Proceedings Volume 12148

Integrated Photonics Platforms II

Roel G. Baets, Peter O'Brien, Laurent Vivien
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Proceedings Volume 12148

Integrated Photonics Platforms II

Roel G. Baets, Peter O'Brien, Laurent Vivien
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Volume Details

Date Published: 25 May 2022
Contents: 8 Sessions, 20 Papers, 14 Presentations
Conference: SPIE Photonics Europe 2022
Volume Number: 12148

Table of Contents

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Table of Contents

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  • Front Matter: Volume 12148
  • Light Emitters
  • Passive and Active Photonic Devices I
  • Simulation and Modelling
  • Passive and Active Photonic Devices II
  • Special Session on EU-Funded Integrated Photonics Projects II
  • Special Session on EU-Funded Integrated Photonics Projects III
  • Poster Session
Front Matter: Volume 12148
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Front Matter: Volume 12148
This PDF file contains the front matter associated with SPIE Proceedings Volume 12148, including the Title Page, Copyright information, Table of Contents, and Committee Page.
Light Emitters
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Mid-IR emission from integrated rare earth (Dy3+, Pr3+)-doped chalcogenides waveguides for sensing applications
Loïc Bodiou, Marion Baillieul, Virginie Nazabal, et al.
The mid-infrared (mid-IR) spectral region is of great interest to many areas of science and technology as it contains two important transparency windows (3-5 and 8-13 μm) of the Earth’s atmosphere and strong characteristic vibrational transitions displayed by a large number of molecules. Praseodymium (Pr3+) and dysprosium (Dy3+) ions feature characteristic transitions in the mid-IR and transmission range of chalcogenides-based materials spans a large part of the mid-IR. The combination of efficient waveguiding properties with mid-IR light emitters would therefore be a key enabler of the development of mid-IR sensors-on-a-chip for health, security and environmental applications. In this paper, RF magnetron co-sputtering is used to deposit a Dy3+/Pr3+-doped chalcogenides guiding layer based on the quaternary system composed of Ga, Ge, Sb and Se atoms on silica cladding layer. The fabrication process of straight ridge waveguides using photolithography and RIE/ICP dry etching is then described. Finally, Dy3+ and Pr3+ mid-IR guided photoluminescence around 2.5 and 4.5 μm is demonstrated at room temperature using co-propagating pumping at telecommunication wavelengths (respectively around 1.3 and 1.55 μm).
Erbium-doped sol-gel derived silica-titania films
In this paper, we presented the technology of erbium-doped SiOx:TiOy films with different concentrations of erbium (0, 2, 4,6 wt.%) were fabricated using the sol-gel method and dip-coating technique. Tetraethyl orthosilicate (Si(OC2H5)4; TEOS) and titania (IV) ethoxide (Ti(OC2H5)4; TET) were used as precursors of silica, and titania, respectively. Erbium(III) nitrate pentahydrate (Er(NO3)3·5H2O) were used as doping sources of Er ions. The influence of erbium concentration on the optical properties were analyzed using monochromatic elipsometry and UV-Vis spectrophotometry. Using the reflectance spectrophotometry method, optical homogeneity of erbium-doped SiOx:TiOy films were confirmed. The optical band gaps (Eg) were estimated from UV-Vis spectrophotometry. The results indicates to slight decrease in crystallite size of erbium-doped SiOx:TiOy films with increasing erbium concentration. Photoluminescence properties in visible region of erbium-doped SiOx:TiOy films have been demonstrated.
Passive and Active Photonic Devices I
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Highly efficient silicon nitride grating couplers with metal back-reflector enabled by cryogenic deep silicon etching
E. Lomonte, M. Stappers, F. Lenzini, et al.
