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In this work, the authors present their recent progress in the development of a platform for the mid-infrared wavelength range, based on suspended silicon waveguides with subwavelength metamaterial cladding. The platform has some intrinsic advantages, which make it a very promising candidate for sensing applications in the molecular fingerprint region. Specifically, it can cover the full transparency window of silicon (up to a wavelength of 8 μm), only requires one lithographic etch-step and can be designed for strong light-matter interaction. Design rules, practical aspects of the fabrication process and experimental results of a complete set of elemental building blocks operating at two very different wavelengths, 3.8 and 7.7 μm, are discussed. Propagation losses as low as 0.82 dB/cm at λ0 = 3.8 μm and 3.1 dB/cm at λ0 = 7.7 μm are attained for the interconnecting waveguides.

In this work different silicon photonic devices, including straight waveguides, multi-mode interference devices and Mach-Zehnder interferometers, were fabricated and characterized on hot-wire chemical vapor deposition (HWCVD) silicon nitride (SiN) layers deposited at temperatures below 350 °C. These layers presented a hydrogen concentration of 13.1%, which is lower than that achieved with plasma enhanced chemical vapor deposition at these deposition temperatures. The lowest reported optical propagation losses of 6.1 dB/cm and 5.7 dB/cm, 1550 nm and 1310 respectively, for straight SiN waveguides prepared by HWCVD was measured. We demonstrated that silicon nitride SiN, prepared using HWCVD, is a viable material for silicon photonics fabrication.

A novel technique for realization of configurable/one-time programmable (OTP) silicon photonic circuits is presented. Once the proposed photonic circuit is programmed, its signal routing is retained without the need for additional power consumption. This technology can potentially enable a multi-purpose design of photonic chips for a range of different applications and performance requirements, as it can be programmed for each specific application after chip fabrication. Therefore, the production costs per chip can be reduced because of the increase in production volume, and rapid prototyping of new photonic circuits is enabled. Essential building blocks for the configurable circuits in the form of erasable directional couplers (DCs) were designed and fabricated, using ion implanted waveguides. We demonstrate permanent switching of optical signals between the drop port and through the port of the DCs using a localized post-fabrication laser annealing process. Proof-of-principle demonstrators in the form of generic 1×4 and 2×2 programmable switching circuits were fabricated and subsequently programmed.

High performance silicon optical modulators underpin a number of current and emerging applications based upon silicon photonic technology. Here we present our recent breakthroughs in this field.

Critical coupling control is an important concept used in integrated photonics to obtain functionalities such as single and coupled resonator optical filters and wavelength multiplexers. Realization of critical coupling depends strongly on device fabrication, and reproducibility is therefore an ongoing challenge.Post-fabrication trimming offers a solution for achieving optimal performance for individual devices. Ion implantation into silicon causes crystalline lattice damage which results in an increase of the material’s refractive index and therefore creates a platform for realization of various optical devices. In recent years, we have presented results on the development of erasable gratings, optical filters and Mach-Zehnder interferometers using ion implantation of germanium into silicon. Here, we report the design, fabrication and testing of silicon-on-insulator racetrack resonators, trimmed by localised annealing of germanium ion implanted silicon using continuous and pulsed wave laser sources. The results demonstrate the ability to permanently tune the critical coupling condition of racetrack resonators. Compared to the pulsed lasers used for annealing, continuous wave lasers revealed much higher extinction ratio due to improved material quality after silicon recrystallization.

The mid-infrared (MIR) wavelength region is attracting more and more research for applications such as medical diagnostics, environmental monitoring, and free space communications. In the MIR, thermal detectors play an important role because they can operate over a large wavelength range, can be fabricated using CMOS compatible processes, and do not require cooling. Today no other MIR detector technology is able to fill this gap. We demonstrate the first uncooled silicon waveguide-based bolometers, in the Silicon-on-Insulator (SOI) and suspended silicon waveguide platforms. The bolometers comprise gold plasmonic antennas on the waveguide surface that heat up when they absorb light, and amorphous silicon thermometers (formed by ion implantation), whose electrical resistance changes by 0.90 ± 0.26 % K-1 when they are heated. We show that suspending the bolometers improves their performance, and achieve sensitivities of up to 1.13 ± 0.04 % change in resistance per milliwatt of input power, with a noise equivalent power of 66 μW/√Hz. Calculations suggest the NEP could in future, be further reduced by 4 orders of magnitude.

