Advanced Nanophotonics: Silicon-Organic Hybrid Technology

Integrated photonic devices have gained increasing research interests. Especially silicon photonics have become very attractive for various optical applications. Using silicon-on-insulator as a material platform provides the ability to fabricate photonic devices with electronic devices on a single chip. Driven by substantial research investments, the integration of photonic devices on silicon-on-insulator substrates has reached a degree of maturity that already permits industrial adoption. However, silicon has the disadvantage of linear electro-optical effects, and, therefore, advanced modulation formats are difficult to realize when using silicon-based high-speed modulators. Hence, a new approach was proposed: the silicon-organic hybrid technology. This technology is a viable extension of the silicon-on-insulator material system for efficient high-speed modulation. We herewith present our theoretical and experimental investigations of the silicon-organic hybrid slot-waveguide ring resonator. The advanced device design is described in detail, which allows using both, the efficient silicon-on-insulator strip-waveguides and the silicon-organic hybrid slot-waveguides in single ring resonator. For the first time, we report the transmission spectra of such a resonator covered with an electro-optical polymer.Integrierte photonische Bauelemente werden in der Forschung immer bedeutender. Besonders die Siliziumphotonik ist für verschiedene optische Anwendungen sehr attraktiv. Die Verwendung von Silizium-auf-Isolator-Materialsystemen bietet die Möglichkeit, photonische Bauelemente mit elektronischen Geräten auf einem einzelnen Chip zu entwickeln. Durch erhebliche Forschungsinvestitionen hat die photonische Integration auf Silizium-auf-Isolator-Substraten einen Reifegrad, der bereits Industriemaßstäben genügt. Jedoch hat Silizium keinen linearen elektrooptischen Effekt und damit sind moderne Modulationsformate nur schwierig zu realisieren. Daher wird seit eingen Jahren ein neuer Ansatz, die Silizium-Organik Hybridtechnologie, verfolgt. Diese Technologie ist eine tragfähige Ausdehnung des Silizium-auf-Isolator-Materialsystems für eine effiziente Hochgeschwindigkeitsmodulation und optische Signalverarbeitung. In diesem Artikel präsentieren wir unsere theoretischen und experimentellen Untersuchungen zu einem Silizium-Organik Hybrid Ringresonator. Das Design und die Herstellung des neuartigen nanophotonischen Bauelements werden im Detail beschrieben. Der demonstrierte Ringresonator kombiniert die Vorteile zweier verschiedener Wellenleiterarten in einem einzelnen Ring, dem verlustarmen Kanal-Wellenleiter und dem Silizium-organischen Hybridschlitzwellenleiter. Wir demonstrieren erstmals ein Transmissionsspektrum eines solchen Ringresonators, der mit einem elektro-optischen Polymer beschichtet ist

On-Chip Dispersion Measurement of the Quadratic Electro-Optic Effect in Nonlinear Optical Polymers Using a Photonic Integrated Circuit Technology

A novel method to determine the dispersion of the quadratic electro-optic effect in nonlinear optical materials by using a silicon-on-insulator microring resonator is presented. The microring consists of a silicon slot waveguide enabling large dc electric field strength at low applied voltages. The dispersion of third-order hyperpolarizability of a linear conjugated dye is approximated by using a two-level model for the off-resonant spectral region. As an example, the dispersion of the resonance wavelength of the resonator filled with a dye doped polymer was measured in dependence of the applied dc voltage. The polymer was poly (methylmethacrylate) doped with 5 wt% disperse red 1 (DR1), and the measurements have been carried out at the telecommunication wavelength band around 1550 nm (optical C-band). The described measurements represent a new technique to determine the dispersion of the third-order susceptibility and molecular hyperpolarizability of the material filled into the slot of the ring-resonator. © 2019 IEEE

Nonlinear Optical Characterization of CsPbBr3 Nanocrystals as a Novel Material for the Integration into Electro-Optic Modulators

The present work is concerned with the investigation of the nonlinear optical response of green emissive CsPbBr3 nanocrystals, in the form of colloidal dispersions in toluene, synthesized via a room-temperature ligand-assisted supersaturation recrystallization (LASR) method. After carrying out a preliminary characterization via X-Ray Diffraction (XRD) and Absorption and Photoluminescence (PL) Spectroscopies, the optical nonlinearity of the as-obtained colloids is probed by means of a single-beam Z-scan setup. Results show that the material in question, within the sensitivity of the experimental apparatus, exhibits a nonlinear refractive index n2 that is the order of 10-15 cm2/W. Moreover, a three-photon absorption mechanism (3PA) is postulated, according to the fitting of the recorded Z-scan traces and the fundamental absorption threshold, which turns out to be off resonance with twice the energy of the laser radiation. A figure of merit is, then, calculated as an indicator of the quality of the CsPbBr3 nanocrystals as a candidate material for photonic devices, for instance, Kerr-like electro-optic modulators (EOMs)

