Abstract
In photonic integrated circuits (PICs), optical isolators and circulators are essential to prevent lasers from backreflections and to reroute the light flow. In this paper, an integrated polarization-independent device that can be operated as an optical isolator or an optical circulator, based on an InP membrane on silicon platform, is demonstrated. A cerium-doped yttrium iron garnet die is adhesively bonded on a Mach–Zehnder interferometer, in combination with four polarization converters. The device shows maximum optical isolations of 27.0 dB for transverse-electric (TE)-mode input and 34.0 dB for transverse-magnetic TM-mode input. The device also works as a four-port optical circulator. Optical isolations of at least 18.6 dB and 16.4 dB are measured between each circulator port pair for TE- and TM-mode input, respectively. This work could remove the optical interfaces between laser and isolator for robust production. It also provides a step forward toward a multifunctional and high-density PIC.
Highlights
Non-reciprocal optical components, like optical isolators and circulators, are indispensable in the optical communication systems
We demonstrate an integrated non-reciprocal device by connecting PCs with a Mach-Zehnder interferometers (MZIs) structure and adhesive bonding of a cerium-doped yttrium iron garnet (Ce):YIG layer on the InP membrane on silicon (IMOS) platform [25]
It is realized with adhesively bonding a Ce:YIG die to a MZI-based structure on the IMOS platform
Summary
Non-reciprocal optical components, like optical isolators and circulators, are indispensable in the optical communication systems. The integration of optical isolators and circulators with other integrated optical components presents crucial design and fabrication challenges [1,2,3,4] These challenges mainly arise from the incompatibility of magneto-optic material with the semiconductor platforms that are commonly used for photonic integration. To date, integrated optical isolators and circulators mainly rely on non-reciprocal phase shift (NRPS) [5], which means the forward- and backward-propagating waves have a different propagation constant when the magnetooptic (MO) material is magnetized transversely. Based on this effect, optical isolators and circulators are extensively developed in interferometric structures [6,7], like micro-ring resonators and Mach-Zehnder interferometers (MZIs). The designed device can be operated as a polarization-independent isolator or as a polarization-independent circulator
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