Advanced photonic probing techniques are of great importance for the development of non-contact wafer-scale testing of photonic chips. Ultrafast photomodulation has been identified as a powerful new tool capable of remotely mapping photonic devices through a scanning perturbation. Here, we develop photomodulation maps into a quantitative technique through a general and rigorous method based on Lorentz reciprocity that allows the prediction of transmittance perturbation maps for arbitrary linear photonic systems with great accuracy and minimal computational cost. Excellent agreement is obtained between predicted and experimental maps of various optical multimode-interference devices, thereby allowing direct comparison of a device under test with a physical model of an ideal design structure. In addition to constituting a promising route for optical testing in photonics manufacturing, ultrafast perturbation mapping may be used for design optimization of photonic structures with reconfigurable functionalities., Advanced photonic probes are important for the development of non-contact wafer-scale testing of photonic chips. Here, Vynck et al. develop a quantitative technique based on mapping of transmittance variations by ultrafast perturbations to analyze arbitrary linear multi-port photonic devices.

Light-induced manipulation techniques have been utilized to transport, trap, or levitate microscopic objects for a wide range of applications in biology, electronics, and photonics. Without making direct physical contact, they can provide simple yet powerful means for high-precision assembly of microscale functional blocks and components within the integrated circuit platforms, thereby offering a viable alternative to the conventional heterogeneous integration techniques, such as wafer/die bonding and transfer printing. Using a microbubble-based optofluidic pick-and-place assembly process, heterogeneous integration of compact III-V semiconductor photodetectors on a silicon-based photonic integrated circuit chip, enabling direct high-speed vertical electrical contacts for significantly improved photogenerated carrier transit distance/time, is experimentally demonstrated. The microdisk-shaped InGaAs p-i-n photodetector integrated on the silicon waveguide has a 3 dB bandwidth exceeding 50 GHz under the applied bias voltage of -1 V for near-infrared wavelengths around 1.55 mu m. The light-induced optofluidic assembly will provide a promising route for seamless heterogeneous integration of various optoelectronic components with high-speed and low-noise electrical interconnection on the fully processed silicon photonic/electronic integrated circuit platforms.

We propose and experimentally demonstrate an apodized bidirectional grating coupler for high-efficiency, perfectly vertical coupling. Through grating apodization, the coupling efficiency (CE) can be notably improved, and the parasitic reflections can be minimized. For ease of fabrication, subwavelength gratings are introduced, which are also beneficial for the coupling performance. Simulation shows a record CE of 72%. We found that the coupler is quite robust to the variation of incidence mode field diameter and fiber misalignment. A CE of −1.8 dB is experimentally measured with a 1-dB bandwidth of 37 nm.

Protein sensing in biological fluids provides important information to diagnose many clinically relevant diseases. Mid-infrared (MIR) absorption spectroscopy of Bovine Serum Albumin (BSA) is experimentally demonstrated on a germanium on silicon (GOS) waveguide in the 1900-1000 cm-1 (5.3-10.0 µm) region of the MIR. GOS waveguides were shown to guide light up to a wavelength of 12.9 µm. The waveguide absorption spectrum of water, showing molecular bending vibrations, was obtained experimentally and compared with a theoretical model showing good agreement. Measurement of a concentration series of BSA protein in phosphate buffered saline (PBS) from 0.1 mg/ml to 100mg/ml was performed on the waveguide using filter paper as a flow strip and the amide I, II and III peaks were observed and quantified.

