Analysis for dispersion characteristics of elliptic- and parabolic-groove waveguides

In this paper, the dispersion characteristics of elliptic-and parabolic-groove guides are analysed by using the equivalent network method with rectangular step approximation. The results have important values in the studying of the transmission characteristics of curvilineal-groove guides as well as its manufacture and application.     

Transmission of 1.6 J Er:YAG laser light by ZnS-coated silver hollow waveguides

A maximum energy of 1.6 J at 5 pps of Er:YAG laser light has been transmitted through a flexible ZnS-coated silver hollow waveguide which has an inner diameter of 800 μm and is 116 cm long. The straight waveguide loss is 0.6 dB m⁻¹ and no significant loss and mechanical changes have been found after an endurance test of 10000 pulse transmissions and bending 400 times with a bending radius of 30 cm.     

Influence of dispersion on spectral characteristics of GADC optical filters

This text deals with the study of the characteristics of GADC filters by taking into account the dispersion. After having defined the characteristics of the filter, the influence of separation between the guides and filter length on the characteristics of the filter are studied. It is shown that dispersion plays a very important role in the evaluation of spectral features of the filter and can not be neglected.     

Discreteness in time

In this paper we discuss the joint propagation of a periodically modulated field and a pulse of different frequency in an optical fiber. The pulse experiences the action of an index lattice induced via cross-phase modulation by the periodic field. We predict effects of discreteness to show up both in the temporal and in the spatial domain. For large walk-off between the two fields one should observe Bloch oscillations in frequency space, where discrete diffraction is expected to occur for equal velocities of both waves. Presented at 9-th International Workshop on Nonlinear Optics Applications, NOA 2007, May 17–20, 2007, Świnoujscie, Poland     

Waveguides with Combined Dirichlet and Robin Boundary Conditions

We consider the Laplacian in a curved two-dimensional strip of constant width squeezed between two curves, subject to Dirichlet boundary conditions on one of the curves and variable Robin boundary conditions on the other. We prove that, for certain types of Robin boundary conditions, the spectral threshold of the Laplacian is estimated from below by the lowest eigenvalue of the Laplacian in a Dirichlet-Robin annulus determined by the geometry of the strip. Moreover, we show that an appropriate combination of the geometric setting and boundary conditions leads to a Hardy-type inequality in infinite strips. As an application, we derive certain stability of the spectrum for the Laplacian in Dirichlet–Neumann strips along a class of curves of sign-changing curvature, improving in this way an initial result of Dittrich and Kříž (J. Phys. A, 35:L269–275, 2002).      

铌酸锂集成光路：孕育自主产业链的前沿基础研究

大数据、人工智能、光量子信息等变革性领域对信息处理能力提出了前所未有的要求,而集成光路技术有望实现更快速、更有效、成本更低廉的信息处理器件,由此带来新的自主产业机会。铌酸锂集成光路技术在近年获得迅猛发展,展示了优越的器件性能,已经吸引了产业界的关注。文章将介绍该领域的研究背景以及若干近期的重要突破。     

On the efficiency of the second harmonic generation in optical waveguides: TM case

In this paper we analyse the second harmonic generation of TM polarisation in a planar waveguide with a non-linear anisotropic substrate using the coupled mode theory under the non-depleted pump approximation. It is an extention of our previous paper in which we treated TE polarisation. Moreover, both guided waves and erenkov radiation are now taken into account simultaneously. It is shown both analytically and numerically that the erenkov efficiency peak follows the L ^3/2 dependence on the interaction length L also for TM polarisation. In an anisotropic KTP/Si₃N₄/SiO₂ waveguide, higher maximum attainable second harmonic generation (SHG) efficiency was calculated for the TM polarisation than for the optimum TE case.     

A compact wavelength division de-multiplexer based on directional coupling of one-dimensional photonic crystal waveguides

A fundamental dual-channel wavelength division de-multiplexer (WDDM) based on directional coupling of one-dimensional photonic crystal waveguides is presented, and its transmission characteristics of the WDDM are investigated by using finite-difference time-domain method. Calculated results indicate that for this WDDM, without any structural optimization, a high transmittance of more than 95% is observed at output ports. Combining the fundamental dual-channel WDDM with flexible bends of one-dimensional photonic crystal waveguides, we construct a simple and compact four-channel WDDM. Those WDDMs are expected to be applied to highly dense photonic integrated circuits.     

Resonances of three transverse standing-wave modes in a waveguide with periodic wall undulations

Interactions of three transverse modes are investigated in a waveguide with periodic walls. Resonances of two guided wave modes always result in forbidden bands for wave propagations when the wavenumber matching conditions are satisfied. As a third mode is involved due to the selected wall corrugations, we find that a single high-order mode can penetrate through the forbidden band based on the complex interactions. A method for generating a single high-order transverse mode is proposed by manipulating the multimode interactions. The numerical simulations on acoustic waveguides, showing the extreme suppression of the unwanted modes in the Bragg and non-Bragg gaps, demonstrate the validity and the efficiency of the proposed method.