The development of efficient coupling interfaces is a crucial requirement to fully harness the on-chip performance of photonic integrated circuits. Optical access is commonly implemented by either edge or vertical coupling, the latter one often relying on diffractive grating structures. At present, edge couplers are preferred when broadband and efficient operation is required, while grating couplers are mostly employed for wafer-scale and fast prototyping of photonic devices, at the expenses of a decreased efficiency. Here we present apodized surface grating couplers, characterized by a negative diffraction angle resulting in a self-imaging effect of the Gaussian-like diffracted beam and a metal back-reflector, which can successfully redirect upward all the optical power otherwise leaking into the substrate. Simulations predict that the effective combination of these two properties can open to the possibility of realizing fiber-to-chip interconnects that feature a coupling efficiency larger than 95%, together with pliant positioning on chip. As a proof of principle of our coupling approach, in our implementation we choose Si3N4 as photonic platform in which the grating coupler is fully etched, while the fabrication of the metal mirror is enabled by cryogenic deep silicon backside etching. Preliminary experimental results show a coupling efficiency of approximately -3 dB at an operating wavelength of λ≃1550 nm, almost doubling the efficiency of grating couplers on the Si substrate (≃ -5 dB). We anticipate that, by a proper optimization of the fabrication process, couplers with insertion loss smaller than 0.5 dB can be demonstrated.
Highlight of polarization filtering effect in passive porous silicon ridge waveguides
F. Cassio, L. Poffo, N. Lorrain, et al.
Porous silicon is a material used in integrated optics with few studies on its structuration impact on the polarization in the near infra-red range. In this letter, we report optical characterizations around 1550 nm for different input polarization of porous silicon ridge waveguide used either as is or in a micro-resonator structure. We highlight a filtering of light polarization that attenuate transverse electric mode by observing the extinction of the resonance peaks during the transmission response of the micro-resonator based on passive porous silicon ridge waveguides.
Low-loss all-optical ns-switching for single-photon routing in scalable integrated quantum photonics
Fabian Ruf, Lars Nielsen, Mircea Balauroiu, et al.
Efficient single-photon routing and switching are crucial for optical quantum computing and communication. For this purpose, all-optical switches are designed for gigahertz bandwidths. The switching mechanism is based on the optical Kerr effect via cross-phase modulation (CPM) of the single-photon signal by a strong 1550-nm pump pulse. For energy-efficient switching, this nonlinear effect is exploited in a microresonator that can either be used directly as an intensity switch in a typical add–drop configuration or as a phase shifter in a Mach–Zehnder interferometer (MZI) structure. To speed up resonance build-up and quenching, a pre-emphasis build and an off-resonance wipe pulse are used. The proposed designs are verified by traveling-wave simulations which demonstrate that 0.1 dB insertion loss and ~1 ns switching windows can be achieved. For a scalable out-of-the-lab transfer, we investigate the feasibility of the proposed switch designs for fabrication in a mature photonic integrated circuit (PIC) platform. In particular, silicon nitride PICs have demonstrated record-low losses which makes them suitable for single-photon applications. By parametric modelling of the microresonator’s directional couplers based on Lumerical EME and 2.5-dimensional varFDTD simulations, the required power transmission coefficients for both signal and pump wavelength can be achieved. This results in an all-optical switch design ready for fabrication in a commercial PIC foundry which can potentially enable scalable architectures for quantum photonic applications.
Development of a SiON-based integrated platform for the blue/near-UV wavelength range
L. Bodiou, P. P. Kamath, J.-C. Simon, et al.

