Coherent receivers with integrated narrow-linewidth lasers

Research Area: Integrated lasers and LEDs , Heterogeneous integration technology for silicon photonics , Silicon photonics for telecom, datacom and interconnect

Main Researcher: Jing Zhang

This work is aimed at developing high-performance coherent receivers with on chip narrow-linewidth lasers as the local oscillators (LOs). These lasers are heterogeneously integrated by bonding the III-V epitaxial layer stack with a thin divinylsiloxane-benzocyclobutene (DVS-BCB) layer to a silicon waveguide circuit. As a key component, the local oscillator is used to provide an absolute phase reference. Since linewidth determines how much phase noise will be introduced to the detection, the linewidth of the LO is of much importance.
Based on Schawlow-Townes-Henry theory, narrow linewidth can be realized by balancing internal losses, cavity length and mirror losses. In order to decrease the cavity loss, adiabatic tapers in the III-V and silicon waveguide are used for coupling. We also focus on designing passive filters such as microrings and sampled gratings with low loss as the wavelength selective elements.
For the coherent receivers in WDM systems, tuning ability is also expected. In order to meet this requirement, thermal tuning will be realized. Using a single heater, the tuning range is generally less than 10nm. In order to broaden the tuning range, the Vernier effect can be used by applying two comb filters with different free spectral range.

Other people involved:

• Shahram Keyvaninia
• Jing Zhang
• Adam Barzanji

PhD thesises