1.3/1.55 μm optical directional coupler by photonic crystal with a defect shifting design

This study demonstrated a use of photonic crystal directional coupler to separated two lights of 1.3 μm and 1.55 μm wavelength. The photonic crystal structure consists of the InAlGaAs nano-rods arranged in square-shaped lattice, and the device was fabricated by the electron beam lithography. For the measurement results, the optical power extinction ratio between the 1.3 μm and 1.55 μm output ports are 10 dB and 17 dB, respectively. This behavior helps in designing devices to split two wavelengths, and the measurement results confirm that 1.3/1.55 μm directional coupler can be realized in the photonic crystal. Additionally, the defect shifting effect was also discussed in this study. By moving a defect lattice near the bend region appropriately, the transmission loss could be reduced significantly. Therefore this effect can be considered into the design of the photonic crystal directional coupler to improve the device performance.