Multilayer Slab Waveguide Research Articles

Halide Perovskite Thin Film Lasing Mode Control.

Metal halide perovskite semiconductors have emerged as highly efficient amplifying materials; to ensure practical applicability, it is important to have precise control over the spectral and polarization characteristics of lasing emission. In this study, we present effective strategies for manipulating single- and multimode lasing from surface-emitting and optically pumped perovskite distributed feedback lasers. We show that cladding structures can be made to modify the optical properties of guided transverse electric and magnetic modes within the gain medium. This leads to spectral tuning of multipeak lasing emission and the generation of linear polarization modes. Our results are supported with a comprehensive multilayer slab waveguide model and confirmed with two different perovskite materials: methylammonium lead iodide and cesium lead bromide.

Design of high-efficiency InP/InGaAsP diluted waveguide for edge couplers

To transition integrated optical communication devices from laboratory settings to practical applications, efficient coupling between optical fibers and chip waveguides remains pivotal. This paper presents a systematic design of a diluted waveguide, a key component in the edge couplers of photonic integrated circuits. The primary purpose of the diluted waveguide lies in facilitating superior edge coupling with fiber waveguides, thereby seamlessly integrating external light sources into the waveguide structure. To commence, we employ the transfer matrix and effective refractive index techniques to simplify the 3-dimensional diluted waveguide into 2-dimensional multi-layer slab waveguides. By computing the field distribution of the fundamental mode within the diluted waveguide, the fiber-to-waveguide coupling efficiency can be derived using a simplified overlap equation and optimized diluted waveguide structure through particle swarm optimization algorithms. Consequently, we achieve a remarkable fiber-to-waveguide coupling efficiency exceeding 95% for TE-mode and 92% for TM-mode, with a polarization dependent loss (PDL) of merely 0.13 dB. Interestingly, the optimized diluted waveguide exhibits quasi-single mode behavior, as the fundamental mode containing 98% of the total energy propagates within it. Additionally, the diluted waveguide edge coupler demonstrates favorable alignment tolerance, with 1-dB excess losses of ±2.3 μm and (−2.5, +3) μm along the horizontal and vertical directions, respectively. Notably, our approach offers a versatile methodology for designing multi-layer waveguides across various materials. This method has the potential to be universally applied.

Enhancement of THz resonance using a multilayer slab waveguide for a guided-mode resonance filter.

We propose a multilayer slab waveguide (SWG) to enhance the resonance of the transmittance with a guided-mode resonance (GMR) filter. The resonance characteristics of the GMR filter were studied in three types according to the method of attaching the grating film to a SWG, which consists of 25 µm thick polyethylene terephthalate (PET) film layers separated by 25 µm air layers. The resonance depth with the multilayer SWG was improved over that of the monolayer SWG because the refractive index and absorption of the multilayer SWG were reduced. However, because resonance with a high Q-factor in the monolayer SWG has a large attenuation loss due to material absorption, the resonance enhancement was insufficient even for the multilayer SWG. We were able to make the resonance depth up to 5.2 times larger than the monolayer SWG in the TE1,1 mode using a five-layer SWG. We verified the enhancements with the multilayer SWG using a finite-difference frequency-domain (FDFD) simulation.

Four-Layer Slab Waveguide Sensors Supported with Left Handed Materials

The present paper deals with a multilayer slab waveguide structure for sensor applications. We assume a four layer slab waveguide structure with one of these layers made of a left-handed material (LHM) of negative permittivity () and permeability (). Using the Fresnel reflection coefficients, the reflectance of the structure is studied in details. The sensitivity of the effective refractive index to variations in the refractive index of a measurand homogeneously distributed in the cladding layer is also presented.

Design of quantum cascade microcavity lasers based on Q factor versus etching depth

The choice of the etching depth for semiconductor microcavities is a compromise between a high Q factor and a difficult technique in a practical fabricating process. In this paper, the influences of the etching depth on mode Q factors for mid-infrared quantum cascade microcylinder and microsquare lasers around 4.8 and 7.8 μm are simulated by three-dimensional (3D) finite-difference time-domain (FDTD) techniques. For the microcylinder and the microsquare resonators, the mode Q factors of the whispering-gallery modes (WGMs) increase exponentially and linearly with the increase in the etching depth, respectively. Furthermore, the mode Q factors of some higher order transverse WGMs may be larger than that of the fundamental transverse WGM in 3D microsquares. Based on the field distribution of the vertical multilayer slab waveguide and the mode Q factors versus the etching depth, the necessary etching depth is chosen at the position where the field amplitude is 1% of the peak value of the slab waveguide. In addition, the influences of sidewall roughness on the mode Q factors are simulated for microsquare resonators by 2D FDTD simulation.

