This PDF file contains the front matter associated with SPIE Proceedings Volume 10242, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

This paper gives a review of the recent progresses in our research on nanophotonics and hybrid plasmonic geometries, structures and devices. In the first part we present SOI-nanowire-based integrated components. The concept and different configurations of hybrid plasmonic structures will be then discussed. Finally different fabricated devices for applications in optical interconnects and sensing will be presented and characterized.

Long-range surface plasmon waveguides, and their application to various transducer architectures for amplitude- or phase-sensitive biosensing, are discussed. Straight and Y-junction waveguides are used for direct intensity-based detection, whereas Bragg gratings and single-, dual- and triple-output Mach Zehnder interferometers are used for phasebased detection. In either case, multiple-output biosensors which provide means for referencing are very useful to eliminate common perturbations and drift. Application of the biosensors to disease detection in complex fluids is discussed. Application to biomolecular interaction analysis and kinetics extraction is also discussed.

A plasmonic integrated circuit configuration comprising plasmonic and electronic components is presented and the feasibility for high-speed signal processing applications is discussed. In integrated circuits, plasmonic signals transmit data at high transfer rates with light velocity. Plasmonic and electronic components such as wavelength-divisionmultiplexing (WDM) networks comprising metal wires, plasmonic multiplexers/demultiplexers, and crossing metal wires are connected via plasmonic waveguides on the nanometer or micrometer scales. To merge plasmonic and electronic components, several types of plasmonic components were developed. To ensure that the plasmonic components could be easily fabricated and monolithically integrated onto a silicon substrate using silicon complementary metal-oxide-semiconductor (CMOS)-compatible processes, the components were fabricated on a Si substrate and made from silicon, silicon oxides, and metal; no other materials were used in the fabrication. The plasmonic components operated in the 1300- and 1550-nm-wavelength bands, which are typically employed in optical fiber communication systems. The plasmonic logic circuits were formed by patterning a silicon oxide film on a metal film, and the operation as a half adder was confirmed. The computed plasmonic signals can propagate through the plasmonic WDM networks and be connected to electronic integrated circuits at high data-transfer rates.

A design for a high Q factor photonic crystal ring resonator (PCRR) is presented. The PCRR is based on 2D pillar type photonic crystals, which consist of a hexagonal array of silicon rods. The cavity is created by removing elements from the regular PhC grid. Achieving strong confinement of light intensity in the low index region (filled with the gaseous analyte) is the advantage of this PCRR. In that manner, the interaction of light and analyte, which can be a liquid or a gas, will be enhanced. The high quality factor of the cavity (Q=1.2×10⁴ ), along with strong overlap between the field of the resonant mode and the analyte as well as the low group velocity of PCRR modes yield enhanced light-matter interaction. An enhancement factor of 1.149×10⁵ compared to the bulk light absorption in a homogenous material provides the potential for highly sensitive gas detection with a photonic crystal ring resonator.

We present an integrated optical wavelength meter based on a Si₃N₄/SiO₂ micro ring resonator (operating over a free spectral range of ≈ 2.6 nm) whose output response is immune to temperature changes. The wavelength meter readout is performed by a neural network and a non-linear optimization algorithm. This novel approach ensures a high wavelength estimation precision (≈ 50 pm). We observe a long-term reproducibility of the wavelength meter response over a time interval of one week. We investigate the influence of the ambient temperature on the estimated wavelength. We observe an immunity of the displayed output wavelength to temperature changes of up to several degrees. The temperature-drift immunity appears to be caused by deviations from the theoretically expected (perfect) transmission function of a ring resonator, i.e., caused by deviations that are usually undesired in spectroscopic devices.

As the link capacity increases dramatically, it is also becoming more and more important to develop smart photonic networks-on-chip so that the bandwidth/channels can be utilized optimally and flexibly. One of the keys for realizing smart (reconfigurable) photonic networks is reconfigurable photonic integrated devices and circuits. As silicon has a large thermo-optic (TO) coefficient as well as a high heat conductivity, it is promising to realize efficient thermallyreconfigurable silicon photonic integrated devices and circuits with simple fabrication processes. This paper gives a review of our recent work on reconfigurable photonic integrated devices and circuits on silicon, including: (1) tunable microring-resonator (MRR)-based optical filters; (2) ultra-broadband optical switches; (3) monolithically-integrated reconfigurable optical add-drop multiplexers (ROADMs) for wavelength-division-multiplexing (WDM), mode-divisionmultiplexing (MDM), as well as hybrid WDM-MDM systems.

