Search Results (1,391)

Femtosecond laser writing (FLW) enables mask-free three-dimensional photonic integration in transparent materials and offers a flexible route for prototyping glass-based photonic circuits. Here, we present a monolithic fabrication approach that combines femtosecond laser waveguide writing, femtosecond laser-induced chemical etching (FLICE), laser ablation, and metallization to realize reconfigurable photonic circuits in borosilicate glass. The process is implemented in a CAD-to-device workflow that allows optical, mechanical, and electrical structures to be co-designed and fabricated within the same substrate. A stress-assisted waveguide-writing regime is developed in borosilicate glass, enabling single-scan fabrication of optical waveguides, directional couplers, and Mach–Zehnder interferometers at writing speeds of 30 mm/s. The fabricated devices demonstrate stable guiding, directional coupling, and interferometric operation, providing a practical basis for implementing reconfigurable photonic building blocks in this material platform. FLICE is then used to fabricate suspended glass microbridges incorporating femtosecond-laser-written waveguides and integrated resistive microheaters. These structures act as thermally isolated thermo-optic phase shifters and enable a full 2π phase shift with an electrical power consumption of approximately 17 mW. The results demonstrate the feasibility of combining FLW and FLICE within a single borosilicate glass substrate to monolithically integrate passive photonic circuits with actively tunable thermo-optic phase shifters. This work establishes a laser-based fabrication route for reconfigurable three-dimensional photonic circuits in glass and provides a basis for future optimization toward larger programmable photonic systems. Full article

Bacterial biofilm formations on dental implant–bone borders risk the development of periimplantitis (PI). Treatment, ranging from conservative to invasive options, is effective but associated with significant patient burden. In vitro Photodynamic Inactivation (PDI) waveguided by zirconium dioxide ceramic (ZrO₂) dental implants shows promising bactericidal effects and is envisioned to function as an additive treatment reducing patient burden while maintaining therapy outcomes. To facilitate clinical application, this study mathematically quantified the expected waveguiding abilities of ZrO₂ implants in a computed tomography (CT)-based Monte Carlo Simulation of Radiation Transport (MCRT). The latter implemented previously photographically determined optical properties from human and porcine jawbone tissues. ZrO₂ implants displayed effective light propagation beyond the implant–bone border, with power-per-area values above a minimum baseline for effective PDI of 10 mW/cm², thus delivering enough light power to reach bactericidal levels in a standard PDI regimen. Modifying the implant design and light-source placement influenced the topographic distribution of the light power around the implant, eventually allowing to target case-specific changes in biofilm distribution. No major interspecies difference was observed, which fosters the transferability of potential mammal testing. All findings therefore support the envisioned application of waveguiding ZrO₂ dental implants in PDI to target oral health issues. Full article

To prevent the collapse of strip waveguides caused by complete undercut during hydrofluoric acid (HF) release in SOI-based cavity optomechanical accelerometers, we propose using rib waveguides as the on-chip optical transmission medium. Based on a 250-nm-thick SOI wafer, we systematically analyze the photonic crystal (PhC) microcavity, rib waveguide transmission, edge coupling, mode conversion to the PhC waveguide, and evanescent coupling. The PhC microcavity has a quality factor of 2.26 × 10⁵ at 1549.15 nm. The optimized rib waveguide (rib width 500 nm, rib height 220 nm) shows a transmission loss of 0.16 dB over 5000 μm. The rib-to-PhC waveguide coupling efficiency is 94.3% (0.25 dB loss), and a 90-μm-long tapered edge coupler achieves 65% efficiency (1.9 dB loss). The total optical path loss (including two edge couplers, rib waveguide transmission, and rib-to-PhC taper) is 4.21 dB. While maintaining optical performance comparable to strip waveguides, the rib waveguide design significantly improves post-release structural integrity at the design level. This work provides a viable optical circuit design foundation for reliable monolithically integrated cavity optomechanical accelerometers, with device fabrication and full system-level characterization planned as future work. Full article

