Search Results (100)

A multi-mode interferometer (MMI) spectrometer is a type of reconstructive micro-spectrometer based on imaging light propagation patterns in MMI waveguides. A waveguide scattering surface accentuates imaging light patterns in the multi-mode interferometer. This technology has been proven with an SU-8 core waveguide with an etched SU-8 nanograss scattering surface. This paper describes our creation of a fully silicon-based spectrometer using a silica core MMI waveguide. Scattering features were created in silica using SU-8 nanograss as an etch mask in a reactive ion etch (RIE). With optimized etch parameters, the silica core MMI spectrometer achieved an SNR of three with an incident light power of −68 dBm, which was almost 6 dB lower than designs with an SU-8 core. Full article

This research presents a lens-based light collection system that integrates a handmade glass conical waveguide (GCW) with a single silica multimodal optical fiber (SMMF) and a concentrator Fresnel lens (FL). The GCW functions as a secondary optical element (SOE), effectively expanding the fiber’s receptive area and enabling efficient coupling of concentrated light. Calibrated ray-tracing simulations confirm that the complete FL + GCW + SMMF configuration maintains low transmission losses, thereby validating efficient coupling into the SMMF. Experimental results demonstrated a maximum net optical efficiency of 41% at an FL numerical aperture (NA) of 0.08, with GCW transmission reaching 60% and splice losses to the SMMF around 34%. With a luminous flux input of 155 lumens, the system delivered up to 63 lumens at the fiber output. Importantly, the FL + GCW + SMMF configuration combines reproducible fabrication, straightforward assembly, and reliable characterization, establishing a scalable pathway for daylight harvesting. The major contribution of this work is the demonstration that a simple, manufacturable GCW can substantially expand the effective collection area of multimodal fibers while preserving low optical losses, thereby bridging practical design with efficient energy transfer for sustainable photonics applications. Full article

We developed a complete packaging strategy for a 128-channel optical phased array (OPA) for Light Detection and Ranging (LiDAR) applications operating at a 1550 nm wavelength. The process comprised three major steps: waveguide end-facet polishing, fiber-to-optical waveguide pigtailing, and electrical wire bonding. Sequential polishing with silicon carbide paper followed by colloidal silica reduced coupling losses to 0.74 dB per facet. An automated fiber alignment setup was used to perform edge coupling. The electrical connections, formed under optimized wire-bonding conditions (18 mW ultrasonic power), achieved a bond strength of 4.66 gf while maintaining electrode-pad integrity. The final packaged device demonstrated uniform optical throughput, with a throughput power variation maintained below 0.2 dB following the packaging process, and a uniform electrical resistance of 0.48% across all 128 channels, verifying the process stability and packaging integrity. These results confirmed that the proposed packaging scheme offers a dependable route for photonic integration in LiDAR applications. Full article

Reconfigurable mode switches can provide more flexible and advanced data exchange functions for complex on-chip optical networks. A reconfigurable mode-selective optical switch based on adiabatic progressive three-waveguide coupling (TWC) is proposed. As a proof of concept, the switching of E₀₀ (E₂₀)/E₁₀ (E₃₀) dual-mode channels was successfully implemented and demonstrated. At 1550 nm, the insertion losses for E₀₀/E₁₀ and E₂₀/E₃₀ mode switches were lower than 7.86 and 10.76 dB, respectively. These values include the loss of the mode demultiplexer. The crosstalk was lower than −22.84 (−18.28) dB at 1550 nm. The switching rise time (10–90%) and fall time (10–90%) were 0.86 ms and 0.64 ms, respectively. On the silica platform, the scalability of the structural scheme was also verified, and the arbitrary selection and switching of the E₀₀, E₁₀, E₂₀, and E₃₀ modes were achieved via the cascading of TWCs. The device can be used as an important component for the future large-scale integration and flexible switching of on-chip optical networks. Full article

Silicon–nitride (SiN) waveguides have emerged as fundamental building blocks in silicon photonic integrated circuits (Si-PICs), offering advantages that compensate for the intrinsic limitations of silicon-on-insulator (SOI) and silica-on-silicon (SOS) platforms. In this work, two sizes of single-mode SiN strip waveguides are investigated: (i) 600 nm wide strip waveguide cores on a 400 nm thick Si₃N₄ film and (ii) 1.0 µm wide strip waveguide cores on a 1.0 µm thick Si₃N₄ film. First, we design two AWG architectures and develop a generalized theoretical model for one of the key specifications—polarization mode dispersion (PMD)—by considering a pair of orthogonal polarization states in these two waveguides. Then, as the two-size SiN waveguides are generally fabricated via multiple operating processes of coating, photolithography, and etching, we investigate the dependences of PMD performances on the device errors of the two AWG architectures caused by the coating/manufacturing qualities and accuracies, and the dependences of PMD performance on the refractive index errors of the waveguide core. As a consequence, the softwaretool simulations for the two AWG architectures of 40-channel 0.8 nm channelspacing show that the average PMDs of the above two waveguide sizes are <0.50 ps and <0.35 ps, respectively, and the PMD responses to the ±10% fabrication error are < ±0.20 ps and ±10% fluctuation, respectively, but the ±2.5% variations have no obvious impacts upon the PMD performance. Therefore, it turns out that the PMD performance of a smaller waveguide has a relatively strong error sensitivity to the AWG architecture, while the larger waveguide size has a relatively weak error sensitivity to the AWG architecture. Full article

