This work presents an integrated plasmophotonic interferometric sensor providing environmental temperature and thermo-optic coefficient (TOC) measurement capabilities. By exploiting extreme light field concentration on the plasmonic metal stripe, the sensor employs a liquid dielectric layer deposited on the plasmonic sensing area for refractive index changes versus temperature. Experimental characterization was conducted with four different liquids, achieving a record temperature sensitivity of +23.86 nm/degrees C for a 70% ethanol-water solution. Additionally, by leveraging the sensor's high sensitivity, the TOC of an unknown liquid was determined with a relative error of 13.1%.

La co-intégration de guides d’onde plasmonique et photonique sur une puce silicium suivant une configuration interférométrique à branche unique, dite bimodale permet d’atteindre une sensibilité inégalée lors de la détection de traces de molécules. Des puces fabriquées à bas coût et un prototype d’instrument complet démontrent leur capacité à détecter des contaminants d’intérêt pour le secteur agricole.

Efficient near-infrared (NIR) light sources are essential for a wide range of applications such as telecommunications, optoelectronic devices, biomedical sciences, infrared imaging, and machine vision. Colloidal quantum dots (QDs) have emerged as a promising platform for NIR technologies due to their tunable optical properties across the NIR spectrum, compatibility with silicon-based technology infrastructure, and ease of large-scale integration into nanophotonic systems. Coupling colloidal QDs with plasmonic structures provides an enhanced control over their optical properties. In this work, we investigate the coupling of a gold plasmonic crescent metasurface with NIR-emitting colloidal PbS/CdS QDs, at the telecommunication wavelength of 1.55 mu m. The metasurface was specifically designed to allow for the selective excitation photoluminescence (PL) enhancement with polarization control, capitalizing on the anisotropic nature of the plasmonic crescents. Maximum PL enhancement factors of 1.6 were observed, with a strong dependence on the excitation wavelength and polarization. These findings, supported by full-wave three-dimensional finite-difference-time-domain (FDTD) numerical simulations, offer strategies to control and optimize the performance of colloidal QD-based NIR light sources for a wide range of applications.

We demonstrate a self-referenced plasmonic augmented photonic Mach-Zehnder interferometer (MZI) for biosensing applications, incorporating a 70 mu m long aluminum plasmonic waveguide in both arms of a silicon nitride (Si3N4) MZI. Experimental results matched well with numerical simulations, showing extinction ratio (ER) values that exceed 55 dB and bulk sensitivity of 2322 nm/RIU. Wavelength stability measurements revealed 5x10-3 nm thermal dependance for an ambient temperature fluctuation of 1-degree Celsius which is 50 times better than a conventional hybrid plasmo-photonic asymmetric MZI (aMZI) configuration, highlighting the robustness of the proposed balanced sensor scheme to ambient temperature fluctuations. Moreover, the experimental results show that the proposed sensor has a limit of detection up to 2.6 x10-6 RIU. Surface sensitivity of the proposed sensing transducer was evaluated through a C-reactive protein (CRP) surface saturation measurements and found equal to 10.45 nm/RIU for protein binding. Our validated simulation model was then benchmarked against a diverse set of target bio-analytes (proteins, viruses, bacteria, fungi) with surface sensitivity values reaching up to 2306 nm/RIU, indicating the sensor's heterogeneous detection capabilities. The presented self-referencing sensor configuration offers a cost-effective yet scalable and highly sensitive approach for multiplexed on-chip detection of diverse target analytes. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Photonic integrated circuits (PICs) are crucial for advanced applications in telecommunications, quantum computing, and biomedical fields. Silicon nitride (SiN)-based platforms are promising for PICs due to their transparency, low optical loss, and thermal stability. However, achieving efficient thermo-optic (TO) modulation on SiN remains challenging due to limited reconfigurability and high power requirements. This study aims to optimize TO phase shifters on SiN platforms to enhance power efficiency, reduce device footprint, and minimize insertion losses. We introduce a CMOS-compatible plasmo-photonic TO phase shifter using a SiOC material layer with a high TO coefficient combined with aluminum heaters on a SiN platform. We evaluate four interferometer architectures—symmetric and asymmetric Mach–Zehnder Interferometers (MZIs), an MZI with a ring resonator, and a single-arm design—through opto-thermal simulations to refine performance across power, losses, footprint, and switching speed metrics. The asymmetric MZI with ring resonator (A-MZI-RR) architecture demonstrated superior performance, with minimal power consumption (1.6 mW), low insertion loss (2.8 dB), and reduced length (14.4 μm), showing a favorable figure of merit compared to existing solutions. The optimized SiN-based TO switches show enhanced efficiency and compactness, supporting their potential for scalable, energy-efficient PICs suited to high-performance photonic applications.