Driven by the rich variety of molecular and atomic spectral features to probe in the NUV (near ultraviolet), photonic devices operating in this spectral range, like coherent sources and optical functions, may address multiple applications such as biosensing, environment, and security issues. Leveraging from mature semiconductor manufacturing industry, silicon photonics and in particular Silicon On Insulator (SOI) has emerged, over the past two decades, as the preferred technology for photonic integration. However, due to its low energy bandgap, Silicon strongly absorbs at wavelengths shorter than 1100 nm, prohibiting the use of SOI platform at near-UV wavelengths. To circumvent the Si absorption issue at short wavelengths, different materials, including Si3N4, Al2O3 or polymers, have been proposed to achieve low propagation loss in the blue and violet spectrum range.

This paper presents the use of silicon oxynitride (SiOxNy) to develop a platform enabling the development of near-UV integrated photonics. The optical design of integrated ridge waveguides for single-mode propagation at near-UV wavelengths is presented. Physical characterizations (refractive index, rugosity) of Plasma Enhanced Physical Vapor Deposition (PECVD) deposited SiOxNy on silica and fabrication process of integrated ridge waveguides using i-lines photolithography and RIE dry etching techniques are then described. To characterize these integrated waveguides, a microlensed fiber is developed in the NUV to improve the coupling efficiency between the fiber and the input of the integrated waveguide based on SiOxNy. Single-mode propagation of near-UV light (405 nm) is also observed in ridge structures by optical near field imaging.
Simulation and Modelling
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Dimensionality reduction for efficiency human and computer codesign in integrated photonics
Anastasiia Sheveleva, Christophe Finot, Pierre Colman
Computer design of photonic integrated chip results usually into more efficient solutions, but the key geometrical features that constitute the core of the design, and explain most of its performance and the logic behind them, are difficult to identify. Taking as example densely packed arrays of waveguides, we explain how the knowledge of the physics governing these systems allows the construction of a new representation basis that has much less degrees of freedom than the direct space representation. The analysis of the results of a subsequent Genetic Algorithm optimization reveals new innovative strategy that mediate the shortcomings of human designing.
Mask synthesis for silicon photonics devices
Rainer Zimmermann, Luis Orbe, Bernd Küchler, et al.
Photonics represents a growing opportunity to design and manufacture devices and integrated circuits for applications in high-speed data communications, advanced sensing, and imaging. Photonic technologies provide orders-of-magnitude speed improvements with reduced power consumption for data transmission and ultra-sensitive sensing capabilities in multiple application domains. Curvilinear patterns are required to maintain the physical properties of light propagation. We investigate the readiness of state-of-the-art mask synthesis tools to meet the challenges for photonics devices in terms of mask data preparation and verification. We apply OPC and ILT to photonic integrated circuit designs containing components sensitive to fabrication variation, to generate Manhattan and curvilinear mask data. Results are validated using a lithography verification tool considering smoothness of the printed curved structures, a key factor to maintain the correct functionality of the photonic devices. Rather than using ideal targets, we take simulation contours from corrected layouts for initial assessment of light propagation through wave guides. The impact of lithographic patterning related perturbations such as resist line edge roughness on optical performance is investigated based on results from a rigorous lithography process simulation model. Experimental data from fabricated devices underline the usefulness of lithography simulation to predict unwanted impact on device performance and the need of correction tools to counteract these effects.
Reducing loss and crosstalk in two-mode ridge waveguide bend by step-like thickness structuring
We proposed a simple method of reducing bend-related loss and inter-mode crosstalk in two-mode ridge waveguide by step-like thickness structuring of bent section. It is already known that the effect of bend can be compensated by linear variation of the waveguide thickness or effective index, however, fabrication of such waveguides requires complicated technologies, which limits mass applications of such structures. We show that the two-step like structuring of the ridge waveguide thickness is sufficient to significantly reduce pure bending loss, bend-related inter-mode crosstalk and excess loss at the interface between straight and bent waveguides sections. Based on the rigorous numerical simulation conducted using transformation optics formalism, we determined the thickness change required to compensate for bend-induced effects and confirmed effectiveness of the proposed approach.
Optimization study of all-dielectric metamaterial cladding for increased integration density of PIC
Andraž Debevc, Marko Topič, Janez Krč
