Waveguide Polarizer Research Articles

Configurable TE- and TM-Pass Graphene Oxide-Coated Waveguide Polarizer

A configurable optical waveguide polarizer using graphene oxide (GO) as a polarizing element has been demonstrated. The propagation characteristics of the GO-coated optical waveguide are changed from TM-pass to TE-pass by controlling the GO coating thickness in the sub-micron range during the deposition process. The highest extinction ratio measured for a TM-pass waveguide polarizer is 34.9 dB, using a coating length and thickness of 1.0 mm and $0.34~\mu \text{m}$ respectively, while the highest extinction ratio measured for a TE-pass polarizer is 46.0 dB, using a coating length and thickness of 1.0 mm and $0.71~\mu \text{m}$ respectively. The polarization extinction ratio has also been measured across the wavelength range from 1520 nm to 1620 nm - and a variation of less than 3.0 dB was obtained. Control of the coating thickness dependent characteristics of the GO-coated waveguides provides an avenue for tailoring of the polarization selection.

Large polarization response of planarized optical waveguide functionalized with 2D material overlays

ABSTRACTWe propose a planarized optical waveguide structure functionalized with 2D materials that exhibits strong polarization dependent light interaction. Numerical study on both TE – and TM-polarized lights propagation in the 2D material coated optical waveguide is carried out. The effective index, neff of optical waveguide increases with the increase of refractive index of the 2D material overlay but decreases when its extinction coefficient is increased. On the other hand, the effective extinction coefficient, keff of 2D material coated waveguide increases with the increase of both the real and imaginary parts of 2D material refractive index. It is found that TE-mode has a stronger interaction with 2D material overlay compared to TM-mode, giving rise to potential application like waveguide polarizer. By optimizing the coating thickness, TM-pass waveguide polarizer with high polarization extinction ratio of 78.5 and 97.7 dB can be produced using black phosphorus and graphene oxide, respectively, with a coating length of only 1 mm.

Design of silicon waveguide polarization beam splitter based on reversed Δβ directional coupler

We report a directional coupler type polarization beam splitter using silicon waveguides designed for 1550–1600 nm wavelengths. The device uses the coupling strength difference between the TE and TM modes. We use a reversed Δβ structure to achieve a wide operational wavelength range. The gap between the waveguides needs to be wide enough to attain a sufficient extinction ratio for the TE mode. Simulation results show that an over 100 nm operational 20 dB extinction ratio wavelength range can be attained at 1520–1620 nm wavelengths by this simple structure. The fabrication width tolerance exceeds 10 nm which is enough for foundry processes.

Compact cross-slot waveguide polarization beam splitter using a sandwich-type coupler.

A compact silicon-based cross-slot waveguide (CSW) polarization beam splitter (PBS) utilizing a sandwich-type coupler is proposed. The coupler consists of two identical CSWs separated by a horizontal slot waveguide (HSW), and S-bend sections at each end of the coupling section are introduced to decouple and separate the light. Owing to the strong birefringence of the HSW, the coupling length ratio between two different polarized modes (TE and TM) is adjustable in a suitable range by simply changing the gap width between the CSW and the HSW. The coupling length of the TM mode can be easily made half of that of the TE mode with a proper gap width, which is a favorable condition to realize a short PBS. Then, by making the length of the coupling section equal to the coupling length of the TE mode, the TE and TM modes are split. The PBS has the advantages of a small footprint and a high polarization extinction ratio (PER) and may be useful in the polarization management of a CSW-based on-chip optical system. Numerical results indicate that a PBS of ∼12µm with an insertion loss (IL) of 0.17 (0.53) dB, PER of 24.12 (21.14) dB for the TM (TE) mode is achieved at the wavelength of 1.55 µm, with a bandwidth covering the full C band for keeping PER>15dB and IL<1dB.

Ultra-broadband mid-infrared Ge-on-Si waveguide polarization rotator

The design, modeling, micro-fabrication, and characterization of an ultra-broadband Ge-on-Si waveguide polarization rotator are presented. The polarization rotator is based on the mode evolution approach where adiabatic symmetric and anti-symmetric tapers are utilized to convert from the fundamental transverse magnetic to electric mode. The device is shown to be extremely fabrication tolerant and simple to fabricate. The fabricated devices demonstrate a polarization extinction ratio of ≥15 dB over a 2 μm bandwidth (9–11 μm wavelength) with an average insertion loss of <1 dB, which is an order of magnitude improvement compared to previously demonstrated devices. This device will provide polarization flexibility when integrating quantum cascade lasers on-chip for mid-infrared waveguide molecular spectroscopy.

