This work aims to present a complex mid-infrared (L-band : 3.4 mu m - 4.1 mu m) astrophotonic chip made in Lithium Niobate (LiNbO3), an electro-optic crystal, using Titanium diffused waveguides. The L-band presents several key characteristics interesting in astrophysics, notably for imaging and characterise young exo-planetary systems, as well as exo-zodiacal disks. With the increasing interest in exo-planetary science, new instruments and projects are focusing in the mid infrared, such as METIS (ground-based), NOTT (ground based), or LIFE (space-based). Combining such projects with photonics and on-chip beam combination will allow for more compact instruments, easing their integration on ground or, even more so, space based projects, hence the interest for improving the performances of photonic building blocks used for astrophysics. Here, we are presenting building blocks such as Y-splitters, directional couplers, unbalanced beam splitters... that have been optimised for the L-band in Lithium Niobate. Although such blocks have already been developed in the mid-IR in this material, we are here using a different crystal orientation and newer design that are producing lower losses and birefringence. In particular, a 4-telescope mid-infrared combiner (linked to the NOTT project) was made in order to achieve nulling interferometry in the L-band. We show that we have relatively low loss waveguides, controlled photometric splitters (20/80 flux ratio), as well as functional couplers and beam splitting techniques. Furthermore, we will implement the electro-optic effect in this chip, in order to have internal modulation, and to be able to finely tune the fringes and improve the contrast, allowing for a step further into compact nulling interferometry.

This work aims to present the first results towards a mid-infrared (L-band : 3.4 mu m - 4.1 mu m) high resolution integrated spectrometer, based on the Gabor approach of SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer). In this configuration, a stationary wave is obtained by injecting the light from the source on both sides of a channel waveguide. The centre of the coherent interferogram is obtained in the middle of the waveguide, allowing for full characterisation of the source, and all differential dispersion effects between the two optical paths. The stationary wave is sampled by nano-scattering centres (= nanogrooves) placed on top of the waveguide. They extract the interferogram, and the spectrum of the source is retrieved through a Fourier Transform. In the mid-infrared, the detection area of the detectors is buried : using only one groove per scattering centre leads to a diffracted signal too wide and causes pixel crosstalk. Several grooves per scattering centres have therefore been implemented, as this configuration creates a small diffraction grating, and reduces the angular divergence of the flux. In addition to avoiding crosstalk, this allows to extract more flux per scattering centre, thus increasing the signal to noise ratio. Our samples are made in Lithium Niobate (LiNbO3), an electro-optic crystal, using two technologies. First, Direct Laser Writing for both the waveguides and the nanogrooves, and secondly Titane diffusion for the waveguides and Focused Ion Beam for the nanogrooves. Because of the electro-optic properties of Lithium Niobate, applying an electric field ramp modulation will change the refractive index of the material, allowing to finely scan the fringe packet under the sampling centres, thus increasing the sampling rate of the interferogram by temporal multiplexing. We demonstrate that our waveguides are fully functional and have a correct transmission rate, and that our antennas are extracting the stationary wave as expected, in both technologies.

This paper focuses on the development of an essential building block needed to achieve high spectral etendue in integrated optical spectrometers based on Fourier Transform methods: the active phase modulation of the fringes to sample. The long term objectives of this project are to achieve high -resolution spectrometry in a large spectral range, using compact spectrometers based on the SWIFTS (Standing Wave Fourier Transform Spectrometer) approach. The primary applications in astronomy will be precise measurement of atmospheric compositions of detected exoplanets as well as other celestial bodies, such as the detection and analysis of specific gases like carbon dioxide (CO2) and methane (CH4) that are linked to life. The proposed on -chip Fourier transform spectrometer (SWIFTS) approach offers several advantages, including high spectral resolution, compact size, and a robust design. However, the principle of sampling in a simple, passive SWIFTS, implies to extract the signal with the spatial frequency of the detector's pixel pitch. As the pixels' pitch is typically 10 p.m, the interferogram is strongly under -sampled, and the resulting spectral range without aliasing is small (typically tens of nm). The work presented in this paper is devoted to increasing the spectral range by temporal multiplexing, achieving on -chip phase modulation thanks to electro-optic properties of Lithium Niobate. By phase shifting the fringes under the sampling centers, we are able to reduce the effective distance between sampled values, therefore increasing the spectral etendue. After a brief introduction on the SWIFTS principle, we will focus on the electro-optic modulation of the fringes, and show preliminary results that validate the temporal multiplexing approach and discuss further improvements and the range of application of this active phase spectrometer.

