Nonlinear waveguide modes caused by generation of excitons and biexcitons in semiconductors in a symmetrical three-layer structure

A theory of nonlinear TE-polarized waveguide modes propagating inside a symmetrical planar three-layer structure with a linear core and nonlinear coatings is developed. The coatings are assumed to be nonlinear due to the optical exciton-biexciton conversion. The dispersion laws of the propagating waves are derived and investigated.     

Dynamics of an optical signal in a multimode waveguide structure

A mathematical model of linear dynamic distortions of average signal power in a planar optical waveguide stemming from the intermodal coupling and dispersion of waveguide modes caused by macroscopic bends and irregularities of the optical waveguide surface has been developed on the basis of pulse intermodal scattering matrix. It is shown that the elements of this matrix are determined at a waveguide segment whose length greatly exceeds the correlation scale of the field of irregularities but is much smaller than the normalization length of waveguide modes and are described by rectangular functions with a duration proportional to the relative velocity of the corresponding modes. The dependences of the pulse intermodal scattering matrix on the intensities of absorption, Rayleigh scattering, and optical signal scattering from waveguide irregularities have been established. It is shown that, at waveguide lengths exceeding the normalization length, the optical signal shape becomes almost stable and can be expressed in terms of the pulse characteristic of an integrating circuit. It has been established that irregularities of the film in a bent optical waveguide lead not only to additional attenuation but also to enhancement of multimode distortion. A matrix method is proposed for taking into account these distortions, which is based on the effect of equalization (scrambling) of the signal energy over the spectrum of the bent waveguide modes. The model developed was used to process the experimental data on the dynamics of a signal in a weakly guiding multimode polymer optical fiber in order to estimate the parameters of attenuation and irregularities of the waveguide surface.     

Numerical investigation of characteristics of laser radiation scattered in an integrated optical waveguide with three-dimensional inhomogeneities

Specifics of theoretical analysis of wave phenomena in irregular integrated optical waveguides are investigated. The object of the investigation and the main types of irregularities (smooth, statistical, and sharp) are described. The goals of the numerical modeling are formulated. The structure of the program and the general structure of the algorithm allowing numerical investigation of guided modes’ scattering from 3D-irregularities of an integrated optical waveguide are described. The dispersion relations of the TE and TM modes of the integrated optical waveguide under investigation, as well as field patterns of the radiating TE modes of the substrate and the laser radiation scattered from the three-dimensional guiding-layer inhomogeneities of an integrated optical waveguide, are presented. The results are analyzed in detail. The methods developed can be used for numerical investigation of the characteristics of laser radiation scattered in various optical waveguides with three-dimensional irregularities.     

Multielement integrated optical devices based on high-refractive-index materials

The effect of an additional high-refractive-index layer on the properties of planar waveguides for multielement integrated optical devices is considered. The conditions for highly efficient coupling (self-coupling) upon beam propagation from the three-layer to the four-layer region are determined. Technological recommendations for the production of optical waveguide beam splitters with an increased number of output elements are given.     

Frequency response of metal clad planar optical waveguides

The propagation characteristics of metal clad planar optical waveguide as a function of wavelength are investigated theoretically for Al, Ag, and Au. The results obtained show that attenuation of the propagation modes in these guides is highly dependent on wavelength, which can be used to design an efficient integrated optical waveguide polarizer with high extinction ratios, or to select the wavelength for the surface plasmon based metal clad optical waveguide sensors. It is observed that Al is the only metal that still supports the surface plasmons in the UV region.     

Analysis and Calculations of Forbidden Regions for Transverse-Electric-Guided Waves in the Three-Layer Planar Waveguide with Photonic Metamaterial

Abstract

In this article, the modal theory was used to analyze transverse electric waves in the three-layer planar waveguide with photonic metamaterial. The formulas for the electric fields of transverse electric modes in this structure have been proposed. There always exist two forbidden regions for transverse electric waves in the three-layer planar waveguide with photonic metamaterial. The complete set of modes of all possible solutions for the transverse electric waves in the three-layer planar waveguide with photonic metamaterial had been analyzed and discussed. Similar processes can be extensively used to predict the propagation characteristics of TM waves in the three-layer planar waveguide with photonic metamaterial. The analytical and numerical results show excellent agreement.     

