitude of the order parameter at T c. In the incommensurate phase the observed second-harmonic signals are generated by the symmetry-allowed coefficients of the ferroelectric phase and are explained to be due to the presence of a defect-induced unipolar domain structure. In the ferroelectric phase the nonlinear optical coefficients d32, d33, and d24 are shown to be proportional to the spontaneous polarization.
Research Interests:
Photorefractive effects (due to electro-optic index change driven by photoinduced space-charge fields) have been found in a wide range of inorganic materials such as LiNbO3, KNbO3, Bi12SiO20, BaTiO3, GaAs, InP:Fe and others. To our... more
Photorefractive effects (due to electro-optic index change driven by photoinduced space-charge fields) have been found in a wide range of inorganic materials such as LiNbO3, KNbO3, Bi12SiO20, BaTiO3, GaAs, InP:Fe and others. To our knowledge, no such effects have been reported yet for an organic crystal. In this paper we report the observation of photoinduced gratings in an electro-optic molecular crystal which has been intentionally doped to induce photorefractive properties.
Research Interests:
Research Interests:
Research Interests:
We present temperature-dependent measurements of carrier transport in n-type Bi12SiO20 which were performed by holographic time-of-flight (HTOF) in diffusion mode. We measure a band mobility of photoexcited electrons of 3.5 0.4 cm2/ (Vs)... more
We present temperature-dependent measurements of carrier transport in n-type Bi12SiO20 which were performed by holographic time-of-flight (HTOF) in diffusion mode. We measure a band mobility of photoexcited electrons of 3.5 0.4 cm2/ (Vs) at 300 K that increases monotonically to 7.5 1.3 cm2/ (Vs) as the temperature is decreased to 200 K. Our results are predicted by strong coupling polaron theory if the band mass of the electrons is chosen to be 2.0 electron masses as reported in [1, 2]. Below 200 K we observe a mobility which decreases with falling temperature.
Research Interests:
MeV He ion implantation is used to produce optical waveguides in KTa1−xNbxO3 (x=0.37). The detailed refractive index profiles of the implanted planar waveguides are reconstructed from the measured mode spectra at the wavelength of 632.8... more
MeV He ion implantation is used to produce optical waveguides in KTa1−xNbxO3 (x=0.37). The detailed refractive index profiles of the implanted planar waveguides are reconstructed from the measured mode spectra at the wavelength of 632.8 nm. The absorption and the tunneling losses of the lowest mode of the waveguides are determined. Ionic collision is proposed to be the mechanism which causes the observed variation of the refractive index.
Research Interests:
Research Interests:
Research Interests:
Thin film optical waveguides are very promising for nonlinear optical applications because they provide strong beam confinement over long propagation distances leading to high conversion efficiencies in nonlinear optical processes even at... more
Thin film optical waveguides are very promising for nonlinear optical applications because they provide strong beam confinement over long propagation distances leading to high conversion efficiencies in nonlinear optical processes even at power levels of compact semiconductor diode lasers. One approach to fabricate waveguides for integrated frequencydoublers are Langmuir-Blodgett (LB) films [1]. In contrast to other organic processing methods such as poled polymers [2] or deposition of an organic single crystal on a substrate [3] the LB technique has the advantage of a thickness fabrication tolerance of about 4 nm. Such a tolerance is very favourable if phase-matched second-harmonic generation (SHG) by mode conversion in waveguide configuration is to be used.