The complexity scaling of silicon photonics circuits is raising novel needs related to control. Reconfigurable architectures need fast, accurate and robust procedures for the tuning and stabilization of their working point, counteracting temperature drifts originated by environmental fluctuations and mutual thermal crosstalk from surrounding integrated devices. In this contribution, we report on our recent achievements on the automated tuning, control and stabilization of silicon photonics architectures. The proposed control strategy exploits transparent integrated detectors to monitor non-invasively the light propagating in the silicon waveguides in key spots of the circuit. Local monitoring enables the partitioning of complex architectures in small photonic cells that can be easily tuned and controlled, with need for neither preliminary circuit calibration nor global optimization algorithms. The ability to monitor the Quality Of of Transmission (QoT) of the optical paths in Photonic Integrated Circuits (PICs) is also demonstrated with the use of channel labelling and non-invasive light monitoring. Several examples of applications are presented that include the automatic reconfiguration and feedback controlled stabilization of an 8×8 switch fabric based on Mach-Zehnder interferometers (MZIs) and the realization of a wavelength locking platform enabling feedback-control of silicon microring resonators (MRRs) for the realization of a 4×10 Gbit/s wavelength-division-multiplexing transmitter. The effectiveness and the robustness of the proposed approach for tuning and stabilization of the presented architectures is demonstrated by showing that no significant performance degradation is observed under uncooled operation for the silicon chip.

We report on a record broad 3-dB bandwidth of 14 nm (~1.8 THz around 1532 nm) optical frequency comb generated from a passively mode-locked quantum-well (QW) laser in the form of photonic integrated circuits through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by two on-chip reflectors incorporating intracavity phase modulators followed by an out-of-cavity SOA as booster. Under certain operating conditions, an ultra-wide spectral bandwidth is achieved along with an autocorrelation trace confirming the mode locking nature exhibiting a pulse width of 0.35 ps. The beat note RF spectrum has a linewidth of sub-MHz and 35-dB SNR.

The evolving field of optics for information and communication is currently seeking directions to expand the data rates in all concerned devices, fiber-based or on chips. We describe here two possibilities where the new concept of PT-symmetry in optics [1,2] can be exploited to help high data rate operation, considering either transverse or longitudinal aspects of modal selection, and assuming that data are carried using precise modes. The first aspect is transverse multimode transport. In this case, a fiber or a waveguide carries a few modes, say 4 to 16, and at nodes, they have to undergo a demux/mux operation to add or drop a subset of them, as much as possible without affecting the others. We shall consider to this end the operation as described in ref. [3] : if a PT-symmetric “potential”, which essentially consists of a transverse gain-loss profile with antisymmetry, is applied to a waveguide, it has a very different impact on the different modes and mode families in the waveguide. One can in particular find situations where only two modes of the passive waveguide to be analyzed may enter into a gain regime, and not the other ones. From this scheme and others [4], we will discuss what is the road left towards an actual device, either in dielectrics or in case plasmonics is envisioned [5], i.e. with rather constant losses, but the possible advantage of miniaturization. The second aspect is longitudinal mode selection. The special transport properties of PT-symmetric Bragg gratings are now well established. In order to be used within a data management system, attention has to be paid to the rejection rate of Bragg gratings, and to the flatness of their response in the targeted window. To this end, a slow modulation of both real and imaginary parts of the periodic pattern of the basically PT-symmetric waveguide can help, in the general spirit of “apodization”, but now with more parameters. We will detail some aspects of the designs introduced in [6] , notably their ease of implementation in established optoelectronic fabrication platforms. To conclude these considerations, the perspectives offered by the combination of transverse multimode systems and PT-symmetric type of periodicity will be discussed. [1] C. M. Bender and S. Boettcher, “Real spectra in non-Hermitian Hamiltonians having PT-symmetry,” Phys. Rev. Lett. 80, 5243 (1998). [2] J. Čtyroký, V. Kuzmiak, and S. Eyderman, “Waveguide structures with antisymmetric gain/loss profile,” Opt. Express 18, 21585-21593 (2010). [3] H. Benisty, A. Lupu, A. Degiron, “Transverse periodic PT symmetry for modal demultiplexing in optical waveguides,” Phys. Rev. A 91, 053825 (2015). [4] N. Rivolta, B. Maes, "Symmetry recovery for coupled photonic modes with transversal PT symmetry", Opt. Letters, 40, 16, 3922-3925, (2015) [5] A. Lupu, H. Benisty, A. Degiron, “Switching using PT symmetry in plasmonic systems: positive role of the losses,” Opt. Express 21, 21651-21668 (2013). [6] A. Lupu, H. Benisty, A. Lavrinenko, “Tailoring spectral properties of binary PT-symmetric gratings by using duty cycle methods,” JSTQE 22, 35-41 (2016).

