High Index Glass Research Articles

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.

Enhanced efficiency of correlated photon pairs generation in silicon nitride with a low-loss 3D edge coupler

We demonstrate the generation of correlated photon pairs by using a hybrid integrated quantum photonic platform, where the dual-layer platform consists of a high-index doped silica glass (HDSG) layer to accommodate low-loss linear components and an SiN-based layer to accommodate the photon source. Leveraging the low-loss fiber coupling to the HDSG waveguide and the high nonlinearity of the SiN waveguide, we experimentally realize integrated source of photon pairs with high heralding efficiency. The directly measured photon pair rate is up to 87 KHz (corresponding to 1.74 × 10−3 pairs per pulse) when the coincidence-to-accidental ratio is greater than 10. The raw heralding efficiency can reach 18%. If the filtering loss is excluded, the heralding efficiency can further reach 29%.

Low-loss and polarization insensitive 32 × 4 optical switch for ROADM applications

Integrated switches play a crucial role in the development of reconfigurable optical add-drop multiplexers (ROADMs) that have greater flexibility and compactness, ultimately leading to robust single-chip solutions. Despite decades of research on switches with various structures and platforms, achieving a balance between dense integration, low insertion loss (IL), and polarization-dependent loss (PDL) remains a significant challenge. In this paper, we propose and demonstrate a 32 × 4 optical switch using high-index doped silica glass (HDSG) for ROADM applications. This switch is designed to route any of the 32 inputs to the express ports or drop any channels from 32 inputs to the target 4 drop ports or add any of the 4 ports to any of the 32 express channels. The switch comprises 188 Mach-Zehnder Interferometer (MZI) type switch elements, 88 optical vias for the 44 optical bridges, and 618 waveguide-waveguide crossings with three-dimensional (3D) structures. At 1550 nm, the fiber-to-fiber loss for each express channel is below 2 dB, and across the C and L bands, below 3 dB. For each input channel to all 4 drop/add channels at 1550 nm, the loss is less than 3.5 dB and less than 5 dB across the C and L bands. The PDLs for all express and input channels to the 4 drop/add channels are below 0.3 dB over the C band, and the crosstalk is under −50 dB for both the C and L bands.

Adjustment-Free Long-Distributed-Cavity Laser Using Small Glass Ball Cat-Eye Retroreflector

We report an adjustment-free long-distributed-cavity laser using a small high-index glass ball cat-eye retroreflector as the receiver. When the glass ball cat-eye was rotated or off-axis moved, its working characteristics were studied via the single cat-eye structure and the double cat-eyes structure. With the single cat-eye structure and an incident pump power of 4.22 W, the end-pumped Nd: YVO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {4}}$ </tex-math></inline-formula> laser delivered 985 mW continuous-wave output at a working distance of 2.85 m, whose full rotation angle at half power was ±27°. In addition, with the double cat-eyes structure and the same incident pump power, the laser delivered 385 mW output at a working distance of 1.20 m, which had a full rotation angle of ±19° and a transverse displacement tolerance of ±21 mm. As far as we know, this is the first time that a ball-shaped cat-eye retroreflector is used to establish an adjustment-free long-distributed-cavity laser.

High-Q chalcogenide racetrack resonators based on the multimode waveguide.

We propose and demonstrate a highquality (Q) factor racetrack resonator based on uniform multimode waveguides in high-index contrast chalcogenide glass film. Our design features two carefully designed multimode waveguide bends based on modified Euler curves, which enable a compact 180° bend and reduce the chip footprint. A multimode straight waveguide directional coupler is utilized to couple the fundamental mode without exciting higher-order modes in the racetrack. The fabricated micro-racetrack resonator shows a record-high intrinsic Q of 1.31×106 for selenide-based devices, with a relatively low waveguide propagation loss of only 0.38dB/cm. Our proposed design has potential applications in power-efficient nonlinear photonics.

Low-loss fiber-to-chip edge coupler for silicon nitride integrated circuits.

Silicon nitride (SiN) integrated optical waveguides have found a wide range of applications due to their low loss, broad wavelength transmission band and high nonlinearity. However, the large mode mismatch between the single-mode fiber and the SiN waveguide creates a challenge of fiber coupling to these waveguides. Here, we propose a coupling approach between fiber and SiN waveguides by utilizing the high-index doped silica glass (HDSG) waveguide as the intermediary to smooth out the mode transition. We achieved fiber-to-SiN waveguide coupling efficiency of lower than 0.8 dB/facet across the full C and L bands with high fabrication and alignment tolerances.

