Silicon/Silica-Hybrid-Integrated Delay Line Interferometer for Demodulation of PSK Formats

We propose a 1-bit delay line interferometer (DLI) with a hybrid Mach–Zehnder structure for demodulation of phase-shift-keying (PSK) signals. Each arm contains silicon (Si)/Si-rich silica waveguides and spot size converters to generate optical delay using both of physical length and refractive index changes. This report covers the numerical analysis and experimental investigations, ranging from basic characterization to application. We employed a DLI with a free spectral range of 10.2 GHz in a demodulation experiment of 10.0-Gb/s NRZ-DPSK signals. As a result, very clear eye patterns and error-free operation are obtained from the C- to L-telecommunications bands with a device size per channel of 1.6
$\hbox{mm}^{2}$
. The novel and effective design provides a demodulator in simple and high-density device integration.