Compact low-birefringence polarization beam splitter using vertical-dual-slot waveguides in silicon carbide integrated platforms

Abstract

The polarization beam splitter is a key component for polarization manipulation in photonic integrated circuits, but it is challenging to design for low-refractive-index optical materials, due to the low birefringence of the waveguides. We propose what we believe is a novel compact vertical-dual-slot waveguide-based coupling scheme for silicon carbide, enabling efficient low-birefringence polarization splitting by extensively modulating the transverse-magnetic mode distribution. We numerically and experimentally demonstrate the device in the 4H-silicon-carbide-on-insulator integrated platform, with a small footprint of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mtext>.</mml:mtext> <mml:mn>2</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>μm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>15</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>μm</mml:mi> </mml:mrow> </mml:math> . The device, easy to fabricate via a single lithography process as other components on the chip, exhibits low insertion loss of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mo form="prefix">&lt;</mml:mo> <mml:mn>0.71</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>dB</mml:mi> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mo form="prefix">&lt;</mml:mo> <mml:mn>0.51</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>dB</mml:mi> </mml:mrow> </mml:math> for the transverse-electric and transverse-magnetic polarized light, respectively, and polarization extinction ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mo form="prefix">&gt;</mml:mo> <mml:mn>13</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>dB</mml:mi> </mml:mrow> </mml:math> , over 80 nm wavelength range.