Photonic crystal cavity based optical induced transparency

  • Changyu Hu

Student thesis: Doctoral Thesis (PhD)


Nowadays, information technology has been deeply integrated in our daily life. However, within its rapid development, it faces a serious bottleneck due to the prohibitive power consumption and limited transmission bandwidth of electrical interconnects. Silicon photonics introduces a potential solution for information technology based on optical communication. In this field, delay-bandwidth devices offer a high bandwidth optical interconnection and low power consumption for the next generation information communication technology. Through introducing the slow light effect, I can realise time domain control and store the light to achieve a new functional component, which is the optical buffer for optical information processing. The optical buffer allows us to control and store the light, using as the optical information process and transit. However, the current optical buffer devices are limited by high optical loss and the ability to produced tunable group delay of the light. In this thesis, I examine different configurations of the coupled photonic crystal resonator system and then introduce a novel tuneable delay line, based on photonic crystal cavity structures. Through the optical analog to electromagnetically induced transparency (EIT), an EIT-like transmission spectrum has been achieved in coupled photonic crystal cavities. By tuning the phase difference between two coupled resonators and resonance wavelength, I can achieve the desired analog conditions and reach to a maximum group delay of 360 ps. By adding thermal tuning pattern, I have demonstrated a tuning of the group delay of over 120 ps range at a low input power and a maximum delay of 300 ps group delay in coupled photonic crystal cavities system. All devices are with a footprint at only 200 μm², and with integrated compatibles as well. By employing a new vertical coupling technique, a record low loss 15 dB/ns is presented making this system very promising for practical optical information applications.
Date of Award1 Dec 2020
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorLiam O'Faolain (Supervisor)


  • Photonic crystal
  • Electromagnetically induced transparency
  • Coupled cavities system

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