Nanoplasmonic waveguides can efficiently manipulate the propagation characteristics of chiral light and hold great promise for integrated nano optics and on-chip optical information processing. Previous studies have demonstrated that gap plasmon structures composed of gold nanorod and silver nanowire can break the propagation symmetry of chiral light, thereby enabling asymmetric directional propagation. However, there remains considerable scope for enhancing the directional selectivity of these structures. In this work, we systematically investigate the mechanism of how the geometrical parameters of nanostructures regulate the directional propagation of chiral light. Based on the finite-difference time-domain method, the propagation behavior and evolution of directionality of chiral light in nanoplasmonic waveguides are analyzed in detail by changing the morphology and length of gold nanorods. The results show that the geometrically optimized nanostructures can significantly enhance the stability of directional chiral light propagation. At the same light-source position, the directionality of the gold nanorod with tips is approximately 56%, whereas that of the gold nanorod without tips remains approximately 89%. Further investigations show that structural modification of the silver nanowire or geometrical optimization of the structure can effectively reshape the local electromagnetic field distribution, enabling precise control over the propagation direction of chiral light. This work elucidates the physical mechanism underlying geometry-controlled chiral plasmonic propagation and provides a new design strategy for the structural design and performance optimization of high-performance chiral nanophotonic devices, with promising potential applications in chiral optical recognition, on-chip optical information processing, and nanoscale optical communication. Full article

In this paper, we report a novel self-smoothed gradient index cladding waveguide for low-loss, high-density photonic integrated circuits (PICs). In conventional PIC waveguides, there is a fundamental trade-off between propagation loss and bending loss. High-index-contrast waveguides can provide strong mode confinement and small bending radius, but they are highly sensitive to sidewall roughness and therefore exhibit increased scattering loss. In contrast, low-index-contrast waveguides can reduce propagation loss, but they require a much larger bending radius and are not suitable for dense photonic integration. To overcome this limitation, we propose a self-smoothed double-cladding waveguide architecture composed of a high-index core, a gradient index first cladding layer, and a low-index second cladding layer. The first cladding layer can be formed by advanced conformal coating processes, such as non-uniformly cycled atomic layer deposition and gradient index dip coating, which provide both a gradual refractive index transition and a self-smoothing effect on the rough sidewall. We perform quantitative analyses of the propagation loss, bending loss, and mode field distribution of the proposed structure. The numerical results confirm that the propagation loss can be reduced by approximately two orders of magnitude while maintaining low bending loss and mode confinement comparable to that of a conventional rib-shaped waveguide. We also experimentally verify the self-smoothing effect by using atomic layer deposition (ALD)-grown non-uniformly cycled nanolaminates and coating a rough sapphire bar with a high-refractive-index polymer, which significantly reduces the measured surface roughness and improves optical transparency. These results confirm that the proposed self-smoothed gradient index cladding waveguide can be an effective platform for realizing low-loss, high-density PICs. Full article

We demonstrate an integrated eight-wavelength high-power laser source on a 4H-silicon carbide (SiC)-based optical integration platform. Eight discrete Fabry–Perot laser diodes emitting at 445 nm, 637 nm, 789 nm, 806 nm, 846 nm, 978 nm, 1316 nm, and 1552 nm are integrated on a single SiC chip, each delivering ≥100 mW continuous-wave output power. A complete fabrication process is developed, including lift-off metallization (Ni/Ti/Pt/Au), surface hydrophilic activation bonding, and multi-step blade dicing to form SiC waveguides with a width of 500 μm and a thickness defined by the ~510 μm dicing depth, matching the output aperture of the multimode laser diodes. The resulting waveguides exhibit a facet misorientation of <1° and an approximate facet mean surface roughness of ~2 nm. The laser diodes are directly butted against the waveguide facets for edge coupling, and fixed using In₅₂Sn₄₈ solder bonding with pulse temperature control. Under controlled temperature, all eight channels operate stably with measured peak wavelengths matching the design targets. This work provides a scalable and practical solution for multi-wavelength, high-power on-chip light source integration on the SiC platform, addressing critical thermal and integration challenges for dense wavelength division multiplexing. Full article