Research Interests:
Research Interests:
The terahertz range of the electromagnetic spectrum reveals important insights when studying material properties. An ultra‐broadband terahertz time‐domain spectroscopy system based on state‐of‐the‐art, high‐stability organic nonlinear... more
The terahertz range of the electromagnetic spectrum reveals important insights when studying material properties. An ultra‐broadband terahertz time‐domain spectroscopy system based on state‐of‐the‐art, high‐stability organic nonlinear optical crystals used as both THz wave generator and detector is presented. In transmission geometry, a broad spectrum exceeding 20 THz and a high dynamic range of more than 80 dB is achieved using a compact 100 MHz femtosecond laser working at telecom wavelength 1560 nm. In the normal‐incidence reflection geometry, a similar bandwidth with a dynamic range surpassing 60 dB is reported. The experimental results are supported by a complete theoretical model, which includes the pump pulse duration, THz phonon/vibrational modes of the organic crystals and optical/THz beam path optimizations. The effectiveness of the newly developed system is demonstrated by measuring pharmaceutical samples with distinct THz features in the ultra‐broadband THz range and by ...
Research Interests:
We report on the preparation of a series of polyimide-side-chain and polyamide-main- chain polymers for electro-optic applications. Thin films prepared by spin casting were analyzed for their linear, nonlinear, and electro-optic... more
We report on the preparation of a series of polyimide-side-chain and polyamide-main- chain polymers for electro-optic applications. Thin films prepared by spin casting were analyzed for their linear, nonlinear, and electro-optic properties. The time–temperature behavior of the chromophore relaxation has been modeled to obtain estimates of the lifetimes of electro-optic devices using these polymers.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
ABSTRACT The electro-optic coefficients rij and birefringence components of lithium thallium tartrate (LTT) single crystals have been measured in the 5-300 K temperature range, as also have the refractive indices at room temperature. The... more
ABSTRACT The electro-optic coefficients rij and birefringence components of lithium thallium tartrate (LTT) single crystals have been measured in the 5-300 K temperature range, as also have the refractive indices at room temperature. The coefficients r41, ra and rb behave in an anomalous way in the vicinity of Tc approximately=12 K where LTT undergoes a phase transition; below Tc, r41 reaches a high value of 500 pm V-1. Their behaviour can be explained by considering the transition to be of a proper ferroelectric-proper ferroelastic nature, triggered by a balance between the values of clamped susceptibility, elastic stiffness and piezoelectric coefficient, as suggested earlier. A model of built-in strain is employed to interpret the existence of the symmetry-breaking coefficients ra and rb in the symmetric phase. The measured optical properties are used to re-examine the possibility of distinguishing domains in polarised light.
Research Interests:
Research Interests:
ABSTRACT Cerenkov-type second-harmonic generation using KNbO3 channel waveguides produced by MeV He+-ion implantation is presented from the viewpoint of device design. We derive the Cerenkov phase-matching condition for multimode... more
ABSTRACT Cerenkov-type second-harmonic generation using KNbO3 channel waveguides produced by MeV He+-ion implantation is presented from the viewpoint of device design. We derive the Cerenkov phase-matching condition for multimode waveguides and utilize Cerenkov-angle analysis as a tool for contact-free measurement of the effective indexes of guided modes of ion-implanted KNbO3 channel waveguides at a wavelength of 860 nm. The measured mode indexes are in full agreement with calculations based on the effective-index method and the refractive index-depth profiles of ion-implanted KNbO3 waveguides. The efficiency of Cerenkov-type second-harmonic generation is modeled using analytical approximations of the field distributions of the fundamental and the Cerenkov-radiation modes in embedded-channel waveguides. The acceptance width for Cerenkov-type frequency doubling in these ion-implanted waveguides is about one order of magnitude wider than for noncritical phase-matched second-harmonic generation in bulk KNbO3 crystals. Based on the theoretical simulations, guidelines for optimum device design are given, and the possibility to increase the ultimate conversion efficiency to about 30% W-1 cm-1 through lateral-resonance enhancement of the second-harmonic field in KNbO3 channel waveguides is demonstrated
Research Interests:
ABSTRACT Summary form only given. Interband photorefractive effects in Sn2P2S6 was investigated for dynamic holography and light-induced waveguides. The absorption constant of the crystals was determined in the highly absorbing... more
ABSTRACT Summary form only given. Interband photorefractive effects in Sn2P2S6 was investigated for dynamic holography and light-induced waveguides. The absorption constant of the crystals was determined in the highly absorbing band-to-band regime with a new method by measuring the photocurrent. Continuous-wave interband photorefractive experiments at the visible wavelengths 514 nm showed grating response times of around 100 mus at moderate light intensities. Two-wave mixing experiments yielded an intensity amplification of the weak signal beam by the strong pump beam with the exponential gain coefficient.