Silica-based splitters, couplers, and arrayed waveguide gratings are key components in optical communication. However, the high tuning power consumption of silica chips limits their development and application in fields such as Reconfigurable Optical Add/Drop Multiplexers and Mode Division Multiplexing. In this work, we demonstrate a silica thermo-optic switch based on polymer cladding within a Mach–Zehnder Interferometer framework, in which a UV-curable polymer is employed as the upper cladding to enhance thermal efficiency. The device exhibits a power consumption of 48 mW, rise and fall response times were 215 µs and 271 µs, compared to all-silicon switches, the power consumption is reduced by 75%, and the switching speed is improved by nearly a factor of two, while maintaining a comparable insertion loss. Experimental results demonstrate an insertion loss of 8.53 dB and an extinction ratio of 10.12 dB. Full article

With the increasing demand for ultrafast optical signal processing, silicon-on-silica (SoS) waveguides with ring resonators have emerged as a promising platform for integrated all-optical logic gates (AOLGs). In this work, we design and simulate a SoS-based waveguide structure, operating at the telecommunication wavelength of 1550 nm, consisting of a circular ring resonator coupled to straight bus waveguides using Lumerical FDTD solutions. The design achieves a high Q-factor of 11,071, indicating low optical loss and strong light confinement. The evanescent coupling between the ring and waveguides, along with optimized waveguide dimensions, enables efficient interference, realizing a complete suite of AOLGs (XOR, AND, OR, NOT, NOR, NAND, and XNOR). Numerical simulations demonstrate robust performance across all gates, with high contrast ratios between 11.40 dB and 13.72 dB and an ultra-compact footprint of 1.42 × 1.08 µm². The results confirm the device’s capability to manipulate optical signals at data rates up to 55 Gb/s, highlighting its potential for scalable, high-speed, and energy-efficient optical computing. These findings provide a solid foundation for the future experimental implementation and integration of SoS-based photonic logic circuits in next-generation optical communication systems. Full article

In the field of acoustic wave detection, optical sensors have significant potential applications in numerous civilian and military fields due to their high sensitivity and immunity to electromagnetic interference. This study designed an undercoupled silica optical waveguide resonator (OWR) with a 2% refractive index contrast. Mode spot converters were introduced at both ends of the straight waveguide to achieve efficient optical transmission between the fiber and the waveguide. The resonator was fabricated using plasma-enhanced chemical vapor deposition (PECVD) and inductively coupled plasma (ICP) etching technologies. The results show that the quality factor (Q-factor) of the resonator reached 2.75 × 10⁶. Compared with a resonator with a refractive index difference of 0.75%, the Q-factor remained at the same order of magnitude while the sensor size was significantly reduced. To achieve high-sensitivity acoustic wave detection, this study employed an intensity demodulation method to realize acoustic wave detection with the resonator. Test results demonstrate that the OWR can detect acoustic signals in the frequency range of 25 Hz to 20 kHz, with a minimum detectable sound pressure of 1.58 μPa/Hz^1/2 @20 kHz and a sensitivity of 1.492 V/Pa @20 kHz. The sensor exhibits a good signal-to-noise ratio and stability. The proposed method shows broad application prospects in the field of acoustic sensing and is expected to enable large-scale applications in scenarios such as communication, biomedical monitoring, and precision industrial sensing. Full article

Whispering-gallery-mode (WGM) microresonators are amongst the most promising optical sensors for detecting bio-chemical targets. A number of laser interrogation methods have been proposed and demonstrated over the last decade, based on scattering and absorption losses or resonance splitting and shift, harnessing the high-quality factor and ultra-small volume of WGMs. Actually, regardless of the sensitivity enhancement, their practical sensing operation may be hampered by the complexity of coupling devices as well as the signalprocessing required to extract the WGM response. Here, we use a silica microsphere immersed in an aqueous environment and efficiently excite optical WGMs with a free-space visible laser, thus collecting the relevant information from the transmitted and back-scattered light without any optical coupler, fiber, or waveguide. We show that a 640-nm diode laser, actively frequency-locked on resonance, provides real-time, fast sensing of dielectric nanoparticles approaching the surface with direct analog readout. Thanks to our illumination scheme, the sensor can be kept in water and operate for days without degradation or loss of sensitivity. Diverse noise contributions are carefully considered and quantified in our system, showing a minimum detectable particle size below 1 nm essentially limited by the residual laser microcavity jitter. Further analysis reveals that the inherent laserfrequency instability in the short, -mid-term operation regime sets an ultimate bound of 0.3 nm. Based on this work, we envisage the possibility to extend our method in view of developing new viable approaches for detection of nanoplastics in natural water without resorting to complex chemical laboratory methods. 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

