This paper describes the theoretical and experimental analysis of the channel drop filter using a single defect formed near the two-dimensional (2-D) photonic crystal slab waveguide. First, we calculate a transmission spectrum of a 2-D photonic crystal waveguide and show that high transmittance for a wide wavelength range (∼60 nm) is obtained at the 1.55-µm region. We also show that the defect state having a wavelength within the high transmission wavelength range can be formed in the photonic bandgap by introducing a single defect of appropriate radius, as determined by theoretical calculation. Next,we fabricate several devices having different defect radii and show that the emission wavelength from each defect can be tuned by changing the defect radius. In addition, the measured tuning characteristics coincide well with the calculated results. From the near-field pattern of the device, we estimate the emission efficiency of the present device at almost a few tens percent. Then, from the theoretical calculation, we clarify the structural condition in order to obtain the maximum output efficiency and show that the tuning of emission wavelength while maintaining the high output efficiency is possible by selecting appropriate defect radius and position. Based on these results, we successfully indicate the possibility of the realization of an ultrasmall channel drop filter for a wavelength-division-multiplex optical communication system.
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