Modeling and Analysis of a Multilayer Dielectric Slab Waveguide With Applications in Edge-Coupled Terahertz Photomixer Sources

The waveguiding properties of a multilayer dielectric slab waveguide structure with applications in edge-coupled terahertz photomixer sources are studied. The structure guides two interfering laser beams, which their central frequency difference falls into the terahertz spectrum. The top layer of the dielectric waveguide structure is made of an ultrafast photoabsorbing material, wherein the power of the guided modes are being absorbed and converted into a terahertz signal. The optical field and power distributions inside the waveguide structure are studied for different physical parameters of the dielectric layers. The absorbed optical intensity and the generated terahertz photocurrent and terahertz power inside the photoabsorbing layer are calculated

A leaky-mode directional coupler for waveguide grating lens

A leaky-mode directional coupler, based on a multi-layered slab waveguide, was designed to obtain an output beam with single radiation angle emerging from the waveguide for the sake of highly efficient focusing waveguide grating coupler (FWGC). An inner cladding in the waveguide was adopted to facilitate the effective power leakage of the propagating leaky mode. The ratio of the output to the input beam that was analyzed using the beam propagation method was estimated to be 99% for 1 mm coupler length. Eventually, we obtained a Gaussian-like intensity profile of the output beam.

Quadridirectional eigenmode expansion scheme for 2-D modeling of wave propagation in integrated optics

The propagation of guided and nonconfined optical waves at fixed frequency through dielectric structures with piecewise constant, rectangular permittivity is considered in two spatial dimensions. Bidirectional versions of eigenmodes, computed for sequences of multilayer slab waveguides, constitute the expansion basis for the optical electromagnetic field. Dirichlet boundary conditions are sufficient to discretize the mode sets. Superpositions of two such expansions (bidirectional eigenmode propagation (BEP) fields), oriented along the two perpendicular coordinate axes, establish rigorous semianalytical solutions of the relevant Helmholtz wave equation on an unbounded, cross-shaped computational domain. The overlap of the lateral windows of the two BEP sets can be viewed as a rectangular computational window with fully transparent boundaries. Simulation results for a series of model systems (Gaussian beams in free space, Bragg gratings, waveguide crossings, a square cavity with perpendicular ports, and a 90° bend in a photonic crystal waveguide) illustrate the performance of the approach.

A simple analytical method for calculating the leakage loss of a buried rectangular waveguide

A simple and efficient analytical method is presented for studying leaky modes in a buried rectangular waveguide on a high-refractive-index substrate. The cross-sectional profile of the refractive index for the buried rectangular waveguide is decomposed into three parts. The two main parts correspond to two independent multilayered slab waveguide structures and the remaining part is treated as a small perturbation term. The contributions from all three parts to the leakage loss are given analytically. Numerical results are presented and compared with those calculated with the semi-vectorial finite difference method. Fast speed, satisfactory accuracy and simplicity are the main advantages of the present method.

Component synthesis in optoelectronics modelling

AbstractA CAD package was developed that accepts a functional design specification for a multilayered optical slab waveguide and returns a physical description of a structure in a form immediately suitable for fabrication. It is shown that the definition of a figure of merit for the design requires that the importance of the design criteria be suitably weighted. The implications of the present work for the synthesis of more general optoelectronic components and circuits are discussed. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 325–327, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10310

Quality of a‐Si:H/Si3N4 multilayer films fabricated by double tubed coaxial line type MPCVD system and application of the films to optical circuit element

AbstractThe object of this research was the fabrication of high‐quality a‐Si:H/Si3N4 multilayer films with ultrathin multilayered configurations to serve as a new photonic material, as well as the evaluation of the film quality and applications to photonics. The authors have succeeded in controlling the thickness of the multilayer film at subnanometer order as indicated by the X‐ray diffraction peak of the a‐Si:H/Si3N4 multilayer film. The theoretical curve and the experimental results for the optical energy band gap agree well for multilayer films fabricated by varying the thickness of the a‐Si:H layer while the thickness of the Si3N4 layer is kept constant, and hence excellent multilayer films are obtained. These multilayer films are applied to optical waveguides. The optical waveguide with an ultrathin multilayer structure, much thinner than the wavelength λ of the guided light, is expected to exhibit an anomalous propagation characteristic. It is found that the TM mode is transmitted while the TE mode is cut off in the present multilayer slab waveguide. © 2001 Scripta Technica, Electron Comm Jpn Pt 2, 84(12): 1–7, 2001

Lossy multilayer channel optical waveguides analyzed by the transmission line matrix method

We demonstrate that the three-dimensional vectorial transmission line matrix (TLM) method is applicable to the analysis of lossy multilayer optical waveguiding structures. Any lossy multilayer waveguide geometry, including sharp discontinuities in the transverse plane, can be treated taking into account the coupling between all optical field components. The complex propagation constants (propagation constants and the attenuation coefficients) for the fundamental TE-like and TM-like modes can be determined. These parameters of the fundamental TM-like mode of a typical lossy multilayer rib dielectric waveguide are obtained as functions of free-space wavelength. Calculation of the electric-field pattern is also included. Numerical comparisons with the argument principle method (for the case of lossy multilayer slab waveguides) and the spectral-index technique (for the case of lossy multilayer rib waveguides) are also included, and it is shown that the application of the TLM method to lossy multilayer optical waveguides is accurate.