基于倏逝场耦合的石墨烯波导光传输相位特性仿真与实验研究

石墨烯材料应用到各种光波导器件中正成为新一代光子器件的重要发展方向之一,目前基于石墨烯的光纤和集成光子器件研究越来越受到国内外的重视. 本文建立了一种由微纳光纤耦合光倏逝场,并在石墨烯薄膜中传输的模型. 通过有限元分析法,研究了光在这种石墨烯波导中传输光场的强度分布和相位特性,并通过实验进行了验证. 结果表明,沿着微纳光纤-石墨烯光波导传播的倏逝场的强度分布和相位均受石墨烯材料作用,石墨烯材料能有效聚集和导行波导中传输的高阶模,在单位传输长度上具有更密集的等相位面. 本文提出了一种利用微纳光纤耦合光倏逝场研究石墨烯相位响应特性的新方法,对基于石墨烯波导的新型调制器、滤波器、激光器和传感器等光子器件的设计和应用具有一定的参考意义. 关键词： 石墨烯平面光波导 倏逝波 光场强度 相位     

Waveguide Modes in a Planar Graphene–Dielectric Thin-Layer Structure

Particular features of waveguide propagation of modes in a planar structure that consists of alternating layers of a dielectric and graphene are investigated. Within the effective-medium approximation, dispersion relations are obtained for symmetric and antisymmetric waveguide modes. Based on their numerical analysis, the frequency dependences of the propagation and decay constants, of the group and phase velocities, and of the energy flux carried by waveguide modes are constructed. The influence of the fraction of graphene in the structure on the behavior of waveguide modes is analyzed.     

Radiation field propagation in low-contrast single-mode optical waveguides

In short waveguides used in integrated optical circuits, the radiation field is often present in the guiding region of a waveguide as well as the guided modes. We show that this can be investigated efficiently by extracting the radiation part from the total input field and simulating its evolution along the waveguide by use of the beam propagation method. The results are presented for a single-mode waveguide and a waveguide junction excited by a Gaussian beam. For a noncentred excitation, a considerable fraction of the radiation power is still in the guiding region after propagation over several tens of micrometres, and can be coupled to guided modes past the junction.     

A fast integrated optical sensor of gaseous substances

We consider the design and operation of an absorption integrated optical chemical sensor, which provides control of the content of ammonia and other hazardous gaseous and liquid substances in the air. An integrated optical sensor based on a diffusion waveguide is studied. The advantage of measurement schemes in which an analog signal from the integrated-optical sensor is converted into a digital form to be processed is shown. The limiting sensitivity of such a waveguide-sensor cell istheoretically evaluated. Prospects of using such a type of integrated-optical sensors are discussed.     

平面光波导用于实时测试生化反应新方法的研究

在分析经典消逝波光波导生化传感器的基础上,为寻找性能更佳的传感器,探讨用更为直观的截止特性来进行生化传感。分别对三层及四层平板波导进行了研究,指出了作为基于截止特性的生化传感器三层波导结构存在的局限性。在理论上研究了可以在四层波导中使用变折射率材料来进行基于截止特性的生化传感,并给出了由空气隙、极化聚合物、高折射率薄膜、待测物组成的传感器结构示意图。用数值分析的方法绘出了此装置的灵敏度与高折射率薄膜厚度的关系曲线,并将它同经典消逝波光波导生化传感器灵敏度与薄膜厚度关系图进行了比较。结果表明,这种新型传感器理论上可以在较厚的薄膜结构中达到很高的灵敏度。     

An He-implanted optical planar waveguide in an Nd:YGG laser crystal preserving fluorescence properties

We report the formation of a planar waveguide in an Nd:YGG laser crystal by low-energy He-ion implantation at liquid nitrogen temperature (77 K). The optical properties are measured by the prism coupling and end-face coupling methods, the absorption properties the waveguide and Nd:YGG substrate are obtained. The fluorescence spectrums are investigated by confocal methods. The experimental results revealed that the planar waveguide preserved the absorption and fluorescence properties of the Nd:YGG laser crystal. Thus, the planar waveguide formed by the ion implantation method is a promising candidate in waveguide lasers.     

Integrated optical proximity microsensor

This paper presents the design, simulation and experimental results of an integrated proximity sensor manufactured on silicon substrate. The sensor was designed for microrobotic applications like integration into a microgripper arm or detection of the position of gripper arms relative to an object. The structure is based on an SU8 polymeric optical waveguide splitted into three arms, integrated with a multielement photodetector on silicon substrate. Each element of the photodetector is a metal-semiconductor-metal (MSM) photodiode with Ti/Al Schottky interdigitated electrodes.The operation principle of this sensor consists in the light coupling in the central arm of the optical waveguide, interaction with the object (reflection) of the radiation which exits from this principal arm, the coupling of the “affected” radiation which comes back through the end of the waveguide and its splitting into three arms of the optical waveguide. From the optical waveguide, the light is coupled in photodiode and the photogenerated carriers are collected to the electrodes giving the electrical signal which is read and processed in real time.The optimal parameters of the waveguide (width, thicknesses of the core and the claddings) of the photodetector and the coupling between them were defined by simulation, using FDTD and BeamProp method (Opti FDTD software). Our microsensor can detect the position of an object in the range of 0-300 μm, as position sensor and with high precision in the range of zero to twice the wavelength, as proximity sensor.     

Sensitivity of prismatic integrated optical sensors under nearly critical conditions

The sensitivity of integrated optical sensors based on prismatic excitation of planar waveguides is analyzed. It is shown that the sensitivity peak is attained when the waveguide modes are excited under nearly critical conditions.     