The atmospheric-transmission window and the fingerprint region of many substances overlaps with the long-wave infrared band. This has enabled the emergence of a new path for photonic integrated circuits, which could exploit the potential applications of this wavelength range, including chemical and bio sensing. In this work we review our latest advances in the suspended silicon platform with subwavelength grating lateral cladding at 7.7-μm wavelength. Suspended waveguides only require one lithographic etch step and can be specifically designed to maximize sensitivity when used as sensors. Waveguides with propagation loss of 3.1±0.3 dB/cm are demonstrated, as well as bends with less than 0.1 dB/bend. Suspended waveguides based on shifted Bragg grating lateral cladding are also reported, with propagation loss of 5.1±0.6 dB/cm. These results prepare the ground for the development of a platform capable of covering the entire mid-infrared band., 2019 21st International Conference on Transparent Optical Networks (ICTON), July 9-13, Angers, France

We present interlayer slope waveguides, designed to guide light from one level to another in a multi-layer silicon photonics platform. The waveguide is fabricated from hydrogenated amorphous silicon (a-Si:H) film, deposited using hot-wire chemical vapor deposition (HWCVD) at a temperature of 230°C. The interlayer slope waveguide is comprises of a lower level input waveguide and an upper level output waveguide, connected by a waveguide on a slope, with vertical separation to isolate other crossing waveguides. Measured loss of 0.17 dB/slope was obtained for waveguide dimensions of 600 nm waveguide width (w) and 400 nm core thickness (h) at a wavelength of 1550 nm and for transverse electric (TE) mode polarization.

Germanium has become a material of high interest for mid-infrared (MIR) integrated photonics due to its complementary metal-oxide-semiconductor (CMOS) compatibility and its wide transparency window covering the 2-15 μm spectral region exceeding the 4 μm and 8 μm limit of the Silicon-on-Insulator (SOI) platform and Si material respectively. Here, we present suspended germanium waveguides operating at wavelengths of 3.8 μm and 7.67 μm with propagation losses of 2.9 ± 0.2 dB/cm and 2.6 ± 0.3 dB/cm respectively.

Experimental demonstrations of silicon-on-insulator waveguide-based free-carrier effect modulators operating at 3.8 μm are presented. PIN diodes are used to inject carriers into the waveguides, and are configured to (a) use free-carrier electroabsorption to create a variable optical attenuator with 34 dB modulation depth and (b) use free-carrier electrorefraction with the PIN diodes acting as phase shifters in a Mach–Zehnder interferometer, achieving a V π L π of 0.052 V · mm and a DC modulation depth of 22 dB. Modulation is demonstrated at data rates up to 125 Mbit/s.

We demonstrate low-loss hydrogenated amorphous silicon (a-Si:H) waveguides by hot-wire chemical vapor deposition (HWCVD). The effect of hydrogenation in a-Si at different deposition temperatures has been investigated and analyzed by Raman spectroscopy. We obtained an optical quality a-Si:H waveguide deposited at 230°C that has a strong Raman peak shift at 480 cm−1, peak width (full width at half-maximum) of 68.9 cm−1, and bond angle deviation of 8.98°. Optical transmission measurement shows a low propagation loss of 0.8 dB/cm at the 1550 nm wavelength, which is the first, to our knowledge, report for a HWCVD a-Si:H waveguide.