The progress of nanotechnologies has triggered the emergence of many photonic artificial structures: photonic crystals, metamaterials, plasmonic resonators. Recently the intriguing class of PT-symmetric devices, referring to Parity-Time symmetry [1] has attracted much attention. The characteristic feature of PT-symmetry is that the structures' refractive index profile is complex-valued due to the presence of alternating gain and loss regions in the system. Apart from fundamental research motivations, the tremendous interest in these artificial systems is strongly driven by the practical outcomes expected to foster a new generation of tunable, reconfigurable and non-reciprocal devices. The principle of gain-loss modulation lying in the heart of PT-symmetry optics enables a range of innovative solutions in the field of integrated optics at 1.5μm [2-7]. By using PT-symmetric coupled waveguides and Bragg reflectors as fundamental building blocks, it is possible to build a wide variety of functional optical devices. The PT-symmetry principle provides an alternative way for the realization of active devices that could become functional in a new platform for integrated optics. For instance one major bottleneck of the III-V/Si hybrid integration approach is that each type of active devices (laser, modulator, etc) requires a specific composition of III-V semiconductor alloy, involving a variety of (re)growth challenges. The advantage of the PT-symmetry solution is that the fabrication of all these devices can be done with a single stack of III-V semiconductor alloys that greatly simplifies the technological process. The aim of the current contribution is to provide a survey of the most promising applications of PT-symmetry in photonics with a particular emphases on the transition from theoretical concepts to experimental devices. The intention is to draw attention to the risks and issues related to the practical implementation that are most often overlooked in the basic theoretical models. An analysis of solutions to circumvent or overcome these issues to achieve a proper devices operation will be presented. Preliminary results on the experimental realization of PT symmetric structures using III-V's technology will be communicated. [1] C. M. Bender and S. Boettcher, “Real spectra in non-Hermitian Hamiltonians having PT-symmetry,” Phys. Rev. Lett. 80, 5243 (1998). [2] J. Čtyroký, V. Kuzmiak, and S. Eyderman, “Waveguide structures with antisymmetric gain/loss profile,” Opt. Express 18, 21585-21593 (2010). [3] A. Lupu, H. Benisty, A. Degiron, “Switching using PT symmetry in plasmonic systems: positive role of the losses,” Opt. Express 21, 21651-21668 (2013). [4] S. Phang, A. Vukovic, H. Susanto, T. M. Benson, and Ph. Sewell, “Ultrafast optical switching using parity-time symmetric Bragg gratings. J. Opt. Soc. Am. B 30, 2984 (2013). [5] H. Benisty, A. Lupu, A. Degiron, “Transverse periodic PT symmetry for modal demultiplexing in optical waveguides,” Phys. Rev. A 91, 053825 (2015). [6] S. Phang, A. Vukovic, S. C. Creagh, P. D. Sewell, G. Gradoni, T. M. Benson, T. M. “Localized Single Frequency Lasing States in a Finite Parity-Time Symmetric Resonator Chain,” Scientific Reports, 6, 20499 (2016). [7] A. Lupu, H. Benisty, A. Lavrinenko, “Tailoring spectral properties of binary PT-symmetric gratings by using duty cycle methods,” JSTQE 22, 35-41 (2016).

