The wavelength sensor using optical directional coupler

This paper proposes a wavelength sensor based on an optical directional coupler. The finite-difference time-domain (FDTD) method is used to calculate of the light intensity propagating thorough the structure, and to find the appropriate dimensions of the structure. The device with the width and thickness of 0.4 /spl mu/m/spl times/0.6 /spl mu/m, which corresponds to the coupling length of 40 /spl mu/m, would provide a linear relationship between the coupling efficiency against the wavelengths of the transverse-magnetic-mode input. Then, the structure could be employed as a wavelength sensor for wavelength in a range between 1.5 /spl mu/m and 1.6 /spl mu/m, with continuous resolution.