Research Interests:
Scattering of laser beam by acoustohelicon waves in magnetoactive noncentrosymmetric semiconducting crystals Schlieren and dye laser resonance absorption photographic investigations of KrF excimer laser-ablated atoms and molecules from polyimide, polyethyleneterephthalate, and aluminum Experiment...more
Research Interests:
* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or... more
* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or longer. For further details, please see shipping policy. ... Listed below are the papers found in this volume. Click the paper title to view an abstract or to order an individual paper.
Research Interests:
* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or... more
* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or longer. For further details, please see shipping policy. ... Listed below are the papers found in this volume. Click the paper title to view an abstract or to order an individual paper. ... Sign up for monthly alerts of new titles released.
Research Interests:
Research Interests: Materials Engineering, Materials Science, Photonics, Optical Waveguides, Integrated Optics, and 13 moreThin Films, Thin Film, Optical Waveguide, Wafer Bonding, Optical physics, Chip, Optical Materials, Electro-optic modulators, High Index Contrast, Single Mode, Lithium Niobate, Optical Activity, and High density
Research Interests: Materials Science, Optics, Hydrogen, Nonlinear Optics, Nonlinear dynamics, and 12 moreCrystallization, Medicine, Terahertz, Optical devices, Hydrogen Bond, Optical physics, Microwaves, Equipment Design, Equipment Failure Analysis, High Efficiency, Electrical And Electronic Engineering, and Infrared Rays
ABSTRACT We report on the design of the nonlinear optical organic phenolic polyene crystals for tailoring their physical properties to achieve optimized crystals for applications. New phenolic OH2... more
ABSTRACT We report on the design of the nonlinear optical organic phenolic polyene crystals for tailoring their physical properties to achieve optimized crystals for applications. New phenolic OH2 (2-(3-(4-hydroxystyryl)-5-methylcyclohex-2-enylidene)malononitrile) molecules keep the main supramolecular interaction sites and the high hyperpolarizability of the previously studied state-of-the-art OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile) and OH3 (2-(3-(4-hydroxystyryl)cyclohex-2-enylidene)malononitrile) molecules but contain different substituents in the non-π-conjugated part of the molecule, which affects the crystal packing and the physical properties. The acentric OH2 crystals exhibit an improved molecular ordering compared to OH1 crystals, leading to a high order parameter cos3 θp = 0.92, which is close to optimal for electro-optics and terahertz generation applications. They also exhibit a considerably improved solution growth characteristics compared to the isomorphous OH3 crystals, based on the increase of the solubility by a factor of 2. The acentric OH2 crystals exhibit a large macroscopic nonlinearity with up to twice the second harmonic generation efficiency of OH1 and OH3 crystals as well as the possibility to grow bulk crystals suitable for optical investigations. Furthermore, we evaluate theoretically that the head-to-tail intermolecular hydrogen bonds occurring in phenolic polyene crystals may enhance the hyperpolarizability of the molecules by 50% or more.
Research Interests:
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select... more
ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
... 4b . Clearly, the stepped surface morphology of TGS is seen from Fig. 4a which, again, is found to be decorated with islands. Additionally, some ghost traces of ferroelectric domain walls can be distinguished in the upper right... more
... 4b . Clearly, the stepped surface morphology of TGS is seen from Fig. 4a which, again, is found to be decorated with islands. Additionally, some ghost traces of ferroelectric domain walls can be distinguished in the upper right corner, which, when compared with Fig. ...