Evanescent coupling between optical waveguides (WGs) in photonic integrated circuits (PICs) is the origin of unwanted optical cross-talk between adjacent WG structures. Employing an all-dielectric metamaterial cladding, consisting of two periodically exchanging dielectric materials, can potentially reduce the cross-talk between WGs, and thus, paves the way towards higher integration density. In this contribution we present the results of numerical simulations in the process of optimization of all-dielectric metamaterial cladding of silicon strip WGs to achieve the lowest possible gap width between WG cores that still satisfies the chosen reference cross-talk level (-30 dB at the distance of 2 mm). We also investigate how the performance of WGs with metamaterial cladding is affected, if the metamaterial cladding is present only in the spacing between WGs. We show that the gap width can be in best case decreased by 60 % representing a 45 % improvement in integration density for the case of 450 nm core width. We also investigate the wavelength dependence of effects and determine the usable wavelength range of optimized structures. Furthermore, we extend the study to account for fabrication variability of the sub-wavelength structures. A general trend is observed that structures with the lowest achieved gap width exhibit the narrowest wavelength range and the highest sensitivity to fabrication variability. However, we still demonstrate a sizable decrease in gap width of 37 % and a relatively wide usable wavelength range of > 75 nm when accounting for a feature size variation in the range of ± 5 nm.
A fiber-to-waveguide, 1D grating coupler design using genetic algorithm for 1550 nm applications
Silicon photonics on silicon-on-insulator (SOI) technology has great potential in the integrated photonics field. Propagation modes are mostly confined within Silicon waveguides because of the high refraction index difference between silicon waveguide and silicon dioxide cladding. Nowadays, couplers designed using this special feature of SOI are in demand. Edge coupler and grating coupler are the two most preferred coupler types for coupling light between integrated photonic circuits and single-mode optical fibers. In this work, we focused on grating couplers to couple light from fiber to horizontal waveguide since their advantages are easy fiber alignment, lower cost, compact design, and more possible optic inputs/outputs. However, in the literature, the fabrication process of grating couplers with high coupling efficiency is complicated. Therefore, in this paper, we are proposing a grating coupler design with standard SOI lithography technology with a minimum feature size of 250 nm. In our research, the finite difference time domain (FDTD) method is utilized to analyze and design the grating coupler structure with a center of 1.55 μm. We used a genetic algorithm (GA) and particle swarm optimization (PSO) to optimize grating coupler features. SiO2 cladding thickness, SiO2 buried oxide layer thickness, grating widths, and fiber distance from grating couplers are optimized with these optimization processes. Our design is an apodized grating coupler with a -3.29 dB (46.8%) coupling efficiency and a 3 dB bandwidth of 78 nm. The design layer of the grating coupler is 12 μm × 16 μm.
Passive and Active Photonic Devices II
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Silicon photonic free-space beam steered optical switch using wavelength tuned nanoantennas
Konstantinos S. Lekkas, George T. Kanellos
As optical interconnects data rates increases, the Opto–Electro–Optical (OEO) conversion in the ports of the traditional electronic packet switches (EPS) will not be an acceptable solution anymore because of lack of scalability, high cost and excess losses [9]. High speed and scalable optical switches could replace EPS and completely eliminate the need for the OEO conversion. Free–Space Optical (FSO) switches such as Micro ElectroMechanical System switches (MEMS) have high scalability but low switching speed [2]. Whereas, photonic integrated circuit (PIC) switches have shown high switching speed which ranges from some nanoseconds to 10s of microseconds but low scalability with up to 32 ports [6]. The perfect switch would combine the high scalability and high switching speed of the FSO and PIC switches, respectively. In this communication, a novel PIC switch architecture is presented to use grating couplers and their ability to diffract light to the free space. Grating couplers are facing each other and are used as transmitting and receiving nanoantennas. The switch has one input transmitting and four output receiving nanoantennas. The angle of emission of the diffracted beam depends on the wavelength which ranges from 1.3 to 1.55μm. Tuning the wavelength, the beam is steered to one of the receiving nanoantennas. The results monitoring the nanoantennas S parameters reveal satisfactory coupling between the input and output ports with insertion losses in the range between -6 to -8dB, while the interchannel crosstalk isolation from the other ports is less than -9dB from the value of coupling.
Self-heating analysis of monolithically integrated hybrid III-V/Si PIN diode
Self-heating is a crucial effect in integrated nanophotonic devices regarding their power consumption. In this work, we employ coupled 3D thermo-electrical simulations to gain insight into the thermal behavior related to traps in a monolithic InP-InGaAs-InP pin-diode fabricated at IBM-Research Zurich. From transport study, two types of defects are found to be very likely present in the studied device: (i) positive oxide charges close to the interface between III-V materials and top oxide layer and (ii) electron-type traps at the p-InP/i-InGaAs interface. Thermal simulations show that the presence of electron-type traps at the p/i interface enhances the self-heating in the device
Special Session on EU-Funded Integrated Photonics Projects II
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INSPIRE: InP on SiN photonic integrated circuits realized through wafer-scale micro-transfer printing
M. J. R. Heck
