Demonstration of a bi-directionally tunable arrayed waveguide grating with ultra-low thermal power using S-shaped architecture and parallel-circuit configuration

Abstract

A thermally bi-directionally tunable arrayed waveguide grating (TBDTAWG) is proposed and demonstrated on a silicon-on-insulator (SOI) platform. The device is composed of passive and active designs for realizations of an AWG and fine tuning of its filtering responses. Given that the required length difference between adjacent arrayed waveguides for the SOI platform is considerably short (∼3–5 µm) due to a high index contrast, an S-shaped architecture with a larger footprint instead of a rectangular one is employed in the AWG. Bi-directionally tunable functions, i.e., both red- and blue-shift tunable functions, can be achieved by using two triangular thermal-tuning regions with complementary phase distributions in the S-shaped architecture despite using only materials with positive thermo-optic coefficients, i.e., Si and SiO2. Measurement results illustrate that both red- or blue-shifted spectra can be achieved and a linear bi-directional shift-to-power ratio of ±30.5 nm/W as well as a wide tuning range of 8 nm can be obtained under an electrical voltage range of 0–2.5 V, showing an agreement between the measurement results and two-dimensional simulation results. This also shows the potential of the proposed TBDTAWG for automatically stabilizing the spectral responses of AWG-based (de)multiplexers for coarse or dense wavelength division multiplexing communication systems by using a feedback control circuit.

Femtosecond Laser Modification of Silica Optical Waveguides for Potential Bragg Gratings Sensing

“…Wavelength-division multiplexing (WDM) devices can effectively improve data transmission bandwidth and have been extensively utilized in optics communications and multiparameter sensings [1][2][3]. Several approaches for WDM have been investigated, including Mach-Zehnder interferometers (MZIs) [4,5], microring resonators [6], arrayed waveguide gratings (AWGs) [7,8], thin film filters (TFFs) [9], and Bragg gratings [10]. MZIs and microring-based devices are usually limited by free spectral range (FSR) and channel bandwidth.…”

“…For tunable AWGs, different approaches have been proposed in order to relax the limitations imposed by wavelength tolerances [11]. Multimode waveguides, doublepeaked electric field distribution, and thermo-optic effect can be used for wavelength tuning, but they will increase the insertion loss and fabrication complexity [8]. TFFs have the advantages of a narrow passband, low loss, and good temperature stability.…”