Multimode Waveguide Structures Research Articles

Silicon Loop-Type Multimode Waveguide Structure With Fan-Out Output for Photonic Reservoir Computing

Silicon Loop-Type Multimode Waveguide Structure With Fan-Out Output for Photonic Reservoir Computing

On-Chip Multichannel Dispersion Compensation and Wavelength Division MUX/DeMUX Using Chirped-Multimode-Grating-Assisted Counter-Directional Coupler

On-chip optical dispersion compensation and wavelength division multiplexing/demultiplexing (WDM) are highly demanded functions for optical communications. In this work, we proposed a multichannel dispersion compensation structure based on chirped multimode grating within a counter-directional coupler (CMG-CDC). Simultaneous wavelength division multiplexing and demultiplexing can be realized within a compact footprint. A device design for four-channel CMG-CDC at the C/L (1530–1565 nm) band is presented with a channel spacing of 20 nm assisted by a grooved multimode waveguide structure. The average dispersion for all channels is about −2.25 ps/nm with a channel bandwidth of about 3.1 nm. The device is highly compact and highly scalable, which makes it rather convenient for increasing the group velocity dispersion (GVD) and channel number, indicating flexible applications for versatile systems, including typically coarse wavelength division multiplexer four-lane (CWDM4) transceivers.

Superradiant Phase Transition in Microstructures with a Complex Network Architecture

A new concept of topological organization of microstructures that maintain the ultrastrong coupling of two-level systems to a photon field and have the topology of a network (graph) with a power-law node degree distribution has been proposed. A phase transition to the superradiant state, which leads to the formation of two dispersion branches of polaritons and is accompanied by the appearance of a nonzero macroscopic polarization of two-level systems, has been studied within the mean field theory. It has been found that the specific behavior of such a system depends on the statistical characteristics of the network structure, more precisely, on the normalized second moment zeta equiv langle {{k}^{2}}rangle {text{/}}langle krangle of the distribution of node degrees. It has been shown that the Rabi frequency can be significantly increased in the anomalous regime of the network structure, where ζ increases significantly. The multimode (waveguide) structure of the interaction between matter and field in this regime can establish a ultrastrong coupling, which is primarily responsible for the high-temperature phase transition.

Ultracompact Channel Add-Drop Filter Based on Single Multimode Nanobeam Photonic Crystal Cavity

Ultracompact channel add-drop filter utilizing a single nanobeam photonic crystal cavity is analyzed, designed, and demonstrated. Anti-symmetric multimode periodic waveguide structure is employed to implement mode conversion and thus produce degenerate resonant states in the involved nanobeam cavity. Theoretical analysis results indicate that the inter-modal conversion coefficient and the waveguide-cavity coupling coefficient have significant effects on the lineshape of the filter. By carefully engineering the structure of the multimode nanobeam cavity and its side-coupled configuration, we successfully achieve an ultracompact add-drop filter with device area around 20 μm2. The experimental results on silicon-on-insulator (SOI) platform show that the insertion losses of drop port, the crosstalk of add port of the fabricated filter are -1.1 dB and -14.7 dB, respectively. The modal volume of the involved nanobeam cavity are small as 1.2(λ/n) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , indicating huge potentials in developing low-power consumption tunable devices for future very large scale integration (VLSI) photonic applications.

SPR Biosensor Based on Polymer Multi-Mode Optical Waveguide and Nanoparticle Signal Enhancement.

We present a surface plasmon resonance (SPR) biosensor that is based on a planar-optical multi-mode (MM) polymer waveguide structure applied for the detection of biomolecules in the lower nano-molar (nM) range. The basic sensor shows a sensitivity of 608.6 nm/RIU when exposed to refractive index changes with a measurement resolution of 4.3 × 10−3 RIU. By combining the SPR sensor with an aptamer-functionalized, gold-nanoparticle (AuNP)-enhanced sandwich assay, the detection of C-reactive protein (CRP) in a buffer solution was achieved with a response of 0.118 nm/nM. Due to the multi-mode polymer waveguide structure and the simple concept, the reported biosensor is well suited for low-cost disposable lab-on-a-chip applications and can be used with rather simple and economic devices. In particular, the sensor offers the potential for fast and multiplexed detection of several biomarkers on a single integrated platform.