Plasmonic refractive index sensors are essential for detecting subtle variations in the ambient environment through surface plasmon interactions. Current efforts utilizing CMOS-compatible, plasmo-photonic Mach-Zehnder interferometers with active power balancing exhibit high sensitivities at the cost of fabrication and measurement complexity. Alternatively, passive bimodal plasmonic interferometers based on SU-8 waveguides offer cost-effectiveness and a smaller device footprint. However, their waveguides are exposed to ambient conditions and currently lack the necessary opto-mechanical isolation. In this work, we introduce the new SX AR LWL 2.0 polymer cladding material, which provides a high refractive index contrast to the SU-8 core, while ensuring compatibility with SU-8 waveguides. Our sensors consist of an aluminum plasmonic stripe and a bilayer SU-8 photonic waveguide core which is cladded with the SX AR LWL 2.0 polymer. They achieve a sensitivity of (6108 ± 13) nm/RIU (refractive index unit), where the error indicates the data fitting tolerance, and a limit of detection of 1.6 × 10-7 RIU, in aqueous solutions, surpassing both traditional and polymer-based bimodal plasmo-photonic sensors. This new cladding material paves the way for more efficient and integrated bimodal plasmonic refractive index sensing platforms for a wide range of applications.

Plasmonic refractive index sensors are essential for detecting subtle variations in the ambient environment through surface plasmon interactions. Current efforts utilizing CMOS-compatible, plasmo-photonic Mach-Zehnder interferometers with active power balancing exhibit high sensitivities at the cost of fabrication and measurement complexity. Alternatively, passive bimodal plasmonic interferometers based on SU-8 waveguides present a cost-effective solution with a smaller device footprint, though they currently lack opto-mechanical isolation due to exposed photonic waveguides. In this work, we introduce innovative polymer-core and polymer-cladded bimodal plasmonic refractive index sensors with high refractive index contrast. Our sensors feature an aluminum stripe, a bilayer SU-8 photonic waveguide core, and the experimental optical cladding polymer SX AR LWL 2.0. They achieve a sensitivity of (6300 ± 460) nm/RIU (refractive index unit), surpassing both traditional and polymer-based plasmo-photonic sensors. This approach enables integrated, wafer-scale, CMOS-compatible, and low-cost sensors and facilitates plasmonic refractive index sensing platforms for various applications.

Integrated quantum photonic circuits require the efficient coupling of photon sources to photonic waveguides. Hybrid plasmonic/photonic platforms are a promising approach, taking advantage of both plasmon modal confinement for efficient coupling to a nearby emitter and photonic circuitry for optical data transfer and processing. In this work, we established directional quantum dot (QD) emission coupling to a planar TiO2waveguide assisted by a Yagi-Uda antenna. Antenna on waveguide is first designed by scaling radio frequency dimensions to nano-optics, taking into account the hybrid plasmonic/photonic platform. Design is then optimized by full numerical simulations. We fabricate the antenna on a TiO2planar waveguide and deposit a few QDs close to the Yagi-Uda antenna. The optical characterization shows clear directional coupling originating from antenna effect. We estimate the coupling efficiency and directivity of the light emitted into the waveguide.

We report on the thermo-optic properties of electron-beam evaporated amorphous titanium dioxide (TiO2) at different timescales. We investigate the thermo-optic response of TiO2 from static regime down to the micro-second regime by applying Joule heating on hybrid metallo-dielectric integrated Mach-Zehnder interferometers. We show that amorphous TiO2 exhibits a very large negative thermo-optical coefficient in the range of -6.5×10−4 K−1 at 1550 nm at typical timescales of a few seconds. Such a slow thermo-optic response is consistent with an organic origin of amorphous TiO2 negative thermo-optic coefficient. However, when observed at the micro-second timescale, we show that the same amorphous TiO2 has a positive thermo-optic coefficient, just like many other materials. Based on our results, TiO2 can be conveniently deployed in energy-effective integrated optic devices by taking into account the specific multi-timescale thermo-optic properties of this material.