COMPACT KU-BAND IRIS POLARIZERS FOR SATELLITE TELECOMMUNICATION SYSTEMS

In this article, the results of development, optimization, and analysis of new compact iris polarizers based on a square waveguide are presented. The polarization and matching characteristics of the polarizers with the different number of irises were optimized within the operating Ku-band 10.7-12.8 GHz. The numerical simulations and optimization of waveguide polarizer characteristics were carried out using a finite integration technique. The improvement of the performance of optimal polarizers and evolution of their dimensions was investigated for the polarizers with a number of irises ranging from 2 to 5. The best characteristics among the analyzed waveguide iris polarizers are achieved for the polarizer with 5 irises. Optimized compact square waveguide polarizer with 5 irises shows efficient polarization and matching performance in the whole operating Ku-band 10.7-12.8 GHz. Developed compact iris polarizers can be widely applied in modern dual-polarization antennas for satellite telecommunication systems.

Broadband Septum Polarizer With Triangular Common Port

This article presents a novel broadband septum polarizer with a relative bandwidth (BW) of 37.8%. This is significantly more than the approximate 25% BW of square and circular waveguide polarizers. It is enabled by using an equilateral triangular common port waveguide, which guarantees the largest possible frequency range between fundamental and next higher order mode cutoff. The transition between the triangular section and the rectangular input waveguides, which includes the septum, is designed to accommodate this large BW. The simulation is validated using a polarizer designed for 75–110 GHz and fabricated by conventional precision milling. A second polarizer is realized for the 18-to-26 GHz range by employing additive manufacturing to demonstrate the advantages of this technology in this context. In both cases, the axial ratio remains below 1.3 dB, whereas the input port isolation and the input return loss exceed 17 and 15 dB, respectively.

Design of a Compact 3-D Metal Printed Ka-band Waveguide Polarizer

This letter presents design, development, and characterization of compact wideband three-dimensional (3-D) printed circular waveguide-based polarizer operating in Ka-band (28-34 GHz). The polarizer structure is investigated using fundamental and higher-order modes, based on which a simplified equivalent structure is derived, giving physical insight into its mechanism of operation. The design consists of a pair of radially opposite grooves inside a circular waveguide and excited using a coaxial probe, which makes the design simple and highly compact as compared to other conventional circular polarizers. The design is compared with other existing waveguide-based polarizers in terms of electrical and physical parameters. Fabrication is done using high-resolution direct metal aluminum 3-D metal printing. The measured axial ratio is better than 3 dB over the frequency band. The design simplicity makes it attractive for application in millimeter-wave frequencies and beyond.

Fast full-wave technique for CAD of polarizers based on double-ridge waveguide sections

ABSTRACTFull-wave technique for a computer-aided design (CAD) of a wide class of square waveguide 90-degree polarizers based on double-ridge sections is presented. The proposed hybrid full-wave technique for analysis of polarizers is based on the Galerkin method with taking into account the edge condition, mode-matching technique and generalized scattering matrix method. The weighted Gegenbauer polynomials are used as the basis functions taking into account the field asymptotic at the edges when solving the eigenvalue problem for a ridge waveguide. Compact Ku-band waveguide 90-degree polarizers are designed for operation within frequency bands 12–12.5/14–14.5 GHz and 12.1–12.5/17.7–18.1 GHz. VSWR within two operational bands of polarizers is less than 1.04, differential phase shift is about 90° ± 0.5° and 90° ± 1.5°, respectively. The length of polarizers is reduced at a factor about 2 in comparison with the known corrugated square waveguide polarizers.

A Ka-Band Circularly Polarized Substrate Integrated Cavity-Backed Antenna Array

A high-gain 4 × 4 substrate integrated waveguide (SIW) circularly polarized (CP) antenna array at a Ka-band with a quadruple-ridge waveguide polarizer is proposed in this letter. The antenna array consists of 16 cavity-backed slot antenna elements, quadruple ridge waveguide polarizers, and SIW T-type power dividers. Dominant resonant mode TE110 is excited in the cavity-backed slot antenna element. The measured impedance bandwidth ( S 11 < –10 dB) is from 35.3 to 35.55 GHz, and 3 dB axial-ratio bandwidth is from 35.24 to 35.57 GHz. In addition, the maximum measured gain of 18.14 dBi at the boresight is experimentally obtained at 35.42 GHz. The antenna prototype was fabricated by a multilayer printed circuit board technology. To the best of our knowledge, the quadruple-ridge waveguide is used as polarizer to produce CP signals for the first time. Compared with an aperture antenna with a conventional rectangle or a circular waveguide polarizer, this work has high aperture radiation efficiency as well as compact size. This design idea may open a new way for development of millimeter-wave high-efficiency arrays.