Design of a 2D fiber mode converter using a planar 2D multi-mode interference structure

In this work, we present a new design of a fiber mode converter using a two dimensional multi-mode interference waveguide (2D MMI) Structure. The proposed structure allows the conversion of the fundamental fiber mode LP01 to the second order LP21 fiber mode in multimode fiber. The 2D MMI is used as a 1 × 4 splitter and followed by a phase shifter to construct the proper phase map of the higher order LP21 mode. The design is based on the self- imaging properties of the 2D MMI structure and can thus be generalized to higher order modes. The proposed structure shows an insertion loss of about −0.96 dB and a Wavelength Dependent Loss (WDL) of about 0.4 dB over a spectral range of 140 nm around 1550 nm.

Polymer selective laser curing for integrated optical switches

A simple in-layer electro optical switch has been prepared by selectively curing a photocurable optical polymer with a UV laser. The core of the device is a NOA-81 multimode waveguide grown by selective laser curing. The cladding is a positive calamitic liquid crystal, which allows tunability and switching of the waveguide by external driving electric signals. The effective refractive index in the guide changes upon switching the liquid crystal. Depending on the geometry, this setup leads to an electrooptical modulator or a switch between two levels of transmitted light. Full Text: PDF ReferencesT. Ako, A. Hope, T. Nguyen, A. Mitchell, W. Bogaerts, K. Neyts, and J. Beeckman, "Electrically tuneable lateral leakage loss in liquid crystal clad shallow-etched silicon waveguides", Opt. Express 23, 2846 (2015). CrossRef K. Kruse, C. Middlebrook, "Laser-direct writing of single mode and multi-mode polymer step index waveguide structures for optical backplanes and interconnection assemblies", Photon. Nanostruct. - Fundamentals and Appl. 13, 66 (2015). CrossRef A. Günther, A.B. Petermann, M. Rezem, M. Rahlves, M. Wollweber, and B. Roth, European Conf. Lasers and Electro-Optics - European Quantum Electronics Conference, Munich, Germany (2015).C. Florian, S. Piazza, A. Diaspro, P. Serra, M. Duocastella, "Direct Laser Printing of Tailored Polymeric Microlenses", ACS Appl. Mater. Interfaces, 8(27), 17028 (2016). CrossRef F. Costache, M. Blasl, "Optical switching with isotropic liquid crystals", Opt. Photonik 6, 29 (2011). CrossRef M. Cano-Garcia, R. Delgado, T. Zuo, M.A. Geday, X. Quintana, Jose M. Otón, 16th OLC Topical Meeting on the Optics of Liquid Crystals, Sopot, Poland (2015).S. Ishihara, H. Wakemoto, K. Nakazima, Y. Matsuo, "The effect of rubbed polymer films on the liquid crystal alignment", Liq. Cryst. 4(6), 669 (1989). DirectLink

Vibration Fiber Sensors Based on SM-NC-SM Fiber Structure

A novel vibration sensor based on the single mode (SM)-no core (NC)-SM fiber structure is proposed and experimentally sensing results demonstrated. By numerical simulation, we use an NC fiber (NCF) as the multimode waveguide structure for the multimode interference (MMI) sensing. Through intensity demodulation, the vibration sensing structure can detect continuous vibration disturbances with the frequencies of ranging from 100 Hz to 29 kHz and the inherent frequency of cantilever slab of 700 Hz. The frequency sensing resolution is 1 Hz in real-time monitoring. The proposed compact structure is easy to fabricate and has low cost.

