Laser written 3D 3T spectro-interferometer: Study and optimisation of the laser-written nano-antenna

Stationary Wave Integrated Fourier Transform Spectrometers (SWIFTS) are based on the sampling of a stationary wave using nano-sampling centres on the surface of a channel waveguide. Single nanogroove sampling centres above the waveguide surface 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 diffraction nano-grooves (antenna) for each sampling position is proposed as an alternative solution to improve directivity towards the detector pixel by narrowing the scattering angle of the extracted light. Its efficiency is demonstrated from both simulated and measured far field radiative patterns exhibiting a promising method to be used for future integrated IR-SWIFTS. The implementation of the antennas will allow for a high resolution spectrometer in Infra-Red (here 1550nm) with no crosstalk problem (ref. [1]). These antennas, combined with the technology used (direct laser writing) will provide a robust, low-cost efficient tool that can be implemented as a 3D-3T spectro-interferometer (multi telescope beam-combiner), useful for astrophysics applications, such as phase closure studies.