INSPIRE will sustain Europe’s industrial leadership in photonics by combining the generic integrated foundry technology at the pioneering pure-play foundry SMART Photonics, and the silicon photonics pioneer imec, with the micro-transfer printing technology developed at X-Celeprint. This will be a world-first platform combining the strengths to create best-in-class photonic integrated circuit (PIC) manufacturing. Furthermore, INSPIRE will strengthen the European manufacturing base by developing and implementing processing steps that are key to removing expensive assembly steps in PIC-based product realization. The methods will be developed for silicon nitride – indium phosphide integration. Since the optical coupling happens through a silicon intermediate layer the developed technology can be further ported to silicon, CMOS-compatible, photonics as well. INSPIRE will connect state-of-the-art manufacturing capability to leading-edge applications, and also to industry clusters through JePPIX, ePIXfab and the EC manufacturing pilot lines.
Special Session on EU-Funded Integrated Photonics Projects III
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Photonics integrated circuits from innovations to commercial solutions: MedPhab pilot line for accelerated industrial uptake
Medical device industry is a rapidly growing area providing significant opportunities for the photonics technology suppliers. The heterogeneous nature of photonics and lack of available fabrication processes with medical certificates set challenges for a rapid adaption of the latest photonics technologies. The aim of MedPhab photonics pilot line is to establish seamless research and development chains between research organization and industry accelerating the product launch in regulated domain.
MORPHIC: MEMS enhanced silicon photonics for programmable photonics
We present our work in the European project MORPHIC to extend an established silicon photonics platform with low-power and non-volatile micro-electromechanical (MEMS) actuators to demonstrate large-scale programmable photonic integrated circuits (PICs).
Poster Session
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Design, simulation and performance comparison of SoI rectangular waveguide and SMF for methane detection
Sensing analysis of methane gas has been presented in this paper by using Silicon on Insulator (SoI) based gas sensor. Methane a primary component of natural gas and a significant contributor in global warming. Sensing of methane is important because it is highly combustible gas which may leak from the voids of caverns and can explode during mining activities. To avoid fire in underground coal mines optical sensors, need to be designed. To evaluate sensing performance in this research work, gas detectors are investigated using two types of optical waveguides, one is Single Mode Fiber (SMF) and other is SoI based optical rectangular waveguide. These two-waveguide structure works for sensing application of several liberated gases in atmosphere and can detect the presence of methane. However, SoI based rectangular waveguide is more sensitive to the change in the Refractive Index (RI) corresponding to methane volume concentration in air. Further to increase the sensitivity, integrated circuit ring resonator is designed to detect the very low concentration of methane in air. On comparison of SM fiber and SoI waveguide in its straight and ring form, the SoI ring resonator structure is found to be sensitive to ~1% methane concentration.
Genetic algorithm based, on-chip, fishbone grating waveguide and transition design for time-domain operation
The limited bandwidth of conventional phase-shifter-based antenna arrays, which is caused by steering in different angles at different frequencies named as the beam-squint effect, is a problem that should be taken into consideration for the ultrawide band systems. To overcome this problem, designing optical true time delay (TTD) lines for the antenna arrays is crucial for the development of next-generation, wideband communication, and imaging systems, which employ short pulses for wideband operation. One of the important problems for employing such short pulses is the dispersion during the propagation along the on-chip optical waveguides, which cause the distortion in the pulse shape and decrease in the amplitude of the pulse. Therefore, we propose a one-dimensional (1D) fishbone grating waveguide with a “Lego” type of step taper on silicon-on-insulator (SOI) substrate, both of which are designed for time-domain operation. The designed grating waveguide/taper pair is excited by a pulsed Gaussian light source, having a FWHM of 90 fs at a center wavelength of 1550 nm, where we investigate the possibility of controlling the dispersion by using SiO2 cladding modulation and taper structure optimization using genetic algorithm. The simulation results show that it is possible to decrease the dispersion in terms of the amplitude of the pulse up to 85%. The simulation results also show that the coupling efficiency from the taper to the waveguide can be increased up to 73%, which also decrease the dispersion of the pulse significantly. The simulated bandwidth of the grating waveguide/taper pair is found to be 56 nm, which allows ultrawide band operation.
Waveguide-to-substrate, vertical bend coupler design for 3D photonic integrated circuits
A waveguide-to-substrate, vertical bend coupler that is based on genetic algorithm is introduced to couple and direct the optical flow in 3D photonic integrated circuits. The vertical coupler device enables high-efficiency broadband optical transmission between different dielectric layers over comparable distances to the coupler’s length. The vertical coupler attains an adept transition between a silicon waveguide and a planar Si layer separated by a SiO2 spacer. The simulation results of the designed vertical coupler device show a coupling ratio of -3.4 dB at 1550 nm wavelength and at 1 μm vertical transition depth, thanks to the effective manipulation of light. The coupler possesses a miniscule area of 2 μm × 2 μm compared to its conventional counterparts. Our proposed waveguide-to-substrate coupler represents an unprecedented, elevated solution with high-efficiency and broadband operation for the vertical transition in 3D photonic integrated circuits. It can take an important part in overcoming the obstacles on the way of 3D photonic integrated circuits for virtual reality and quantum computing applications.