Glass Waveguides Research Articles

A low quantum defect and power scalable Yb-doped glass waveguide laser

We present a continuous wave laser action in ytterbium (Yb)-doped phosphate glass buried channel waveguides. The 25 mm long waveguides were fabricated by the standard ion exchange method. When pumped with a 976 nm laser diode, the waveguide laser emits at 982.4 nm, yielding an ultralow quantum defect of 0.66 %. The impact of coupling and pump power variation on the laser emission wavelengths is demonstrated. Furthermore, the results of pulsing using a monolayer graphene as a saturable absorber (SA) are presented and a pulse train with a repetition rate of 1 MHz and a pulse width of 700 ns was obtained.

Ultrafast Laser-Fabricated Fluoride Glass Waveguides with Exceptionally High Positive Refractive Index Change for Mid-Infrared Integrated Optics

Ultrafast Laser-Fabricated Fluoride Glass Waveguides with Exceptionally High Positive Refractive Index Change for Mid-Infrared Integrated Optics

High responsivity zero-biased Mid-IR graphene photodetector based on chalcogenide glass waveguide

Graphene’s unique properties have made it a promising material for high-performance photodetectors due to its interesting features including broadband absorption, fast speed, and strong photothermoelectric effect. Here, an optimized waveguide photodetector incorporating double graphene layers with two cores is presented to boost the responsivity (∼twice), at Mid-IR range. The proposed structure operates in the zero-bias regime to eliminate the dark current issue associated with the zero bandgap nature of graphene and leads to lower noise equivalent power. The presented photodetector operating based on split gates to electrostatically induce the p-n junction in graphene channels, operates based on the photothermoelectric effect and provides responsivity, NEP, and 3 dB bandwidth of 6.3 V/W, 0.34 nW/Hz1/2, and 1.54 GHz, respectively for the detection at λ = 5.2 μm. The feasibility of the proposed structure is proved according to recent experimentally demonstrated photodetectors. Hence, the obtained results are reliable, in practice. The study has been accomplished by numerical simulation of mode profiles and solving the heat equation to extract the characteristics of the proposed photodetector. The zero-power consumption and tunability of the proposed structure make it a promising candidate for sensing, industrial, defense, and environmental monitoring applications with high accuracy.

Third-order nonlinear wavelength conversion in chalcogenide glass waveguides towards mid-infrared photonics

Abstract The increasing demand in spectroscopy and sensing calls for infrared (mid-IR) light sources. Here, we theoretically investigate nonlinear wavelength conversion of Ge28Sb12Se60 chalcogenide glass waveguide in the mid-IR spectral regime. With waveguide dispersion engineering, we predict generation of over an octave wavelength (2.8 μm–5.9 μm) tuning range Raman soliton self-frequency shift, over 2.5 octaves wavelength cover range supercontinuum (1.2 μm–8.0 μm), as well as single soliton Kerr comb generated in suspended Ge28Sb12Se60 waveguide. Our findings evidenced that Ge28Sb12Se60 chalcogenide glass waveguides can simultaneously satisfy the generation of Raman soliton self-frequency shift, supercontinuum spectrum, and Kerr frequency comb generation through dispersion engineering towards mid-IR on chip.

Polarized and Evanescent Guided Wave Surface-Enhanced Raman Spectroscopy of Ligand Interactions on a Plasmonic Nanoparticle Optical Chemical Bench.

