Determination of multiphoton absorption coefficient of cadmium iodide using nonlinear transmittance and photoluminescence methods

2009

J. Phys. Chem. B

We generate spin-polarized electrons in bulk GaAs using circularly polarized two-photon pumping with excess photon energy (DeltaE) and detect them by probing the spin-dependent transmission of the sample. The spin polarization of conduction band electrons is measured and is found to be strongly dependent on DeltaE. The initial polarization, pumped with DeltaE=100 meV, at liquid helium temperature is estimated to be approximately 49.5%, which is very close to the theoretical value (50%) permitted by the optical selection rules governing transitions from heavy-hole and light-hole states to conduction band states in a bulk sample. However, the polarization pumped with larger DeltaE decreases rapidly because of the exciting carriers from the split-off band.

Section: Methodsmentioning

confidence: 99%

Two-Photon Spin-Polarization Spectroscopy in Silicon-Doped GaAs

2009

J. Phys. Chem. B

“…The insertion of the Cu impurities favours a stronger local electron–phonon interaction, particularly its anharmonic part, through the alignment of the local anharmonic dipole moments by the pumping light [ 9 ]. As a particular role of the local electron–phonon anharmonicity is described by third-order rank tensors in disordered systems [ 10 ], the PSSHG is very similar to that introduced for the third-order nonlinear optical susceptibility, which has been confirmed by observing the relatively large third-order susceptibility of undoped CdI 2 single crystals [ 7 ]. The local disordering of the Cu agglomerates plays additional role in the nanosize-confined effects.…”

Section: Resultsmentioning

confidence: 89%

Cu-Doping Effects in CdI2Nanocrystals: The Role of Cu-Agglomerates

2008

Nanoscale Res Lett

Cu-doping effects in CdI2nanocrystals are studied experimentally. We use the photostimulated second harmonic generation (PSSHG) as a tool to investigate the effects. It is found that the PSSHG increases with increasing Cu content up to 0.6% and then decreases due to the formation of the Cu-agglomerates. The PSSHG for the crystal with Cu content higher than 1% reduces to that for the undoped CdI2crystal. The results suggest that a crucial role of the Cu-metallic agglomerates is involved in the processes as responsible for the observed effects.

“…The role of photo-induced electron-phonon anharmonic interactions in SHG was explored [9]. The thermoluminescence and photoluminescence studies revealed that this material processes higher order optical nonlinearity [10][11][12][13][14]. Materials exhibiting higher order optical nonlinearities have received much attention due to their potential in applications such as optical switching, amplification and limiting [15].…”

Section: Introductionmentioning

confidence: 99%

Size- and Temperature-control Optical Direct/indirect Band Tuning in Layered Compounds: Band Gap Engineering

2021

Preprint

The X-ray diffraction (XRD) is studied in thermally evaporated cadmium iodide (CdI2) thin films with various thicknesses. The grain size, calculated from the XRD, is found to increase with increasing the thickness of the film, while the reflectivity and refractive index decease with increasing the wavelength of the exciting light. The optical absorption spectra show both allowed direct and indirect interband transitions across a fundamental gap in CdI2. It is found that both indirect and direct band gap (Eg) decrease with increasing the thickness of the film and that the indirect Eg is lower than the direct Eg by an amount of about 0.7 eV. The direct Eg is also decreased with increasing both the grain size and temperature. However, the temperature dependence of Eg follows the Varshni relation. Our results highlight the possibility of engineering or tuning the Eg of CdI2 by controlling the thickness of the film, grain size as well as temperature.