III-nitride-based waveguides for ultrafast all-optical signal processing at 1.55 μm

Abstract

We present an overview of the recently developed III-nitride-based optical waveguides for application in ultrafast signal processing at telecom wavelengths. We focus on different active and passive optical devices for further implementation within all-optical integrated circuits. Optical waveguides based on GaN/AlN quantum dots have been demonstrated to act as saturable absorbers requiring ∼3 pJ of input pulse energy to reach +3 dB transmittance contrast for TM-polarized light. On the contrary, sputtered-InN-based devices show -3 dB transmittance contrast associated to two-photon absorption for input pulse energies of ∼1 pJ, making them suitable to act as highly-efficient reverse saturable absorbers. Finally, the passive optical nature of waveguides based on sputtered AlN at 1.55 μm makes them suitable for further connections between different III-nitride-based active devices. Similar to the development of electronic integrated circuits, photonic integrated circuits are being widely investigated to implement active and passive optical functions in different material platforms. III-nitrides on sapphire substrates emerge as efficient all-optical solutions within the photonic integrated circuit presenting high nonlinear behavior and ultrafast response. These heterostructures make possible the full exploitation of the optical fiber bandwidth which is highly required in today's globalized world. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.