Fabrication Of Photonic Devices Research Articles

Ultra-Fast Fabrication of Mechanical-Water-Responsive Color-Changing Photonic Crystals Elastomers and 3D Complex Devices.

The traditional fabrication of opal-structured photonic crystals is constrained by the rate of solvent evaporation, a process that is not only time-consuming but also labor-intensive. This study introduces a paradigm shift by incorporating silica nanoparticles (SiNPs) with high zeta potentials and hydrogen bonding capabilities into an elastomeric matrix, resulting in a novel non-close-packed structure. This innovation circumvents the limitations of conventional methods by enabling the rapid formation of photonic inks (PI) into vibrant and luminous photonic elastomers (PEs) within seconds. These PEs demonstrate remarkable mechanochromic properties, exhibiting dynamic color changes across the visible spectrum in response to tensile and compressive deformations. Furthermore, the presence of hydroxyl groups endows the PEs with superior water-responsiveness, which can be finely tuned through the ink formulation. The elimination of solvent evaporation dependency facilitates the fabrication of macroscopic photonic crystal devices with complex geometries using digital light processing (DLP)-based 3D printing. This approach ensures exceptional optical performance and high customization potential. The resulting PEs hold significant promise for applications in smart wearables, soft robotics, and advanced human-machine interface technologies.

Tuning the Electronic Properties of Bridged Dithienyl-, Difuryl-, Dipyrrolyl-Vinylene as Precursors of Small-Bandgap Conjugated Polymer.

Optoelectronic properties of linear π-conjugated polymers/oligomers are of great importance for the fabrication of organic photonic and electronic devices. To this end, the π-conjugated polymers/oligomers need to meet both optoelectronic and key structural properties in order to fulfill their implementation as active components. In particular, they need to possess low bandgap and high thermal, conformational, and photochemical stabilities. So far, several strategies have been developed to attain such requirements including the covalent and non-covalent rigidification concepts of the π-conjugated systems. On the basis of these findings, we describe herein the theoretical studies of novel series of covalently bridged derivatives demonstrating the benefits of the strategy. Comparison of these derivatives with compounds previously described in the literature highlights enhanced optoelectronic properties and behaviors that would be beneficial for the construction and development of new linear π-conjugated polymers.

Nickel stanogermanides thin films: Phases formation, kinetics, and Sn segregation

Ge1−xSnx thin films with a Sn content of x ≥ 0.1 present a direct bandgap, which is very interesting for the fabrication of efficient photonic devices. The monostanogermanide phase, Ni(GeSn), is promising to form ohmic contact in GeSn-based Si photonic devices. However, the formation kinetics of Ni stanogermanides and the incorporation of Sn in Ni–GeSn phases are not fully understood. In this work, Ni thin films were deposited on Ge and Ge0.9Sn0.1 layers grown in epitaxy on an Si(100) substrate using magnetron sputtering technique. In situ x-ray diffraction measurements were performed during the solid-state reaction of Ni/Ge and Ni/Ge0.9Sn0.1. 1D finite difference simulations based on the linear parabolic model were performed to determine the kinetics parameters for phase growth. The nucleation and growth kinetics of Ni germanides are modified by the addition of Sn. A delay in the formation of Ni(GeSn) was observed and is probably due to the stress relaxation in the Ni-rich phase. In addition, the thermal stability of the Ni(GeSn) phase is highly affected by Sn segregation. A model was developed to determine the kinetic parameters of Sn segregation in Ni(GeSn).

Polarization splitter-rotator on thin film lithium niobate based on multimode interference

Polarization splitter-rotators (PSRs) are the key elements to realize on-chip polarization manipulation. Current PSRs on thin film lithium niobate (TFLN) rely on sub-micron gaps to realize mode separation, which increases the difficulties of lithography and etching. In this paper, a PSR on TFLN based on multimode interference (MMI) is demonstrated. Mode division is achieved by an MMI-based mode demultiplexer. The minimum feature size of the PSR is 1.5 µm, which can be fabricated with low-priced i-line contact aligners. Experimental results show a polarization extinction ratio (PER) > 16 dB and an insertion loss (IL) < 1.0 dB are achieved in a wavelength range of 1530-1578 nm for TE-polarized light. And a PER > 10.0 dB and an IL <2.1 dB are achieved in a wavelength range of 1530-1569 nm for TM-polarized light. This PSR could find application in the low-cost fabrication of dual-polarization TFLN-integrated photonic devices.