Selective energy conversion in confined catalytic nanocavities is examined through a coupled reactive–photonic framework. The practical target is a combustor-integrated selective emitter for thermophotovoltaic (TPV) conversion and cascaded thermoelectric (TEG) recovery, in which Pt-coated anodic porous alumina (APA) functions simultaneously as a catalytic reactor, a cavity-modified electromagnetic environment and a heat-routing structure. Visible/near-infrared spectra (380–780 nm) show that Pt-coated APA exhibits a substantially stronger non-grey red-edge depression than a smooth zirconia reference. This observation establishes a spectral contrast in the measured window but is not used to identify an experimental cutoff wavelength, because a finite, open, lossy and array-coupled pore does not exhibit the abrupt edge predicted for an ideal cylindrical waveguide. For the mid-infrared, analytical scaling shows that the principal H₂O and CO₂ bands at 2.7, 4.3, 6.3 and 15.0 µm all lie deep in the evanescent regime relative to the ideal TE₁₁ cutoff wavelength λc ≈ 0.513 µm for a 300 nm pore. A converged finite-difference time-domain benchmark at the CO₂ 4.3 µm band yields a source-local Purcell factor F_p ≈ 0.38, indicating suppression of the total local density of optical states, while aperture flux is more than six orders of magnitude smaller than the near-field power budget. The specific contribution is therefore not the established fact of below-cutoff attenuation, but the co-design and separate quantification of a catalytic nanocavity as a reactive compartment, photonic environment and energy-branching element. The results provide a bounded mechanistic basis for combustor-integrated TPV and hybrid TPV/TEG architectures. Full article

The present work analyzes light propagation in asymmetric waveguides with dielectric cores and anisotropic multilayer claddings based on nanometric planar hyperbolic metamaterials. A generalized definition of asymmetry, incorporating both structural and physical parameters, is introduced by varying metal composition and filling ratios in the claddings. The influence of wavelength, material permittivity, metal filling fraction, and core thickness on surface wave modes is examined using effective medium theory and considering experimentally derived material data. Propagation distances on the order of 400 µm have been achieved for optimized waveguide configurations operating within the C-band used in optical telecommunications. Full article

Semiconductor lasers are key devices in optical communication, optical storage and other fields. Achieving single-mode, high-power and high-beam-quality output is an important research goal in laser technology. Conventional slab-coupled optical waveguide lasers can effectively suppress higher-order modes, but suffer from a low optical confinement factor and limited ridge width. This paper proposes a 1064 nm deep-etched wide-ridge waveguide slab-coupled photonic crystal semiconductor laser. A photonic crystal structure is introduced into the conventional slab-coupled optical waveguide. The optical field and mode characteristics are analyzed by numerical simulation, verifying the feasibility of the structure in improving the optical confinement factor and realizing single-mode operation with a deep-etched wide-ridge waveguide. Different from traditional photonic crystal lasers, this design provides a new route for high-performance photonic crystal semiconductor laser design. Full article