Laser-direct writing of single mode and multi-mode polymer step index waveguide structures for optical backplanes and interconnection assemblies

A laser direct writing (LDW) method is implemented as a cost efficient polymer waveguide (WG) fabrication method for prototyping large substrates for optical backplanes and optical interconnection assemblies. The LDW setup utilizes a 3-axis air-bearing motion platform to reduce WG fabrication error to within ±0.15μm. A UV laser diode coupled single mode fiber with a focusing lens module is capable of LDW WGs at both multimode (50μm) and single mode (6μm) dimensions. Correlation between LDW parameters and fabricated WG dimensions using Dow Corning® OE-4140 UV-Cured Optical Elastomer (ncore=1.5142, nclad=1.5064) is discussed theoretically and confirmed experimentally for both applications. A theoretical model is developed and utilized for producing LDW multi-mode (0.04dB/cm, λ=850nm) and single mode (0.55dB/cm, λ=1310nm) WGs. Measured propagation losses of LDW WGs are comparable to losses of photolithographic multi-mode (0.04dB/cm @ 850nm) and single mode (0.59dB/cm @ 1310nm) WG builds. LDW multi-mode and single mode WG radial bend and crossing losses are evaluated for advanced optical communication channel routing capabilities and do not exhibit significant deviations from photolithographic-manufactured WG device loss.

Integrated photonic building blocks for next-generation astronomical instrumentation I: the multimode waveguide

We report on the fabrication and characterization of composite multimode waveguide structures that consist of a stack of single-mode waveguides fabricated by ultrafast laser inscription. We explore 2 types of composite structures; those that consist of overlapping single-mode waveguides which offer the maximum effective index contrast and non overlapped structures which support multiple modes via strong evanescent coupling. We demonstrate that both types of waveguides have negligible propagation losses (to within experimental uncertainty) for light injected with focal ratios >8, which corresponds to the cutoff of the waveguides. We also show that right below cutoff, there is a narrow region where the injected focal ratio is preserved (to within experimental uncertainty) at the output. Finally, we outline the major application of these highly efficient waveguides; in a device that is used to reformat the light in the focal plane of a telescope to a slit, in order to feed a diffraction-limited spectrograph.

Mode-filtered electron injection into a waveguide interferometer

Injection of mode-filtered electrons into a phase-sensitive four-terminal waveguide Aharonov–Bohm (AB) ring is studied. An individually tuneable quantum point contact (QPC) in a waveguide lead of the GaAs/AlGaAs-ring allows to selectively couple to one-dimensional modes in the ring. Thus, we demonstrate single-mode transport in a multimode waveguide structure. Coherent mode-filtering by the lowest QPC subband is verified by nonlocal bend resistance and phase-sensitive AB interference measurements.

Investigation of parameters of the multimode four-layer waveguide structures and their influence on the light propagation

Investigation of parameters of the multimode four-layer waveguide structures and their influence on the light propagation

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

Dynamics of an optical signal in a multimode waveguide structure

A mathematical model of linear dynamic distortions of average signal power in a planar optical waveguide stemming from the intermodal coupling and dispersion of waveguide modes caused by macroscopic bends and irregularities of the optical waveguide surface has been developed on the basis of pulse intermodal scattering matrix. It is shown that the elements of this matrix are determined at a waveguide segment whose length greatly exceeds the correlation scale of the field of irregularities but is much smaller than the normalization length of waveguide modes and are described by rectangular functions with a duration proportional to the relative velocity of the corresponding modes. The dependences of the pulse intermodal scattering matrix on the intensities of absorption, Rayleigh scattering, and optical signal scattering from waveguide irregularities have been established. It is shown that, at waveguide lengths exceeding the normalization length, the optical signal shape becomes almost stable and can be expressed in terms of the pulse characteristic of an integrating circuit. It has been established that irregularities of the film in a bent optical waveguide lead not only to additional attenuation but also to enhancement of multimode distortion. A matrix method is proposed for taking into account these distortions, which is based on the effect of equalization (scrambling) of the signal energy over the spectrum of the bent waveguide modes. The model developed was used to process the experimental data on the dynamics of a signal in a weakly guiding multimode polymer optical fiber in order to estimate the parameters of attenuation and irregularities of the waveguide surface.

