TE Pass Research Articles

High extinction ratio TE-Pass polarizer using the effect of superstrate layer in Ge-Clad optical waveguide

Attenuation characteristics of germanium (Ge) film clad planar optical waveguide are theoretically studied at the spectral wavelength of 0.6328 μm. Thin films of Ge are found to possess greater attenuation values than the other recognized materials. The existence of these greater attenuations is caused by lossy modes that are sustained by these films. It has been shown that the attenuation of the TM mode can be greatly increased by adding a high-index buffer layer between the Ge layer and the dielectric guide. It occurred because of the resonant coupling between the lossy modes supported by the Ge layer and the waveguide modes. Moreover, it is claimed that by adding a dielectric superstrate layer above the Ge thin film, the strength of the TM mode in the proposed structure can be further attenuated to an ultra-high value. In this study, a TE pass polarizer is proposed having a high extinction ratio of 30582.15 dB. Attenuation results are presented, after optimization of several parameters like thicknesses of Ge, buffer, and superstrate layers along with environmental stability of the suggested structure. The generated field distribution profiles are also in good agreement with the obtained attenuation results.

Design and simulation of tunable TE and TM pass polarizers based on VO2/Si hybrid waveguide

Active transverse electric and transverse magnetic pass polarizers with lengths of only 1.92 μm and 5.95 μm based on silicon waveguides and phase change material VO2 films are theoretically demonstrated. The optical characteristics of the polarizers are simulated by using finite difference mode simulation. By controlling the phase state of VO2 film, the polarizers can realize the regulation of TE and TM polarizations. The insertion losses of both polarizers are less than 2.2 dB in the insulating state. When trigger to the metallic state, the unwanted polarization attenuation exceeds 21.07 dB while insertion losses are kept below 0.71 dB at a center wavelength of 1550 nm. Both polarizers have a high extinction ratio in the operating bandwidth of 200 nm. This provides a new way for polarizers based on VO2 film and silicon waveguide.

A Compact TE-Notch Filter With Simultaneous Capability of TM-Suppression and Sensing Applications

An optical notch filter has been designed based on a silicon-slab Photonic Crystal (PhC) W1 waveguide. Birefringence originated usual performance degradation of notch filters has been eliminated by optimizing the slab-thickness and radius of the holes to embed a TE pass filter in the same structure. This resulted in TE and TM transmittances as $\approx$ $\mathrm{-1.5}$ dB and $\approx$ $\mathrm{-28}$ dB respectively at the wavelength $\mathrm{1550}$ nm. Structural parameters of the device are represented by normalizing them with respect to the lattice constant such that the structure can be scaled based on the application wavelength. Thereafter, generation of the mini stop band (MSB), i.e. notch-band, has been studied for various relative longitudinal-shifts of the lateral cladding for different filling fractions. Two different longitudinal-shifts are combined in a footprint of $\mathrm{9.8 \times 7.35}$ ${\mu \rm {m}^{2}}$ to realize a $\mathrm{10}$ nm notch-band having a notch suppression of $\approx$ $\mathrm{27}$ dB. Application of the notch-filter as a refractive index sensor has been investigated that exhibits its sensitivity as $\mathrm{500}$ nm/RIU. The potentiality of the device in applications like - bio-sensing (e.g., detection of morphological forms of certain bacteria, and some typical viral particles) and industrial measurements (typically, sensing of Ethyl Alcohol percentage in aqueous solution) has also been explored.

Develop TE/TM Pass Filters on double-loaded-on-ridge Structure with ITO/TiN for Upstream FTTH Optical Access Networks

In this paper, TE/TM pass filters are introduced as a dual optical multiplexer in the fiber-to-the home (FTTH) uplink transmission. The architecture is implemented at 1330 nm wavelength, with a double-loaded-on-ridge structure. In the TE pass filter, TM mode couples with plasmonic mode while TE mode is guided through the core with low losses due to the effect of the two plasmonic materials. The TM mode is directed through the heart, though, in the TM pass filter. Transparent conductive oxides (TCOs) as Indium Tin Oxide (ITO), in addition to Titanium Nitride (TiN) are proposed as plasmonic materials in optoelectronics devices. TCOs possess advantages for their transparency, functionality in the NIR region, and its low real permittivity compared to other plasmonic materials. ITO/TiN combination shows better performance than single plasmonic material on the filtration process. At 1330 nm of operating wavelength, the TE-pass filter operates with an extinction ratio of 20.62 dB and an insertion loss of 0.44 dB. Moreover, the TM pass filter performs with an extinction ratio of 20.2 dB and an insertion loss of 0.36 dB. The TE and TM pass filters have a device length of 2.5 μm and 2 μm, respectively.

Effect of buffer layer index on short range surface plasmon polariton based TE pass polarizer

We investigate theoretically the dependence of the extinction ratio, metal layer thickness and buffer thickness of a short length plasmonic polarizer on the buffer layer index. The polarizer section consists of a thin metal layer above the single mode dielectric waveguide separated by a low index dielectric buffer layer. Strong coupling between the surface plasmon polariton (SPP) mode and the guided mode takes place when their phase constants are matched. The SPP mode being of TM type, interacts with the guided TM mode and is completely absorbed by metal film due to resonant coupling between the two modes. The TE guided mode does not couple to the SPP mode and is passed un-attenuated through the polarizer. The buffer layer thickness can be optimized to maximize the TM mode attenuation and reduce the TE losses, which provides a large extinction ratio. Since the polarizer is based on the interference of the SPP mode and the waveguide mode, a periodic coupling of the field takes place between these two modes. It is shown that for properly optimized layer thicknesses, an extinction ratio exceeding 200 dB can be achieved for various buffer layer indices. Effect of buffer layer index on the polarizer length is also presented.