Ultrahigh precision laser nanoprinting based on defect-compensated digital holography for fast-fabricating optical metalenses.

The 3D structured light field manipulated by a digital-micromirror-device (DMD)-based digital hologram has demonstrated its superiority in fast-fabricating stereo nanostructures. However, this technique intrinsically suffers from defects of light intensity in generating modulated focal spots, which prevents from achieving high-precision micro/nanodevices. In this Letter, we have demonstrated a compensation approach based on adapting spatial voxel density for fabricating optical metalenses with ultrahigh precision. The modulated focal spot experiences intensity fluctuations of up to 3% by changing the spatial position, leading to a 20% variation of the structural dimension in fabrication. By altering the voxel density to improve the uniformity of the laser cumulative exposure dosage over the fabrication region, we achieved an increased dimensional uniformity from 94.4% to 97.6% in fabricated pillars. This approach enables fast fabrication of metalenses capable of sub-diffraction focusing of 0.44λ/NA with the increased mainlobe-sidelobe ratio from 1:0.34 to 1:0.14. A 6 × 5 supercritical lens array is fabricated within 2 min, paving a way for the fast fabrication of large-scale photonic devices.

Waveguide-Coupled Light Photodetector Based on Two-Dimensional Molybdenum Disulfide.

The integration of transition metal dichalcogenides with photonic structures such as sol-gel SiOx:TiOy optical waveguides (WGs) makes possible the fabrication of photonic devices with the desired characteristics in the visible spectral range. In this study, we propose and experimentally demonstrate a MoS2-based photodetector integrated with a sol-gel SiOx:TiOy WG. Based on the spectroscopic measurements performed for our device, we concluded that the light entering the WG is almost completely channeled out from the WG and absorbed by the MoS2 flake, which is deposited on the WG. Therefore, this device works as a photodetector. The light coupling into the MoS2 region in this device construction is due to the high contrast of refractive index between the van der Waals crystal and the sol-gel WG, which is ∼4 and ∼1.8, respectively. The obtained MoS2-based photodetectors exhibit a photoresponsivity of 0.3 A W-1 (n-type MoS2) and 7.53 mA W-1 (p-type MoS2) at a bias voltage of 2 V. These results reveal great potential in the integration of sol-gel WGs with van der Waals crystals in optoelectronic applications.

Silicon nanocrystal slab optical waveguide by multi-energy ion implantation: Linear and nonlinear optical properties

Silicon nanocrystals (Si-nc) have gained attention in optics and photonics research areas in recent years due to their advanced optical nonlinear properties. However, a nonlinear integrated optical platform that allows the fabrication of photonic devices with different Si-nc composition is yet under investigation. In this work, we experimentally demonstrated a nonlinear optical waveguide based on ion implantation that offers advantages in terms of material composition, low propagation losses, and enhanced nonlinear optical properties, such as a high nonlinear refractive index. In this work we present the fabrication of Si-nc containing waveguiding structures, and a study of their linear and nonlinear optical properties. Our nonlinear integrated optical platform presents a two-photon absorption coefficient β = 3.17 × 10−6 cm W−1 and a nonlinear refractive index n2 = 1.19 × 10−10 cm2 W−1, which shows potential applications in all-optical signal processing devices, such as single-photon sources.

Hybrid Photonic Structures: Gallium Phosphide Nanowires Decorated with Carbon Dots for Enhanced Broadband Emission

AbstractCarbon dots (CDs) are promising nanostructures in the field of photonics owing to the ease of fabrication, tunable and efficient emission. Gallium phosphide (GaP) nanowires are known for high surface area, optical density, waveguiding, resonant optical properties but lacking the luminescence due to the indirect bandgap. Here, hybrid photonic structures – GaP nanowires decorated with the CDs are fabricated and studied. Feasible drop‐casting deposition technique allows fabrication of dense vertical structures exhibiting efficient photoluminescence. Deposition of the CDs over the nanowires does not affect their luminescent properties demonstrating tolerance of the approach toward the surface aggregation. Tuning of the emission spectrum is obtained via variation of the excitation wavelength and CDs’ synthesis protocol. The structures emitting throughout the visible range are obtained. Analysis of the photoluminescence of an individual structure demonstrates the most intense and fast recombination processes at the ends of a nanowire. It is shown that the luminescence of the CDs’ covering a nanowire acting as a Fabry–Perot cavity is enhanced up to a factor of 3 governed by the Purcell effect. The obtained results unveil a path for fabrication of novel photonic devices via decoration of optically dense nanowires with CDs for enhanced and directed broadband emission.