Densely integrated photonic integrated circuits (PICs) require efficient solutions for monitoring the light intensity on chip in order to implement control and configuration operations to set and stabilize the working point of the circuit. To this end, waveguides supporting the propagation of surface plasmon polaritons (SPPs) are good candidates to realize small-footprint light detectors. In this work, we report on the realization of an in-line Surface Plasmon Detector (SPD) that exploits the photothermal effect to monitor the optical power in a titanium dioxide (TiO2) optical waveguide. Detailed design guidelines are provided to maximize the responsivity of the SPD, taking into account the effects of the metal geometry on the coupling between the dielectric and plasmonic modes, the power dissipated in the metal, and the equivalent thermal resistance of the structure. Experimental validation of the proposed device is provided demonstrating an ultra-compact 1.6- $\mu \text{m}$ -long SPD operating at a wavelength of 1550 nm with a sensitivity of–20 dBm and a bandwidth higher than 100 kHz. The proposed device concept can be ported to generic dielectric platforms and to other wavelength ranges where SPP propagation is supported.

We present a new, ultracompact bimodal interferometric plasmonic sensor integrated on a SU-8 photonic waveguide platform. Two access SU-8 photonic waveguides are separated by an aluminum-based stripe, which resides on top of a thinner SU-8 waveguide layer. In this way, two metal/insulator interfaces are formed at the top and bottom metal surfaces, which are capable of supporting two respective surface plasmon polariton (SPP) modes that are subsequently interfering with the output photonic waveguide. The upper metal surface is exposed to the surrounding medium and serves as the sensing element, while the lower surface serves as the reference branch of the interferometer. After a thorough optimization process, the device was fabricated and experimentally characterized. A clear bimodal interferometric response was obtained when the upper metallic surface was exposed to air and water, with both cases revealing an excellent agreement between the simulated and experimental values for the free spectral range. The experimental bulk refractive index sensitivity of the bimodal interferometer was evaluated by using water solutions on top of the upper metallic surface, demonstrating experimental sensitivity values of 4386 nm/RIU that are in good agreement with the value of 5806 nm/RIU expected from the simulation. The proposed sensing device takes advantage of the polymeric material SU-8 for the photonic waveguide, reducing in this way fabrication time and overall fabrication cost.

We propose obtaining TiO2 films by ICPCVD for the fabrication of low-loss waveguides. The challenge is to produce a dense and homogeneous layer with a high refractive index and low absorption in the visible range. Crystallized layers with features such as grains and amorphous layers have a rather low index for the application targeted, so we aimed for an intermediate state. We investigated the influence of plasma power, pressure, deposition time and annealing temperature on the structural, crystalline, and optical properties in order to tailor them. We showed that crystallization into rutile at the nanoscale occurred during deposition and under wisely chosen conditions, we reached a refractive index of 2.5 at 630 nm without creating interfaces or inhomogeneity in the layer depth. Annealing permits one to further increase the index, up to 2.6. TEM analysis on one sample before and after annealing confirmed the nano-polycrystallization and presence of both anatase and rutile phases and we considered that this intermediate state of crystallization was the best compromise for guided optics.

We provide the experimental proof of concept of on-chip 90° corner waveguide arrays based on ultra-long-range surface plasmon polariton waveguides working in TM-polarization at 1.55 μm. The single-mode waveguides comprise a thin gold-photoresist core embedded into SU-8 claddings and show typical propagation loss of ~1 dB/mm. A prismatic cavity integrated into the cladding layers and aligned with the waveguide's corner assures the total internal reflection. We present a fabrication method to integrate the waveguide corner mirror based on self-alignment of multiple lithography steps. This chip has potential as low-loss perpendicular interface for single-mode high speed communication interconnects.

Micro-ring resonators made of titanium dioxide were decorated with local light sources comprising CdSe/CdS colloidal quantum dot aggregates. The active micro-resonators are operated to achieve efficient evanescent excitation of nearby co-planar integrated waveguides. Coupled-mode analysis and numerical simulations are used to capture the dynamic of the optical interaction between locally activated resonators and integrated waveguides. In this context, we exemplify the key role of resonator intrinsic loss. Next, we show that locally activated or bus-waveguide excited resonators are in optimum waveguide interaction for the same so-called critical coupling condition, although the physical origin of this property is different for each configuration. More importantly, we found that a locally activated resonator is a fabrication imperfection tolerant configuration for the coupling light of local sources into waveguides. This remarkable property originates from the opposite change of the power cycling into the resonator and the waveguide coupling efficiency as a function of the resonator-waveguide separation gap. By operating an 8-μm-radius ring resonator with loaded quality factors around Q = 2100, we experimentally demonstrate a 5.5-dB enhancement of the power coupled into the output waveguide compared to a direct local source waveguide excitation.

