Planar Slab Waveguide Research Articles

Manufacturing of Er[formula omitted]-doped planar waveguides on silica-on-silicon using femtosecond laser-induced plasma

We report fabrication and characterisation of the erbium-doped planar waveguide on a silica-on-silicon (SOS) wafer-offering low loss and strong light confinement suitable for engineering optical waveguide amplifier for the C-band (1530–1565 nm) of the optical fibre communication. Here we describe an ultrafast laser plasma doping (ULPD) technique that is carried out using the plasma induced by a femtosecond laser (wavelength 800 nm) with a repetition rate of 10 kHz and a pulse duration of 45 fs. The ULPD method presented here had been applied successfully for rare earth materials doping on SOS substrates previously using a fs-laser with a pulse duration of ∼100 fs and at a repetition rate of 1 kHz. The fabricated planar optical waveguide layer onto the SOS substrate has been analysed for thickness, refractive index, optical propagation loss, photoluminescence intensity, and photoluminescence lifetime. We report a low propagation loss of <0.4 dB/cm in the C-Band, a long lifetime of 13.21 ms at 1532 nm, and the largest lifetime-density product 6.344 ×10 19 s cm −3. The low loss planar slab waveguide and a high lifetime-density product promise the further possibility of fabricating strip-loaded waveguides on the SOS platform. The proposed active waveguide fabrication methodology is potentially useful for manufacturing planar integrated optical waveguide amplifiers and lasers compatible with silicon-based photonic integrated circuits.

Slab cholesteric waveguide with randomly fluctuating propagation constant

In this work, we present a stochastic theoretical analysis of an electromagnetic wave propagating inside a planar slab waveguide filled with a cholesteric material. In this system, the propagation constant of the wave is assumed to be a randomly fluctuating parameter. By means of the van Kampen systematic expansion method, Maxwell’s electromagnetic equations with random coefficients, and appropriate boundary conditions, are obtained. Numerical examples of the effects of the randomness on the propagating constant, on the ratio between magnetic and electric modes, on the field profiles, and on the energy flow are given. The results show that the stochastic waveguide can support multiple Transverse Magnetic (TM) or Transverse Electric (TE) modes with the same cutoff frequency, and furthermore, they support a distribution of electric and magnetic fields with phase shift. Our results are consistent with those of an isotropic waveguide.

Slab cholesteric waveguide with randomly fluctuating director

A stochastic theoretical analysis of electromagnetic wave propagation inside a planar slab waveguide filled with a cholesteric material, whose azimuthal angular component on its director n is randomly fluctuating is presented in this article. By means of van Kampen systematic expansion method, Maxwell's electromagnetic equations with random dielectric tensor and appropriate boundary conditions are obtained. As numerical examples, the effects of the randomness on the propagating constant, on the ratio between magnetic and electric modes, on the field profiles, and on the energy flow are presented and discussed. The results in this paper are consistent with those corresponding to the deterministic conventional waveguide.

Angular-insensitive optical filtering based on meta-GMR.

In this study, the optical properties of a meta-GMR consisting of a metasurface stacked on a planar dielectric slab waveguide were theoretically investigated. Two different metasurfaces, namely chiral split-ring resonator dimer arrays with/without a rod-shaped antenna, were investigated and compared. Conventional GMR filters utilize gratings to couple the free-space electromagnetic field to the waveguide. The highly dispersive nature of grating leads to low angular tolerance. Here, the grating is replaced by metasurfaces. The metasurface unit cell can be regarded as a polarizable dipole that couples the free-space electromagnetic field to the waveguide and decouples the waveguide mode to the radiation modes. Based on the localized nature of the resonant metasurfaces, the metasurface/GMR hybrid mode exhibits a superior angular tolerance as compared with a conventional GMR filter. This study can open a new avenue to tailor the optical properties of GMR-based devices.

Analysis of Novel Chirped Types of Refractive Index Profile Metamaterial Planar Slab Optical Waveguide by Finite-Element Method for Sensor Application

In this paper, a finite-element method (FEM) has been applied to estimate the power confinement properties for a highly complicated linear chirp types of metamaterial planar slab waveguide. The accuracy of the method has been tested with respect to the number of core division into FEM formulations. The solution converges well for only 30 core divisions. In the beginning of this paper, we compute the power confinement factor, power flow in the core/cladding region for the case of normal α-profile and normal chirped type of profile, respectively. Then, we compute the effective refractive index of metamaterial planar slab waveguide for the various cases. We try to establish the relation between leakage power loss factors versus normalized frequency. To obtain the accurate expressions, we derive the higher order polynomials. It has been found while analyzing that metamaterial slab waveguide has a special feature for better sensing capability like flat effective refractive index over the band, large power flow into cladding region, and so on. It is expected that metamaterial planar slab waveguide having chirped types of refractive index profile has a huge application in leaky fibre sensor, gas sensor, chemical sensor for oil and under grounds mining industries.