Silicon-organic hybrid photonics: Overview of recent advances, electro-optical effects and CMOS-integration concepts

In recent decades, much research effort has been invested in the development of photonic integrated circuits, and silicon-on-insulator technology has been established as a reliable platform for highly scalable silicon-based electro-optical modulators. However, the performance of such devices is restricted by the inherent material properties of silicon. An approach to overcoming these deficiencies is to integrate organic materials with exceptionally high optical nonlinearities into a silicon-on-insulator photonic platform. Silicon–organic hybrid photonics has been shown to overcome the drawbacks of silicon-based modulators in terms of operating speed, bandwidth, and energy consumption. This work reviews recent advances in silicon–organic hybrid photonics and covers the latest improvements to single components and device concepts. Special emphasis is given to the in-device performance of novel electro-optical polymers and the use of different electro-optical effects, such as the linear and quadratic electro-optical effect, as well as the electric-field-induced linear electro-optical effect. Finally, the inherent challenges of implementing non-linear optical polymers on a silicon photonic platform are discussed and a perspective for future directions is given

Periodic arrangement of mono-dispersed gold nanoparticles for high performance polymeric solar cells

We report on 80 nm diameter mono-dispersed gold nanoparticles ordered along lines by means of soft lithographic method on PEDOT:PSS layers. Silicon based mold engraved with Bragg gratings were employed to accomplish the periodic nanoparticles arrangement on large area surface. The results are promising for an increase of the power conversion efficiency in polymeric solar cells

Even-parity excited states of Ag-centers in alkali halides

Two-photon excitation of the Ag- centers in RbCl, RbBr, and KCl have been measured. From the dependence of luminescence on the polarization of the exciting beams, the symmetry of the final levels could be obtained. In all three host crystals, we observed an intense band assigned to the 1A1g1A1g transition. At higher energies 1A1g1Eg and 1A1g1T2g transitions could be identified but their presence and intensity change in the different crystals. On the high-energy side of the investigated range, we could observe an intense luminescence signal arising from a two-step excitation process; the exciting photon energy becoming resonant with the 3T1u state (A band). © 1991 The American Physical Society

Bragg grating optical filters by UV nanoimprinting

Results on an optical waveguide filter operating in the near IR region are reported. The device consists of a hybrid sol-gel -based grating loaded waveguide, obtained through the merging of conventional photolithography and UV-nanoimprinting. Starting from submicrometric gratings, fabricated by electron beam lithography, a soft mould has been produced and the original structures were replicated onto sol-gel photosensitive films. A final photolithographic step allowed the production of grating-loaded channel waveguides. The devices were optically characterized by transmission measurements in the telecom range 1450–1590 nm. The filter extinction ratio is −11 dB and the bandwidth is 1.7 nm

Polystyrene Opals Responsive to Methanol Vapors

Photonic crystals (PCs) show reflectance spectra depending on the geometrical structure of the crystal, the refractive index (neff), and the light incident angle, according to the Bragg-Snell law. Three-dimensional photonic crystals (3D-PCs) composed of polymeric sub-micrometer spheres, are arranged in an ordered face cubic centered (fcc) lattice and are good candidates for vapor sensing by exploiting changes of the reflectance spectra. We synthesized high quality polystyrene (PS) 3D-PCs, commonly called opals, with a filling factor f near to the ideal value of 0.74 and tested their optical response in the presence of different concentrations of methanol (MeOH) vapor. When methanol was present in the voids of the photonic crystals, the reflectance spectra experienced energy shifts. The concentration of methyl alcohol vapor can be inferred, due to a linear dependence of the reflectance band maximum wavelength as a function of the vapor concentration. We tested the reversibility of the process and the time stability of the system. A limit of detection (LOD) equal to 5% (v/v0), where v was the volume of methanol and v0 was the total volume of the solution (methanol and water), was estimated. A model related to capillary condensation for intermediate and high methanol concentrations was discussed. Moreover, a swelling process of the PS spheres was invoked to fully understand the unexpected energy shift found for very high methanol content