Improving the performances of basic optical functions (splitting, directional coupling, phase modulation) is compulsory for the development of new astronomical instruments based on integrated optics. In particular, for the mid-infrared domain, where a number of projects are being developed (ASGAARD-NOTT instrument for VLTI [1], METIS for EELT [2] or future spatial projects such as LIFE [3]), these functions have to be validated in terms of achromaticy, polarization dependence and transmission losses.

This Research article document discussed about a new structure composed of a sub-micron-thick layer of a single-crystal piezoelectric material on a substrate. Longitudinal waves are used for experimental demonstration with 4'' collective processes. Electrical experimental-computation validate the concept with Q x f products near 10(12).

Acoustic wave resonators are promising candidates for gravimetric biosensing. However, they generally suffer from strong acoustic radiation in liquid, which limits their quality factor and increases their frequency noise. This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal (SPC) consisting of periodic high aspect ratio electrodes to address the above issue. The acoustic wave generated in the SPC is slower than the sound wave in water, hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface. This energy confinement results in a significant quality factor improvement and reduces frequency noise. The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process. Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency. The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators. Thus, this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.

Micro-moulding is a critical rapid prototyping process chain used for a wide range of applications. This study demonstrates that it is possible to manufacture mould at low excitation frequency plasma (380 kHz), on a silicon substrate using fluorinated chemistry. According to the mask aperture designed and process time, the cavities profile characteristics, depending on the plasma chemistry, were analysed to predict the degree of anisotropy and the curvature. We show the possibility of creating curvature shapes with a desirable conic constant k of 1.25. In particular, we highlighted the smallest aperture sizes are more attractive for replicating optical micro-lens arrays using silicon moulds. Otherwise, the largest aperture sizes gain more attention for optoelectronics, microsystems, and microfluidics applications.

To improve the mapping speed, multi-pixel radio astronomy receivers are favored [1]. Observation speed will be increased by a factor of the pixel number of the receiver. Therefore, high science throughput can be produced. Currently, there are only few heterodyne array receivers at THz. One of the challenges is the distribution of the local oscillator (LO) beam to all pixels. Often phase gratings are used to split a single LO beam into multiple beams. Here we propose a waveguide-based beam divider. In order to evaluate the performance of waveguide splitters, we use a single LO generated by a VDI Amplifier / Multiplier Chain. The LO beam is captured by a horn, transferred to waveguide and T-junctions split the signal first in two signals and then in four signals. These signals exit through circular horns into free space and are then overlayed onto the astronomical signal using a beam splitter [2]. The two signals are subsequently focused by lenses onto HEB mixers. We designed a waveguide splitter for 1.37 THz. The cross-sectional size of the WR0.65 waveguide is only 164 μm X 82 μm and is challenging to fabricate. The beam divider contains two parts: feeding network and circular horn array [2]. The feeding network consists of one E-plane junction and two H-plane junctions. The feeding network has been fabricated using two technologies: a new technology, named Femtosecond laser assisted wet etching or 3D-laser microfabrication technology [3], and silicon etching using an inductively coupled plasma-deep reactive ion etching (ICP-DRIE) [4]. The 3D-laser microfabrication can fabricate highly accurate 3D -geometries based on fused silica by direct f-s laser writing and wet etching. The SEM pictures of the fabricated feeding networks by the two technologies are shown in Fig. 1. The total thickness of the feeding network is 400 μm, and the designed waveguide channel depth is 82 μm. A comparison of both 3D-laser and ICP-DRIE microfabrication is summarized in Table I. The feeding network fabricated by 3D-laser was plated with a 1.9-μm thick gold layer. The 3D-laser is easier to fabricate, but the bottom layer is rougher. On the other hand, the side wall of the feeding network manufactured by the ICP-DRIE is rougher. The estimated simulated waveguide insertion

