Two-dimensional infrared photonic crystal based on macroporous silicon

The propagation of electromagnetic radiation in periodic dielectric media can be described similar to the case of electrons propagating in a crystal. A photonic bandgap, a frequency range where no electromagnetic modes exist, may open up in two or three dimensions and greatly affect the radiative dynamics within the structure. Requiring wavelength-scale structures, a photonic band material for optical and infrared frequencies is at the limit of today's fabrication techniques. Macroporous silicon offers a way to meet the requirements of regularity and high refractive index contrast for a two-dimensional (2D) photonic material in the infrared regime. By controlled formation of macropores in n-type silicon, we fabricated a 2D photonic lattice with photonic bandgaps in the infrared region between 250 and 500 cm(-1) (20-40 mu m). The transmission spectra between 50 and 650 cm(-1) were in good agreement with the theoretically calculated structure.