We propose a three-dimensional (3D) integrated optical switch that leverages liquid crystal (LC) birefringence to achieve reconfigurable light routing for particular suitability for quantum optical communication. In our design, the large refractive index contrast between an LC’s ordinary (n_o) and extraordinary (n_e) indices is exploited by using n_o as an effective cladding and n_e as the core of voltage-controlled waveguides. This allows dynamic waveguide formation not only in-plane (horizontal routing on chip) but also vertically through stacked polymer layers, realizing a 3D switching architecture beyond traditional planar photonic circuits. A prototype multi-layer structure on a silicon substrate is described, incorporating alternating polymer cladding and core films with embedded LC cells that act as switchable waveguide segments. Simulations confirm that the LC switch can confine and direct light between different layers with low loss, enabling compact 3 × 3 and potentially up to 10 × 10 port-count switching matrices. The device is electrically driven (no moving parts) and can be operated at low voltages, ensuring compatibility with photonic integrated circuit fabrication. The simulated LC response time on ON/OFF is on the order of 1.1 ms/45 ms, which is slower than MEMS or electro-optic switches, but, however, sufficient for quantum key distribution and other quantum network applications where ultrafast switching is not required. Overall, this LC cell-based 3D optical switch offers a promising route toward scalable, low-loss photonic switching nodes for next-generation quantum communication networks. Full article

The Enterobacteriaceae family is a significant source of foodborne pathogens and represents a severe threat to human and animal health. These bacteria can penetrate the dairy supply chain through direct contact with cattle and the livestock environment and can survive production processes. Escherichia coli (E. coli), one of the most diffuse bacteria in raw and processed milk, exposes consumers to the risk of contaminated milk. As a result of this exposition, several milk-borne illness outbreaks have been reported worldwide, underscoring the urgent need for effective detection and prevention measures. Conventional analysis methods are effective but have significant limitations, including the requirement of pre-treatment and pre-enrichment steps. Thus, the need for advanced detection techniques that can accurately identify these pathogens without pre-treatment steps is critical. In this work, a proof-of-concept biosensor based on a spoon-shaped optical biochip was developed to detect E. coli via surface plasmon resonance (SPR) phenomena and was combined with a polyclonal antibody layer against E. coli as a molecular recognition element (MRE). The proposed label-free biosensing strategy, achieved by exploiting simple SPR spoon-shaped biochips, exhibits a remarkable detection limit (6.8 colony-forming units, CFU/mL) and high specificity towards other interfering bacteria belonging to the Enterobacteriaceae family. In addition, tests on commercial milk samples were carried out, achieving recovery values of 95% and 102% for whole milk and infant milk, respectively. The proposed spoon-shaped biosensor enables label-free biosensing without the need for microfluidic systems. It provides a rapid response (10 min), paving the way for its use as a point-of-care test (POCT) in real-world settings. Full article

Traditional tunable Bragg waveguide grating filters, which rely on thermo-optic or carrier effects, often face limitations such as high energy consumption, low tuning efficiency, and difficulty in achieving independent multi-parameter control. To overcome these bottlenecks, this work proposes a novel optical waveguide filter based on the heterogeneous integration of silicon nitride and the phase-change material Sb₂Se₃. The device leverages the substantial refractive index contrast between crystalline and amorphous states of Sb₂Se₃ to construct a programmable Bragg grating within the thin film layer. This is realized through laser-induced phase transition method, enabling nonvolatile manipulation of the light field. Simulation results indicate that the independent tuning of central wavelength over 19.2 nm range was achieved by adjusting the grating width and ripple width simultaneously. Likewise, the extinction ratio could be independently controlled over 22.3 dB through coordinated adjustments of the grating length and position shift. Beyond its tuning capabilities, the proposed device theoretically exhibits exceptional performance characteristics, including an ultra-low insertion loss of 0.1 dB and strong side lobe suppression. These advantages highlight the potential of this approach to provide a low energy consumption, multifunctional solution for integrated photonic devices, offering a promising pathway for the next generation of programmable photonic integrated circuits. Full article