Lithium niobate (LN)-based devices are widely used in integrated and nonlinear optics. This material is robust and resistive to high temperatures, which makes the LN-based devices stable, but challenging to fabricate. In this work, we report on the design, manufacturing, and characterization of engineered dielectric media with thin-film LN (TFLN) on top for the coupling and propagation of electromagnetic surface waves at telecommunication wavelengths. The designed one-dimensional photonic crystal (1DPhC) sustains Bloch surface waves (BSWs) at the multilayer-air interface at 1550 nm wavelength with a propagation detected over a distance of 3 mm. The working wavelength and improved BSW propagation parameters open the way for exploration of nonlinear properties of BSW-based devices. It is also expected that these novel devices potentially would be able to modify BSW propagation and coupling by external thermal-electrical stimuli due to the improved quality of the TFLN top layer of 1DPhC.

Two immiscible metals (W and Cu) were deposited using two metallic targets by GLAD co-sputtering. A wet chemical etching technique was implemented to remove the copper and modify the typical inclined microstructure into a more porous architecture. The electrical resistivity behavior of the co-sputtered W-Cu film was characterized as a function of temperature before and after wet chemical etching. The results show that the columnar microstructure exhibits metallic-like electrical properties. The average DC electrical resistivity rho changes from 1.66 x 10 (5) Omega m to 4.28 x 10 (5) Omega m after etching. The anisotropy at room temperature is A = 1.8 +/- 0.1 for as-deposited W-Cu film and reaches 2.8 +/- 0.1 after the etching procedure. (C) 2018 Elsevier B.V. All rights reserved.

: We report on the production of hybrid photonic microsystem made by the dynamic structuration and assembly of photonic building blocks in F.I.B. (Focused Ion Beam) environment. More particularly, we show how to produce a low-loss integrated LiNbO 3 resonator composed of a free-suspended microguide and a microdisk, which shows great potential for electro-optic sensors or comb generators. The method opens the way toward new 3D electro-optical or mechanical hybrid photonic micro and nanosystems.

BSWs are non-radiative electromagnetic waves confined at the interface between a truncated periodic dielectric multilayer and a surrounding media. As an alternative to SPPs (Surface Plasmon Polaritons), BSWs show dramatically enhanced propagation lengths up to several millimeters range and provide new optical opportunities such as the possibility to obtain TE or TM-polarized surface waves. They have found numerous applications in vapor sensing, biosensing, fluorescence detection and imaging, and integrated optics. In this work, we propose a 1DPhC with a thin film of LiNbO3 (TFLN) as the top layer of the multilayer structure. The bonding of LiNbO3 into the 1DPhC structure brings anisotropy and nonlinear properties into the whole crystal allowing the tunability of the BSW devices. Here we present 1DPhCs, which are able to sustain surface waves at the LiNbO3/air interface. Two different geometries have been studied, fabricated and optically characterized. The first one is based on the LiNbO3 membrane suspended in air and the second one is held by a stable glass platform. The multilayer of the membrane based crystal is as following: air/6 pairs of Si3N4(200nm) and SiO2(215nm)/TFLN(1.1μm) – polished from bulk LN/air. The multilayer of the glass supported crystal is as following: glass/UV glue/6 pairs of Si3N4(220 nm) and SiO2(490nm)/TFLN(386nm)/air. 1DPhCs were characterized in Kretschmann configuration at visible and IR wavelengths.

Strong nonlinear, electro-optical, and thermo-optical properties of lithium niobate (LN) have gained much attention. However, the implementation of LiNbO3 in real devices is not a trivial task due to difficulties in manufacturing and handling thin-film LN. In this study, we investigate an optical device where the Bloch surface wave (BSW) propagates on the thin-film LN to unlock its properties. First, access to the LN film from air (or open space) is important to exploit its properties. Second, for sustaining the BSW, one-dimensional photonic crystal (1DPhC) is necessary to be fabricated under the thin-film LN. We consider two material platforms to realize such a device: bulk LN and commercial thin-film LN. Clear reflectance dips observed in far-field measurements demonstrate the propagation of BSWs on top of the LN surface of the designed 1DPhCs.