Extremely Short Length and High Extinction Ratio Plasmonic TE Mode Pass Polarizer

Extremely short length and ultrahigh extinction ratio TE pass polarizer is proposed for wavelength $1.55\mu \text{m}$ . The polarizer section consists of an optical dielectric waveguide separated from the thin metal film plasmonic guide by a low index buffer layer. The thin film metal layer supports only Short Range Surface Plasmon Polariton (SRSPP) because effective indices below and above the metal film are different. Periodic coupling between the SRSPP mode and the optical waveguide mode takes place and varies with the length of the polarizer. It is shown that for a properly optimized metal and the buffer layer thicknesses, an extinction ratio of 223 dB can be achieved for a polarizer of length $4.6~\mu \text{m}$ . Dependence of polarizer length on the optimized buffer and metal layers is also discussed.

Ultra-Compact Active TE and TM Pass Polarizers Based on Ge2Sb2Te5 in Silicon Waveguide

Active transverse electric and transverse magnetic-pass polarizers with only 1 μm length based on Ge 2 Sb 2 Te 5 (GST) silicon waveguides are theoretically demonstrated. The tunability of both polarizers relies on the phase change of GST. The analysis predicts that both devices exhibit insertion losses (ILs) below 0.8 dB in an amorphous phase. With the change to the crystalline phase, the undesired polarization is attenuated above 18.2 dB, whereas ILs are maintained below 0.8 dB (TM pass) and 2.6 dB (TE pass) at a center wavelength of 1550 nm. The operation bandwidth over a range of 100 nm is also achieved.

High Extinction Ratio and Short Length Surface Plasmon Polariton Polarizer

An ultrahigh extinction ratio and extremely short length resonant integrated optic TE pass polarizer are proposed, which is based on the interaction between the short range surface plasmon polaritons and the mode guided by the dielectric waveguide. It is shown that a compact very high extinction ratio and very low insertion loss TE pass polarizer can be designed by optimizing the buffer and metal layer thicknesses. The layer thicknesses and indices are chosen in a way, such that the multilayer plasmonic structure supports only asymmetric eigenmodes. It is shown that, as a result of interference (beat formation) between these asymmetric eigenmodes, a polarizer with an extinction ratio of 171 dB and insertion loss less than 0.01 dB can be designed for 49.4 $\mu \text{m}$ of its length.

Graphene Based Waveguide Polarizers: In-Depth Physical Analysis and Relevant Parameters.

Optical polarizing devices exploiting graphene embedded in waveguides have been demonstrated in the literature recently and both the TE- and TM-pass behaviors were reported. The determination of the passing polarization is usually attributed to graphene’s Fermi level (and, therefore, doping level), with, however, no direct confirmation of this assumption provided. Here we show, through numerical simulation, that rather than graphene’s Fermi level, the passing polarization is determined by waveguide parameters, such as the superstrate refractive index and the waveguide’s height. The results provide a consistent explanation for experimental results reported in the literature. In addition, we show that with an accurate graphene modeling, a waveguide cannot be switched between TE pass and TM pass via Fermi level tuning. Therefore, the usually overlooked contribution of the waveguide design is shown to be essential for the development of optimized TE- or TM-pass polarizers, which we show to be due to the control it provides on the fraction of the electric field that is tangential to graphene.

APPLICATION OF BILAYER ANISOTROPIC STRUCTURES FOR DESIGNING LOW-PASS FILTERS AND POLARIZERS

Arrangements of bilayer anisotropic structures are in- spected in this paper that manifest wonderful behaviors. One of these arrangements can pass TM & TE modes spontaneously in low frequen- cies and re∞ect them in higher frequencies and function as a low-pass fllter. Another arrangement can re∞ect TE mode and pass TM mode in a particular frequency band and vice versa and function as a polarizer. All the analyses are based on the calculations of the hybrid matrix of layers by means of a recursive algorithm. Also the efiect of the & tensors on the speciflcations of the fllters is discussed.

Integrated optic TE/TM pass polarizers using resonant coupling between ITO thin film lossy modes and dielectric waveguide modes

The resonant coupling between the lossless dielectric waveguide modes and the lossy modes supported by the absorbing indium–tin oxide (ITO) film is analyzed theoretically. It is observed that by changing the thickness of an ITO cladding layer placed above the planar dielectric waveguide, the TE or TM propagating modes may be selectively attenuated. This polarization effect can be used to design a TE or TM pass polarizer. Further it is also proposed that an electro-optic buffer layer inserted between the waveguide and ITO film can be used to design a high extinction ratio integrated optic polarizer at wavelength of 1.3μm. A polarizer (both TE and TM pass) with extinction ratio of about 254dB and insertion loss of about 10dB can be easily designed for a 1mm of its length.