Search Results (147)

Polymer-based photonic sensors are emerging as cost-effective, scalable alternatives to conventional silicon and glass photonic platforms, offering unique advantages in flexibility, functionality, and manufacturability. This review provides a comprehensive assessment of recent advances in polymer photonic sensing technologies, focusing on material systems, fabrication techniques, device architectures, and application domains. Key polymer materials, including PMMA, SU-8, polyimides, COC, and PDMS, are evaluated for their optical properties, processability, and suitability for integration into sensing platforms. High-throughput fabrication methods such as nanoimprint lithography, soft lithography, roll-to-roll processing, and additive manufacturing are examined for their role in enabling large-area, low-cost device production. Various photonic structures, including planar waveguides, Bragg gratings, photonic crystal slabs, microresonators, and interferometric configurations, are discussed concerning their sensing mechanisms and performance metrics. Practical applications are highlighted in environmental monitoring, biomedical diagnostics, and structural health monitoring. Challenges such as environmental stability, integration with electronic systems, and reproducibility in mass production are critically analyzed. This review also explores future opportunities in hybrid material systems, printable photonics, and wearable sensor arrays. Collectively, these developments position polymer photonic sensors as promising platforms for widespread deployment in smart, connected sensing environments. Full article

Optical tactile sensing is gaining traction as a foundational technology in collaborative and human-interactive robotics, where reliable touch and pressure feedback are critical. Traditional systems based on total internal reflection (TIR) and frustrated TIR (FTIR) often require complex infrared setups and lack adaptability to curved or flexible surfaces. To overcome these limitations, we developed OptoSkin—a novel tactile platform leveraging direct time-of-flight (ToF) LiDAR principles for robust contact and pressure detection. In this extended study, we systematically evaluate how key optical properties of waveguide materials affect ToF signal behavior and sensing fidelity. We examine a diverse set of materials, characterized by varying light transmission (82–92)%, scattering coefficients (0.02–1.1) cm⁻¹, diffuse reflectance (0.17–7.40)%, and refractive indices 1.398–1.537 at the ToF emitter wavelength of 940 nm. Through systematic evaluation, we demonstrate that controlled light scattering within the material significantly enhances ToF signal quality for both direct touch and near-proximity sensing. These findings underscore the critical role of material selection in designing efficient, low-cost, and geometry-independent optical tactile systems. Full article

This work presents a novel $C{O}_2$ gas sensor based on a slotted polymer-phaseshift Bragg grating (SP-PSBG) waveguide filled with polyhexamethylene biguanide (PHMB) as the sensing medium. The transmission resonance, characterized by a narrow peak with a full width at half maximum (FWHM) of 1.6 nm within the Bragg grating bandgap, is highly responsive to refractive index changes in PHMB caused by variations in $C{O}_2$ concentration. Numerical simulations demonstrate a sensitivity of 14.4 pm/ppm, outperforming conventional gas sensors based on functional material coatings. This enhanced performance comes from the direct interaction between the PHMB-filled resonant structure and the cladding that contains $C{O}_2$ molecules, eliminating the need for polymer-coated cladding layers. The optimization approach employed in this design focuses on maximizing the optical confinement factor within the PHMB-filled slot, leading to an effective overlap between the guided optical mode and the sensing material. Full article

The article discusses the design, fabrication, and experimental evaluation of a large-area vertical grating coupler (VGC) enabling simultaneous coupling of multiple input optical beams. The presented VCG was fabricated by direct nanoimprinting of a grating pattern in a non-hardened SiO_X:TiO_Y waveguide (WG) film. The WG film was deposited on a glass substrate using a combination of the sol–gel method and the dip-coating technique. The fabrication process allowed precise control of the waveguide film thickness and refractive index, as well as the VGC geometry. The relevance of the process was proved by a demonstration of optical coupling of multiple quasi-parallel input beams via the VGC to the WG layer. To make this possible, a dedicated optical coupling system was designed, including a polymer microlens array and optical fiber array positioned in a V-groove. This opens promising perspectives on using the proposed structure for the fabrication of low-cost multichannel optical sensor chips, as highlighted in the article’s final section. Full article

Optical–chemical sensors based on optical fibers can be made in reflection or transmission schemes. In the reflection scheme, the sensing area is typically present at the end of the fiber, and the light source and the detector are placed on the same side of the fiber. This approach can be exploited to achieve chemical probes useful in several application fields where remote sensing is required. In this work, to obtain an extrinsic optical fiber chemical sensor in a reflection scheme, two optical fibers are used to monitor a chemically sensitive region achieved by a C-shaped waveguide with a molecularly imprinted polymer (MIP) as a core between the optical fibers. The proposed micrometer-sized probe is developed and tested as a proof of concept via a MIP for 2-Furaldehyde (2-FAL) detection of interest in food and industrial applications. The experimental results of the proposed sensing approach showed several advantages, such as a nanomolar detection limit and an ultra-wide concentration detection range due to different kinds of MIP recognition sites in the optical path between the fibers. Full article

