Soliton frequency comb generation in CMOS-compatible silicon nitride microresonators

Abstract

The monolithic integration of soliton microcomb devices with active photonic components and high-frequency electronics is highly desirable for practical applications. Among many materials, silicon nitride ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>SiN</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ) waveguide layers prepared by low-pressure chemical vapor deposition (LPCVD) have been the main platform for on-chip optical frequency comb generation. However, the high temperatures involved in LPCVD render it incompatible as a back-end process with complementary metal oxide semiconductor (CMOS) or active III-V compound semiconductor fabrication flows. We report the generation of coherent soliton frequency combs in micro-ring resonators fabricated in deuterated silicon nitride ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>SiN</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> <mml:mtext>:</mml:mtext> <mml:mi mathvariant="normal">D</mml:mi> </mml:mrow> </mml:math> ) waveguides with a loss of 0.09 dB/cm. Deposited at 270°C by an inductance-coupled plasma chemical vapor deposition (ICP-CVD) process, the material preparation and fabrication flow are fully CMOS-compatible. These results enable the integration of silicon-nitride-based optical combs and photonic integrated circuits (PICs) on prefabricated CMOS and/or III-V substrates, therefore marking a major step forward in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>SiN</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> photonic technologies.

Topics & Concepts