SiN layers are typically deposited by low-pressure chemical vapour deposition (LPCVD) and plasma-enhanced chemical vapour deposition (PECVD). The issue with these deposition techniques is that they require high temperature processing (>400ºC) in order to produce waveguides with low propagation losses. As a result, they are incompatible with multilayer platforms in which the integration of active devices is intended, because the fabrication of these devices requires processes that are sensitive to high temperatures such as metallisation and doping. To address this situation, we are proposing hot wire chemical vapour deposition (HWCVD) as a means to deposit SiN layers at temperatures below 400ºC. This technique has already been used in solar cell applications [1,2] to produce amorphous SiN layers with low hydrogen content and high mass density [3]. In this study, several deposition recipes were defined with a design of experiments methodology (DoE) in which different combinations of deposition parameters were investigated to understand how they affect the material structure of the SiN layers in order to optimise the quality and the losses of the deposited materials. The physical, chemical and optical properties of the obtained SiN layers were characterised using ellipsometry, scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and atomic force microscopy (AFM). Also, waveguide structures were fabricated on the deposited materials to measure their propagation losses at 1310 and 1550nm using the cutback method. SiN layers with good uniformity, roughness as low as 0.61nm, H concentration as low as 10.4x1021 atoms/ cm3 and losses of 7.1dB/cm at 1310nm and 12.3dB/cm at 1550nm were obtained. [1] H. D. Goldbach, C. H. M. van der Werf, J. Löffler, A. Scarfo, A. M. C. Kylner, B. Stannowski, W. M. Arnoldbik, A. W. Weeber, H. Rieffe, W. J. Soppe, J. K. Rath, and R. E. I. Schropp,“Hot-wire chemical vapor deposition of silicon nitride for multicrystalline silicon solar cells,” in Conference Record of the Thirsy-first IEEE Photovoltaic Specialists Conference, pp. 1249–1252, IEEE, January 2005. [2] J. K. Holt, D. G. Goodwin, A. M. Gabor, F. Jiang, M. Stavola, and H. A. Atwater, “Hot-wire chemical vapor deposition of high hydrogen content silicon nitride for solar cell passivation and anti-reflection coating applications,” Thin Solid Films 430, pp. 37–40, April 2003. [3] V. Verlaan, R. Bakker, C. H. M. van der Werf, Z. S. Houweling, Y. Mai, J. K. Rath, and R. E. I. Schropp, “High-density silicon nitride deposited at low substrate temperature with high deposition rate using hot wire chemical vapour deposition,” Surface and Coating Technologies 201, pp. 9285–9288, September 2007.

The high speed conversion of signals between the optical and electrical domains is crucial for many key applications of silicon photonics. Electro-optic modulators integrated with electronic drive amplifiers are typically used to convert an electrical signal to the optical domain. Design of these individual elements is important to achieve high performance, however a true optimisation requires careful co-design of the photonic and electronic components considering the properties of each other. Here we present our recent results in this area together with a MOSCAP type modulator with the potential for high speed, high efficiency and highly linear modulation.

A four-port grating coupler with etched square holes is proposed and demonstrated for surface-normal and polarization independent coupling. Benefiting from the perfectly vertical coupling and 1 × 4 power splitting/combing scheme, efficient polarization independent operation was achieved. The coupling efficiency was further improved by grating apodization. According to the simulations, the proposed 2D apodized grating coupler can achieve a coupling efficiency (CE) of 64.5% (-1.9 dB), a low upward back-reflection of 8.5% (-11 dB), and polarization-dependent loss (PDL) lower than 0.04 dB across the wavelength range of 1520-1620 nm. A CE of 56.3% (-2.5 dB) was experimentally measured, with PDL below 0.3 dB within the C-band and lower than 0.5 dB within the L-band. Waveguide delay lines were used to compensate the waveguide channel phase differences at the output port.

The growing demand for fast, reliable and low power interconnect systems requires the development of efficient and scalable CMOS compatible photonic devices, in particular optical modulators. In this paper, we demonstrate an innovative electro absorption modulator (EAM) developed on an 800 nm SOI platform; the device is integrated in a rib waveguide with dimensions of a 1.5 µm x 40 µm, etched on a selectively grown GeSi cavity. High speed measurements at 1566 nm show an eye diagram with dynamic ER of 5.2 dB at 56 Gbps with a power consumption of 44 fJ/bit.