To meet diverse industrial needs, temperature sensors with a wide measurement range have become a key element. In this paper, we propose an asymmetric Mach–Zehnder interferometer (MZI) temperature sensor based on polymer optical waveguides. Experimental results show that the output interference signal exhibits periodic changes with temperature variations. The device exhibits a temperature measurement range of 120 °C and a sensitivity of 0.27 rad/°C. This study provides an effective new approach for developing high-performance, low-cost temperature sensors suitable for an extended temperature measurement range. Full article

Recent advancements in hybrid photonic integrated circuits (PICs) for wireless communications are reviewed, with a focus on innovations developed at Fraunhofer HHI. This work leverages hybrid integration technology, which combines indium phosphide (InP) active elements, silicon nitride (Si₃N₄) low-loss waveguides, and high-efficient thermal-optical tunable polymers with micro-optical functions to achieve fully integrated wireless transceivers. Key contributions include (1) On-chip optical injection locking for generating phase-locked optical beat notes at 45 GHz, enabled by cascaded InP phase modulators and hybrid InP/polymer tunable lasers with a 3.8 GHz locking range. (2) Waveguide-integrated THz emitters and receivers, featuring photoconductive antennas (PCAs) with a 22× improved photoresponse compared to top-illuminated designs, alongside scalable 1 × 4 PIN-PD and PCA arrays for enhanced power and directivity. (3) Beam steering at 300 GHz using a polymer-based optical phased array (OPA) integrated with an InP antenna array, achieving continuous steering across 20° and a 10.6 dB increase in output power. (4) Demonstration of fully integrated hybrid wireless transceiver PICs combining InP, Si₃N₄, and polymer material platforms, validated through key component characterization, on-chip optical frequency comb generation, and coherent beat note generation at 45 GHz. These advancements result in compact form factors, reduced power consumption, and enhanced scalability, positioning PICs as an enabling technology for future high-speed wireless networks. Full article

Molecularly imprinted polymers (MIPs) can be combined with optical fibers (OFs) to create various sensor configurations, yielding low-cost and highly sensitive extrinsic and intrinsic sensors. In this work, an MIP-based extrinsic optical fiber sensor is obtained by two silica OFs connected via an optical waveguide using an MIP as a core of micrometer size (micro OF-MIP-OF sensor). The proposed sensing approach can be used only with MIP receptors and implements an intensity-based sensor configuration. MIPs present several advantages over bio-receptors and can be exploited to realize novel sensing methods. The MIP used in this work is specifically designed for 2-furaldehyde (2-FAL) detection, and the experimental results demonstrate that the micro-probe performs well in terms of sensitivity and selectivity, with capabilities applicable to several application fields. In particular, a nanomolar detection range, from 1.5 nM to 150 nM, has been achieved. Moreover, the results are comparable to or better than those of other previously proposed MIP optical fiber sensors for 2-FAL, which employ more complex sensing principles or fabrication steps. Full article

We propose a simple and innovative configuration consisting of a quantum dot and micro-optical resonator that emits single photons with good directionality in a plane parallel to the substrate. In this device, a single quantum dot is placed as a light source between the slits of a triangular split-ring micro-optical resonator (SRR) supported in an optical polymer film with an air-bridge structure. Although most of the previous single photon emitters in solid-state devices emitted photons upward from the substrate, operation simulations confirmed that this configuration realizes lateral light emission in narrow regions above, below, left, and right in the optical polymer film, despite the absence of a light confinement structure such as an optical waveguide. This device can be fabricated using silica-coated colloidal quantum dots, focused ion beam (FIB) lithography, and wet etching using an oxide layer on a silicon substrate as a sacrificial layer. The device has a large tolerance to the variation in the position of the SRR in the optical polymer film and the height of the air-bridge. We confirmed that Pt-SRRs can be formed on the optical polymer film using FIB lithography. This simple lateral photon emitter is suitable for coupling with optical fibers and for fabricating planar optical quantum solid-state circuits, and is useful for the development of quantum information processing technology. Full article

In this paper, our work in the field of fluorinated UV-curable polymers is reviewed. These polymers possessing tunable low refractive indices and low optical propagation losses for telecommunication wavelengths are intended to be used as core and cladding materials for the fabrication of passive channel waveguides in optical microchips on the polymer platform. This application requires low thermo-optic coefficients. With this goal, we used a combination of fluorinated polymers with low-refractive index inorganic nanoparticles of SiO₂ and MgF₂. Another application requiring extremely low refractive indices is polymer cladding for optical glass fibers. UV-curable fluorinated monomers/oligomers were used. Full article

On-chip Fourier transform spectrometer (FTS) is a promising technology due to the compact size, low cost, and relatively high throughput. In this work, we design, fabricate, and characterize a Mach-Zehnder interferometer (MZI) FTS based on SU-8 polymer waveguide. The optical path length difference of MZI is tuned by a heater with a maximum power consumption of 2.2 W. The interference signal is analyzed by Fourier transform algorithm, to retrieve the spectrum of light source. The footprint of the fabricated FTS device is only 2 × 12 mm², with the spectral bandwidth of ~100 nm and resolution <20 nm. Full article

