Biography
Biography: Giuseppe Leo
Abstract
Frequency conversion can be very efficient in whispering gallery mode semiconductor microresonators, thanks to high optical confinement and modal overlap. The crystallographic symmetry of AlGaAs, along with the circular geometry, provides effective quasi-phase matching without the burden of domain inversion. In this framework, some experimental studies have been recently reported on Second Harmonic Generation (SHG) in GaAs WGM microdisks. However, GaAs does not allow working with a Fundamental Frequency (FF) mode in the third fiber window of the telecom range, since the SH photon energy exceeds the energy gap and two-photon absorption losses are high up to 1800 nm.
Here we report on the demonstration of CW SHG in Al0.4Ga0.6As suspended microdisks on GaAs pedestal, with FF wavelength around 1.55 µm and an efficiency ï¨ = 0.7ï‚´10-3 W-1 comparable to state-of-the-art monolithic telecom devices. This result was obtained via the evanescent coupling between the disk and a tapered fiber, with 3.5 mW input power injected in the fiber.
Then we discuss the down-conversion that can occur in the same microdisk, with inverted roles for the SH (which becomes the input pump) and FF (which corresponds to the output signal and idler). In this case, with 3 ps pulses and a repetition rate of 300 kHz, a peak power of about 10 kW at 775 nm can provide signal and idler peak power of about 5 µW at degeneracy.
Finally, we illustrate the fabrication of the monolithic counterpart of such submicron-system, with a suspended AlGaAs nanowire in lieu of the fiber.