Analysis of partially depleted absorber waveguide photodiodes

This paper presents the analysis and characterization of partially depleted absorber (PDA) photodiodes. Coupling to these photodiodes is achieved through a planar short multimode waveguide (PSMW) structure. Electric transport in the PDA structure has been investigated and an equivalent electric circuit was developed. Measurements on 5/spl times/20 /spl mu/m/sup 2/ PSMW PDA photodiodes have shown 0.80 A/W responsivity with a fiber mode diameter as high as 6 /spl mu/m. The transverse electric/transverse magnetic polarization dependence was <0.5/spl plusmn/0.3 dB with -1-dB input coupling tolerances as high as /spl plusmn/2.0 and /spl plusmn/1.3 /spl mu/m for horizontal and vertical directions. The -3-dB bandwidth was 50 GHz, and the -1-dB compression current at 40 GHz was 17 mA corresponding to +4.5 dBm radio frequency (RF) power. Compared to similar evanescently coupled p-i-n photodiodes, the saturation current has been significantly improved while maintaining comparable bandwidth and high responsivity.

3D scalar FDTD method for waveguides with circular symmetry

AbstractA 3D scalar finite‐difference time‐domain (FDTD) method in cylindrical coordinates is formulated in order to analyze the wave propagation in circularly symmetric waveguides. The 2nd‐order Mur's absorbing boundary condition (ABC) is provided as well. This method can be used to simulate the propagation and coupling between the modes in a multimode waveguide structure. An isotropic point source propagating in either a symmetric medium or multimode step‐index fiber and a plane‐source propagation in multimode fiber are simulated in this paper. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 218–221, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20774

PLC platform for bidirectional transceiver with wide multimode output waveguide to receiver

We present a new configuration of a thin-film-filter (TFF)-embedded planar-light-circuit platform for a bidirectional transceiver module to enhance a tolerance of the insertion loss to the positional deviation of the TFF, by using a wide multimode waveguide structure that guides a reflected light from the TFF to a photoreceiver. It is experimentally shown that the new scheme has a merit in a high tolerance to the positional deviation of the TFF, and that it maintains a considerably high optical isolation by a proper arrangement of waveguides.

Generation of correlated photons in controlled spatial modes by downconversion in nonlinear waveguides

We report the observation of correlated photon pairs generated by spontaneous parametric downconversion of a 400-nm pump pulse in a quasi-phase-matched KTiOPO(4) nonlinear waveguide. The highest ratio of coincidence to single-photon count rates observed near 800 nm exceeds 18%. This suggests that nonlinear waveguides will be a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the downconverted photons produced in multimode waveguide structures.

High-performance polymeric componentry for telecom and datacom applications

We review a polymeric waveguide technology developed to produce affordable high-performance optical components that address the needs of both the telecom and the datacom industries. We engineer advanced organic polymers that can be readily made into planar single- mode, multimode, and micro-optical waveguide structures of controlled numerical apertures and geometries. These materials are formed from highly crosslinked acrylate monomers with specific linkages that deter- mine properties such as flexibility, toughness, optical loss, and environ- mental stability. These monomers are intermiscible, providing for precise continuous adjustment of the refractive index over a wide range. In poly- mer form, they exhibit state-of-the-art loss values, suppressed polariza- tion effects, and exceptional stability, enabling their use in a variety of demanding applications. Waveguides are formed photolithographically, with the liquid monomer mixture polymerizing upon illumination in the UV via either mask exposure or laser direct writing. A wide range of rigid and flexible substrates can be used. The devices we describe include a va- riety of passive and thermo-optically active elements that achieve a va- riety of coupling, routing, and filtering functionalities. These devices can be either individually pigtailed and packaged components or they can be part of a massively parallel photonic integrated circuit on the multichip module (MCM), board, or backplane level. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)01003-5)

Reflection resonances and natural oscillations of two-aperture iris in rectangular waveguide

The total reflection resonances that take place at the excitation of a two-slot resonant iris in rectangular waveguide are discussed in this paper. Considering the iris as an open-resonator-waveguide structure, the pair of natural oscillations responsible for such resonances was numerically found and investigated. It is pointed out to a parallel between the rejection resonances in two-slot irises and "locked"-mode resonances in multimode waveguide structures.