Multiport Couplers Research Articles

The perspective of topological photonics for on-chip terahertz modulation and sensing

Terahertz (THz) technology has seen significant advancements in the past decades, encompassing both fundamental scientific research, such as THz quantum optics, and highly applied areas like sixth-generation communications, medical imaging, and biosensing. However, the progress of on-chip THz integrated waveguides still lags behind that of THz sources and detectors. This is attributed to issues such as ohmic losses in microstrip lines, coplanar and hollow waveguides, bulky footprints, and reflection and scattering losses occurring at sharp bends or defects in conventional dielectric waveguides. Inspired by the quantum Hall effects and topological insulators in condensed matter systems, recent discoveries of topological phases of light have led to the development of topological waveguides. These waveguides exhibit remarkable phenomena, such as robust unidirectional propagation and reflectionless behavior against impurities or defects. As a result, they hold tremendous promise for THz on-chip applications. While THz photonic topological insulators (PTIs), including wave division, multiport couplers, and resonant cavities, have been demonstrated to cover a wavelength range of 800–2500 nm, research on tunable THz PTIs remains limited. In this perspective, we briefly reviewed a few examples of tunable PTIs, primarily concentrated in the infrared range. Furthermore, we proposed how these designs could benefit the development of THz on-chip PTIs. We explore the potential methods for achieving tunable THz PTIs through optical, electrical, and thermal means. Additionally, we present a design of THz PTIs for potential on-chip sensing applications. To support our speculation, several simulations were performed, providing valuable insights for future THz on-chip PTI designs.

Topology-empowered membrane devices for terahertz photonics

Control of terahertz waves offers a profound platform for next-generation sensing, imaging, and information communications. However, all conventional terahertz components and systems suffer from bulky design, sensitivity to imperfections, and transmission loss. We propose and experimentally demonstrate on-chip integration and miniaturization of topological devices, which may address many existing drawbacks of the terahertz technology. We design and fabricate topological devices based on valley-Hall photonic structures that can be employed for various integrated components of on-chip terahertz systems. We demonstrate valley-locked asymmetric energy flow and mode conversion with topological waveguide, multiport couplers, wave division, and whispering gallery mode resonators. Our devices are based on topological membrane metasurfaces, which are of great importance for developing on-chip photonics and bring many features into terahertz technology.

Wideband isolation-improved substrate-integrated waveguide power dividers/combiners

AbstractIn this paper, a 3 dB H-plane substrate-integrated waveguide (SIW) power divider/combiner with improved isolation is reported. By adding two isolated ports into the Y-junction, it will perform like a multi-port coupler, so that the isolation between its dividing ports can be effectively improved as the newly-added ports are properly matched. To verify the availability and effectiveness of this concept, two prototypes, one is terminated by coaxial terminations and the other is loaded with lumped resistors, are developed. Their measured results are separately in good agreement with their corresponding simulations. Meanwhile, isolations better than 16 dB with fractional bandwidth (FBW) of 35 and 25% are achieved, respectively, as well as low phase and amplitude imbalances. Compared with some reported similar SIW power dividers, the proposed ones exhibit wider FBW with similar isolation, insertion loss, phase, and amplitude balance performance.

Mirrored Coupling Structures for Microwave Signal Splitting and Combining

This paper presents a method of creating multi-port couplers by mirroring conventional coupler structures, such as 90° hybrids, Saleh power dividers, and Wilkinson couplers. These created structures maintain some very useful features of the original structures, for example, stable phase shifting between ports, equal power dividing, and port isolation. Theoretical analysis method of these structures is discussed for S-parameter derivation. Example structures: a four-way coupler by mirroring 90° hybrid couplers, and an eight-way coupler by mirroring Saleh power-dividing couplers were built and tested according to the method discussed. A good match was found between theoretical analysis and measurements.

Analysis of long-period waveguide grating arrays

The authors analyze an array of long-period waveguide gratings with coupled-mode theory and show that the grating array can provide effective power transfer among the waveguides at specific wavelengths in the absence of evanescent-field coupling. In particular, they derive the general conditions for obtaining an arbitrary distribution of power splitting ratios among the waveguides and discuss several special cases. They also present a design example using practical waveguide parameters to demonstrate the feasibility of forming such grating arrays for the realization of multiport broadband couplers and add/drop multiplexers

Creation of a polarization W state using optical fibre multiports

A scheme for experimental creation of a polarization W state is reported in this paper. This scheme is based on a common commercial multiport fibre coupler and single photon source and it is feasible using current technology. This scheme has a higher efficiency and can be easily extended to generate a multiphoton W state with a photon number larger than 4.

Monitoring Bench and Procedure for Measurement of the Parameters of Multiport Fiber-Optic Couplers

A monitoring bench and procedure for measurement of the transmission matrix of (N × N)-type multiport fiber-optic couplers using mechano-optical scanning of the bench to achieve a high measurement rate are presented. It is shown that it is possible to measure the elements of the transmission matrix with error at most ±0.2 dB.

Semi-Active Multimatrix Reflector Antennas

ABSTRACT This paper covers recent work on a novel concept for multibeam transmit reflector antennas, called semi-active antennas since the feed array elements are not directly connected to the power modules, as in an active antennas, but separated from them by several multiport hybrid couplers. By controlling the phase of the low level equi-amplitude signals at the inputs of the amplifiers, these can be directed to selected feeds in the focal area of the reflector to generate multiple fixed or movable pencil or shaped beams. More or less channels can be routed into the beams by low level switching at the beam forming network input ports. Under all beam pointing and beam loading conditions, all amplifiers operate at nominal power, therefore with optimum efficiency. The basic principle of this new antenna architecture is presented and discussed and designs are evaluated for regional and global coverage satellite applications.

Phase-controlled switching in nonlinear multiport fiber couplers

The background of the phase-controlled switching behavior of nonlinear multiport couplers is investigated. For the two-core device a direct correlation between the concept of nonlinear eigenmodes and the spatial dynamics can be found. In aligned and triangular three-core geometries the interpretation of the dispersion relations of the nonlinear eigenmodes, as well as the introduction of power portraits, turns out to be useful in identification of those initial states that prepare the system for sensitive switching operations. Some opportunities for optimizing the input–output characteristics are discussed.

Power transfer in asymmetric multiport couplers

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Hardy, E. Marom, and Y. Shama, "Power transfer in asymmetric multiport couplers," Appl. Opt. 27, 447-448 (1988) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Coherent optical receiver for 680 Mbit/s using phase diversity

A coherent optical receiver using a multiport optical coupler to provide phase diversity is described. By this means, only homodyne bandwidth is required in the signal processing, but with tolerances on the frequency tracking typical of heterodyne systems. Measured sensitivities with limited local-oscillator power are −47.5 dBm at 320 Mbit/s and −42 dBm at 680 Mbit/s. The results at the higher bit rate are strongly influenced by limited receiver module bandwidth.

Design technique for multiport combline couplers with single port excited

Design technique for multiport combline couplers with single port excited

Asymmetrical star coupler for optical fiber systems

A technique has been developed for fabricating M x N fiber couplers that use different core-size fibers to improve the interconnection efficiency of multiterminal optical fiber systems. Experimental results are described for a 2 x 8 transmissive asymmetrical star coupler using 125-microm core diam input fibers and 63-microm core diam output fibers. This construction procedure also has the important advantage of improving the fiber throughput uniformity of fused biconical taper multiport couplers.