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Characterization and control of the electro-optic phase dispersion in lithium niobate modulators for wide spectral band interferometry applications in the mid-infrared

By Samuel Heidmann, Gwenn Ulliac, Nadège Courjal and Guillermo Martin

Abstract

International audienceMid-infrared wideband modulation (3.2–3.7 μm) is achieved in an electro-optic Y-junction using lithium niobatewaveguides in TE polarized light. Comparison between external (scanning mirror) and internal (electro-optical)modulation allows studying the chromatic polynomial dependence of the relative phase. Internal modulationconsists on a V AC ramp up to 370 V at 0.25 Hz, applied over 14 mm long electrodes with 14 μm separation.The overall V πLπ obtained is 17.5 V·cm, meaning that using a 300 V generator we can actively scan and track thewhole L-band (3.4–4.1 μm) wideband fringes. We observe a dramatic reduction of the coherence length underelectro-optic modulation, which is attributed to a strong nonlinear dependence of the electro-optic effect on thewavelength upon application of such high voltages. We study the effect of applying a V DC offset, from −50 V to200 V (50 V step). We characterize this dispersion and propose an improved dispersion model that is used to showactive dispersion compensation in wideband fringe modulation in the mid-infrared. This can be useful for longbaseline interferometry or pulse compression applications when light propagates along fibers, in order to compensatefor chromatic effects that induce differential dispersion or pulse spreading, respectively

Topics: [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics]
Publisher: HAL CCSD
Year: 2017
OAI identifier: oai:HAL:hal-02134471v1
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