Sensitivity enhancement in TE mode nonlinear planar optical waveguide sensor with metamaterial layer

The dispersion equation of the TE mode nonlinear planar optical waveguide with metamaterial layer was derived, and the sensitivity of the waveguide sensor was analyzed. The influences of structural parameters on the sensitivity of the waveguide sensor were investigated. We verify that the waveguide sensor with metamaterial layer can dramatically enhance the sensitivity compared with other waveguide sensors.     

Field transformation in a multimode optical waveguide with random irregularities of the film surface

A self-consistent mathematical model for the transformation of the average intensity of the mode spectrum I(z) of a waveguide field in a multimode planar optical waveguide with a step profile and rough surface is developed. This model is based on the matrix model for multiple scattering of modes in an optical waveguide. The elements of the intermode scattering matrix are found, which describe the process of mutual transfer of the energy of modes along a waveguide and their transformation into radiation modes. The transformation of the I(z) modes in waveguides with large-and small-scale inhomogeneities is investigated. It is shown that the largest qualitative differences in the noted dependences manifest themselves only in the initial portions of the optical waveguide. The length z of these portions is much smaller than the characteristic scale length L _k at which the fundamental energy of the kth mode excited in the optical waveguide is renewed. The effect of self-filtration of the mode spectrum I(z) is described, as a result of which a stable (normalized), independent of distance z, distribution I* is formed. It is established that irregularities of the optical waveguide boundaries exert a depolarizing effect on a guided light beam. The specific features of the normalization of the radiative dissipation of a group of modes I_i(z) in an optical waveguide are investigated. It is ascertained that, in the case of small-scale irregularities, the attenuation coefficient is described by a nonlinear monotonic dependence α(z), which asymptotically converges to the value α*, characteristic of the normalized field I*. When the optical-waveguide film has large irregularities, the dependence α(z) is characterized by a pronounced maximum due to the formation of alternative channels of radiative dissipation of the energy of waveguide modes.     

Theoretical model of a planar waveguide refractive index sensor assisted by a corrugated long period metal grating

A theoretical model of a novel planar integrated refractive index sensor based on surface plasmon-polariton (SPP) excitation with a corrugated metal long period grating (LPG) is presented and comprehensively investigated. The main principle of the operation this device is based on co-directional energy transfer by means of a corrugated metal LPG between a p-polarized guided mode propagating in a waveguide layer and the SPP propagating a metal layer separated from the waveguide layer by a buffer. The corrugated LPG is engraved in the metal layer in contact with the sensed medium. The power transmitted through the LPG in the guided mode serves as an input signal for an interrogation unit. This device is free from any moving parts and can be simply integrated into any planar waveguide system. Our sensor simulations are based on the local-normal-mode transfer matrix method and performed in telecom wavelength range.     

Integrated Nd-doped borosilicate glass microsphere laser

A neodymium-doped BK7 glass microsphere laser integrated with a planar ion-exchanged waveguide pumped at 0.8 μm has been demonstrated. The pump radiation was launched by evanescent coupling from the waveguide, and the signal radiation was coupled out through the same waveguide, offering the potential for robustly assembled fully integrated active optical circuits. The dependence of the lasing spectra on pump power and wavelength were studied in detail to clarify the whispering-gallery-mode behavior at the pump and lasing wavelengths.     

Modelling of rib waveguide bends for sensor applications

Wave propagation through curved bends in integrated optical waveguides is governed by the evanescent field and the radiation loss of the eigenmodes. Since these parameters are influenced by the refractive index of the surrounding medium, circular bends in rib waveguides have been successfully employed as chemical sensors for liquids and gases. In this paper the electromagnetic field, the refractive index and the radiation loss of the eigenmodes are precisely determined by a fully vectorial approach based on the method of lines. An axial discretization and Bessel functions of complex order are employed for the rigorous computation of the evanescent field. The intensity distributions of the first modes in a rib waveguide are presented. The influence of the rib height on the sensitivity of the modal index to the refractive index of the surrounding medium is investigated. The results are useful for the optimization of the sensor design.     

Recording of dynamic gratings in the nonlinear optical coating of a planar waveguide

The possibility of controlled energy exchange between interfering waveguide modes in a singlemode planar waveguide with a nonlinear optical coating is analyzed. As the coating, a suspension of bacteriorhodopsin D96N was used, which makes it possible to realize two spectrally separated mechanisms of recording and controlling dynamic gratings, i.e., the spatial modulation of the trans-cis excitation rate and the spatial modulation of the cis-trans relaxation rate. The method of phase-modulated beams was used to implement the energy exchange. The dynamic gratings in the coating were recorded by using both radiation with a wavelength within the absorption band of the trans state (630 nm) and radiation with a wavelength within the absorption band of the cis state (440 nm). Efficient control of the energy exchange between the waveguide modes by means of uniform exposure of their interference region to radiation with another wavelength was observed. A completely integral geometrical layout for optically controlled energy exchange was realized. The results obtained are compared with known data on energy exchange between beams in the bulk of a similar nonlinear medium.