We design and fabricate meter-scale long connectorized paper-like flexible multimode polymer waveguide film with a large bandwidth-length product (BLP) for board-level optical interconnects application. The measured BLP of the multimode waveguide is greater than 57.3 GHz·m at a wavelength of 850 nm under the strictest overfilled launch condition with a maximum length of 2.1 m and 10-dB insertion loss. The fabricated waveguide films are as flexible as regular printing paper and can be conveniently interfaced with standard mechanically transferable (MT) fiber connectors with low loss. The average insertion loss of the connectorized waveguide is about 0.042 dB/cm with inter-channel crosstalk as low as −46.4 dB, and the bending loss is less than 1 dB at a bending radius of 1 mm under the overfilled launch condition. We also demonstrate a vertical-cavity surface-emitting laser (VCSEL)-based single-lane 100 Gbps PAM4 transmission. Our results show that the meter-scale long paper-like polymer waveguide film has both excellent optical properties and large bandwidth and is ideal for high-speed board-level optical interconnects application with a single-lane data rate of 100 Gbps and beyond, especially those that have a strict requirement on the length of connection and compactness. Full article

In the fabrication of optical polymer-based components, such as diffractive gratings and waveguides, high throughput and high precision are required. The non-destructive evaluation of these complex polymer-based structures is a significant challenge. Different measurement techniques can measure the structure geometry directly or via its functionality indirectly. This study investigates various measurement techniques aimed at assessing these structures from 200 nm up to 20 µm. Environmental scanning electron microscopy (ESEM), white light interferometry (WLI), atomic force microscopy (AFM), micro computed tomography (µCT), optical coherence tomography (OCT), phase contrast microscopy (PCM), and Mueller matrix ellipsometry (MME) are investigated for their practical limits of lateral resolution and aspect ratio. The impact of the specimens’ complexity factors, including structure width and aspect ratio, on measurement quality is discussed. A particular focus of this study is on the suitability of different measurement systems for evaluating undercuts and enclosed structures while considering structure size, slant angle, and cover thickness. The aim is to discuss the specific advantages of the individual measurement systems and their application areas in order to be able to quickly select suitable measurement systems for a non-destructive evaluation of polymer-based micro and nanostructures. Full article

Polymer-based optical sensors represent a transformative advancement in biomedical diagnostics and monitoring due to their unique properties of flexibility, biocompatibility, and selective responsiveness. This review provides a comprehensive overview of polymer-based optical sensors, covering the fundamental operational principles, key insights of various polymer-based optical sensors, and the considerable impact of polymer integration on their functional capabilities. Primary attention is given to all-polymer optical fibers and polymer-coated optical fibers, emphasizing their significant role in “enabling” biomedical sensing applications. Unlike existing reviews focused on specific polymer types and optical sensor methods for biomedical use, this review highlights the substantial impact of polymers as functional materials and transducers in enhancing the performance and applicability of various biomedical optical sensing technologies. Various sensor configurations based on waveguides, luminescence, surface plasmon resonance, and diverse types of polymer optical fibers have been discussed, along with pertinent examples, in biomedical applications. This review highlights the use of biocompatible, hydrophilic, stimuli-responsive polymers and other such functional polymers that impart selectivity, sensitivity, and stability, improving interactions with biological parameters. Various fabrication techniques for polymer coatings are also explored, highlighting their advantages and disadvantages. Special emphasis is given to polymer-coated optical fiber sensors for biomedical catheters and guidewires. By synthesizing the latest research, this review aims to provide insights into polymer-based optical sensors’ current capabilities and future potential in improving diagnostic and therapeutic outcomes in the biomedical field. Full article

SU-8 is an emerging polymer material for integrated optical circuits that has demonstrated good structural properties in a cryogenic environment. In this article, we investigate the thermo-optical properties of SU-8 for a wavelength $\lambda =850\mathrm{n}\mathrm{m}$, from room temperature to cryogenic temperature down to 14 K. To measure the material properties, we designed and fabricated SU-8 racetrack resonators via electron beam lithography. While cooling the device in a closed-cycle cryostat, we measured the resonance spectrum as a function of the temperature from which we determined the temperature-induced variations of the group and effective indices of the waveguide. With the aid of waveguide eigenmode simulations, we used these data to derive the temperature dependence of the SU-8 refractive index $n_{SU-8}\left(T\right)$. At room temperature (T~295 K), the thermo-optic coefficient ${dn}_{SU-8}/dT=-5.3\pm {0.2\times {10}^{-5}\mathrm{K}}^{-1}$. At low temperature (T~14 K), ${dn}_{SU-8}/dT=-1.27\pm {0.05\times {10}^{-4}\mathrm{K}}^{-1}$. Our research shows the potential of SU-8 photonics in a cryogenic environment, suitable for the integration with quantum light sources emitting in the near infrared (NIR). Full article