Photonic crystal straight waveguides are a key component for the realization of integrated photonic circuits. To date, there have only been a few experimental demonstrations of 2D photonic crystal waveguides patterned into GaAs-based heterostructures at near-IR wavelengths [1]. We present quantitative results on the characterization of PC waveguides realized on an epitaxial GaAs/AlGaAs slab. 2D PC waveguides with varying widths, lengths and periodicities were studied using our previously described experimental setup [2]. We demonstrate efficient transmission accross as much as 240 rows of a PC bounded waveguide. In PC waveguides of width corresponding to two missing rows or more, the periodic boundaries induce coupling of the fundamental mode to a higher order mode, which results in a stop-band of about 10 nm width in the transmission spectrum of the guides. Experimental results are validated by eigenmode dispersion calculations using a supercell method [3]. This previously unnoticed coupling mechanism may be useful in future photonic integrated circuits for filtering applications or coupling to other PC-based structures [4].
References
[1] T. Baba et al., "Observation of light propagation in photonic crystal optical waveguides with bends," Electronics Letters, 35, 654-655, 1999.
[2] D.Labilloy et al., "Quantitative measurements of transmission, reflection and diffraction of two-dimensional photonic bandgap structures at near-infrared wavelengths," Phys. Rev. Lett., 79, 4147-4150, 1997.
[3] H.Benisty., "Modal analysis of optical guides with two-dimensional photonic band-gap boundaries," J. Appl. Phys., 79, 7483-7490, 1996.
[4] H. Benisty et al., "All-photonic-crystal coupled cavity and guide", to be presented at CLEO 2000, San Francisco, May 7-12, 2000.