Measurement of large group delay in photonic crystal waveguides using phase sensitive lock-in techniques

We present measurements of the transmission and group delay properties of W1 triangular-lattice photonic crystal waveguides (PCWs) using a phase sensitive lock-in technique. Using a lock-in amplifier improved the SNR of the power transmission measurements by at least one order of magnitude, and also correlated features in the group delay spectra (obtained from phase measurements) to the complex transmission properties of the PCWs. We observed large group delay dips at two specific frequencies, which can be attributed to the edge of the photonic mode gap (PMG) and modal parity changes between the even and the odd modes.