Mr. Ehsan Ordouie Profile

Ehsan Ordouie

at Rose-Hulman Institute of Technology

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Publications (3)

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Proceedings Article | 1 March 2019 Paper

Design, fabrication, and characterization of a disordered one-dimensional broadband photonic bandgap structure

Gavin La Rue, Ehsan Ordouie, Hossein Alisafaee, Azad Siahmakoun

Proceedings Volume 10919, 109192O (2019) https://doi.org/10.1117/12.2510288

KEYWORDS: Photonic crystals, Reflectivity, Transmittance, Disordered photonic crystals, Reflector design

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Disordered one-dimensional photonic bandgap (PBG) structures could prove useful in designing broadband reflectors capable of filtering chosen polarizations of incoming light. By capitalizing on the similarities between defects and disorder, it is possible to construct a 1D PBG structure such that the layers are non-uniform but the structure can retain its most novel properties. This is done by allowing the thickness of the layers in the structure to deviate uniformly around an average thickness by a preselected amount of deviation. A mathematical model using the Transfer Matrix Method for simulation has been previously constructed by this group. This model has been verified using FDTD simulation as well. The PBG structure was then fabricated consisting of TiO₂ deposited by electron-beam physical vapor deposition (e-beam PVD) first at normal incidence and then at a 70o oblique angle. This pattern was repeated to create six bilayers of TiO₂ films. This alternating pattern gives rise to the novel structure of a PBG structure by creating a repeating pattern of amorphous and biaxial, columnar, birefringent TiO₂ ,which is analogous to using two different materials. Through testing using a polarizer, analyzer, and HeNe laser with a wavelength of 632.8 nm, it has been found that the sample does in fact match well with the expected theoretical results and acts as a broadband reflector for the TM polarization designed for a 70º incidence angle. The average layer thickness of the fabricated TiO₂ PBG is 22.7 nm.

Proceedings Article | 19 September 2018 Paper

Coupling light into silicon waveguides using surface plasmon polaritons

JeongRok Kim, Ehsan Ordouie, Azad Siahmakoun

Proceedings Volume 10722, 107222B (2018) https://doi.org/10.1117/12.2320300

KEYWORDS: Waveguides, Prisms, Silicon, Metals, Silver, Dielectrics, Surface plasmon polaritons, Interfaces, Etching, Dispersion

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In this work, we demonstrated a new method for coupling light, using prism with a small index of refraction and surface plasmon polaritons (SPP), into a crystalline silicon (Si) waveguides and performed simulation work using Lumerical FDTD Solutions. The designed structure is comprised of a dielectric prism, air-gap, metal (Ag) film, Si and silicon dioxide (SiO₂). The system follows the Otto configuration for the excitation of SPP which includes a fused silica prism and a 100 nm layer of silver metal sputtered on top of SiO₂ with an air-gap between the prism and the metal film. A 0.75×100 μm (height×width) silicon waveguide with tapered coupler is located on the same buried oxide along the silver layer for optical input channel. A p-polarized (TM mode) light with an incident angle of 44° at the wavelength of 1550 nm is incident at the interface of the fused silica/air-gap to excite the SPP. The 2D simulation shows a coupling efficiency of 54% which reveals the potential for application of this I/O coupling method in silicon photonics. For proof of concept, we fabricated and characterized the materials layout described above on an SOI substrate. For the Si structure, a tapered coupler and waveguide is fabricated using a XeF₂ dry-etch and lift-off for the metal structure. Also, the experimental setup is suggested to locate the prism on the right position of the wafer and measure the output light from the waveguide by butt coupling.

Proceedings Article | 7 September 2018 Presentation + Paper

Design, fabrication, and characterization of a one-dimensional polarizing photonic crystal

Ehsan Ordouie, Hossein Alisafaee, Azad Siahmakoun

Proceedings Volume 10731, 107310I (2018) https://doi.org/10.1117/12.2320303

KEYWORDS: Polarization, Dielectric polarization, Refractive index, Reflectivity, Thin films, Reflection, Data modeling, Photonic crystals, Finite-difference time-domain method, Transmittance

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A one-dimensional, single-material polarizing photonic bandgap structure is designed and fabricated using e-beam PVD and oblique angle deposition technique. In order to obtain high- and low-index layers, we deposited alternate layers of titanium dioxide (TiO₂) at deposition angles of 0° and 70°on top of a fused silica substrate. This approach is chosen since at deposition angle of zero degree, deposited TiO₂ using e-beam PVD, show a negligible birefringence while the obliquely deposited TiO₂acts as a biaxial material with significant birefringent behavior. As a result, deposition of a bilayer film at two angles is analogous to using two different materials with the advantage of simplifying fabrication and modeling this polarizing device. The bandgap of the bilayer structure is modeled in a way that only a specific wavelength with certain polarization, p polarization, could pass through while the s polarization is reflected. For modeling we used Transfer Matrix Method and numerical FDTD analysis to simulate behavior of the 1D photonic band gap structure. The simulations produce better than 98% reflection for s polarization and almost no reflection for p polarization for the center wavelength of 632.8 nm. The fabricated device shows 94% reflection for s polarization and less than 6% reflection for p polarization at the red HeNe laser wavelength at an incident angle of 70°. The results demonstrate that a 1D multi-layer photonic crystal, fabricated from a single material, can be designed to selectively reflect or transmit p or s polarization of an incident light beam.

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