Optical-Nonlinearity-Induced Phase Shift via Selective-Area Grown InAs Quantum Dots in a Photonic Crystal Waveguide

Abstract

The selective-area growth (SAG) of InAs quantum dots (QDs) in a GaAs two-dimensional photonic crystal waveguide (2DPC-WG) slab was performed by a metal-mask molecular beam epitaxy (MBE) method, and phase shifts induced by an optical nonlinearity (ONL) of the QD were characterized by two-color pump and probe measurements. The phase shift is caused by the refractive index change (Án) in the PC-WG, while the Án is induced by the absorption saturation as a third-order ONL effect of the QD. For the samples with different SAG-QD lengths, it was confirmed that the phase shift is proportional to the length of the SAG area and to the pump energy. For application to the PC/QD-based symmetrical Mach-Zehnder (SMZ)-type all-optical switch, that is, PC-SMZ, a bright prospect for the design criterion was obtained such that the 180 phase shift, necessary for the PC-SMZ, can be achieved using the four-stacked-layer-QD WG with a 250 mm length at a pump energy of 100 fJ if a slow light with a group velocity of 0:05c (c is the light velocity in vacuum) is used.

Monolithic Fabrication of Two-Color InAs Quantum Dots for Integrated Optical Devices by Using a Rotational Metal Mask

“…The excitation is triggered by a set/reset pulse and the changes in the effective refractive index are a consequence of the optical nonlinearity of the QDs embedded in the waveguide. 7) For the fabrication of the PC-FF, including twocolor QDs, e.g., QDs with absorption wavelengths of 1280 and 1300 nm, an SAG method should be used.…”