Coupling and Fabrication for Micro-Transfer-Printed O-Band Quantum Dot Lasers on Silicon Nitride Platforms

Quantum-dot (QD) semiconductor optical gain is highly regarded for its wide gain spectra, high saturation power, and superior thermal properties, making it an excellent choice for laser applications, especially in high power and mode-locking operation regimes<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,2,3,4</sup>. In this work, we present the development progress of heterogeneous integrated O-band InAs/GaAs quantum dot lasers on an 800 nm thick silicon nitride (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Si_{3}N_{4}$</tex>) platform using micro-transfer-printing (μTP), a technology available under license from X-Celeprint, Ltd. Among different light coupling schemes for the III-V devices to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Si_{3}N_{4}$</tex> circuits, we choose edge-coupling approach which offers a good thermal sink, broadband, low-loss and polarization agnostic coupling, and a small footprint<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5,6,7</sup>. We employed adiabatic taper coupling structures (see Fig. 1A) that have large mode areas at the edges to achieve high coupling efficiency (> 92%). These wide taper structures demonstrate promising fabrication and misalignment tolerance, as illustrated by the FDTD simulation in Fig. 1.B,C, and D. Integration of the InAs/GaAs amplifiers on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Si_{3}N_{4}$</tex> platforms, utilizing the discussed coupling scheme, shows great potential for high-power and mode-locked laser applications in on-chip optical atomic clocks, LIDAR, and datacom systems.