Near infrared spectro-interferometer usingfemtosecond laser written GLS embeddedwaveguides and nano-scatterers

• Published in: Optics express 2017-04, Vol.25 (7)
• Main Authors: Martin, Guillermo, Bhuyan, Manoj, Troles, Johann, d'Amico, Ciro, Stoian, Razvan, Lecoarer, Etienne
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Optics; Photonic
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.25.008386

Guided optics spectrometers can be essentially classified into two main families:based on Fourier transform or dispersion. In the first case, an interferogram generated insidean optical waveguide and containing the spectral information is sampled using spatiallydistributed nanodetectors. These scatter quasi-non-perturbingly light into the detector that isin contact with the waveguide, helping to reconstruct the stationary wave. A dedicated FFTprocessing is needed in order to recover the spectrum with high resolution but limited spectralrange. Another way is to directly disperse the different wavelengths to different pixels, eitherintroducing differential optical path in the same propagation plane (multiple Mach-Zehnderinterferometers or Arrayed Waveguides Gratings), or using a periodic structure toperpendicularly extract the optical signal confined in a waveguide (photonic crystals orsurface gratings), and by means of a relay optics, generate the spectrum on the Fourier planeof the lens, where the detector is placed. Following this second approach, we present a laserfabricatedhigh-resolution compact dispersive spectro-interferometer (R>2500, 30nm spectralrange at λ = 1560nm), using four parallel waveguides that can provide up to three nonredundantinterferometric combinations. The device is based on guided optics technologyembedded in bulk optical glass. Ultrafast laser photoinscription with 3D laser indexengineering in bulk chalcogenide Gallium Lanthanium Sulfide glass is utilized to fabricatelarge mode area waveguides in an evanescently-coupled hexagonal multicore arrayconfiguration, followed by subsequent realization of nanoscaled scattering centers via onedimensional nanovoids across the waveguide, written in a non-diffractive Besselconfiguration. A simple relay optics, with limited optical aberrations, reimages the diffractedsignal on the focal plane array, leading to a robust, easy to align instrument.