Research Interests:
ABSTRACT A simple non-scanning microscope for the in situ and real-time investigation of many kinds of interfaces and ultrathin films is described. Polarization microscopy images the complex index of refraction of the sample,... more
ABSTRACT A simple non-scanning microscope for the in situ and real-time investigation of many kinds of interfaces and ultrathin films is described. Polarization microscopy images the complex index of refraction of the sample, second-harmonic microscopy images the second-order optical susceptibility.
This report presents the synthesis, growth, crystal structure determination and second-harmonic generation efficiency of nonlinear optical co-crystal 4-N, N-dimethylamino-4-N-methyl-stilbazolium (m-nitrobenzenesulfonate)0.6I0.4 (DSIMNS).... more
This report presents the synthesis, growth, crystal structure determination and second-harmonic generation efficiency of nonlinear optical co-crystal 4-N, N-dimethylamino-4-N-methyl-stilbazolium (m-nitrobenzenesulfonate)0.6I0.4 (DSIMNS). It is co-crystal of two DAST (4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate) derivatives. X-ray crystallographic analyses revealed that the crystal structure of DSIMNS is monoclinic, with space group P21. Kurtz powder test has shown that DSIMNS exhibits a large second-harmonic generation efficiency 500 times of that of urea.
Research Interests:
ABSTRACT
Research Interests:
Research Interests:
We measured, for the first time to our knowledge, a net two-beam coupling gain in an organic crystal. Our photorefractive measurements were carried out in nominally pure organic crystals of 4-N,... more
We measured, for the first time to our knowledge, a net two-beam coupling gain in an organic crystal. Our photorefractive measurements were carried out in nominally pure organic crystals of 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium toluene-p-sulfonate (DAST). Because of its large electro-optic coefficient, r(11) = 83 pm/V at lambda = 750 nm, and a photoconductivity of up to sigma = 6.7 x 10(-12) ?(-1) cm(-1) at intensity I = 570 mW/cm(2), DAST showed a gain of 2.2 cm(-1) for an absorption of alpha = 1.8 cm(-1). With grating buildup times below 1 s at light intensities of 300 mW/cm(2), DAST is a promising candidate for photorefractive applications in the near infrared.
Research Interests:
Polar organic crystals show great promise for use in photonic devices such as electro-optic amplitude or phase modulators for telecommunication. We discuss the structural requirements for large electro-optic effects and demonstrate... more
Polar organic crystals show great promise for use in photonic devices such as electro-optic amplitude or phase modulators for telecommunication. We discuss the structural requirements for large electro-optic effects and demonstrate through high frequency electro-optic experiments that acoustic phonon contributions to the linear electro-optic effect can be neglected in the crystals presented here. The small effect of acoustic modes was found to result from a compensation between the effects of piezoelectric length change and elasto-optic contributions. Moreover, we show that the effects of electro-absorption and linear electro-optics can be well understood in the terms of the linear Stark effect.
Research Interests:
Research Interests:
ABSTRACT
Research Interests:
ABSTRACT We demonstrate electro-optic modulation in hybrid organic-crystal/silicon photonic waveguides. The organic material is the newly developed organic crystal OH1 with very high electro-optic figures of merit, n3r = 530 pm/V at 1319... more
ABSTRACT We demonstrate electro-optic modulation in hybrid organic-crystal/silicon photonic waveguides. The organic material is the newly developed organic crystal OH1 with very high electro-optic figures of merit, n3r = 530 pm/V at 1319 nm, and the processing possibilities considerably improved compared to previous high-nonlinearity organic crystals. We have developed an epitaxial-like solution growth of OH1 on various substrates and fabricated electro-optic modulators with electro-optic functionality either directly in OH1 wire waveguides or in OH1 active cladding of silicon wire waveguides. OH1-based waveguides offer a great potential for high-bandwidth, sub-1-V half-wave voltage, hybrid organic/silicon electro-optic modulators with high electro-optic activity and stability.