Yanjun Gao

Electro-optic effects induced by the built-in electric field in a ｛001｝-cut silicon crystal

Pockel’s effect and optical rectification induced by the built-in electric field in the space charge region of a silicon surface layer are demonstrated in a ｛001｝-cut high-resistance silicon crystal. The half-wave voltage is about 203 V, deduced by Pockel’s effect. The ratio χzxx(2)/χzzz(2) is calculated to be about 0.942 according to optical rectification. Our comparison with the Kerr signal shows that Pockel’s signal is much stronger. This indicates that these effects are so considerable that they should be taken into account when designing silicon-based photonic devices.

Measurement of electro-optic effects in near-intrinsic silicon

The electro-optic effects in silicon include Kerr effect, plasma dispersion effect, and Franz-Keldysh effect etc.. Silicon does not have the linear electro-optic effect in the bulk because of the inversion symmetry, which restricts the development of the silicon-based optoelectronics and silicon photonics. However, the electric field can destroy the inversion symmetry of silicon, and produce so-called electric-field-induced linear electro-optic effect. In intrinsic or near-intrinsic silicon, these electro-optic effects exist simultaneously. In this paper, a transverse electro-optic modulation system was designed to detect these electro-optic effects. The electric-field-induced linear electro-optic effect was demonstrated in the space charge region of silicon sample and distinguished from Kerr effect based on the different frequency response. The relationship between the linear electro-optic signal and the azimuth angle of the analyzer was measured too, which was used for distinguishing the electric-field-induced linear electro-optic effect from the plasma dispersion effect. The results showed that the electric-field-induced linear electro-optic effect was stronger than Kerr effect and the plasma dispersion effect in the near-intrinsic silicon samples.

Double frequency absorption induced by Al-Si schottky barrier potential and mechanism of two-photon response

By observing two-photon response and anisotropy of the light-induced voltage in Si-Al Schottky barrier potential of the Si MSM (Metal-Semiconductor-Metal) planar structure two-photon response optical detector. It is certified from the experimental and theoretical analysis that the built-in electric field generated by the Schottky barrier potential will induce the phenomena of optical rectification in Si photodiode. Thus, it is deduced that there must be double-frequency absorption (DFA) caused by phase-mismatch in the mechanism of two-photon response of Si photodiode. If the intensity of the built-in electric field is strong enough, the DFA will be the main feature of the two-photon response.