Polarization dependence of photoexcitation in photofield emission

The mechanisms of one-photon photoexcitation in photofield emission have been studied experimentally by measuring the photocurrent from selected crystallographic planes of a tungsten field emitter as a function of the polarization of the incident light. Two distinct components of the photocurrent were identified. The corresponding excitation mechanisms were deduced from the results of the polarization measurements supplemented by band structure considerations. Surface effect emission dominates at large angles of light incidence, and is observed even from within the geometric shadow of the tip. It depends on the light polarization inside the metal in a characteristic way. Indirect bulk photoemission is prominent at small angles of light incidence and is independent of the polarization inside the metal. It is concluded that bulk and surface excitations in photofield emission can be distinguished by appropriately selecting the direction of polarization and the angle of incidence of the incident light.     

Polarization dependence in the UV laser desorption of NO from NiO(100)

- and -polarized radiation. When the yield is related to the incident photon flux, desorption cross sections of (1.9±0.3)×10^-17 cm² and (3.3±0.5)×10^-17 cm² for - and -polarized light, respectively, are deduced. In order to assess the importance of substrate excitation the optical constants of NiO have been determined for the photon energy employed. When the desorption yield is then related to the photon flux absorbed in the NiO film, much larger cross sections are obtained, and an even larger effectiveness of -polarized light. For a direct optical excitation of charge transfer states the implications for the symmetry character of the states involved are discussed. It is concluded that excitations to A^′′ states are preferred. Received: 21 October 1998     

Polarization dependence on the holographic recording in spiropyran-doped polymers

We report on the photoinduced anisotropy in the holographic recording in spiropyran doped polymers as a result of the photoizomerization of spiropyran into merocyanine. Photoizomerization is achieved with UV polarized light ( = 355 nm) from the third harmonic of Q-switched Nd:YAG laser. After UV illumination a strong and broad polarization-dependent absorption peak centered 600 nm appears. Absorption holograms were recorded with low power He–Ne lasers with 2.2% output diffraction efficiency for polarization parallel to the polarization of the UV laser. The extremely long lifetime of the merocyanine states (12 days in the dark) and their high resolution makes this material promising as an optical memory element.     

Temperature dependence of the Pd susceptibility

Experimental results on the temperature dependence of the magnetic susceptibility of pure Pd are compared with the prediction of Stoner theory using accurate energy bands.     

Polarization dependence of two-photon transitions in quantum wells

Summary We give explicitly the polarization dependence of two-photon subband-subband transitions in semiconductor quantum wells. We consider transitions from heavy-hole subbands as well as from light-hole subbands. We study the polarization dependence in the case of absorption of one photon having an energy of the order of the band gap and one having an energy of the order of the subband separation. We show that the absorption structure depends on the polarization of the low-energy photon. We also give, in the case of equal photons with in-plane linear polarizations, the dependence of the transition rate on the angle between the polarizations.     

Polarization dependence of the infrared spectra of TlSbS2

We report an investigation of the long wavelength phonons of TlSbS₂ performed by far-infrared Fourier transform spectroscopy. In close agreement with our previous Raman work, we find strongly polarized data. Significant differences appear between the two set of infra-red and Raman frequencies which correlate well with the centrosymmetric character of some of the linear units which couple to constitute the layer.     

Polarization dependence of the spontaneous radiation of hot electrons

This paper reports on the results of investigations into the polarization dependence of the spontaneous radiation of hot electrons due to their intervalley redistribution in multivalley semiconductors. It is demonstrated that the radiation is predominantly polarized normally to the electric field and the direction of polarization and its intensity can vary according to the degree of electron redistribution, the electron concentration, and the heating electric field.     

载流子导引的折射率变化偏振相关性研究

分析了载流子浓度、张应变量大小、量子阱阱宽和量子阱垒区材料组分对量子阱结构TE模和TM模折射率变化的影响.综合调配以上参数得到1530—1570 nm波长范围内同时具有大的折射率变化量(10^-2量级)和折射率变化低偏振相关(10^-4量级)的量子阱结构.研究表明,不同的调配参数组合可以得到同一波长范围内基本一致的折射率变化谱.     

Polarization dependence of the optical absorption of single-walled carbon nanotubes

Anisotropic optical absorption properties of single-walled carbon nanotubes (SWNTs) are determined from a vertically aligned SWNT film for 0.5-6 eV. Absorption peaks at 4.5 and 5.25 eV are found to exhibit remarkable polarization dependence and have relevance to optical properties of graphite. A method for determining a nematic order parameter for an aligned SWNT film based on the collinear absorption peak at 4.5 eV is presented, followed by the determination of the optical absorption cross section.