Effect of B&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Content on Structure and Properties in High Refractive Index BaO-ZnO-TiO&lt;sub&gt;2&lt;/sub&gt;-SiO&lt;sub&gt;2&lt;/sub&gt; Glass System

In this paper, BaO-ZnO-TiO2-SiO2 is used as the research system of high refractive index glass, and IR, XRD and DTA are used to study the structure, thermal behavior, crystallization and chemical stability of different glasses when B2O3 gradually replaces SiO2. The results show that when B2O3 replaces SiO2, glass still has an amorphous structure, and the density of glass shows a decreasing trend with the increase of B2O3 content. With the increase of B2O3 content, the boron-oxygen tetrahedron gradually transforms into the boron-oxygen triangle, which makes the overall crystallization of the glass structure weaken. The results show that the density, refractive index and water resistance of glass beads without B2O3 are the best. With the increase of B2O3 content, the activation energy of crystallization decreases, the potential barrier to be overcome for crystallization decreases, as the same time the phenomenon of glass crystallization is obvious. Keywords:High refractive index glass; BaO-ZnO-TiO2-SiO2; Crystallization; Chemical stability

Generation of Parabolic pulse by nonlinear pulse reshaping inside a Silicon on Insulator (SOI) Waveguide

In recent times, silicon photonics attracts a lot of attraction of researchers. It is the technology that converts many functions of the circuit on the thumb-size chip. Nowadays, various types of technology platforms are being used to design photonic integrated circuits using various materials such as high index glass, semiconductors, polymers, and silicon. In our work, we have used silicon to design rectangular silicon on Insulator (SOI) buried waveguide. This type of waveguide has shown great potential in the field of pulse reshaping. We have used the effective index method for the calculation of group velocity dispersion and nonlinearity. Though the two-photon absorption and free-carrier generation contribute significantly to loss parameters, the highly nonlinear buried waveguide is found to be capable of reshaping super-Gaussian pulse input into a parabolic shape. Moreover, the values of input chirp, pulse width, and peak power are further optimized for the generation of a high-quality parabolic pulse at shorter lengths. The length required for pulse reshaping is much less when compared to optical fibers. Thus, our design waveguide has potential in the domain of pulse generation, signal processing, and many more.

Effect of Alumina Content on Structure and Properties of High Refractive Index Glass

In this paper, BaO-ZnO-TiO2-SiO2 is used as the research system of high refractive index glass, and IR, XRD and DTA are used to study the structure, thermal behavior, crystallization and chemical stability of different glasses when Al2O3 gradually replaces CaO. The results show that when Al2O3 replaces CaO, the glass still has an amorphous structure. With the increase of Al2O3 content, the glass structure first becomes tight, and then due to the formation of [AlO6], the glass network becomes loose, and the glass density peaks with the increase of Al2O3 content. DTA analysis showed that with the increase of Al2O3 content, the devitrification trend of the glass increased during the cooling process, the crystallization peak moved to the low temperature direction, and the exothermic effect weakened, indicating that the surface crystallization trend of the glass increased and the overall crystallization became weaker. The results show that the density, refractive index and water resistance of glass microspheres containing only CaO are the best, but the crystallization of glass is obvious during heat treatment.

Decolorization of high refractive index glass based on SiO2-(BaO + ZrO2)-TiO2 using transition metal oxides

Decolorization of high refractive index glass based on SiO2-(BaO + ZrO2)-TiO2 using transition metal oxides

High-precision molding simulation prediction of glass lens profile for a new lanthanide optical glass

