Oct 12, 2017: By using high-precision micro-transfer printing techniques, a team of Korean researchers have demonstrated the direct integration of a wavelength-scale InGaAsP nanolaser beam onto a silicon-on-insulator (SOI) waveguiden which has excellent light coupling efficiency.
The resaerchers have explained the result of their research in a paper titled “Printed Nanolaser on Silicon”, which was published in the ACS Photonics letter. The researchers first designed an asymmetric one-dimensional InGaAsP photonic crystal (PhC) nanobeam laser 580nm wide, 8μm long and 280nm thick.
The laser was then fabricated as a standalone, freestanding nanobeam structure, which contained three active quantum wells in the middle, with thin short tether structures at both the ends, which allows easy separation from the substrate during the transferring step.
The laser device was selected from its InGaAsP/InP wafer with the help of a micro polydimethylsiloxane (PDMS) stamp (15×15×40μm in size), breaking the thin tethers before lifting up the nanobeam structure and transferring it to the prepared SOI waveguide.
Using high-resolution optical imaging, the researchers aligned the laser on top of the SOI waveguide about 20nm wider than the nanobeam and designed to operate in a single transverse electric (TE) propagation mode.
Based on an asymmetric one-dimensional photonic crystal cavity, the structure of the III−V nanolaser allows light propagation with high efficiency in one direction only (−x direction).
On the waveguide, the photonic crystal nanobeam laser bridged a 7μm-long air gap to maintain high quality factor and its resonant wavelength.
The research showed an efficiency of 83% between the InGaAsP nanobeam laser and the SOI waveguide, however, the researchers had calculated that theoretically 88% of the light from the printed III−V nanolaser could be coupled to the vertically integrated SOI waveguide. With further integration, an hybrid III−V/Si laser platform will be able to yield fast and compact efficient silicon-based optical communications.