Measurement of the refractive index of GaInAs/InP quantum wells by a grating coupling technique

Effective indices of modes propagating in multiple GaInAs wells on InP barriers (MQW) waveguides are accurately measured in the 1.4–1.75 μm wavelength range using the grating coupling technique. Quantum size effects cause a selective polarization absorption and high birefringence, strongly depending on wavelength. The temperature dependence of refractive index and absorption originating from the temperature-dependent band gap is also observed. In the transparency region the refractive indices of GaInAs wells in InP barriers are deduced for two well widths using a multilayer slab waveguide model and an exciton model based on Lorentzian oscillator.

Rigorous analysis of coupling between laser and passive waveguide in multilayer slab waveguide

An approach that combines the finite-element and boundary-element methods (FEM/BEM) is extended to the analysis of arbitrarily shaped discontinuities in a multilayer slab waveguide. Here all the eigenmodes, namely, guided modes, substrate radiation modes, and substrate-cover radiation modes, are taken into account and are constructed by an extended matrix method. Computed results are given for the rigorous analysis of the coupling between a five-or six-layer laser and a four-layer passive waveguide in a monolithically integrated circuit. Some of the results are for multimode incidence. Since the coupling is one of the most important discontinuity problems in practice, this result confirms the usefulness of the approach.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design and performance of a multiple element slab waveguide spectrograph for multimode fiber-optic WDM systems

A new type of compact (<7 cm/sup 2/) multiple element slab waveguide spectrograph suitable for medium resolution fiber-optic wavelength division multiplexing (WDM) applications in the 700 nm to 900 nm optical band is described. The spectrograph consists of a replicated diffraction grating formed on the convex edge of a multilayer glass-ceramic slab waveguide stack The grating design, based on an aberration corrected derivative of the classic Rowland spectrometer, was first verified holographically, and then implemented by replication from a ruled master grating. A combination of thick-film solder glass glazing, lamination, optical finishing and grating replication was chosen to produce a multiple element spectrograph that enables accurate spectral referencing, and can be interfaced by a passive optical fiber array and detector array alignment procedures.< >

Optical waveguiding of PMMA doped with (t-Bu) 4-Pb-phthalocyanine in anisotropic multilayer (μm) geometries: an m-line study

Films (0.5–2 μm thickness) of PMMA doped with (t-Bu) 4-Pb-phthalocyanine (Pbpc) in the concentration range 0–100% have been studied as multilayer slab waveguides. Multilayer waveguides were made by spin-coating PMMA/Pbpc solutions onto a polyimide system (PIQ). Using the prism coupling method in an m-line set-up, the guiding TE and TM modes were investigated at two wavelengths, 1064 and 514.5 nm, the latter being in the optical window of Pbpc. The value of the refractive index of PMMA/Pbpc was found to be larger at 1064 nm, and in addition anisotropic, the latter indicating partial ordering. It is suggested that the plane of the Pbpc rings tends to be oriented preferentially parallel to the film plane. The results demonstrate the possibility of using a phthalocyanine/polymer system as an active nonlinear waveguide device operating in the optical window ( λ: ∼ 515 nm). Dispersion relations for uniaxial three- and four-layered waveguide geometries, and field distributions of the eigenmodes were derived and used to design (simulate) basic optically-nonlinear waveguide applications in organic multilayer structures. It is shown how the unique properties of Pbpc (an optical window with low value of n) enables phase-matched SHG for TE ω → TE 2 ω for modes of the same order, giving optimal overlap and high conversion.

Dispersion relations of multiple quantum well waveguides with arbitrary refractive index profile base period

Dispersion relations for TE and TM modes of a MQW waveguide with an arbitrary refractive index profile base period, are derived in the thin film approximation with the help of the transfer matrix technique. The accuracy of the theory is examined by comparison with an exact analysis for a simple step-index multilayer slab waveguide. Our results can be used to model the nonlinear optical effects and the impurity induced disordering of the MQW waveguides.

Multilayered slab waveguide design using a hybrid field vector

A model is introduced that facilitates an easy scheme to design planar multilayered waveguides. The basis of this model is a field related vector that follows simply shaped trajectories as a function of the depth coordinate in the waveguide. Its diagram provides qualitative insight into the effects upon guided modes of a change in the number of layers, in their phase thicknesses and in the state of polarization. In addition, the method offers the possibility of studying the corresponding effects upon field components inside the waveguide.

On Single-Mode Polarization Preserving Multi-Layered Optical Fiber

Using the concept of artificial dielectrics, a multi-layered single-mode fiber is designed which possesses an enhanced polarization preserving characteristic. An analysis of the multi-layered slab waveguide problem is first carried out. Numerical results show that this concept is feasible. Then, a finite-element analysis is used to demonstrate the enchanced polarization preserving property of a layered optical fiber.

Contribution of low-index layers to mode number in multilayer slab waveguides

We analyze in detail the contribution of layers with indices lower than the cutoff value of βc/k0 on the mode number in a general multilayer slab waveguide. The formulas are obtained to calculate the number of confined modes in the waveguide and are applied to four-layer and W-structure waveguides.