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The depth profile of electric-field-induced (EFI) optical rectification (OR) and EFI Pockels effect (PE) in a Si(110) crystal are investigated. The results show that EFI OR and PE signals are very sensitive to the electric field strength in the surface layers of the Si crystal. Theoretical formulas that include the electric field parameters and the widths of the space-charge region are presented and agreed very well with the experimental results. The experiments and simulations indicate that EFI OR and PE are potential methods for researching the surface/interface properties along the depth direction in centrosymmetric crystals such as Si.

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.

Different electro-optic effects, such as Kerr effect, Pockels effect induced by the electric field or strain, and plasma dispersion effect exist in silicon. Experimentally distinguishing these effects is necessary for designing silicon-based electro-optic devices. According to their different polarization dependencies and frequency responses, these effects are measured and distinguished successfully via a transverse electro-optic modulation experiment based on the near-intrinsic silicon sample. The results indicate that Pockels effect induced by the electric field or strain is primary among these effects in the near-intrinsic silicon sample.

In this Letter, we have demonstrated significant electric field induced (EFI) optical rectification (OR) effects existing in the surface layers of germanium (Ge) and measured the distributions of EFI OR signals along the normal directions of surface layers of Ge samples. Based on the experimental results, the ratios of the two effective second-order susceptibility components χzzz(2eff)/χzxx(2eff) for Ge(001), Ge(110), and Ge(111) surface layers can be estimated to be about 0.92, 0.91, and 1.07, respectively. The results indicate that the EFI OR can be used for analyzing the properties on surface layers of Ge, which has potential applications in Ge photonics and optoelectronics.

The nonlinear photoresponse to a 1.56-\mu m infrared continuous wave laser in semi-insulating (SI) galliumarsenide (GaAs) is examined. The double-frequency absorption (DFA) is responsible for the nonlinear photoresponse based on the quadratic dependence of the photocurrent separately on the coupled optical power and bias voltage. The electric field-induced DFA remarkably affects the native DFA in SI GaAs. The surface electric field or the surface band-bending of SI GaAs significantly affects the magnitude variation of the photocurrent and dark current.

The transverse electro-optic (EO) modulation system is built based on cubic boron nitride (cBN) single crystals unintentionally doped and synthesized at a high pressure and high temperature. The photoelectric output of the system includes two parts that can be measured respectively and the value of elements in the linear EO tensor of the cBN crystal can be obtained. This method does not need to measure the absolute light intensity. All of the surfaces of the tiny cBN crystals whose hardness is next to the hardest diamonds are {111} planes. The rectangular parallelepiped cBN samples are obtained by cleaving along {110} planes and subsequently grinding and polishing f112g planes of the tiny octahedral cBN flakes. Three identical non-zero elements of the EO tensor of the cBN crystal are measured via two sample configurations, and the measured results are very close, about 3.68 and 3.95 pm/V, respectively, which are larger than the linear EO coefficients of the general III-V compounds.