Controlling behaviour of transparency and absorption in three-coupled multiple quantum wells via spontaneously generated coherence

This article presents a coherent phenomenon called spontaneously generated coherence (SGC) under the regime of electromagnetically induced transparency (EIT) in a three-coupled multiple quantum wells. We demonstrate that the presence of SGC in these quantum wells lead to intriguing modifications in the transparency window within the absorption spectrum. At the same time, modification of the dispersive nature is also demonstrated which enables the feasibility of the system in diverse applications based on light propagation. The absorption and dispersion responses are found to be varied by the individual strength of the first and second control fields in presence as well as in absence of SGC in the EIT regime. The positional shifting of the transparency window and simultaneous modifications in the dispersive profiles by tuning the control field detunings of both the first and second control fields are also revealed. Some absorption and dispersion contours are illustrated for getting better insights into the modifications of the optical responses via SGC. Finally, by manipulating the strength of the SGC parameter, we observe the changes in the respective position of the transparency window and dispersion curve. It is expected that the current investigations will pave novel ways for innovative applications in quantum communications, and fabrication of advanced photonic devices.

Low-loss chalcogenide photonic devices with a secondary coating method.

In the traditional dry etching process for photonic device fabrication, the etching effect is influenced in many ways, usually resulting in relatively large sidewall roughness and high transmission loss. In this study, an effective method, namely the secondary coating method, is proposed to reduce the transmission loss of a Ge-Sb-Se chalcogenide waveguide and increase the quality factor (Q-factor) of a Ge-Sb-Se chalcogenide micro-ring resonator. The Ge-Sb-Se waveguide and micro-ring resonator are fabricated by ultraviolet exposure/electron beam lithography and inductively coupled plasma etching technology. Afterward, a 10 nm-thick Ge-Sb-Se thin film is deposited by thermal evaporation. The measurements show that after secondary coating, the sidewall roughness of the waveguide is reduced from 11.96 nm to 6.52 nm, with the transmission loss reduced from 2.63± 0.19 dB/cm to 1.86± 0.11 dB/cm at 1.55 µm wavelength. Keeping an equal coupling condition with equal radius and coupling distance, the Q-factor of the micro-ring resonator is improved by 47.5% after secondary coating. All results indicate that the secondary coating method is a feasible way to generate low-loss and high Q-factor integrated chalcogenide photonic devices.

Combining thermal scanning probe lithography and dry etching for grayscale nanopattern amplification

Grayscale structured surfaces with nanometer-scale features are used in a growing number of applications in optics and fluidics. Thermal scanning probe lithography achieves a lateral resolution below 10 nm and a vertical resolution below 1 nm, but its maximum depth in polymers is limited. Here, we present an innovative combination of nanowriting in thermal resist and plasma dry etching with substrate cooling, which achieves up to 10-fold amplification of polymer nanopatterns into SiO2 without proportionally increasing surface roughness. Sinusoidal nanopatterns in SiO2 with 400 nm pitch and 150 nm depth are fabricated free of shape distortion after dry etching. To exemplify the possible applications of the proposed method, grayscale dielectric nanostructures are used for scalable manufacturing through nanoimprint lithography and for strain nanoengineering of 2D materials. Such a method for aspect ratio amplification and smooth grayscale nanopatterning has the potential to find application in the fabrication of photonic and nanoelectronic devices.

