A Micro-Processor-Based Feedback Stabilization Scheme for High-Q, Non-Linear Silicon Resonators

Giuseppe Cantarella,Michael Strain

doi:10.3390/app6110316

Abstract

Stabilization of silicon micro-resonators is a key requirement for their inclusion in larger photonic integrated circuits. In particular, thermal refractive index shift in non-linear applications can detune devices from their optimal working point. A cavity stabilization scheme using a micro-processor-based feedback control loop is presented based on a local thermal heater element on-chip. Using this method, a silicon π -phase shifted grating with a cavity Q-factor of 40k is demonstrated to operate over an ambient temperature detuning range of 40 ∘ C and injection wavelength range of 1.5 nm, nearly 3 orders of magnitude greater than the resonant cavity linewidth.

Highlights

Due to strong optical mode confinement and significant non-linearities, silicon photonics is an attractive platform for non-linear optics [1]
A wealth of useful non-linear modes of operation have been demonstrated on this platform, including: Kerr non-linearity for Four-wave mixing (FWM)
In non-linear applications it is desirable to operate the system at the point of maximum resonant enhancement, which in turn requires the alignment of the resonator wavelength and input laser signal

Summary

Introduction

Due to strong optical mode confinement and significant non-linearities, silicon photonics is an attractive platform for non-linear optics [1]. A change of 0.1 K on a grating with a period of 318 nm and an effective index of 2.445, can result in a resonance shift of over 10 pm This is on the order of the linewidth of a high-Q cavity resonance, and can significantly affect the operation of the device given a fixed wavelength laser injection, essentially detuning the device resonant wavelength from the laser signal. A shift of the laser wavelength to the red with respect to the cavity working point can essentially ‘switch off’ the non-linear device operation as the resonant enhancement reverts to the cold cavity case. This produces discontinuities in any experimental setup using the device in this mode and is to be avoided.

Materials and Methods

Optical Transmission Measurement Setup

Cavity Stabilization Scheme

Results and Discussion

Cavity Stabilization

Conclusions