This study examined applications of polarized evanescent guided wave surface-enhanced Raman spectroscopy to determine the binding and orientation of small molecules and ligand-modified nanoparticles, and the relevance of this technique to lab-on-a-chip, surface plasmon polariton and other types of field enhancement techniques relevant to Raman biosensing. A simplified tutorial on guided-wave Raman spectroscopy is provided that introduces the notion of plasmonic nanoparticle field enhancements to magnify the otherwise weak TE- and TM-polarized evanescent fields for Raman scattering on a simple plasmonic nanoparticle slab waveguide substrate. The waveguide construct is called an optical chemical bench (OCB) to emphasize its adaptability to different kinds of surface chemistries that can be envisaged to prepare optical biosensors. The OCB forms a complete spectroscopy platform when integrated into a custom-built Raman spectrograph. Plasmonic enhancement of the evanescent field is achieved by attaching porous carpets of Au@Ag core shell nanoparticles to the surface of a multi-mode glass waveguide substrate. We calibrated the OCB by establishing the dependence of SER spectra of adsorbed 4-mercaptopyridine and 4-aminobenzoic acid on the TE/TM polarization state of the evanescent field. We contrasted the OCB construct with more elaborate photonic chip devices that also benefit from enhanced evanescent fields, but without the use of plasmonics. We assemble hierarchies of matter to show that the OCB can resolve the binding of Fe2+ ions from water at the nanoscale interface of the OCB by following the changes in the SER spectra of 4MPy as it coordinates the cation. A brief introduction to magnetoplasmonics sets the stage for a study that resolves the 4ABA ligand interface between guest magnetite nanoparticles adsorbed onto host plasmonic Au@Ag nanoparticles bound to the OCB. In some cases, the evanescent wave TM polarization was strongly attenuated, most likely due to damping by inertial charge carriers that favor optical loss for this polarization state in the presence of dense assemblies of plasmonic nanoparticles. The OCB offers an approach that provides vibrational and orientational information for (bio)sensing at interfaces that may supplement the information content of evanescent wave methods that rely on perturbations in the refractive index in the region of the evanescent wave.

Fabrication and characteristics of the planar and ridge Er3+-doped germanate glass waveguides

Fabrication and characteristics of the planar and ridge Er3+-doped germanate glass waveguides

Postmelting Encapsulation of Glass Microwires for Multipath Light Waveguiding within Phosphate Glasses.

Glass waveguides are the fundamental component of advanced photonic circuits and play a pivotal role in diverse applications, including quantum information processing, light generation, imaging, data storage, and sensing platforms. Up to date, the fabrication of glass waveguides relies mainly on demanding chemical processes or on the employment of expensive ultrafast laser equipment. In this work, we demonstrate an advanced, simple, low-temperature, postmelting encapsulation procedure for the development of glass waveguides. Specifically, silver iodide phosphate glass microwires (MWs) are drawn from splat-quenched glasses. These MWs are then incorporated in a controlled manner within transparent silver phosphate glass matrices. The judicious selection of glass compositions ensures that the refractive index of the host phosphate glass is lower than that of the embedded MWs. This facilitates the propagation of light inside the encapsulated higher refractive index MWs, leading to the facile development of waveguides. Importantly, we substantially enhance the light transmission within the MWs by leveraging the plasmon resonance effects due to the presence of silver nanoparticles spontaneously generated owing to the silver iodide phosphate glass composition. Employing this innovative approach, we have successfully engineered waveguide devices incorporating either one or two MWs. Remarkably, the dual MW devices are capable of transmitting light of different colors and in multipath direction, rendering the developed waveguides outstanding candidates for extending the functionalities of diverse photonic and optoelectronic circuits, as well as in intelligent signaling applications in smart glass technologies.

Octave spanning and flat-top supercontinuum generation in standard foundry-compatible process-made Ge–Sb–Se chalcogenide glass waveguide

We reported near octave-spanning supercontinuum generation in Ge28Sb12Se60 chalcogenide glass rib waveguides. The waveguides were fabricated using foundry-compatible deep ultra-violet lithography, followed by plasma etching. We demonstrated an average propagation loss of ∼1.3 dB/cm at the 1550 nm telecommunication wavelength. With dispersion engineering, optimizing waveguide geometry, and pumping by a multi-wavelength femtosecond soliton fiber laser, we achieved a flat-top supercontinuum generation spanning from 1290 to 2400 nm and beyond . It has a 3 dB bandwidth of 436 nm and a 20 dB bandwidth of more than 900 nm. The implementation of such waveguides provides a practical broadband light source solution for on-chip spectroscopy and sensing systems.