Uniform broad-area deposition and patterning of SiO2 nanofilms by 172 nm photochemical conversion of liquid tetraethoxysilane layers at 300 K

Oxide films of the quality required for the fabrication of electronic and photonic devices are typically deposited at elevated temperatures and thermal equilibrium, thereby adversely impacting thermal budgets. We report the deposition and patterning of silicon dioxide (SiO2) films of high electrical and optical quality on Si(100) or polymer substrates in a N2 atmosphere and at 300 K by the photochemical conversion of thin liquid tetraethoxysilane (TEOS) layers with narrowband vacuum ultraviolet radiation [vacuum ultraviolet (VUV), 172 nm] provided by efficient microplasma lamps. Irradiating liquid TEOS layers, produced by spin-coating the precursor onto a substrate, with a VUV intensity of 13 mW cm−2, yields 40 nm-thick SiO2 films having a dielectric breakdown strength (Eb) of 5 MV cm−1, for which no precedent exists in the deposition of oxide films at 300 K. If room temperature-deposited films are post-annealed at 200 °C, Eb rises to 7.5 MV cm−1, which is <12% below the measured value (8.5 MV cm−1) for 40 nm SiO2 films grown by thermal oxidation. The deposition of 1 µm thick, stoichiometric SiO2 films requires only 20 min of VUV illumination at low optical fluences, and films with thicknesses of ∼35–60 nm exhibit a refractive index of 1.45 (633 nm). X-ray photoelectron spectrometry and Rutherford backscattering analysis indicate that, despite the deposition temperature, hydrocarbon impurity levels are near or below the detection limit. The capability for depositing 960 nm-thick SiO2 films uniformly (to within 0.6%) by liquid → solid photochemical conversion over a 5 cm diameter Si substrate and patterning films onto flexible polymer substrates has also been demonstrated.

Amphiphilic acetylacetone-based carbon dots

The use of acetylacetone in combination with benzoic acid and ethylenediamine led to amphiphilic carbon dots formation with bright blue emission, which allowed us to produce LEDs, luminescent inks, and films for solar concentrators.

Inversion of the Chiroptical Responses of Chiral Gold Nanoparticles with a Gold Film.

The deposition of chiral nanoparticles (NPs) onto various substrates is crucial for the fabrication of high-density photonic devices. Understanding the interaction of chiral light and chiral NPs supported on substrates is essential for developing optical sensors and modulators. However, the chiroptical responses of plasmonic chiral NPs on substrates have remained elusive. Here we provide an important understanding of the correlation between the substrate material and the chiroptical response. The scattering dissymmetry factors of individual chiral Au nanocubes are inverted and enhanced with a gold film. Qualitative theories are proposed to analyze the observed variations in the chiroptical signals of chiral NPs on different substrates. Our results offer an encouraging route for modulating and amplifying the chiroptical signals in the use of chiral NPs in light control, light-based quantum technologies, and sensing.

Femtosecond laser-induced glass refractive index change in tellurite glass

Tellurite glass has excellent infrared optical properties and is widely used in lasers, optical communications, and sensing. Femtosecond laser direct writing is a preferred method for manufacturing tellurite photonic devices, which requires precise control of the variable of refractive index. However, accurate testing of the refractive index changes induced by femtosecond laser in tellurite glass is challenging due to the small magnitude of change and localized region. In this study, we present a novel approach to measure the refractive index change of tellurite glass through the utilization of volume phase grating (VPG) diffraction. We first investigated the laser-induced damage threshold (LIDT) of tellurite glass and then proceeded to prepare VPGs inside the glass by using femtosecond laser direct writing technology, ensuring that the laser energy remained below the LIDT. By measuring the thickness and diffraction efficiency of VPGs prepared under different laser energies, we determined the associated change in refractive index. In our experiment, when subjected to laser incidence with wavelengths of 632.8 and 808 nm, the maximum values of refractive index change in the laser-modified region are measured to be 1.97 × 10−3 and 1.61 × 10−3, respectively. This method offers a precise means of measuring refractive index change within the microregion of tellurite glass induced by femtosecond laser. This capability holds great significance for the fabrication of high-quality tellurite glass photonic devices using lithography-based techniques.

Structural polymorphism, electronic, and optical properties of NaSbS2: A computational approach toward eco-friendly and emerging semiconductor