Precision glass lens molding (PGLM) is a recently developed method for fabricating glass optical components with high precision in large volumes. Lanthanum optical glasses are extensively used as optical materials owing to their superior optical properties, such as high refractive index, low dispersion, and high transparency. However, the transformation temperature of currently available high refractive index glass is generally above 650 °C and poses a challenge in manufacturing ultra-hard molds, durable coatings, and high-temperature molding equipment using PGLM. In this study, a preparation method for obtaining high refractive index, low -melting -point lanthanide optical glass (B-ZLaT198) used in PGLM was developed to reduce the transformation temperature. The developed method also characterizes the glass refractive indices and thermal-mechanical properties. To achieve the high-precision prediction of a molding shape in a simulation, a viscoelastic constitutive model of glass was established based on a micro-deformation uniaxial compression creep test. Moreover, by solving the Tool-Narayanasway-Moynihan model parameters based on the specific heat capacity fitting of optical glass at different heating and cooling rates, the input parameters of the structural relaxation model (SRM) for simulation prediction of aspheric glass lens profile deviation in the annealing stage were obtained. Finally, the profile deviation of the aspheric lens was predicted using a finite element model simulation. The results showed that the simulation’s predicted profile of an aspheric lens using the SRM model was in good agreement with that of experimental molding profile. In addition, using the SRM provided a higher prediction accuracy than that of the thermal expansion model in the annealing stage. Adopting the SRM was necessary for the annealing simulations of molding pressing and also verified the accuracy of the proposed viscoelastic characterization method for calculating the thermomechanical parameters of optical glasses.

Single Fiber Optical Tweezer for Particles Multi-Dimensional Arrangement

We propose and demonstrate a single fiber optical tweezer for particle multi-dimensional arrangement based on an optical bottle beam produced by concatenating a few-mode fiber and a step-index multimode fiber. We use the mode division multiplexing technology to produce the optical bottle beam with uneven energy distribution. The LP₁₁ and LP₂₁ mode beams are excited by docking a 980 nm single-mode fiber at the outlet of the light source to a few-mode fiber with a defined offset. The few-mode fiber allows LP₀₁, LP₁₁, and LP₂₁ mode beams to be spread in. The optical bottle beam is focused on a high refractive index glass microsphere integrated on the fiber end. The LP₀₁ mode beam is used to trap particles and array them in a one-dimension space (linear arrangement), the LP₀₁ and LP₁₁ mode beams are used to trap and array particles in a two-dimension space (planar arrangement), and the LP₀₁, LP₁₁, and LP₂₁ mode beams are used to trap and array particles in a three-dimension space (solid arrangement). The proposed fiber optical tweezer is simple in structure and will allow us to examine the interaction between the cells when held in close proximity.

Ultra-thick inverted green organic light-emitting diodes for high power efficiency over 300 lm/W

We utilize an inverted green OLED architecture with a thick hole transfer layer (HTL) composed of multi-period organic heterojunctions as well as an emitter with horizontal orientation of dipole moment to suppress SP mode loss. The waveguide and substrate mode are extracted by combining the matched high refractive index hemispherical lens on high refractive index glass substrate, Maximum forward-viewing power efficiency (PE) and external quantum efficiency (EQE) of 305.5 lm/W and 71.0% are achieved in the device with 210 nm-thick-HTL, The optical simulation show that our results are very close to the out-coupling theoretical limit. Our work provides a promising strategy to construct OLED with ultra-high PE for achieving low-power environment-friendly display and lighting applications.

Glass-glass bonding for high refractive index glass by low-temperature bonding method

Glass-glass bonding for high refractive index glass by low-temperature bonding method

Analytical Study of Precision Optical Glass Surface and Its Effect on Some Polarimetric Parameters

The performance of many optical glass elements depends on the structure of the surface. The high refractive index of flint glass is advantageous in constructing some optical elements (lenses, prisms, beam splitters, …). Also, high achromaticity and size reduction in oblique incidence TIR (total internal reflection) phase retarders require high-index glass. The present work is interested in studying the optical properties of the thin surface layer formed on TIR rhomb retarder at different wavelengths to indicate the extent to which this surface layer affects the performance of this TIR rhomb retarder and show how to overcome this effect.

Effect of cryogenic cycling on mechanical properties of ZrTiCuNiBe bulk metallic glass

The effect of deep cryogenic cycle treatment (DCT) on Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit-1) bulk metallic glass (BMG) prepared from high-purity raw materials was investigated. After DCT, no obvious rejuvenation of the samples was detected. With an increasing number of cryogenic cycles, the hardness of the samples first decreased and then increased, the room-temperature compression plasticity first increased and then generally remained unchanged, and the impact toughness underwent almost no obvious change. The absence of rejuvenation was attributed to the high fragility index (47–50) and high glass forming ability (GFA) of the material. As lower purity of the raw materials is expected in practical applications, DCT of Vit-1 BMG prepared from low-purity raw materials was also performed. After DCT, the samples prepared with the lower-purity raw materials were clearly rejuvenated, and the room-temperature mechanical properties improved significantly.Both the compression plasticity and impact toughness reached peak values after 5 cryogenic cycles. The initial impurities (including Y and O) had a complex and comprehensive effect on the deformation mechanism of the BMG during DCT. Our findings indicate that the structural heterogeneity, fragility index, and GFA of the BMG alter the effect of DCT.

