The impurity Franz-Keldysh effect in 2D photonic macroporous silicon structures

We investigated the near-IR optical transmission spectra in 2D photonic macroporous silicon structures taking into account the linear electro-optical effect. The spectral dependence of optical absorption of macroporous silicon structures in the near-IR area (impurity absorption) has oscillating structure and varies under the “3/2” law at long wavelengths. This correlates with frequency dependence of the imaginary part of permittivity for optical transitions between impurity levels and the allowed bands of a crystal in an electric field (the impurity Franz-Keldysh effect). The experimental absorption spectra of macroporous silicon agree well with the corresponding spectral dependences of the electro-optical energy and the imaginary part of permittivity in the weak electric field approximation, thus confirming realization of the impurity Franz-Keldysh effect. The electric field of the reflected electromagnetic wave at the grazing angle of light incidence onto macropore surface changes effectively a local electric field on the macropore surface.