Subwavelength gratings (SWGs) are periodic structures with a pitch (Λ) smaller than the wavelength of the propagating wave (λ), so that diffraction effects are suppressed. These structures thus behave as artificial metamaterials where the refractive index and the dispersion profile can be controlled with a proper design of the geometry of the structure. SWG waveguides have found extensive applications in the field of integrated optics, such as efficient fiber-chip couplers, broadband multimode interference (MMI) couplers, polarization beam splitters or evanescent field sensors, among others. From the point of view of nano-fabrication, the subwavelength condition (Λ << λ) is much easier to meet for long, mid-infrared wavelengths than for the comparatively short near-infrared wavelengths. Since most of the integrated devices based on SWGs have been proposed for the near-infrared, the true potential of subwavelength structures has not yet been completely exploited. In this talk we summarize some valuable guidelines for the design of high performance SWG integrated devices. We will start describing some practical aspects of the design, such as the range of application of semi-analytical methods, the rigorous electromagnetic simulation of Floquet modes, the relevance of substrate leakage losses and the effects of the random jitter, inherent to any fabrication process, on the performance of SWG structures. Finally, we will show the possibilities of the design of SWG structures with two different state-of-the-art applications: i) ultra-broadband MMI beam splitters with an operation bandwidth greater than 300nm for telecom wavelengths and ii) a set of suspended waveguides with SWG lateral cladding for mid-infrared applications, including low loss waveguides, MMI couplers and Mach-Zehnder interferometers.

Efficient coupling of light from a chip into an optical fiber is a major issue in silicon photonics, as the dimensions of high-index-contrast photonic integrated waveguides are much smaller than conventional fiber diameters. Surface grating couplers address the coupling problem by radiating the optical power from a waveguide through the surface of the chip to the optical fiber, or vice versa. However, since the grating radiation angle substantially varies with the wavelength, conventional surface grating couplers cannot offer high coupling efficiency and broad bandwidth simultaneously. To overcome this limitation, for the near-infrared band we have recently proposed SOI-based zero-order grating couplers, which, making use of a subwavelength-engineered waveguide and a high-index prism, suppress the explicit dependence between the radiation angle and the wavelength, achieving a 1-dB bandwidth of 126 nm at λ = 1.55 μm. However, in the near-infrared, the bandwidth enhancement of zero-order grating couplers is limited by the effective index wavelength dispersion of the grating. In the mid-infrared spectral region, the waveguide dispersion is lower, alleviating the bandwidth limitation. Here we demonstrate numerically our zero-order grating coupler concept in the mid-infrared at λ = 3.8 μm. Several couplers for the silicon-on-insulator and the germanium-on-silicon nitride platforms are designed and compared, with subdecibel coupling efficiencies and 1-dB bandwidths up to ~680 nm.

Silicon-on-insulator (SOI), as the most promising platform, for advanced photonic integrated structures, employs a high refractive index contrast between the silicon “core” and surrounding media. One of the recent new ideas within this field is based on the alternative formation of the subwavelength sized (quasi)periodic structures, manifesting as an effective medium with respect to propagating light. Such structures relay on Bloch wave propagation concept, in contrast to standard index guiding mechanism. Soon after the invention of such subwavelength grating (SWG) waveguides, the scientists concentrated on various functional elements such as couplers, crossings, mode transformers, convertors, MMI couplers, polarization converters, resonators, Bragg filters, and others. Our contribution is devoted to a detailed numerical analysis and design considerations of Bragg filtering structures based on SWG idea. Based on our previous studies where we have shown impossibility of application of various 2 and “2.5” dimensional methods for the proper numerical analysis, here we effectively use two independent but similar in-house approaches based on 3D Fourier modal methods, namely aperiodic rigorous coupled wave analysis (aRCWA) and bidirectional expansion and propagation method based on Fourier series (BEX) tools. As it was recently demonstrated, SWG Bragg filters are feasible. Based on this idea, we propose, simulate, and optimize spectral characteristics of such filters. In particular, we have investigated several possibilities of modifications of original SWG waveguides towards the Bragg filtering, including firstly - simple single-segment changes in position, thickness, and width, and secondly - several types of Si inclusions, in terms of perturbed width and thickness (and their combinations). The leading idea was to obtain required (e.g. sufficiently narrow) spectral characteristic while keeping the minimum size of Si features large enough. We have found that the second approach with the single element perturbations can provide promising designs. Furthermore, even more complex filtering SWG structures can be considered.

