Fabrication of buried nanostructures by atomic layer deposition.

We present a method for fabricating buried nanostructures by growing a dielectric cover layer on a corrugated surface profile by atomic layer deposition of TiO. Selecting appropriate process parameters, the conformal growth of TiO results in a smooth, nearly flat-top surface of the structure. Such a hard surface can be easily cleaned without damage, making the nanostructure reusable after contamination.

Silicon slot waveguide Fano resonator.

The growing interest for Fano resonators during the past decade is due to the narrow line shape observable in their optical spectra. The drastic phase shift occurring at the resonance yields a steep drop from a high to low amplitude. Fano resonances can be obtained by a combination of nanostructures.

Multi-wavelength add-drop filter with phase-modulated shifted Bragg grating.

We present, for the first time to the best of our knowledge, a multichannel add-drop operation with a phase-modulated shifted Bragg grating based filter. The device is realized in a silicon-on-insulator waveguide platform with TiO as a coating material to reduce the refractive index contrast. The operation is shown for three and five wavelength channels within the telecom C-band.

Multi-wavelength filtering with a waveguide integrated phase-modulated Bragg grating.

We present a multi-wavelength band-rejection filter on a titanium dioxide-coated silicon-on-insulator platform. The concept rests on the use of a finely tuned waveguide-based Bragg grating for which the periods are slightly varied from one to another. This phase-modulated Bragg grating enables precise customization of integrated waveguide filters.

Influence of an AlO surface coating on the response of polymeric waveguide sensors.

The responses of a polymer ridge waveguide Young interferometer with and without a bilayer of AlO/TiO, fabricated by atomic layer deposition, are studied and compared when applied as an aqueous chemical sensor. The phase shift of the guided mode, as a result of the change in refractive index of the cover medium, is monitored. The results indicate that the over-coating affects the linearity of the sensor response.

Strip-loaded waveguide on titanium dioxide thin films by nanoimprint replication.

We present a convenient, low-cost, and mass-production-compatible technique for the fabrication of strip-loaded waveguides. The technique is based on the atomic layer deposition of a slab waveguide, nanoimprinting of a strip, and integration of two structures by lamination. The guiding layer is chosen to be a 200 nm thick titanium dioxide film.

Strip-loaded horizontal slot waveguide.

We introduce a novel concept for an optical waveguide called a strip-loaded slot waveguide. It allows an extraordinary confinement of the field in a waveguide with an extremely tiny (vertical) cross section. Unlike conventional slot waveguides, the proposed configuration has potential for very low propagation losses.

Add-drop filter based on TiO coated shifted Bragg grating.

We present a titanium dioxide coated shifted Bragg grating in a silicon-on-insulator platform enabling optical add-drop functionality. The device works on the basis of mode conversion due to shifted sidewall structure followed by mode splitting based on an asymmetric Y-coupler. We experimentally demonstrate the working principle of the device.

Hybrid layered polymer slot waveguide Young interferometer.

We demonstrate a polymer slot waveguide Young interferometer coated with a bilayer of AlO/TiO. The approach enables relaxed dimensions of the polymer waveguide which simplifies the fabrication of the structure with a resolution of 50 nm. The layers were coated by an atomic layer deposition technique.

Slow-light enhanced electro-optic modulation with an on-chip silicon-hybrid Fano system.

We present the theoretical study of a coupled cavity system yielding a Fano response on a fully on-chip silicon platform hybridized with an electro-optic polymer. This novel Fano system is based on a slot waveguide Bragg grating geometry, enabling a huge enhancement of the electro-optic properties due to slow light effects at the resonance. The modulator shows a high resonance tunability of 1.

Pyrolytic carbon coated black silicon.

Carbon is the most well-known black material in the history of man. Throughout the centuries, carbon has been used as a black material for paintings, camouflage, and optics. Although, the techniques to make other black surfaces have evolved and become more sophisticated with time, carbon still remains one of the best black materials.

Optical characterization of directly deposited graphene on a dielectric substrate.

By using scanning multiphoton microscopy we compare the nonlinear optical properties of the directly deposited and transferred to the dielectric substrate graphene. The direct deposition of graphene on oxidized silicon wafer was done by utilizing sacrificial copper catalyst film. We demonstrate that the directly deposited graphene and bi-layered transferred graphene produce comparable third harmonic signals and have almost the same damage thresholds.

Optical identification based on time domain optical coherence tomography.

We present a novel method for optical identification, i.e., authenticating valuable documents such as a passport, credit cards, and bank notes, using optical coherence tomography (OCT).

Parabolic opening in atomic layer deposited TiO(2) nanobeam operating in visible wavelengths.

We investigate the feasibility of developing a one dimensional photonic crystal cavity on a TiO platform operating in the visible. The atomic layer deposition technique is used to finely adjust the parameters of the structure. We present the experimental demonstration of a nanobeam cavity with a quadratically tapered row of holes, in which a parabolic window is opened in order to facilitate the infiltration of gas, liquid, nonlinear material, or quantum emitters.

Investigation of second- and third-harmonic generation in few-layer gallium selenide by multiphoton microscopy.

