KEYWORDS: Thin films, Second harmonic generation, Phase matching, Frequency conversion, Film thickness, Waveguides, Wave propagation, Standards development, Spectroscopes, Refractive index
We propose an X-cut LiNbO3 non-linear waveguide based on a thin film membrane. The structure allows second harmonic generation by birefringence phase matching between the two fundamental modes TE00 (SHG) and TM00 (Pump) at telecom wavelength. We demonstrate a competitive conversion efficiency compared to a quasi-phase-matched configuration with the advantage of a broadband response of 100nm and high manufacturing tolerance.
FIRST (Fibered Imager foR a Single Telescope instrument) is an instrument that enables high contrast imaging and spectroscopy, thanks to a unique combination of sparse aperture masking, spatial filtering by single-mode waveguides and cross-dispersion in the visible. In order to increase the instrument’s stability and sensitivity, we propose an active hybrid photonic beam combiner. The device consists on a 5T integrated optics beam combiner. The idea is to split the architecture in two parts: A first part, concerning input beam splitting and active phase modulation, requiring relatively simple optical circuits (Y junctions and straight waveguides) is obtained in an electro-optic crystal (Lithium Niobate). A second part, where the complex beam recombination of all the split inputs is achieved (for N inputs, N(N-1)/2 recombinations). This stage implies many waveguide crossings, bendings and lengthy waveguides. Therefore, a high transmission, high confining glass is used. In both cases, classical lithography and ion in-diffusion techniques are used to fabricate the waveguides. Both stages have been optimized in terms of mode matching and single mode spectral bandwidth. They have been assembled together and with input/output fibered V-grooves. The work presented here consists on the characterization of the hybrid 5T beam combiner on the optical bench simulator of the FIRST/SUBARU instrument that is developed at LESIA. We will present results in terms of transmission, polarization and active phase modulation, showing that with relative low voltages, active fringe scan is achieved directly on-chip, at frequencies only limited by the readout time of the camera.
This work aims to present a new miniature spectrometer in the mid InfraRed (L Band), using the SWIFTS (Stationary Wave Integrated Fourier Transform Spectrometer) technology. A stationary wave obtained by injecting light on both sides of a channel waveguide (Gabor configuration) is sampled using nano-scattering centres (grooves) on the surface of the waveguide. A single groove per scattering centre will radiate the sampled signal with wide angular distribution, which is not compatible with the buried detection area of infrared detectors, resulting in crosstalk between pixels. An implementation of multiple grooves (antenna) for each sampling centre is proposed as a solution to improve directivity towards the detector pixel by narrowing the scattering angle of the extracted light. Here, the results are obtained using a Lithium Niobate (LiNbO3) substrate, as its electro-optic properties allow for an active modulation of the phase, and the technology explored for its fabrication is Direct Laser Writing, that allows to have buried 3D waveguides and nanogrooves. In order to integrate the detector in the device, different configurations are explored so as to obtain a robust and high-resolution device useful mainly for astronomical applications such as spectro-interferometry.
KEYWORDS: Sensors, Antennas, Crystals, Waveguides, Terahertz radiation, Optical sensors, Electric field sensors, Plasmas, Optical microsystems, Near field
The measurement of microwave electric-field (E-field) exposure is an ever-evolving subject that has recently led the International Commission on Non-Ionizing Radiation Protection to change its recommendations. With frequencies increasing toward terahertz (THz), stimulated by 5G deployment, the measurement specifications reveal ever more demanding challenges in terms of bandwidth (BW) and miniaturization. We propose a focus on minimally invasive E-field sensors, which are crucial for the in situ and near-field characterization of E-fields both in harsh environments such as plasmas and in the vicinity of emitters. We browse the large varieties of measurement devices, among which the electro-optic (EO) probes stand out for their potential of high BW up to THz, minimal invasiveness, and ability of vector measurements. We describe and compare the three main categories of EO sensors, from bulk systems to nanoprobes. First, we show how bulk-sensors have evolved toward attractive fibered systems that are advantageously employed in plasmas, resonance magnetic imagings chambers or for radiation-pattern imaging up to THz frequencies. Then we describe how the integration of waveguides helps to gain robustness, lateral resolution, and sensitivity. The third part is dedicated to the ultra-miniaturization of components allowing ultimate steps toward electromagnetic invisibility. This review aims at pointing out the recent evolutions over the past 10 years, with a highlight on the specificities of each photonic architecture. It also shows the way to future multi-physics and multi-arrays smart sensing platforms.
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