Fabrication errors pose significant challenges on silicon photonics, promoting postfabricationtrimming technologies to ensure device performance. Conventional approachesinvolve multiple trimming and characterization steps, impacting overall fabricationcomplexity. Here we demonstrate a highly accurate trimming method combining laserannealing of germanium implanted silicon waveguide and real-time monitoring of deviceperformance. Direct feedback of the trimming process is facilitated by a differentialspectroscopic technique based on photomodulation. The resonant wavelength trimmingaccuracy is better than 0.15 nm for ring resonators with 20-μm radius. We also realizeoperating point trimming of Mach-Zehnder interferometers with germanium implanted arms.A phase shift of 1.2π is achieved by annealing a 7-μm implanted segment.

We discuss the latest progress on the development of all-optical signal processing devices in Si-based platform. We discuss the realization of intra- and inter-modal wavelength converters by using our internally developed Si-rich-silicon nitride platform.

Silicon is a low-cost material platform in which it is possible to form photonic integrated circuits serving a number of applications from optical communications to sensing. For optical communications applications, e.g. short reach data communication within data centres, the optical modulator is a key component with its capabilities having a significant bearing on the overall performance of the photonic circuit. In this paper we report our recent work on optical modulators in silicon and their integration with CMOS electronics on silicon.

This work presents an experimental demonstration of a 500μm long MZI carrier accumulation type modulator based on lateral MOS-capacitor integration on a silicon platform. A modulation efficiency (V π L π ) of 1.53V-cm, moderate modulation speed of 20Gbit-s−1 and extinction ratio of 3.65dB have been obtained.

In this paper we present silicon and germanium-based material platforms for the mid-infrared wavelength region and we report several active and passive devices realised in these materials. We particularly focus on devices and circuits for wavelengths longer than 7 micrometers.

Group IV platforms can operate at longer wavelengths due to their low material losses. By combining graphene and Si and Ge platforms, photodetection can be achieved by using graphene’s optical properties and coplanar integration methods. Here, we presented a waveguide coupled graphene photodetector operating at a wavelength of 3.8 μm.

Hydrogel materials offer many advantages for chemical and biological sensoring due to their response to a small change in their environment with a related change in volume. Several designs have been outlined in the literature in the specific field of hydrogel-based optical sensors, reporting a large number of steps for their fabrication. In this work we present a three-dimensional, hydrogel-based sensor the structure of which is fabricated in a single step using thermal nanoimprint lithography. The sensor is based on a waveguide with a grating readout section. A specific hydrogel formulation, based on a combination of PEGDMA (Poly(Ethylene Glycol DiMethAcrylate)), NIPAAm (N-IsoPropylAcrylAmide), and AA (Acrylic Acid), was developed. This stimulus-responsive hydrogel is sensitive to pH and to water. Moreover, the hydrogel has been modified to be suitable for fabrication by thermal nanoimprint lithography. Once stimulated, the hydrogel-based sensor changes its topography, which is characterised physically by AFM and SEM, and optically using a specific optical set-up., The authors acknowledge the financial support from: the EU project, NAPANIL project (No. FP7-CP-IP 214249), the MINECO project PHENTOM (No. FIS2015-70862). ICN2 acknowledges support from the Severo Ochoa Program (MINECO, Grant SEV-2013-0295) and funding from the CERCA Programme/Generalitat de Catalunya.

Hybrid integration of nanoplasmonic devices with silicon photonic circuits holds promise for a range of applications in on-chip sensing, field-enhanced and nonlinear spectroscopy, and integrated nanophotonic switches. Here, we demonstrate a new regime of photon-plasmon coupling by combining a silicon photonic resonator with plasmonic nanoantennas. Using principles from coherent perfect absorption, we make use of standing-wave light fields to maximize the photon-plasmon interaction strength. Precise placement of the broadband antennas with respect to the narrowband photonic racetrack modes results in controlled hybridization of only a subset of these modes. By combining antennas into groups of radiating dipoles with opposite phase, far-field scattering is effectively suppressed. We achieve ultrafast tuning of photon-plasmon hybridization including reconfigurable routing of the standing-wave input between two output ports. Hybrid photonic-plasmonic resonators provide conceptually new approaches for on-chip integrated nanophotonic devices.