Graphene Oxide Waveguide and Micro‐Ring Resonator Polarizers

AbstractIntegrated waveguide polarizers and polarization‐selective micro‐ring resonators (MRRs) incorporated with graphene oxide (GO) films are experimentally demonstrated. CMOS‐compatible doped silica waveguides and MRRs with both uniformly coated and patterned GO films are fabricated based on a large‐area, transfer‐free, layer‐by‐layer GO coating method that yields precise control of the film thickness. Photolithography and lift‐off processes are used to achieve photolithographic patterning of GO films with precise control of the placement and coating length. Detailed measurements are performed to characterize the performance of the devices versus GO film thickness and coating length as a function of polarization, wavelength and power. A high polarization dependent loss of ≈53.8 dB is achieved for the waveguide coated with 2‐mm‐long patterned GO films. It is found that intrinsic film material loss anisotropy dominates the performance for less than 20 layers whereas polarization‐dependent mode overlap dominates for thicker layers. For the MRRs, the GO coating length is reduced to 50 µm, yielding a ≈8.3 dB polarization extinction ratio between transverse electric (TE) and transverse magnetic (TM) resonances. These results offer interesting physical insights and trends of the layered GO films and demonstrate the effectiveness of introducing GO films into photonic‐integrated devices to realize high‐performance polarization selective components.

Highly sensitive label-free in vitro detection of aflatoxin B1 in an aptamer assay using optical planar waveguide operating as a polarization interferometer

This work reports on further development of an optical biosensor for the in vitro detection of mycotoxins (in particular, aflatoxin B1) using a highly sensitive planar waveguide transducer in combination with a highly specific aptamer bioreceptor. This sensor is built on a SiO2–Si3N4–SiO2 optical planar waveguide (OPW) operating as a polarization interferometer (PI), which detects a phase shift between p- and s-components of polarized light propagating through the waveguide caused by the molecular adsorption. The refractive index sensitivity (RIS) of the recently upgraded PI experimental setup has been improved and reached values of around 9600 rad per refractive index unity (RIU), the highest RIS values reported, which enables the detection of low molecular weight analytes such as mycotoxins in very low concentrations. The biosensing tests yielded remarkable results for the detection of aflatoxin B1 in a wide range of concentrations from 1 pg/mL to 1 μg/mL in direct assay with specific DNA-based aptamers.Graphical abstractOptical planar waveguide polarization interferometry biosensor for detection of aflatoxin B1 using specific aptamer.

A circularly polarized horn antenna with elliptical waveguide polarizer

AbstractIn this article, a circularly polarized horn antenna with elliptical waveguide polarizer is proposed. By converting linear polarization into circular polarization in the elliptical waveguide polarizer, circularly polarized radiation can be realized by the proposed antenna in D‐band. The observation shows that the proposed antenna achieves the impedance bandwidth of 16.7% for S11 &lt; −10 dB from 110 to 130 GHz and the axial‐ratio bandwidth of 11.7% from 114 to 128 GHz. The measured gain of the proposed antenna can reach the range 13.6‐17.82 dBic from 110 to 130 GHz. Besides, the measured normalized beam of the proposed antenna at the far field is able to realize a sidelobe below −25 dB, as well as good axial symmetry. With the elliptical waveguide polarizer, it is obtained that the proposed antenna has the potential application of circularly polarized radiation in millimeter and sub‐millimeter wave band.

Sense of Surface Plasmon Polarization Waveguide of Graphene

The honey structure of graphene is used in telecommunications, flexible displays, photonic devices, batteries, and electronic devices, where it achieves high heat dissipation efficiency. In order to obtain the high performances in the field of waveguide and sensor, we proposed a tunable plasmonic waveguide sensor based on periodic grating. The proposed device not only has the outstanding waveguide performance in gain threshold and propagation loss, which can reach 0.00745 dB/nm and 501 cm−1, respectively, but also the temperature sensitivity can achieve 0.28 nm/°C. The performances of waveguide and sensor can be tuned by changing the electronic characteristics of graphene, the structural parameters, and temperature, which indicate that the proposed device has considerable potential in ultra-speed plasma sensor devices, photonic integrated circuits, and tunable optical devices.

A Wideband Circularly Polarized Horn Antenna With a Tapered Elliptical Waveguide Polarizer

This paper proposes a circularly polarized horn antenna with tapered elliptical waveguide and it employs a tapered elliptical waveguide polarizer to achieve wideband circular polarization. The prototype of the proposed antenna is processed through simulation and optimization. The fabricated antenna realizes the result, S(1, 1) <; -10 dB and AR <; 3 dB from 170 to 260 GHz, by measurement. Both the 3 dB AR bandwidth and the impedance bandwidth are 41.86% (170-260 GHz). The RCHP far-field pattern and the gain of the proposed antenna are measured as well. The proposed antenna achieves a gain of 24.4-31.3 dB (0.3 dB) from 170 to 260 GHz. Therefore, this paper finally comes to the conclusion that it is quite convenient for the structure of the proposed antenna to be machined at millimeter- and submillimeter-wave bands and employed in the application of communication and radar.