Optical refractive-index sensors exploiting selective co-integration of plasmonics with silicon photonics has emerged as an attractive technology for biosensing applications that can unleash unprecedented performance breakthroughs that reaps the benefits of both technologies. However, towards this direction, a major challenge remains their integration using exclusively CMOS-compatible materials. In this context, herein, we demonstrate, for the first time to our knowledge, a CMOS-compatible plasmo-photonic Mach-Zehnder-interferometer (MZI) based on aluminum and Si3N4 waveguides, exhibiting record-high bulk sensitivity of 4764 nm/RIU with clear potential to scale up the bulk sensitivity values by properly engineering the design parameters of the MZI. The proposed sensor is composed of Si3N4 waveguides butt-coupled with an aluminum stripe in one branch to realize the sensing transducer. The reference arm is built by Si3N4 waveguides, incorporating a thermo-optic phase shifter followed by an MZI-based variable optical attenuation stage to maximize extinction ratio up to 38 dB, hence optimizing the overall sensing performance. The proposed sensor exhibits the highest bulk sensitivity among all plasmo-photonic counterparts, while complying with CMOS manufacturing standards, enabling volume manufacturing.

We demonstrate a CMOS compatible interferometric plasmo-photonic sensor exploiting Si 3 N 4 photonic and aluminum (Al) plasmonic stripe waveguides. Experimental evaluation revealed bulk sensitivity of 4764 nm/RIU, holding promise for ultra-sensitive and low cost sensing devices.

Optical refractive index (RI) sensors exploiting selective co-integration of plasmonics with silicon photonics in Lab-on-achip configurations are expected to disrupt Point-of-Care (POC) diagnostics, delivering performance and economic breakthroughs. Propagating surface-plasmon-polariton modes offer superior sensitivity due to their extreme overlap with the surrounding medium. In parallel, low-loss photonics act as the hosting platform with which the plasmonic losses can be sustained while allowing for multiplexed layouts via in-plane SPP excitation schemes. However, merging plasmonics with silicon photonics in a cost-effective manner, requires a truly CMOS-compatible manufacturing process. Herein, we demonstrate experimentally, the highest bulk-sensitivity among all the plasmo-photonic interferometric RI sensors, while taking the leap forward in the development of a CMOS-manufactured plasmo-photonic sensing platform merging Si3N4 photonics and aluminum plasmonics. The proposed structure relies on a butt-coupled interface between Si3N4 waveguides and a 70 μm long plasmonic stripe, deployed in one branch of a Mach-Zehnder Interferometer (MZI) serving as the sensing transducer that detects local changes in the refractive index. The lower MZI arm (reference arm) exploits the low-loss Si3N4 platform to deploy a MZI-based variable optical attenuator followed by a thermo-optic phase shifter to optimize the sensor performance achieving resonance extinction ratio values at the MZI output of more than 35 dB. Experimental evaluation of a gold-based sensor revealed a bulk refractive index sensitivity of 1930 nm/RIU. In addition, we experimentally demonstrate that the proposed plasmo-photonic waveguide platform can migrate from gold (Au) to Aluminum (Al), demonstrating the first step towards a fully CMOS compatible plasmo-photonic interferometric sensor.

We present a technology platform supported by a new process design kit (PDK) that integrates two types of aluminum plasmonic waveguides with Si photonics towards CMOS-compatible plasmo-photonic integrated circuits for sensing applications. More specifically, we demonstrate the fabrication of aluminum slot waveguide via e-beam lithography (EBL) on top of the Si$_{3}$N$_{4}$ waveguide and an optimized fabrication process of aluminum plasmonic stripe waveguides within a CMOS foundry using EBL. Experimental measurements revealed a propagation length of 6.2 m for the plasmonic slot waveguide in water at 1550 nm, reporting the first ever experimental demonstration of a plasmonic slot waveguide based on CMOS compatible metal materials in liquid environment. Propagation length in water for the aluminum stripe was measured equal to 66.8 m which is, to the best of our knowledge, the highest value among all single-mode Al-based plasmonic waveguides presented so far at 1550 nm. Moreover, we evince with simulation data the sensing capabilities of the proposed structures when incorporated in a Si$_{3}$N$_{4}$-based interferometric configuration, yielding bulk sensitivity values up to 80 nmRIU and 1300 nmRIU, corresponding to an accumulated phase change per unit length of 0.77 RIUm and 1.26 RIUm for the aluminum slot and aluminum stripe waveguide, respectively.

We report the development of titanium dioxide-based waveguides for applications in the near- and mid- infrared. Thanks to embedded metal grating couplers, we demonstrate error free 10 Gbit/s optical transmissions at 1.55 and 2 μm. With additional management of the dispersion profile, we also demonstrate octave spanning supercontinuum in cm-long TiO 2 waveguides.