Microring resonators, known for their compact size, wavelength selectivity, and high-quality factor, enable efficient light manipulation, making them ideal for photonic logic applications. This paper presents the design and simulation of seven fundamental all-optical logic gates—XOR, AND, OR, NOT, NOR, NAND, and XNOR—using a seven-microring silicon-on-silica waveguide. Operating at the standard telecommunication wavelength of 1.55 µm, the proposed design exploits constructive and destructive interferences caused by phase changes in the input optical beams to perform logic operations. Numerical simulations, conducted using Lumerical FDTD Solutions, validate the performance of the logic gates, with the contrast ratio (CR) as the primary evaluation metric. The proposed design achieves CR values of 14.04 dB for XOR, 15.14 dB for AND, 15.85 dB for OR, 13.42 dB for NOT, 12.02 dB for NOR, 12.75 dB for NAND, and 14.10 dB for XNOR, significantly higher than those reported in previous works. This results in a data rate of 199.8 Gb/s, facilitated by a compact waveguide size of 1.30 × 1.35 μm². These results highlight the potential of silicon photonics and microring resonators in enabling high-performance, energy-efficient, and densely integrated optical computing and communication systems. 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

Many current 1 × 2 splitter couplers based on multimode interference (MMI) face difficulties such as significant back reflection and limited flexibility in waveguide segmentation at the output, which necessitate the addition of transitional structures like tapered waveguides or S-Bends. These limitations reduce their effectiveness as photonic data-center applications, where precise waveguide configurations are crucial. To address these challenges, we propose a novel nanoscale 1 × 2 angled multimode interference (AMMI) power splitter with silicon nitride (SiN) buried core and silica cladding. The innovative angled light path design improved performance by minimizing back reflections back to the source and by providing greater flexibility of waveguide interconnections, making the splitter more adaptable for data-center applications. The SiN core was selected due to its lower refractive index contrast with silica compared to silicon, which helps further reduce back reflection. The dimensions of the splitter were optimized using full vectorial beam propagation method (FV-BPM), finite-difference time domain (FDTD), and multivariable optimization scanning tool (MOST) simulations to support transmission across the O-band. Our proposed device demonstrated excellent performance, achieving an excess loss of 0.22 dB and an imbalance of <0.01 dB at the output ports at an operational wavelength of 1.31 µm. The total device length is 101 µm with a thickness of 0.4 µm. Across the entire O-band range (1260–1360 nm), the performance of the splitter presented excess loss of up to 1.57 dB and an imbalance of up to 0.05 dB. Additionally, back reflections at the operational wavelength were measured at −40.96 dB and up to −39.67 dB over the O-band. This silicon-on-insulator (SOI) complementary metal-oxide semiconductor (CMOS) compatible AMMI splitter demonstrates high tolerance for manufacturing deviations due to its geometric layout, dimensions, and material selection. Furthermore, the proposed splitter is well-suited for use in O-band transceiver systems and can enhance data-center optical networks by supporting high-speed, low-loss data transmission. The compact design and CMOS compatibility make this device ideal for integrating into dense, high-performance computing environments, ensuring reliable signal distribution and minimal power loss. The splitter can support multiple communication channels, thus enhancing bandwidth and scalability for next-generation data-center infrastructures. 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

A silica waveguide thermo-optic mode switch with small radius bimodal S-bends is demonstrated in this study. The cascaded multimode interference coupler is adopted to implement the E₁₁ and E₂₁ mode selective output. The beam propagation method is used in design optimization. Standard CMOS processing of ultraviolet photolithography, chemical vapor deposition, and plasma etching are adopted in fabrication. Detailed characterizations on the prepared switch are performed to confirm the precise fabrication. The measurement results show that within the wavelength range from 1530 to 1575 nm, for the E₁₁ mode input, the switch exhibits an extinction ratio of ≥13.1 dB and a crosstalk ≤−22.8 dB at an electrical driving power of 284.8 mW, while for the E₂₁ mode input, the extinction ratio is ≥15.5 dB and the crosstalk is ≤−18.1 dB at an electrical driving power of 282.4 mW. These results prove the feasibility of multimode S-bends in mode switching. The favorable performance of the demonstrated switch promises good potential for on-chip mode routing. Full article