On chip broadband and high extinction ratios Mach-Zehnder interferometer for DPSK signal demodulation

Differential phase shift keying (DPSK) signals are widely employed in optical communication systems due to the high sensitivity and simple self-delay interference demodulation scheme. In this paper, we demonstrate a broadband on-chip Mach-Zehnder interferometer (MZI) for multiple channel DPSK signal demodulation. The chip is constructed using a single-mode high-index doped silica glass waveguide with fiber-to-fiber insert loss less than 3 dB and small second-order dispersion. The MZI interference fringe extinction ratio is over 25 dB in the range of C- and L-bands. The MZI is employed to demodulate four parallel DPSK signals simultaneously with similar performance, indicating that the broad bandwidth MZI is suitable for a receiver of massive parallel optical communications.

Broadband spin and angle co-multiplexed waveguide-based metasurface for six-channel crosstalk-free holographic projection

Metasurface-based holograms, or metaholograms, offer unique advantages including enhanced imaging quality, expanded field of view, compact system size, and broad operational bandwidth. Multi-channel metaholograms, capable of switching between multiple projected images based on the properties of illuminating light such as state of polarization and angle of incidence, have emerged as a promising solution for realizing switchable and dynamic holographic displays. Yet, existing designs typically grapple with challenges such as limited multiplexing channels and unwanted crosstalk, which severely constrain their practical use. Here, we present a new type of waveguide-based multi-channel metaholograms, which support six independent and fully crosstalk-free holographic display channels, simultaneously multiplexed by the spin and angle of guided incident light within the glass waveguide. We employ a k-space translation strategy that allows each of the six distinct target images to be selectively translated from evanescent-wave region to the center of propagation-wave region and projected into free space without crosstalk, when the metahologram is under illumination of a guided light with specific spin and azimuthal angle. In addition, by tailoring the encoded target images, we implement a three-channel polarization-independent metahologram and a two-channel full-color (RGB) metahologram. Moreover, the number of multiplexing channels can be further increased by expanding the k-space’s central-period region or combing the k-space translation strategy with other multiplexing techniques such as orbital angular momentum multiplexing. Our work provides a novel approach towards realization of high-performance and compact holographic optical elements with substantial information capacity, opening avenues for applications in AR/VR displays, image encryption, and information storage.

Exceeding two octave-spanning supercontinuum generation in integrated As2S3 waveguides pumped by a 2 μm fiber laser

In this work, we demonstrate over two octaves-spanning supercontinuum generation in integrated As2S3 chalcogenide glass waveguides pumped by a 2 μm femtosecond fiber laser. The pump laser provides 182 fs pulses at 50 MHz repetition rate. Through optimization of the waveguide dimensions, a broad supercontinuum spectrum spanning from 0.6 to 2.8 μm was achieved using a 4 μm wide, 5 mm long waveguide with 357 mW coupled pump power. The findings showcase the potential of dispersion engineered, integrated As2S3 photonics for realizing compact, efficient on-chip supercontinuum sources for mid-infrared applications.

Optical properties of the O3+-ion implanted and femtosecond-laser ablated ridge waveguide in the Er3+-doped germanate glass

Er3+-doped germanate glass is a kind of polyfunctional material for optical and photonic applications. The work reports on the preparation and properties of O3+-ion implanted and femtosecond-laser ablated Er3+-doped germanate glass optical ridge waveguide. The energy is 6.0 MeV and the fluence is 5 × 1014 ions cm−2 for the O3+-ion implantation. The pulse energy and the scanning speed of the femtosecond-laser ablation are 3 μJ and 50 μm s−1, respectively. The SRIM 2013 is used to calculate the vacancy profile induced by the implantation in the Er3+-doped germanate glass for the physical mechanisms of the waveguide formation. The optical microscopy images of the cross-section of the waveguide are captured by the Nikon microscope. The light-guiding properties of the ion-implanted and laser-ablated waveguides are studied by the end-face coupling system. The ridge waveguide has been produced by combining the FS ablation with ion implantation technologies for the first time in the Er3+-doped germanate glass. The propagation of light field indicates that it has the potential for photonics applications based on the planar and ridge Er3+-doped germanate glass waveguides.