The development of low-thermal-budget Ge-on-Si epitaxial growth for the fabrication of low-cost Ge-on-Si devices is highly desirable for the field of silicon photonics. At present, most Ge-on-Si growth techniques require high growth temperatures, followed by cyclic annealing at temperatures $>800\ ^{\circ}\hbox{C} $ , often for a period of several hours. Here, we present a low-temperature (400 $^{\circ}{\rm C} $ ) low-cost plasma-enhanced chemical vapor deposition (PECVD) Ge-on-Si growth study and, subsequently, fabricate a high-speed zero-bias 12.5-Gb/s waveguide integrated photodetector with a responsivity of 0.1 A/W at a wavelength of 1550 nm. This low-energy device demonstrates the feasibility of the PECVD method for the fabrication of low-cost low-thermal-budget Ge-on-Si devices.

We report transmission measurements of germanium on silicon waveguides in the 7.5-8.5 μm wavelength range, with a minimum propagation loss of 2.5 dB/cm at 7.575 μm. However, we find an unexpected strongly increasing loss at higher wavelengths, potential causes of which we discuss in detail. We also demonstrate the first germanium on silicon multimode interferometers operating in this range, as well as grating couplers optimized for measurement using a long wavelength infrared camera. Finally, we use an implementation of the "cut-back" method for loss measurements that allows simultaneous transmission measurement through multiple waveguides of different lengths, and we use dicing in the ductile regime for fast and reproducible high quality optical waveguide end-facet preparation.

WDM components fabricated on the silicon-on-insulator platform have transmission characteristics that are sensitive to dimensional errors and temperature variations due to the high refractive index and thermo-optic coefficient of Si, respectively. We propose the use of NH

We present ring resonator (RR)-coupled Mach–Zehnder interferometers (MZIs) based on silicon-on-insulator rib waveguides, operating around the mid-IR wavelength of 3.8 μm. A number of different photonic integrated devices have been designed and fabricated experimentally to obtain the asymmetric Fano resonances in the mid-IR. We have investigated the influence of the coupling efficiency between the RR and the MZI as well as the phase shift between the two arms of the MZI on the Fano-type resonance spectral features, in agreement with theoretical predictions. Finally, wavelength-dependent Fano transmittances have been successfully measured with insertion losses up to ∼1 dB and extinction ratios of ∼20 dB. A slope of sharp Fano resonances as high as −574.6/μm has been achieved and estimated to be 35.5% higher than the slope of single RR Lorentzian-type resonances.

[EN] Universal multiport photonic interferometers that can implement any arbitrary unitary transformation between input and output optical modes are essential to support advanced optical functions. Integrated versions of these components can be implemented by means of either a fixed triangular or a fixed rectangular arrangement of the same components. We propose the implementation of a fixed rectangular universal interferometer using a reconfigurable hexagonal waveguide mesh circuit. A suitable adaptation synthesis algorithm tailored to this mesh configuration is provided and the experimental demonstration of a rectangular multiport interferometer by means of a fabricated silicon photonics chip is reported. The 7¿hexagonal cell chip can implement 2 × 2, 3 × 3 and 4 × 4 arbitrary unitary transformations. The proposed hexagonal waveguide mesh operates in a similar way as a Field Programmable Gate Array (FPGA) in electronics. We believe that this work represents an important step¿forward towards fully programmable and integrable multiport interferometers., The authors acknowledge financial support by the ERC ADG-2016 741415 UMWP-Chip, the Generalitat Valenciana PROMETEO 2013/012 research excellency award, I. G. acknowledges the funding through the Spanish MINECO Ramon y Cajal program. D.P. acknowledges financial support from the UPV through the FPI predoctoral funding scheme. D.J.T. acknowledges funding from the Royal Society for his University Research Fellowship. The chips were fabricated in the frame of the CORNERSTONE project funded by the EPSRC in the UK (EP/L021129/1)

We present the first waveguide electro-absorption modulator in germanium-on-silicon material platform at 3.8 μm wavelength, based on free-carrier injection into a straight waveguide. The fabricated 1 mm long device has modulation depth of >35 dB at 7 V.

