Abstract

Near-to mid-infrared interferometry has played a major role in astrophysics, from nulling interferometer that can distinguish the weak planet light from the strong background star light, to spectrometers devoted to detect and analyse the molecular constituents in exoplanet atmospheres [1]. While most operational interferometry relies on bulk optics and feature sensitive moving parts, integrated optics technologies have been gaining significant traction in recent years [2]. Recently, the development of thin film lithium niobate on insulator (LNOI) provides an integrated photonic platform with wide transparency window from ultraviolet (350 nm) to mid-infrared (MIR) (5 µm) and high electro-optic effect (r₃₃ = 32 pm/V) [3]. In this work, we demonstrate a monolithic LNOI stationary wave integrated Fourier transform spectrometer (SWIFTS) for the near infrared that does not require the confinement from the silicon nitride waveguides as in previous device [4]. We also extended our design for MIR waveguides using thin film lithium niobate on sapphire, supporting optical mode up to 4.6 µm. This type of on-chip electro-optic interferometer is compact, lightweight, with no moving parts and can be assembled into spacecraft or payloads for in-situ analysis of extra-terrestrial environments.

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