PROPAGATION AND CHARACTERIZATION OF NOVEL GRADED AND LINEARLY CHIRPED TYPE'S OF REFRACTIVE INDEX PROFILE SYMMETRIC PLANAR SLAB WAVEGUIDE BY NUMERICAL MEANS

We characterize the alpha power and chirped types of refractive index profile planar slab waveguide in terms of TE/TM mode study, waveguide dispersion study, mode profile properties, power confinement factor and universal b-V graph. Our own developed finite element method has been efficiently applied to analyze the symmetric planar slab waveguide having a complicated refractive index profile. There is a requirement for a high accuracy of numerical technique to analyze the arbitrary refractive index waveguide, as at some frequency the TE and TM modes are smeared on each other, and it is difficult to distinguish them while analyzing. This paper successfully demonstrates the different TE/TM modes supported by the waveguide with respect to alpha-power and linearly chirped types of refractive index profile. The main contribution of our work is to identify the TE/TM mode numerically for a complex refractive index planar slab waveguide and to characterize them in terms of their performance parameters. Then we apply the mode propagation concept to estimate the propagation phenomena in alpha-power and chirped types of refractive index profile waveguide. All the results presented in this paper are simulated in MATLAB only. Our study reveals that waveguide dispersion and number of allowed guided modes are small while for the case of triangular index profile followed by chirped profile and maximum for step index profile case. Hence triangular and chirped types of refractive index profile waveguide seem to be more efficient for long haul optical communication systems.

Analytical model for the coupling constant of a directional coupler in terms of slab waveguides

We present an analytical model for a generic two-wave directional coupler, in the conceptual frame of coupled single-mode planar (slab) waveguides. The modal relation of dispersion is expressed exactly under a matrix form. In the simplest symmetric configuration, the lift of degeneracy between the propagation constants of the even (slow) and odd (fast) supermodes is the exact image of the coupling constant.

Backward wave radiation from negative permittivity waveguides and its use for THz subwavelength imaging

In this paper we demonstrate the possibility of backward radiation from a negative permittivity planar (slab) waveguide. Furthermore, we show that backward radiation can be used to achieve sub-wavelength imaging of a point source placed close to such a slab or to a periodic layered system of slabs. Finally, we demonstrate backward-radiation-based imaging in the case of realistic materials operating in the THz regime, such as polaritonic alkali-halide systems.

Improved fake mode free plane-wave expansion and three planar-slab waveguides method

We compare the extra modes introduced by plane-wave expansion with the two-dimensional (2D) and the three-dimensional (3D) supercell approximation method, and analyze the differences between those two kinds of extra modes. In the band structure of 2D photonic crystal (PhC) using the 2D supercell approximation, the extra modes are created through band folding, and those extra modes can really exist in the 2D PhC. However, in the band structure of a 2D PhC slab using the 3D supercell approximation, the extra modes are mainly generated by the coupling between supercells, and cannot exist in the real 2D PhC slab, thus these extra modes are defined as fake modes in our paper. Through a detailed analysis of the origin of the fake modes and of the energy distribution of the fake modes and of the real modes, we propose an improved fake mode free plane-wave expansion and three planar slab waveguides method which removes the fake modes. This is the first time such a fake mode free band structure is presented. This result can be definitely helpful in designing 3D devices.

Dispersion study of even mode thin planar slab dielectric waveguide without computing d2β/d2k numerically

Waveguide dispersion can be tailored but not the material dispersion. Hence the total dispersion can be shifted at any desired band by adjusting the waveguide dispersion. Waveguide dispersion is proportional to d2β/d2k and need to be computed numerically. In this paper we have tried to compute analytical expressions for d2β/d2k in terms of β for the case of even modes of thin planar slab waveguide. To compute d2β/d2k accurately, β should be accurate enough up to ≈10−5 decimal point. This constraint sometimes generates the error in calculation of waveguide dispersion. Our study reveals that we can compute waveguide dispersion enough accurately for various modes by knowing only –β.

Improved fake mode free plane wave expansion method

We analyze the origin of the fake modes introduced by the plane wave expansion method with three-dimension (3D) supercell approximation. Through the detailed analysis of the energy distribution of fake modes and real modes, we propose the plane wave expansion-three planar-slab waveguides method to remove the fake modes and obtain the fake mode free band structure of a two-dimensional air hole photonic crystal slab. To the best of our knowledge, this is the first time that such a fake mode free photonic crystal band structure is presented. Our method is also definitely useful in designing other 3D devices.

Orthogonal and secondary concentration in planar micro-optic solar collectors

Planar micro-optic concentrators are passive optical structures which combine a lens array with faceted microstructures to couple sunlight into a planar slab waveguide. Guided rays propagate within the slab to edge-mounted photovoltaic cells. This paper provides analysis and preliminary experiments describing modifications and additions to the geometry which increase concentration ratios along both the vertical and orthogonal waveguide axes. We present simulated results for a 900x concentrator with 85% optical efficiency, measured results for small-scale experimental systems and briefly discuss implementations using low-cost fabrication on continuous planar waveguides.