We present our recent work on fibre-chip grating couplers operating around 1310 nm. For the first time, we demonstrate the combination of dual-etch and apodization design approaches which may achieve a coupling efficiency of 85% (-0.7 dB). Subwavelength structures were employed to modify the coupling strength of the grating. -1.9 dB efficiency was measured from a first set of fabricated structures.

We present an interlayer slope waveguide, designed to guide light from one level to another level in a multilayer silicon photonics platform. The waveguide is fabricated using HWCVD a-Si:H at 350oC. Measured loss of 0.5 dB/slope was obtained at a wavelength of 1550 nm and for TE mode polarization.

We propose and demonstrate a fabrication technique to realize extremely narrow dielectric slots in silicon waveguides. Using this method, we have demonstrated a silicon slot waveguide with 10 nm dielectric slot with a measured propagation loss of 13.6 dB/cm.

Slot waveguides are used for many photonic applications. However, existing fabrication techniques impose restrictions on the width of the slot region. Here, we propose and experimentally demonstrate a fabrication process to realize an arbitrarily narrow vertical dielectric slot in a silicon waveguide. Using this fabrication method, we have realized silicon slot waveguides with a 10-nm oxide slot region. The propagation loss of the fabricated slot waveguide was 1.36 ± 0.3 dB/mm.

Germanium based photonic devices can play a significant role in several applications, particularly in the so-called fingerprint wavelength region. Here, we review our recent results on mid-infrared germanium photonic devices that show promising performance in the 2–7.5 μm wavelength range.

Nonlinear silicon photonic devices have attracted considerable attention thanks to their ability to show large third-order nonlinear effects at moderate power levels allowing for all-optical signal processing functionalities in miniaturized components. Although significant efforts have been made and many nonlinear optical functions have already been demonstrated in this platform, the performance of nonlinear silicon photonic devices remains fundamentally limited at the telecom wavelength region due to the two photon absorption (TPA) and related effects. In this work, we propose an alternative CMOS-compatible platform, based on silicon-rich silicon nitride that can overcome this limitation. By carefully selecting the material deposition parameters, we show that both of the device linear and nonlinear properties can be tuned in order to exhibit the desired behaviour at the selected wavelength region. A rigorous and systematic fabrication and characterization campaign of different material compositions is presented, enabling us to demonstrate TPA-free CMOS-compatible waveguides with low linear loss (~1.5 dB/cm) and enhanced Kerr nonlinear response (Re{γ} = 16 Wm−1). Thanks to these properties, our nonlinear waveguides are able to produce a π nonlinear phase shift, paving the way for the development of practical devices for future optical communication applications.

We report the fabrication of low temperature deposited polysilicon waveguides using a laser annealing process. Micro-Raman and XRD measurements reveal the quasi-single crystal-like quality of the material, which exhibits low optical losses of 5.13 dB/cm.

In this paper we demonstrate the implementation of optical delay lines on a programmable hexagonal waveguide mesh integrated in Silicon on Insulator (SOI). This building block enables the synthesis of reconfigurable discrete-time filters and beamforming networks.

In recent years, we have presented results on the development of erasable gratings in silicon to facilitate wafer scale testing of photonics circuits via ion implantation of germanium. Similar technology can be employed to develop a range of optical devices that are reported in this paper. Ion implantation into silicon causes radiation damage resulting in a refractive index increase, and can therefore form the basis of multiple optical devices. We demonstrate the principle of a series of devices for wafers scale testing and have also implemented the ion implantation based refractive index change in integrated photonics devices for device trimming. NRF (Natl Research Foundation, S’pore) Published version

This publisher’s note corrects the data in Table 1 in Photon. Res.7, 1036 (2019)2327-912510.1364/PRJ.7.001036.