Broadband on-chip polarization mode splitters in lithium niobate integrated adiabatic couplers

Publication Type:
Journal Article
Citation:
Optics Express, 2019, 27 (2), pp. 1632 - 1645
Issue Date:
2019-01-21
Full metadata record
© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. We report, to the best of our knowledge, the first broadband polarization mode splitter (PMS) based on the adiabatic light passage mechanism in the lithium niobate (LiNbO 3 ) waveguide platform. A broad bandwidth of ~140 nm spanning telecom S, C, and L bands at polarization-extinction ratios (PER) of >20 dB and >18 dB for the TE and TM polarization modes, respectively, is found in a five-waveguide adiabatic coupler scheme whose structure is optimized by an adiabaticity engineering process in titanium-diffused LiNbO 3 waveguides. When the five-waveguide PMS is integrated with a three-waveguide “shortcut to adiabaticity” structure, we realize a broadband, high splitting-ratio (η c ) mode splitter for spatial separation of TE- (H-) polarized pump (700-850 nm for η c >99%), TM- (V-) polarized signal (1510-1630 nm for η c >97%), and TE- (H-) polarized idler (1480-1650 nm for η c >97%) modes. Such a unique integrated-optical device is of potential for facilitating the on-chip implementation of a pump-filtered, broadband tunable entangled quantum-state generator.
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