We developed a deep etching plasma process on PZT substrate that has been optimized to obtain a good anisotropy and smooth side walls. Cantilevered piezo actuators have been fabricated and tested in order to verify that the process does not modify the PZT properties. The characterization show that the bandwidth of the 4mm-long actuators exceeds 1772Hz and the static deflection coefficient reaches 1.25μm/V, which matches well the theory. These results demonstrate the efficiency of the process to maintain the materials properties.

We demonstrate efficient three-dimensional surface acoustic wave guidance and confinement in a high-aspect ratio electrode transducer. Each electrode acts as an elastic resonator that is evanescently coupled to its neighbors. We observe high amplitude displacement fields confined within the high aspect ratio electrodes. The stored surface waves are found to present a general shear polarization instead of the sagittal polarization expected for classical Rayleigh waves. The elastic energy is mostly distributed in the mass-loaded areas, and waves propagate within the transducer without diffraction, even for very low acoustic apertures.

We here report on the fabrication of electroplated nickel (Ni) masks for dry etching of sub-micron patterns in lithium niobate (LiNbO3). This process allows obtaining 350-nm thick Ni masks defining high air filling fraction holey arrays (e.g. openings of 1800nm in diameter with inter-hole spacing of 300nm, or 330nm diameter holes spaced by 440nm). The mask profile is perfectly vertical (angle≈90°). The obtained metallic masks are used to realise photonic and phononic crystals. High aspect ratio and dense arrays of holey patterns were defined and transferred into LiNbO3 through RIE (Reactive Ionic Etching) in sulphur hexafluoride (SF6) chemistry. Nanometric holes exhibiting sidewall slope angles of the order of 60° have in this way been etched in LiNbO3. The LiNbO3/Ni selectivity is close to 6 and the etch rate around 6nm/min.

In this paper, we discuss fabrication processes implemented for the realization of micron-sized and submicron-sized patterns in lithium niobate for application to nanophotonics or phononics. FIB milling as well as collective processes based on reactive ion etching in fluorine chemistries and their use for the fabrication of photonic and phononic crystal structures is illustrated. We will discuss the limitations of both methods and see how they can affect the actual physical performance of the fabricated devices.

Efficient acoustic waveguides with a confinement in 3-dimensional space were obtained using high aspect ratio interdigital transducers (HAR IDTs). Energy trapping at the substrate surface is ensured by mass loading effect, while lateral confinement is preserved while reducing the acoustic aperture of the HAR IDTs down to one acoustic wavelength. A detailed analysis of such HAR IDTs fabricated on X-cut lithium niobate, with Y-propagating waves is presented. Reflection scattering parameter measurements were performed and are here reported. They show the existence of several modes with a resonance frequency much lower than the one expected for a Rayleigh wave. The wave velocity is indeed reduced from 3639 m/s down to 781 m/s. Using heterodyne laser scanning interferometry, measurements of out-of-plane displacement induced by the generated surface waves were performed. The measurement results show that the elastic energy is strongly localized within the acoustic aperture of the transducer.

Microfluidics on foil is gaining momentum due to a number of advantages of employing thin films combined with the capability of cost-effective high-volume manufacturing of devices. In this work, ultra-thin, flexible Y-microreactors with microchannels of 100 μm width and 30 μm depth were fabricated in thermoplastic polymer foils. The fluidic pattern was hot roll embossed in 125 μm thick poly-methyl-methacrylate (PMMA) and 130 μm thick cyclic-olefin-copolymer (COC) films using a dry-etched microstructured silicon wafer as a flat embossing tool in a laminator. The sealing of the channels was performed with two different techniques, one based on lamination of SU8 dry film resist (DFR) and the other one based on spin-coated poly-dimethylsiloxane (PDMS). Testing of the interconnected microreactor was carried out using two dye colorant solutions to demonstrate mixing.