We discuss recent advances in the modelling of optical frequency comb generation in quadratic and cubic microresonators. Different time domain models are presented and compared, and their solutions are analysed by numerical methods.

In this work, the simplified modeling of silicon phase modulators is presented along with a comparison among different options of modulators. The proposed simplified model enables a substantial reduction in computational effort while maintaining a good accuracy. The presented model is validated against complete 3D-simulations by means of the design of four different modulators. Furthermore, with the help of the model a deep insight on the performances tradeoffs in the choose and design of silicon modulators is provided.

Silicon photonics has generated a strong interest in recent years, mainly for optical communications and optical interconnects in CMOS circuits. The main motivations for silicon photonics are the reduction of photonic system costs and the increase of the number of functionalities on the same integrated chip by combining photonics and electronics, along with a strong reduction of power consumption. However, one of the constraints of silicon as an active photonic material is its vanishing second order optical susceptibility, the so called χ(2) , due to the centrosymmety of the silicon crystal. To overcome this limitation, strain has been used as a way to deform the crystal and destroy the centrosymmetry which inhibits χ(2). The paper presents the recent advances in the development of second-order nonlinearities including discussions from fundamental origin of Pockels effect in silicon until its implementation in a real device. Carrier effects induced by an electric field leading to an electro-optics behavior will also be discussed.

The purpose of this work is to explore an alternative approach for high speed and low power consumption optical modulation based on the use of the Pockels effect in silicon. Unfortunately, silicon is a centro-symmetric crystal leading to a vanishing of the second order nonlinear coefficient, i.e. no Pockels effect. To overcome this limitation, on possibility would be to break the crystal symmetry by straining the silicon lattice with the epitaxial growth of crystalline functional oxides. Indeed, the induced strain due to lattice parameter mismatch and the difference in the thermal expansion coefficients between oxides and silicon are strong and may induce strong strain into silicon. Furthermore, functional oxides can exhibit very interesting multiferroicity and piezoelectricity properties that pave the way to a new route to implement silicon photonic circuits with unprecedented functionalities.

Integrated optics has the potential to play a transformative role in astronomical instrumentation. It has already made a significant impact in the field of optical interferometry, through the use of planar waveguide arrays for beam combination and phase-shifting. Additionally, the potential benefits of micro-spectrographs based on array waveguide gratings have also been demonstrated.

Here we examine a new application of integrated optics, using ring resonators as notch filters to remove the signal from atmospheric OH emission lines from astronomical spectra. We also briefly discuss their use as frequency combs for wavelength calibration and as drop filters for Doppler planet searches. We discuss the theoretical requirements for ring resonators for OH suppression. We find that small radius (< 10 μm), high index contrast (Si or Si₃N₄) rings are necessary to provide an adequate free spectral range. The suppression depth, resolving power, and throughput for efficient OH suppression can be realised with critically coupled rings with high self-coupling coefficients.

We report on preliminary laboratory tests of our Si and Si3N4 rings and give details of their fabrication. We demonstrate high self-coupling coefficients (> 0:9) and good control over the free spectral range and wavelength separation of multi-ring devices. Current devices have Q ≈ 4000 and ≈ 10 dB suppression, which should be improved through further optimisation of the coupling coefficients. The overall prospects for the use of ring resonators in astronomical instruments is promising, provided efficient fibre-chip coupling can be achieved.