In this work, the structural polymorphism and electro-optical characteristics of NaSbS2 ternary chalcogenide are realized using density functional theory (DFT). All of the NaSbS2 polymorphs are energetically stable based on the formation energy. The optimized lattice parameters of the monoclinic and triclinic structures and direct electronic bandgap (1.695 eV) of monoclinic structure are consistent with previous studies. Besides, the trigonal and triclinic structures are indirect bandgap (0.916 and 2.015 eV) semiconductors observed from electronic band structure. The higher degree of ionicity between Na and S atoms while strong covalency in the Sb-S bonds are confirmed from the charge and bond analysis. The lower value of electron-hole effective masses indicates higher carrier mobility leading to outstanding electrical conductivity. It was suggested that the polymorphs would be extremely desired to design Bragg reflectors and waveguides based on the reported high value of the real part of the dielectric constant and refractive index. These polymorphs will contribute significantly to being used as absorbers, as evidenced by their high absorption coefficient and photoconductivity and lower transmittance. All the polymorphs reflect significant optical anisotropy and birefringence, rendering them excellent for usage in the fabrication of waveguides, polarizers, and photonic devices. Thus, the projected good features of NaSbS2 polymorphs would play an essential role in the development of lead-free photovoltaic devices, including solar cells and other optoelectronic devices, and would be able to provide practical information for future theoretical and experimental studies.

Fabrication of freestanding photonic devices combining polymer films with microfabrication techniques and 3D printing.

We report a technological concept for freestanding photonic elements based on metamaterials fabricated on polymer films by clean-room processes and framed using 3D printing. A spin-coated cyclic olefin copolymer (TOPAS) of variable thickness down to one micrometer was used as the substrate onto which metamaterials were fabricated using optical lithography. We demonstrate the possibility of applying a second TOPAS layer to protect the device or to allow for stacking another metamaterial layer. To obtain freestanding elements, frames were 3D printed directly on top of the metamaterial before lift-off from the carrier wafer. This ensured maintaining the flatness of the elements. Both the cleanroom process and the 3D printing enabled the design and manufacturing of elements in different sizes and shapes, e.g., to adapt to specific experimental set-ups and holder geometries or to be compatible with standard optical mounts. While TOPAS is transparent for wavelengths from UV to the far infrared, except for a few infrared absorption lines, we illustrate the concept with the simulation and manufacturing of THz band-pass filters. The performance of the fabricated filters was assessed using THz time-domain spectroscopy. The process is scalable to other wavelength ranges and has the potential for upscaling in manufacturing.

Buried Optical Waveguide in Photo-Thermo-Refractive Glass by Ion Exchange Technology

To realize application of functional material Photo-Thermo-Refractive (PTR) glass for integrated photonic device production, PTR glass material is fabricated and employed as matrix material for planar optical waveguide manufacturing. Buried optical waveguide, with a core dimension of 8.7 μm × 9.0 μm (width by height), and its front edge located at approximately 12.5 μm underneath the glass substrate surface, is obtained by using thermal ion exchange (TIE) and subsequent field-assisted ion migration (FAIM). Transmission loss of these waveguides can be reduced to a value as low as 0.08 dB/cm at the operating wavelength of 1550 nm, and the coupling loss to standard single-mode-fiber is measured to be 0.47 dB/facet, demonstrating the feasibility of low-loss integrated photonic devices fabrication on PTR glass materials by ion exchange technology.

Colloidal Silver Nanoparticle Plasmonic Arrays for Versatile Lasing Architectures via Template‐Assisted Self‐Assembly

AbstractThe characteristic narrow spectral features of surface lattice resonances emerge as great candidates for the rational design of optical nanocavities targeting enhanced light‐matter interaction, ultrasensitive detection, or efficient light‐energy conversion. Traditional fabrication of metal arrays involves thermal evaporation and annealing steps, limiting scalability and adaptability. In contrast, template‐assisted self‐assembly provides a high‐throughput all‐around approach for implementing colloidal plasmonic metasurfaces on a variety of different materials. Here, the use of pre‐synthesized silver nanoparticles is designed and tested for the construction of versatile lasing architectures. Plasmonic arrays are prepared directly on top of the gain media (a photoresist thin film doped with Rhodamine B), creating optical nanocavities with quality factors as high as 85. The proposed architecture circumvents the need for an index‐matching superstrate to promote the generation of collective resonances, leaving the plasmonic surface accessible for post‐assembly modification. Additionally, the angular dispersion of the metasurfaces is used to modify the angle of the lasing emission, achieving both normal and off‐normal lasing upon modification of the lattice parameter of the array. The results demonstrate how state‐of‐the‐art colloidal self‐assembly techniques offer a scalable and versatile alternative for the fabrication of plasmonic and photonic devices targeting advanced and non‐linear optical phenomena.

New organic platform to integrated photonic device fabrication

New organic platform to integrated photonic device fabrication