Gallium selenide (GaSe) is a layered semiconductor and a well-known nonlinear optical crystal. The discovery of graphene has created a new vast research field focusing on two-dimensional materials. We report on the nonlinear optical properties of few-layer GaSe using multiphoton microscopy.

Titanium dioxide slot waveguides for visible wavelengths.

We present the first, to our knowledge, experimental demonstration of a titanium dioxide slot waveguide operating in the visible range of light. Ring resonators based on slot waveguides were designed, fabricated, and characterized for λ≃650  nm. The fabrication method includes atomic layer deposition, electron beam lithography, and reactive ion etching.

High Aspect-Ratio Iridium-Coated Nanopillars for Highly Reproducible Surface-Enhanced Raman Scattering (SERS).

A variety of different gold and silver nanostructures have been proposed over the years as high sensitivity surface-enhanced Raman scattering (SERS) sensors. However, efficient use of SERS has been hindered by the difficulty of realizing SERS substrates that provide reproducible SERS response over the whole active area. Here, we show that atomic layer deposition (ALD) grown iridium can be used to produce highly reliable SERS substrates.

A solution to the fabrication and tarnishing problems of surface-enhanced Raman spectroscopy (SERS) fiber probes.

Surface enhanced Raman scattering (SERS) fiber probes have enormous potential in optical sensing applications. However, their widespread use has been hindered by two major obstacles: the difficulty of fabricating the required silver nanostructures on optical fibers and the tarnishing of silver, rapidly degrading their sensing properties. Here we propose a solution to these dilemmas by abandoning the use of metallic silver and conventional nanofabrication procedures.

One-dimensional photonic crystals with cylindrical geometry.

A one-dimensional photonic crystal (1DPC) consisting of a stack of alternate TiO(2) and Al(2)O(3) layers is deposited on the side wall of a glass rod by Atomic Layer Deposition. The stack is designed to sustain TE-polarized Bloch Surface Waves (BSW) in the visible spectrum at wavelengths shorter than 650 nm. Experimental evidence of light coupling and guiding capabilities of the 1DPC is provided together with a possible application for fluorescence-based remote sensors.

Polarization independent integrated filter based on a cross-slot waveguide.

We investigate an in-line band pass filter, working both for TE and TM polarizations, based on a cross-slot waveguide merged with a Bragg grating and an optical cavity. Different types of cavities (C₂- and C₄-symmetric) are presented in order to optimize the filtering and make the device dependent or independent on the polarization. We show a strong light confinement in an extremely small volume, which offers an advantage for further sensing applications.

Out-diffused silver island films for surface-enhanced Raman scattering protected with TiO2 films using atomic layer deposition.

Unlabelled: We fabricated self-assembled silver nanoisland films using a recently developed technique based on out-diffusion of silver from an ion-exchanged glass substrate in reducing atmosphere. We demonstrate that the position of the surface plasmon resonance of the films depends on the conditions of the film growth. The resonance can be gradually shifted up to 100 nm towards longer wavelengths by using atomic layer deposition of titania, from 3 to 100 nm in thickness, upon the film.

Impact of ALD grown passivation layers on silicon nitride based integrated optic devices for very-near-infrared wavelengths.

A CMOS compatible post-processing method to reduce optical losses in silicon nitride (Si(3)N(4)) integrated optical waveguides is demonstrated. Using thin layer atomic layer deposition (ALD) of aluminum oxide (Al(2)O(3)) we demonstrate that surface roughness can be reduced. A 40 nm thick Al(2)O(3) layer is deposited by ALD over Si(3)N(4) based strip waveguides and its influence on the surface roughness and the waveguide loss is studied.

Enhanced sensitivity in polymer slot waveguides by atomic layer deposited bilayer coatings.

The refractive index sensitivity of a polymer slot waveguide coated with a bilayer of Al₂O₃/TiO₂ was investigated theoretically and optimized for biosensor applications. The influence of atomic-layer-deposition-coated thin high-refractive-index layers on the slot confinement factor and the homogeneous sensitivity of polymer slot waveguides with different geometries were simulated. The results were compared with those of an optimized noncoated polymer slot waveguide, both operating at visible wavelengths.

A merged photonic crystal slot waveguide embedded in ALD-TiO₂.

We demonstrate the concept of a merged nanoscale photonic crystal slot waveguide that acts as a bandpass filter in the near infrared region of the spectrum. The device is based on the integration of a photonic crystal cavity in a slot waveguide on a silicon on insulator substrate. The device is further embedded in amorphous titanium dioxide using atomic layer deposition, which allows to reduce two-photon absorption losses and creates the possibility to combine nonlinear guided-wave optics resulting from the strong field confinement in the slot region with slow light effects in the photonic crystal cavity.

Horizontal slot waveguide channel for enhanced Raman scattering.

Herein we characterize and experimentally demonstrate a new type of a horizontal slot waveguide structure for remarkably enhanced Raman scattering detection in nanometer-scale void channels. As the measurement sensitivity is one of the key limiting factors in nanofluidic detection, it is essential to search advanced solutions for such detection. Combining an all dielectric resonance waveguide grating and a surface enhanced Raman scattering (SERS) substrate in a close proximity it is possible to create high electromagnetic field energy hot zones within an adjustable slot region.