Sense trace gases based surface plasmon polarization waveguide of graphene

To improve the selectivity of carbon nanotubes for gas sensors, we design a surface plasmon polarization waveguide based on graphene that can sense trace gases. In addition, a gas concentration measurement system was designed for a sensor based on optical cavity ring-down spectroscopy. The gas concentration measurement system was composed of two loops, which were combined with the minimum mean square error algorithm to achieve an amplified spontaneous emission noise filter. The experimental results show that the gas concentration measurement error was significantly improved after CO filtering. The slope of the logarithmic ring-down curve and the ring-down time decreased with the increasing gas concentration. The gas concentration and ring-down time showed an improved linear relationship. The design system can detect trace gases as a single gas or a variety of toxic gases in special environments. The device provided a wide range of sensors and measurements. Moreover, the proposed device is relatively simple and easy to implement, with high detection sensitivity.

Synoptic and Large-Scale Determinants of Extreme Austral Frost Events

AbstractWe define and examine extreme frost events at three station locations across southern Australia. A synoptic assessment of the events shows that they are generally characterized by passage of a front or trough followed by a developing blocking high. Frost typically occurs at the leading edge of the block. The very cold air pool leading to the frost event is the result of descent of cold, dry midtropospheric air parcels from regions poleward of the station. The air is exceptionally cold because it is advected across the strong meridional temperature gradients in the storm track. The air is dry because this equatorward meridional pathway requires descent and so must have origins well above the surface in the dryer midtroposphere. The position of the block and location of the dry descent are dynamically determined by large-scale waveguide modes in the polar jet waveguide. The role of the waveguide modes is deduced from composites of midtropospheric flow anomalies over the days preceding and after the frost events. These show organized wavenumber 3 or 4 wave trains, with the block associated with the frost formed as a node of the wave train. The wave trains resemble known waveguide modes such as the Pacific–South America mode, and the frost event projects clearly onto these modes during their life cycle. The strong interannual and decadal variability of extreme frost events at a location can be understood in light of event dependence on organized waveguide modes.

Broadband Polarization Degeneracy of Guided Waves in Subwavelength Structured ZnO Pattern

Polarization degeneracy of electromagnetic plane waves in vacuum and in any bulk isotropic media is the keynote operational principle of many optical devices such as polarizers and interferometers. However, surface and guided waves spectra are typically either not degenerated at all or meet degeneracy only at very specific dispersion points. In this paper, we offer a design of a periodic photonic structure based on zinc oxide (ZnO) nanocylinders providing the broadband polarization degeneracy of the guided waves in the near-IR frequency range. We analyze the impact of the spatial dispersion and substrate on the degeneracy breaking. We offer the design based on ZnO nanocylinders with aluminum-doped zinc oxide substrate, achieving the degeneracy in the vicinity of a telecommunication wavelength, for the practical implementation. Finally, we propose and verify numerically a potentially important device–waveguide polarizer, which is the analogue to the $\lambda /4$ plate for the guided waves.

Effect of Laser Irradiation on Graphene Oxide Integrated TE-Pass Waveguide Polarizer

SiO $_{2}$ –HfO $_{2}$ rib waveguides were fabricated using the UV-photolithography method followed by wet chemical etching technique. Graphene oxide (GO) integrated SiO $_{2}$ –HfO $_{2}$ rib waveguide works as an on-chip TE-pass waveguide polarizer and also allows controlled intensity tuning of the selective state of polarization when irradiated using a 532 nm ns laser. The tuning of the TE polarization intensity was confirmed by performing the experiments at three different pump fluences viz., 0.2, 0.3, and 0.6 mJ/cm $^{2}$ , wherein at low pump fluence, TE polarization intensity showed more controlled absorption. The results indicate that GO integrated glass waveguides can act as efficient polarization dependent power splitters for integrated optic applications.

Quasi-phase-matched second harmonic generation of UV light using AlN waveguides

As an alternative to electrically injected diodes, UV light emission can be obtained via second harmonic generation (SHG). In weakly birefringent materials such as aluminum nitride (AlN), the phase matching of the driving and second harmonic waves can be achieved by the quasi-phase-matching (QPM) technique, where the polarity of the material is periodically changed commensurate with the coherence wavelength. QPM also allows the use of the highest nonlinear susceptibility, and therefore, higher conversion efficiencies are possible. In this work, the QPM SHG of UV light in AlN lateral polar structure-based waveguides is demonstrated. The peak intensity of the frequency doubled laser light was measured at 344 nm and 472 nm wavelengths, in agreement with dispersion-based theoretical predictions. These results confirm the potential of III-nitride-based lateral polar structures for quasi-phase-matched nonlinear optics and for frequency doubling media for UV light generation.