Meandering waveguide distributed feedback structures are novel integrated photonic lightwave and microwave circuit elements. Meandering waveguide distributed feedback structures with a variety of spectral responses can be designed for a variety of lightwave and microwave circuit element functions. Distributed meandering waveguide (DMW) structures [1] show a variety of spectral behaviors with respect to the number of meandering loop mirrors (MLMs) [2] used in their composition as well as their internal coupling constants (Cs). DMW spectral behaviors include Fano resonances, coupled resonator induced transparency (CRIT), notch, add-drop, comb, and hitless filters. What makes the DMW special is the self-coupling property intrinsic to the DMW’s nature. The basic example of DMW’s nature is motivated through the analogy between the so-called symmetric meandering resonator (SMR), which consists of two coupled MLMs, and the resonator enhanced Mach-Zehnder interferometer (REMZI) [3]. A SMR shows the same spectral characteristics of Fano resonances with its self-coupling property, similar to the single, distributed and binary self coupled optical waveguide (SCOW) resonators [4]. So far DMWs have been studied for their electric field intensity, phase [5] and phasor responses [6]. The spectral analysis is performed using the coupled electric field analysis and the generalization of single meandering loop mirrors to multiple meandering distributed feedback structures is performed with the transfer matrix method. The building block of the meandering waveguide structures, the meandering loop mirror (MLM), is the integrated analogue of the fiber optic loop mirrors. The meandering resonator (MR) is composed of two uncoupled MLM’s. The meandering distributed feedback (MDFB) structure is the DFB of the MLM. The symmetric MR (SMR) is composed of two coupled MLM’s, and has the characteristics of a Fano resonator in the general case, and tunable power divider or tunable hitless filter in special cases. The antisymmetric MR (AMR) is composed of two coupled MLM’s. The AMR has the characteristics of an add-drop filter in the general case, and coupled resonator induced transparency (CRIT) filter in a special case. The symmetric MDFB (SMDFB) is composed of multiple coupled MLM’s. The antisymmetric MDFB (AMDFB) is composed of multiple coupled MLM’s. The SMDFB and AMDFB can be utilized as band-pass, Fano, or Lorentzian filters, or Rabi splitters. Distributed meandering waveguide elements with extremely rich spectral and phase responses can be designed with creative combinations of distributed meandering waveguides structures for various novel photonic circuits. References [1 ] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, “Meandering Waveguide Distributed Feedback Lightwave Circuits,” J. Lightwave Technol, vol. 33, no. 9, pp. 1691–1702, May 2015. [2] N. J. Doran and D. Wood, “Nonlinear-optical loop mirror,” Opt. Lett. vol. 13, no. 1, pp. 56–58, Jan. 1988. [3] L. Zhou and A. W. Poon, “Fano resonance-based electrically reconfigurable add-drop filters in silicon microring resonator-coupled Mach-Zehnder interferometers,” Opt. Lett. vol. 32, no. 7, pp. 781–783, Apr. 2007. [4] Z. Zou, L. Zhou, X. Sun, J. Xie, H. Zhu, L. Lu, X. Li, and J. Chen, “Tunable two-stage self-coupled optical waveguide resonators,” Opt. Lett. vol. 38, no. 8, pp. 1215–1217, Apr. 2013. [5] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, “Novel distributed feedback lightwave circuit elements,” in Proc. SPIE, San Francisco, 2015, vol. 9366, p. 93660A. [6] C. B. Dağ, M. A. Anıl, and A. Serpengüzel, “Meandering Waveguide Distributed Feedback Lightwave Elements: Phasor Diagram Analysis,” in Proc. PIERS, Prague, 1986–1990 (2015).

Ion implantation into silicon causes radiation damage. If a sufficient dose is implanted, complete amorphisation can result in any implanted part of an optical device. Amorphous silicon has a refractive index that is significantly different higher than that of crystalline silicon (~10^-1), and can therefore form the basis of a refractive index change in optical devices. This refractive index change can be partially or completely removed by annealing. In recent years we have presented results on the development of erasable gratings in silicon to facilitate wafer scale testing of silicon photonics circuits. These gratings are formed by amorphising selected areas of silicon by utilising ion implantation of Germanium. However, we have now used similar technology for trimming of integrated photonic components. In this paper we discuss design, modelling and fabrication of ring resonators and their subsequent trimming using ion implantation of Germanium into silicon followed by annealing.