The exponential growth of AI-driven data traffic necessitates the evolution of Data Center Networks toward high bandwidths and sub-microsecond latency. While co-packaged optics (CPO) offer a pathway to reduced energy consumption and increased capacity, they introduce significant challenges in optical chip coupling and packaging complexity. This study explores monolithically integrated metasurfaces as an alternative for optical interfaces, potentially reducing the need for bulky external microlens arrays or extremely precise mechanical alignment. We design an amorphous silicon (a-Si) metasurface on a Silicon-On-Insulator (SOI) platform operating at 1310 nm. By spatially mapping nanopillar radii to satisfy a spherical phase profile, we achieved near-vertical beam emission with an emission angle of 0.88° focused at a focal length of 98.99 μm. Broadband characterization across a 20 nm band confirms stable focusing and a confined spot size with moderate roll-off toward the band edges. The sensitivity of the emission profile of the device to fabrication imperfections in pillar radius, height, and sidewall taper is quantified. The coupling to a polymer-based optical redistribution layer (ORDL) is also studied, and the corresponding modal analysis demonstrates a maximum coupling efficiency of 68.2% into an SU-8 polymer waveguide. Tolerance analysis results reveal deterioration of 0.9 dB and 0.4 dB for $\pm 0.6 \mathsf{\mu }\mathrm{m}$ horizontal and $\pm 1.5 \mathsf{\mu }\mathrm{m}$ vertical misalignment respectively, making the interface compatible with relaxed alignment assembly assumptions, although experimental packaging validation remains required. The methodology is further validated at 1550 nm, demonstrating its applicability across telecom bands. These results suggest that integrated metasurfaces may simplify the packaging stack and enhance density for next-generation CPO links by providing precise, on-chip wavefront manipulation. Full article

The integration density of photonic integrated circuits is fundamentally limited by evanescent field overlap and subsequent inter-channel crosstalk. Layered transition metal dichalcogenides (TMDCs) bypass these confinement constraints through intrinsic optical birefringence and high refractive indices. Here, we report the near-infrared optical constants and waveguide dispersion of molybdenum diselenide (MoSe₂). Ellipsometry performed on centimeter-scale crystals yields an in-plane refractive index of 4.1–4.7 over 1000–2000 nm, with an extinction coefficient close to the sensitivity limit of the fit away from strong excitonic resonances. To validate the anisotropic dielectric tensor at the device scale, scattering-type scanning near-field optical microscopy (s-SNOM) was utilized to map the propagation of transverse-magnetic modes in 235 nm thick exfoliated flakes. Spatial Fourier analysis of the edge-scattered near-field interference yields effective mode indices that precisely match the modeled dispersion. Using the verified dielectric tensor, finite-element simulations demonstrate that single-mode MoSe₂ waveguides optically outperform equivalent tungsten disulfide (WS₂) benchmarks. The enhanced evanescent field suppression in the claddings of MoSe₂ waveguide increases the coupling length by a factor of 3.5, reducing the required routing pitch and enabling a 12.5% direct increase in on-chip integration density. The results identify MoSe₂ as a high-index anisotropic platform for compact waveguiding in the near-infrared. Full article

Non-Hermitian photonic lattices offer unconventional control over light evolution owing to modal non-orthogonality and the resulting non-normal dynamical response. In this work, we show that a uniform passive waveguide lattice with dissipation confined to one or a few sites near an edge can exhibit an algebraic(nearly linear) decay of optical power—an absorption law forbidden in orthogonal (normal-mode) dissipative systems, where any superposition of eigenmodes yields purely multi-exponential attenuation. We demonstrate that algebraic absorption arises when the input excitation is appropriately tailored to exploit non-orthogonal modal interference, effectively channeling energy toward the dissipative boundary. In particular, under the condition of coherent perfect absorption (CPA) associated with a spectral singularity of the semi-infinite lattice, nearly complete light absorption accompanied by algebraic decay of the optical power can be achieved. Starting from the minimal configuration of a single lossy edge site, we derive compact analytical expressions for the dynamics and identify the conditions under which linear-like absorption emerges. We then extend the analysis to multiple edge-proximal lossy sites. Our results show that simple dissipative photonic lattices, when driven by suitably prepared input states, enable robust sculpting of absorption laws through non-normal dynamics, providing a new route to programmable attenuation. Full article