Silicon subwavelength grating waveguides with high-index chalcogenide glass cladding.

Silicon subwavelength grating waveguides enable flexible design in integrated photonics through nano-scale refractive index engineering. Here, we explore the possibility of combining silicon subwavelength gratings waveguides with a high-index chalcogenide glass as a top cladding, thus modifying the waveguiding behavior and opening a new design axis for these structures. A detailed investigation of the heterogeneous SWG waveguide with high-index cladding is presented based on analytical and numerical simulations. We design, fabricate and characterize silicon subwavelength grating waveguide microring resonators with an As20S80 cladding. Thanks to As20S80 negative thermo-optic coefficient, we achieve near athermal behavior with a measured minimum thermally induced resonance shift of -1.54 pm/K, highlighting the potential of subwavelength grating waveguides for modal confinement engineering and to control light-matter interaction. We also show that the chalcogenide glass can be thermally reflowed to remove air gaps inside the cladding, resulting in a highly conformal structure. These types of waveguides can find application in reconfigurable photonics, nonlinear optics, metamaterials or slow light.

Super-Resolution Imaging by Dielectric Superlenses: TiO2 Metamaterial Superlens versus BaTiO3 Superlens

All-dielectric superlens made from micro and nano particles has emerged as a simple yet effective solution to label-free, super-resolution imaging. High-index BaTiO3 Glass (BTG) microspheres are among the most widely used dielectric superlenses today but could potentially be replaced by a new class of TiO2 metamaterial (meta-TiO2) superlens made of TiO2 nanoparticles. In this work, we designed and fabricated TiO2 metamaterial superlens in full-sphere shape for the first time, which resembles BTG microsphere in terms of the physical shape, size, and effective refractive index. Super-resolution imaging performances were compared using the same sample, lighting, and imaging settings. The results show that TiO2 meta-superlens performs consistently better over BTG superlens in terms of imaging contrast, clarity, field of view, and resolution, which was further supported by theoretical simulation. This opens new possibilities in developing more powerful, robust, and reliable super-resolution lens and imaging systems.

30‐2: High Refractive Index Glass Wafers for Augmented Reality: Boundary Conditions for an Excellent Optical Performance

Planar, high refractive glass wafers are the backbone of leading Augmented/Mixed Reality devices. They route the virtual image to the user's eye, while helping to keep the form factor small. While the glass characteristic directly affects fundamental design parameters like Field‐of‐View, the optical system of the wafer with its surfaces and interfaces as a whole determines the image quality. Besides surface quality of the glass itself, the adjacent coatings, such as anti‐reflective coating and polymer coating with a grid structure can significantly contribute to the total optical loss. Here we are reporting on optical losses caused by surface effects and polymer coatings that might lead to disadvantages in key quality parameters, such as contrast, brightness and distortion of the image.

Inverted with power efficiency over 220 lm W–1

The white organic light-emitting diodes (WOLEDs) have great potential in the fields of solid-state lighting. Continued efforts have been made to catch up with the power efficiency (PE) of inorganic light-emitting diodes. Apart from low operating voltage and near unity internal quantum efficiency, improvement the efficiency of light extraction, especially suppression of surface plasmon (SP) modes is essential for realizing ultimate PE. In contrast to corrugated structure which could suffer from spectral selectivity, higher leakage current and potential degradation issue stemmed from the rough structure, increasing the distance between the emitter and the metallic electrode becomes an effective avenue towards suppressing SP modes while maintaining the planar structure. In this work, an inverted bottom-emitting structure with thick hole transport layer (HTL) composed of multi-period organic heterojunctions is demonstrated to effectively extract the SP modes without any electrical property degradation in the current density range for lighting. Investigation on electrical properties of thickened HTL with increased count of organic heterojunctions indicates no increase of driving voltage at same current density in lighting application condition. By attaching an matched high refractive index lens, a record maximum forward-viewing PE of 228.4 lm W-1 is obtained for the thick WOLED fabricated on high refractive index glass substrate, exhibiting significant enhancements of 57% compared to the counterpart of the conventional thin WOLEDs. An unambiguous picture is given to depict the regularity derived from increase of emitter-to-metal distance by combination of a full optical simulation and experimental measurements excluded the influence of electrical property degradation.