Mode-division multiplexing (MDM), which allows different guided modes of a few-mode fiber to carry different signals, is a new technology being actively pursued worldwide to increase the signal-carrying capacity of a fiber. For the development of the MDM technology, many mode-controlling devices are needed, such as mode converters, mode (de)multiplexers, mode filters, and mode-selective switches. Among the various technologies available for the implementation of such devices, the polymer waveguide technology offers many distinct advantages. This paper presents a review of polymer waveguide devices for MDM applications, which include grating-based mode converters, 3D mode (de)multiplexers, graphene-based mode filters, and thermo-optic mode-selective switches.

Recent design flows for photonic integrated circuits have been able to take advantage of mature capabilities available in electronic design automation such as schematic driven design and sophisticated circuit verification. Furthermore, new photonic integrated circuit simulators that can interface with electrical circuit simulators have been developed. As a result, photonic design flows are rapidly advancing in maturity. An area that still requires development is the statistical analysis of photonic circuits to be able to predict and improve yield, which is particularly challenging because photonic components tend to be large compared to the wavelength which makes them highly sensitive to phase errors. Furthermore, photonic devices tend to have long range spatial correlations in their parameters that cannot be ignored. In this paper, we present two approaches that enable Monte Carlo analysis of photonic integrated circuits, which include the treatment of spatial correlations, and we show how they can be used to predict the circuit yield. Example circuits include passive filters made from cascaded Mach-Zehnder interferometers and transceivers using active ring modulators.

We propose germanium-rich silicon germanium waveguides as a basic building block for polarization insensitive circuitry on silicon. In this work a detailed study of SiGe waveguides geometries is performed to find optimal parameters to simultaneously obtain low polarization sensitivity and single mode operation at λ=1.55μm. The polarization dependence of the effective index, group index and dispersion coefficient is investigated. Optimized geometries are tolerant to fabrication errors and can be realized with the current state of the art CMOS technology. As a next step polarization insensitive multimode interference structures have been designed.

In this work we correlate the dimension of the waveguide with small variations of the refractive index of the material used for the waveguide core. We calculate the effective modal refractive index for different dimensions of the waveguide and with slightly variation of the refractive index of the core material. These results are used as an input for a set of Finite Difference Time Domain simulation, directed to study the characteristics of amorphous silicon waveguides embedded in a SiO₂ cladding. The study considers simple linear waveguides with rectangular section for studying the modal attenuation expected at different wavelengths. Transmission efficiency is determined analyzing the decay of the light power along the waveguides. As far as near infrared wavelengths are considered, a-Si:H shows a behavior highly dependent on the light wavelength and its extinction coefficient rapidly increases as operating frequency goes into visible spectrum range. The simulation results show that amorphous silicon can be considered a good candidate for waveguide material core whenever the waveguide length is as short as a few centimeters. The maximum transmission length is highly affected by the a-Si:H defect density, the mid-gap density of states and by the waveguide section area. The simulation results address a minimum requirement of 300nm×400nm waveguide section in order to keep attenuation below 1 dB cm^-1.

Current trends in electronic industry, such as Internet of Things (IoT) and Cloud Computing call for high interconnect bandwidth, increased number of active devices and high IO count. Hence the integration of on silicon optical waveguides becomes an alternative approach to cope with the performance demands. The application and fabrication of horizontal (planar) and vertical (Through Silicon Vias - TSVs) optical waveguides are discussed here. Coupling elements are used to connect both waveguide structures. Two micro-structuring technologies for integration of coupling elements are investigated: μ-mirror fabrication by nanoimprint (i) and dicing technique (ii). Nanoimprint technology creates highly precise horizontal waveguides with polymer (refractive index nC = 1.56 at 650 nm) as core. The waveguide ends in reflecting facets aligned to the optical TSVs. To achieve Total Internal Reflection (TIR), SiO2 (nCl = 1.46) is used as cladding. TSVs (diameter 20-40μm in 200-380μm interposer) are realized by BOSCH process¹, oxidation and SU-8 filling techniques. To carry out the imprint, first a silicon structure is etched using a special plasma etching process. A polymer stamp is then created from the silicon template. Using this polymer stamp, SU-8 is imprinted aligned to vertical TSVs over Si surface.Waveguide dicing is presented as a second technology to create coupling elements on polymer waveguides. The reflecting mirror is created by 45° V-shaped dicing blade. The goal of this work is to develop coupling elements to aid 3D optical interconnect network on silicon interposer, to facilitate the realization of the emerging technologies for the upcoming years.