Guided and Leaky Modes of a Multilayer Planar Slab Waveguide

Guided and Leaky Modes of a Multilayer Planar Slab Waveguide

Laser emission from mirrorless waveguides based on photosensitized polymers incorporating POSS

Laser emission from leaky waveguides based in dye-doped organic gain media incorporating Polyhedral Oligomeric Silsesquioxanes (POSS) nanoparticles is reported. The samples consist of thin film gain media deposited onto glass substrate defining a planar asymmetric slab waveguide, which does not incorporate any resonant substructure. The presence of POSS results in additional amplified spontaneous emission (ASE) spectral narrowing, and conditions have been found for which directional multimode laser emission is achieved. The spectral narrowing is ascribed to the photon path enlargement caused by a non-resonant feedback mechanism provided by individual scatterers, which enhances incoherently the magnitude of the amplification process. On the contrary, the appearance of multimode lasing is attributed to coherent random lasing from a many scatterers collective effect.

Coupling Efficiency of Gaussian Beams Into Step-Index Waveguides—An Improved Ray-Optical Approach

The coupling efficiency of Gaussian beams into multimodal waveguides is calculated with the intention of validating ray-optical approaches, that can be used for a simulation tool for optical interconnections. A full-wave analysis using the mode matching technique serves as reference method. Therefore, waveguides with known mode spectra, the circular fiber, and the planar slab waveguide, have been considered. Detailed results especially for the fiber are presented for different geometry and material parameters and varying parameters of the incident Gaussian beam. It is shown that a ray-optical approach regarding a simplified Goos-Haenchen Shift gives accurate results.

Slab waveguides and nanoscale patterning of pulsed laser-deposited Ge0.2Se0.8 chalcogenide films

Planar slab waveguides were fabricated by pulsed laser deposition from GexSe1−x glass compounds with composition (x∼0.2) that lies very close to the floppy to rigid stiffness transition. These high quality active structures, which were deposited on SiO2 cladding layers above silicon substrates, support several transverse-electric (TE) modes, and a loss of 0.24dB∕cm for the TE0 mode was measured at 632.8nm wavelength. The ability to exploit electron beam writing at these special Ge in Se compositions to create nanoscale surface motifs are promising advances to create unique miniature optical processing devices.

Semidiscrete solitons in arrayed waveguide structures with Kerr nonlinearity

We construct families of optical semidiscrete composite solitons (SDCSs), with one or two independent propagation constants, supported by a planar slab waveguide, cross-phase-modulation coupled to a periodic array of stripes. Both structures feature the cubic nonlinearity and support intrinsic modes with mutually orthogonal polarizations. We report three species of SDCSs, odd, even, and twisted ones, the first type being stable. Transverse motion of phase-tilted solitons, with potential applications to beam steering, is considered also.

Patch-fed planar dielectric slab waveguide Luneburg lens

The design of a patch-fed planar dielectric slab waveguide Luneburg lens weighing only 45 g and operated at 27 GHz in TM0 mode is described. The measured half-power beamwidth (HPBW) for a 10.8 λ, 12-cm diameter lens fed by a microstrip patch placed in intimate contact with the lens rim is 6.9° with 16.8 dB gain and 10% bandwidth for –10 dB feed return loss, lens cross-polar levels were below −20 dB. The lens is also capable of operating in the TE0 mode with similar radiation performance to that of the TM0 mode. Here, measured HPBW and gain is 8 and 15.5 dB at 27 GHz. Unlike other planar lens arrangements, because of its ability to handle both TM0 and TE0 modes the lens has the potential to deal with the circularly polarised signals, this aspect is also explored.

Core-Shell Nanowire Optical Antennas Fed by Slab Waveguides

A method of realizing nanoantenna systems at optical frequencies is suggested wherein a plasmonic nanowire is placed near a slab waveguide operating near the plasmonic resonant frequency of the nanowire. The polarizability of a nano-sized concentric cylindrical structure with the core made of an ordinary dielectrics and the shell made of a plasmonic material is calculated using Mie scattering theory. When such a core-shell nanowire is placed near a slab waveguide, the transverse magnetic (TM) surface wave guided by the waveguide can interact with the nanowire, and thus part of its energy is scattered into the open space. By reciprocity, under TM wave incidence, the induced dipole on the nanowire will launch a guided mode in the slab waveguide, thus converting part of the incident energy into the guided mode energy. A rigorous analytical treatment of the problem using the Green function of a dipole near a planar slab waveguide is developed, and the properties of such an optical antenna system are studied in detail. The finite element method is also utilized to demonstrate the idea directly.

ループ型光分岐回路を用いた複合センサの基礎的検討

We have proposed the new multi-functional sensor by using optical branching circuit with loop waveguide. The optical branching circuit consisted of cylindrical and planar slab waveguides fabricated by the ion-exchange process in Pyrex glasses. We discuss the feasibility of the optical branching circuit with loop waveguide from the several essential aspects experimentally such as ion-exchange time, coupling length of branch and refractive index of matching liquid. These experimental results demonstrate that the multi-functional sensor by using the optical branching circuit with loop waveguide has compactness and good sensitivity as compared with the conventional sensors by slab waveguides.