Integrated multimode optical waveguides in glass using laser induced deep etching.

Glass is an ideal material for optical applications, even though only a few micromachining technologies for material ablation are available. These microstructuring methods are limited regarding precision and freedom of design. A micromachining process for glass is laser induced deep etching (LIDE). Without generating micro-cracks, introducing stress, or other damages, it can precisely machine many types of glass. This work uses LIDE to subtractive manufacture structures in glass carrier substrates. Due to its transmission characteristics and refractive index, the glass substrate serves as optical cladding for polymer waveguides. In this paper, the described fabrication process can be divided into two sub-steps. The doctor blade technique and subsequent additive process step is used in manufacturing cavities with U-shaped cross-sections in glass in order to fill the trenches with liquid optical polymers, which are globally UV-cured. Based on the higher refractive index of the polymer, it enables optical waveguiding in the visible to near-infrared wavelength range. This novel, to the best of our knoowledge, manufacturing method is called LDB (LIDE-doctor-blade); it can be the missing link between long-distance transmissions and on-chip solutions on the packaging level. For validation, optical waveguides are examined regarding their geometrical dimensions, surface roughness, and waveguiding ability, such as intensity distribution and length-dependent attenuation.

Delivery of the diode pumped Er:YLF laser radiation by special hollow glass waveguides

Delivery of the diode pumped Er:YLF laser radiation by special hollow glass waveguides

Hollow waveguide CO2 laser sensing system for rapid detection of trace sulfur hexafluoride (SF6) gas

Sulfur hexafluoride (SF6) has been widely applied in electrical facilities due to its excellent electrical insulation and high-voltage arc extinguishing properties, although it is a potent greenhouse gas. Rapid detection of trace SF6 gas is significant for monitoring the operation safety of high-voltage power grid facilities and greenhouse gas emissions. In this work, a SF6 gas sensing system was proposed and built using a CO2 laser as the light source and a 700 μm bore Ag/AgI hollow glass waveguide (HGW) as the gas chamber and laser transmission channel. Sensing performances of the SF6 gas HGW sensors with different lengths were investigated. The gas sensing sensitivity and standard deviation (SD) of blank increase as the waveguide length increases. The limit of detection (LOD) decreases with waveguide length increase but the decline becomes less pronounced after the length exceeds 120 cm. The HGW length exhibits minor effect on the response and recovery time of the sensor system. The sensor sensitivity undergoes a slight reduction as the HGW is bent. Optimization of the sensing performance was achieved based on the straight 120 cm-length HGW SF6 gas sensor system. Its sensitivity reaches 0.384 dB/ppm and the LOD is 148 ppb with good cyclic response characteristics (response and recovery time 2–3 s). The present work provides a feasible idea for building up a trace SF6 gas sensing system with simple structure, easy operation and high performances.

Characterization of optical waveguides in Ce3+-doped phosphate glasses formed by He+ion implantation

In this work, the Ce3+-doped phosphate glass is carried out to fabricate the planar waveguides by the 400 keV He+ ion implantation with a dose of 6.0 × 1016 ions cm−2. The dark-mode spectrum of the waveguide at a wavelength of 632.8 nm is obtained by the prism coupling technique. The SRIM 2013 software is used to analyze the energy deposition induced by the ion implantation and the RCM is employed to reconstruct the refractive index profile of the planar waveguide. The end-face coupling technique is applied to the measurement of the propagation mode image of the waveguide at 632.8 nm. The Ce3+-doped phosphate glass waveguide has the potential for an integrated optical device.