The generations of localized photonic nanojets using core-shell diffraction gratings working in the visible light region are demonstrated numerically. The power flow patterns for the core-shell diffraction gratings are simulated by using the finite-difference time-domain method. The focusing qualities of localized photonic nanojets are evaluated in terms of focal length and transversal width along propagation and transversal directions. Due to surface plasmon polaritons, it has been demonstrated that the metallic shell is critical for power enhancement of photonic nanojet. The high-resolution imaging of the core-shell diffraction grating can be expected from the high-intensity photonic nanojet. The photonic nanojet could be operated in a wide range imaging for nano-scale targets through the core-shell diffraction grating.

The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide layer on glass as the substrate and polysulfone with known refractive index as the material for testing the method. In the paper we provide the theoretical background of the method, demonstrate the experimental results obtained during the implementation of the technique as well as discuss its main strengths and flaws.

Vertical-cavity surface-emitting lasers (VCSELs) have emerged as a pioneering solution for many high-speed data communication challenges. Therefore, higher bandwidth optical interconnects with data rates in the range of 100 Gbit/s require directly modulated VCSELs with ultimate speed ratings. The small-signal modulation response of a VCSEL can be isolated from the entire system, thus providing accurate information on the intrinsic laser dynamics. Until now, it is assumed that the dynamic behavior of oxide-confined multi-mode VCSELs can be fully modeled using the single-mode rate equations developed for edge-emitters, even though the deviation between the single-mode based model and the measured data is substantially large. Using an advanced theoretical approach, rate equations for multi-mode VCSELs were developed and the small-signal modulation response of ultra-high speed devices with split carrier reservoirs corresponding with the resonating modes were analyzed. Based on this theoretical work, and including gain compression in the model, the analyzed VCSELs showed modulation bandwidth around and exceeding 30 GHz. The common set of figures of merit is extended consistently to explain dynamic properties caused by the coupling of the different reservoirs. Furthermore, beside damping and relaxation oscillation frequency, the advanced model, with gain compression included, can reveal information on the photon lifetime and highlights high-speed effects such as reduced damping in VCSELs due to a negative gain compression factor.

To improve the transmittance of THz component and overcome the difficulties of fragile structure as well as ensuring precise alignment of existing methods, a new method involving the mature 3DIC through-silicon via (TSV) technology has been proposed to make anti-reflection layer with suitable effective refractive index based on the robustness of Si wafer. Cu wire-grid polarizers were also fabricated on wafer. The THz polarizers were completed after wafer bonding with Cu sealing ring and In/Sn guard ring. Not only the new method is easier for production with better performance, but also the silicon substrate has several advantages. The novel method has proven that THz optical component could be constructed with a nearly 100% transmittance, or widened the transmittance spectrum range from 0.5 to 2 THz when transmittances is sacrificed to 70% instead of a near 100%. Furthermore, a robust structure could also be expected with broadband transmission and excellent extinction ratio. It is properly optimized for mass production because the fabrication method could be easily done and does not required high cost.

Silicon oxycarbide (SiOC) thin films are produced with reactive rf magnetron sputtering of a silicon carbide (SiC) target on Si (100) and SiO₂/Si substrates under varying deposition conditions. The optical properties of the deposited SiOC thin films are characterized with spectroscopic ellispometry at multiple angles of incidence over a wavelength range 300- 1600 nm. The derived optical constants of the SiOC films are modeled with Tauc-Lorentz model. The refractive index n of the SiOC films range from 1.45 to 1.85 @ 1550 nm and the extinction coefficient k is estimated to be less than 10^-4 in the near-infrared region above 1000 nm. The topography of SiOC films is studied with SEM and AFM giving rms roughness of 0.9 nm. Channel waveguides with a SiOC core with a refractive index of 1.7 have been fabricated to demonstrate the potential of sputtered SiOC for integrated photonics applications. Propagation loss as low as 0.39 ± 0.05 dB/mm for TE and 0.41 ± 0.05 dB/mm for TM polarizations at telecommunication wavelength 1550 nm is demonstrated.