Nanowire array lasers readily coupled to waveguides
By growing periodically arranged InGaAs/InGaP core/shell nanowires aligned on a SOI substrate, the researchers created a one-dimensional (1D) photonic crystal cavity able to achieve a high quality (Q) factor comparable with two-dimensional competing solutions while requiring a much smaller footprint and less nanowires.
Publishing their results in Nano Letters under the title “The Monolithic InGaAs Nanowire Array Lasers on Silicon-on-Insulator Operating at Room Temperature”, the international team of researchers also reveal that their optically-pumped lasers (at 660nm) made up of 21 nanowires (with a total cavity is only 6.7×0.14×0.8μm3) provide strong in-plane optical feedback, with the position of 11 nanowires in the centre linearly tapered to form an artificial defect to confine the field in the photonic bandgap.
The aligned InGaAs nanowire arrays were grown on SOI substrates using a catalyst-free selective-area epitaxy technique, before being capped by InGaP shells to reduce non-radiative surface recombination. Lasing emission peaks at 1133nm with a quality factor of nearly 84,000 and this 1D array was efficiently coupled with SOI waveguides (by growing the nanowires on a pre-patterned SOI platform).
array cavity integrated with a waveguide and
an output coupler (upper), and a close-up image
of the nanowire array in the dashed box (lower).
Scale bars, 5 μm (upper) and 500 nm (lower).
“The lasing action reveals the validity of the proposed design as a compact light source on silicon photonics platforms, whereas SOI waveguide-coupled lasers integrated by growing nanowires on pre-patterned mesas verify the compatibility with PICs” explains the paper, adding that further improvements would be necessary for practical applications, such as implementing electrical injection and the integration of such lasers onto an SOI(001) platform operating in telecom-wavelength regimes.
“Our bottom-up approach to form nanowire-based photonic crystals on SOI substrates offers an attractive degree of freedom in designing novel photonic devices in a low-cost and high-volume process” the researchers wrote, expecting such nanowire array photonic crystal structures to find their way into on-chip nanophotonic devices and lab-on-a-chip applications but also as chip-scale optical links.
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