Supercontinuum Generation in Dispersion Engineered Highly Doped Silica Glass Waveguides

AbstractThe effect of a lower index oxide layer inclusion within a highly doped silica glass slot waveguide is investigated for optimized supercontinuum generation at telecom wavelengths. By controlling the thickness of the oxide slot, it is demonstrated that one can engineer the waveguide dispersion profile in order to obtain supercontinua with vastly different spectral broadening dynamics and bandwidths. Using this approach, a waveguide with a low and flat dispersion profile of less than 43 across a wavelength range spanning over 1000 nm is designed and fabricated. It is shown that, when pumped at the telecom C‐band, a supercontinuum that spans over 1.5 octaves can be generated from 817 to 2183 nm. The numerical simulations, whose parameters are derived from the measured waveguide dimension and material indices, exhibit good agreement with experimental measurements, where one can observe both a qualitative and quantitative match in the supercontinuum overall spectrum and specific features (e.g., soliton and dispersive wave locations). This study represents an important step forward in the control and manipulation of dispersive and nonlinear dynamics in highly doped silica glass waveguides, paving the way toward advanced on‐chip broadband light manipulation.

Polydimethylsiloxane as a more biocompatible alternative to glass in optogenetics

Optogenetics is highly useful to stimulate or inhibit defined neuronal populations and is often used together with electrophysiological recordings. Due to poor penetration of light in tissue, there is a need for biocompatible wave guides. Glass wave guides are relatively stiff and known to cause glia reaction that likely influence the activity in the remaining neurons. We developed highly flexible micro wave guides for optogenetics that can be used in combination with long-lasting electrophysiological recordings. We designed and evaluated polydimethylsiloxane (PDMS) mono-fibers, which use the tissue as cladding, with a diameter of 71 ± 10 µm and 126 ± 5 µm. We showed that micro PDMS fibers transmitted 9–33 mW/mm2 light energy enough to activate channelrhodopsin. This was confirmed in acute extracellular recordings in vivo in which optogenetic stimulation through the PDMS fibers generated action potentials in rat hippocampus with a short onset latency. PDMS fibers had significantly less microglia and astrocytic activation in the zone nearest to the implant as compared to glass. There was no obvious difference in number of adjacent neurons between size matched wave guides. Micro PDMS wave guide demonstrates in vivo functionality and improved biocompatibility as compared to glass. This enables the delivery of light with less tissue damage.

Design and analysis of an optical planar waveguide using Invar as core and silicon nitride as cladding layer to control birefringence

Abstract The main problem with optical planar waveguide is thermal stress which arises when layers inside the planar waveguide get fused together with different coefficient of thermal expansion (CTE) and due to variation in thermal properties, the problem of thermally induced strain and birefringence occurs inside the waveguide glass layer. In proposed work, the mathematical analysis of thermal induced stress and the thermal strain in waveguide glass layer is calculated. ‘C’ software is used for analysis of an optical planar waveguide to calculate the thermal stress. By using material properties of Invar (64 % iron-36 % nickel alloy) and silicon nitride (Si3N4) an optical planar waveguide is designed. Here when silicon nitride (Si3N4) is used as a cladding layer and Invar (64 % iron-36 % nickel alloy) as a core layer in an optical planar waveguide, the problem of birefringence get eradicated as zero thermal stress was achieved.

Optical ridge waveguides in Nd3+‐doped fluorophosphate glasses fabricated by carbon ion implantation and femtosecond laser ablation

AbstractIn this work, the ridge waveguide was formed by the femtosecond laser ablation with a central wavelength of 0.808 μm and a speed of 50 μm/s on the planar Nd3+‐doped fluorophosphate glass waveguide that was fabricated by the C3+ ion implantation with an energy of 6.0 MeV and a fluence of 1.0×1012 C3+s/mm2. The mechanism of the ion‐implanted waveguide was discussed by the Stopping and Range of Ions in Matter 2013. The cross‐section morphology of the ridge waveguide was captured by an optical microscope. Its mode characteristics were analyzed by the end‐face coupling method. The ridge Nd3+‐doped fluorophosphate glass waveguides have potential as fundamental structures for many optoelectronic devices including waveguide amplifiers and lasers.