Colorless directional coupler with dispersion engineered sub-wavelength structure

Halir, Robert; Maese-Novo, Alejandro; Ortega‐Moñux, Alejandro; Molina-Fernández, Í.; Wangüemert‐Pérez, J. Gonzalo; Cheben, Pavel; Xu, Dan‐Xia; Schmid, Jens H.; Janz, Siegfried

doi:10.1364/oe.20.013470

Cited by 128 publications

(93 citation statements)

References 20 publications

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“…1(a). To connect the directional coupler with other on chip devices, waveguide bends must be used at the input and output of the proposed coupler [6]. Because of the high confinement of silicon waveguide modes, the effect of the bend on the coupling ratio is not large even for small bend radius.…”

Section: Using a Phase Delay Section To Create A Broadband Directionamentioning

confidence: 99%

“…Although this wavelength dependence can be used for implementing useful devices such as optical filters [1], it limits the usefulness of the directional coupler for many other applications where a broadband response is required, for example optical sensing [2] and passive optical networking [3]. The bandwidth of the directional coupler can be increased by making the coupler asymmetric [4], adiabatic [5], by using a grating [6], or by introducing a bend in one arm of the coupler [7][8][9]. These approaches significantly increase the length of the coupler (over several hundred microns) and most of these designs are for low index contrast systems e.g., glass or fluorinated ploymide [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…These approaches significantly increase the length of the coupler (over several hundred microns) and most of these designs are for low index contrast systems e.g., glass or fluorinated ploymide [8,9]. There have been only a few reports of SOI compatible broadband directional couplers [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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Compact low loss and broadband hybrid plasmonic directional coupler

Alam¹,

Caspers²,

Aitchison³

et al. 2013

Opt. Express

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Abstract:We propose a novel broadband coupler for silicon photonics using a hybrid plasmonic waveguide section. The hybrid plasmonic waveguide is used to create an asymmetric section in the middle of a silicon nanowire waveguide coupler to introduce a phase delay to allow for a 3-dB power coupling ratio over a 150 nm bandwidth around 1.55 µm. The device is very compact (<8.5 µm) and has a low insertion loss (<0.15 dB).

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Section: Using a Phase Delay Section To Create A Broadband Directionamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Compact low loss and broadband hybrid plasmonic directional coupler

Alam¹,

Caspers²,

Aitchison³

et al. 2013

Opt. Express

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“…This "refractiveindex-engineering" has already been successfully applied to a variety of integrated devices [3,4]. The dispersion properties of SWGs have only very recently been explored [5].Here we use the concept of refractive index engineering to propose and experimentally demonstrate a reduced size, slotted 2x2 MMI coupler. The key point of this device is the design of a longitudinal SWG slot placed at the center of the multimode region (Fig.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Re-inventing multimode interference couplers using subwavelength gratings

Ortega‐Moñux

Halir

Maese-Novo

et al. 2013

2013 Conference on Lasers &Amp; Electro-Optics Europe &Amp; International Quantum Electronics Conference CLEO EUROPE/IQEC

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Multimode-Interference (MMI) devices (see Fig. 1a) are fundamental building blocks in photonic integrated circuits, where they are used for power splitting and combining, optical switches and modulators, Mach-Zehnder interferometers and 90º hybrids for coherent optical receivers [1]. MMIs are based on the self-image principle, by which the guided modes of the multimode region interfere to form replicas of the input field with specific amplitude and phase relations. These relations are known to depend on i) the core/cladding refractive indexes (n 1 /n 2 ), ii) the core width (W) and length (L) of the multimode region and iii) the number, width and position of the access ports. In this work, we show that by using sub-wavelength structures within an MMI, the self-imaging properties can be significantly altered, leading to ultra-short or ultrabroadband devices.Subwavelength gratings (SWGs) are structures with a pitch below the Bragg condition, so that they behave as an effective medium [2]. This means that in Silicon-on-Insulator (SOI) technology, equivalent refractive indexes between those of the core (Si) and the cladding (e.g. SiO 2 or SU-8) can be obtained tuning the SWG pitch and duty cycle. This "refractiveindex-engineering" has already been successfully applied to a variety of integrated devices [3,4]. The dispersion properties of SWGs have only very recently been explored [5].Here we use the concept of refractive index engineering to propose and experimentally demonstrate a reduced size, slotted 2x2 MMI coupler. The key point of this device is the design of a longitudinal SWG slot placed at the center of the multimode region (Fig. 1b). When properly designed, this slot changes the propagation constants of the even modes without affecting the odd modes. As a result the length of the device is halved without degrading its performance: Fig. 1(c) shows that, in a back-to-back configuration, the shortened device even exhibits a slightly better measured extinction ratio than the conventional device. We also present an ultra-broadband 2x2 MMI SWG coupler (Fig. 1d) which is based on SWG dispersion engineering. The tapered SWG structures at the input and output provide low-loss and low-reflection transitions between conventional silicon-wire waveguides and the SWG multimode region. The SWG multimode region is designed to achieve a nearly wavelength independent self-imaging length. The device exhibits a bandwidth of 450nm (1260nm−1675nm), which is five times higher than conventional MMIs. In this range, the insertion loss, power imbalance and MMI phase error, as simulated with 3D FDTD, are below 1dB, 0.6dB and 3º, respectively. References[1] L. B. Soldano and E. C. M. Pennings,"Optical multi-mode interference devices based on self-imaging: Principles and applications," J. Lightw. Technol. 13, 615 (1995).[2] S. M. Rytov, "The electromagnetic properties of finely layered medium," Sov. Phys. JETP, 2, 466-475, 1956.

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Quantum Topological Photonics

Yan

et al. 2021

Advanced Optical Materials

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Quantum topological photonics is a new research field with great potential that is based on developments in both quantum optics and topological photonics. Topological photonics offers unique properties, including topological robustness and an anti‐backscattering property, and these advantages are strongly required in quantum optics. Quantum technology, which includes quantum optics, represents an important direction for future technological development. However, existing quantum light sources are unstable and quantum information may easily be lost during transmission. These disadvantages have troubled researchers for a long time and no perfect solution is available thus far. Fortunately, application of topological photonics to quantum optics can help to generate robust quantum light sources and protect photons from decoherence during photon propagation. This allows the correlation and entanglement to be maintained even when photons travel over long distances. To date, quantum topological photonics has provided major breakthroughs in certain quantum devices. This Review presents the basic concepts of quantum topological photonics and summarizes how the topological protection property works in quantum light sources, quantum information transmission, and other quantum devices. Finally, an outlook is provided on the remaining challenges and potential future directions of quantum topological photonics, which can aid in exploration of additional new phenomena.

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Colorless directional coupler with dispersion engineered sub-wavelength structure

Cited by 128 publications

References 20 publications

Compact low loss and broadband hybrid plasmonic directional coupler

Compact low loss and broadband hybrid plasmonic directional coupler

Re-inventing multimode interference couplers using subwavelength gratings

Quantum Topological Photonics

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