Adalberto Alejo-Molina

Intermixing of InP-based multiple quantum wells for integrated optoelectronic devices

The intermixing characteristics of three widely used combinations of InP-based quantum wells (QW) are investigated using the impurity-free vacancy disordering (IFVD) technique. We demonstrate that the bandgap energy shift is highly dependent on the concentration gradient of the as-grown wells and barriers, as well as the thickness of the well, with thinner wells more susceptible to interdiffusion at the interface between the barrier and well. According to our results, the InGaAsP/InGaAsP and InGaAs/InP are well suited for applications requiring a wide range of bandgap values within the same wafer. In the case of the InGaAs/InGaAsP system, its use is limited due to the significant broadening of the photoluminescence spectrum that was observed. The effect of the top InGaAs layer over the InP cladding is also investigated, which leads to a simple way to obtain three different bandgaps in a single intermixing step.

Model of third harmonic generation and electric field induced optical second harmonic using simplified bond-hyperpolarizability model

We report for the first time a comprehensive study of the fourth rank tensor describing third harmonic generation (THG) and electric field induced second harmonic (EFISH) in centrosymmetric material from two different viewpoints: Group Theory (GT) and the Simplified Bond Hyperpolarizability Model (SBHM). We show that the fourth rank tensor related to THG and direct current (DC) EFISH can be reduced to two independent elements whereas SBHM always gives only one, reproducing perfectly well EFISH experimental results in Metal Oxyde Semiconductor (MOS). We argue that it is possible to reduce the fourth rank tensor describing EFISH to a third rank tensor and further deliver a classical explanation of EFISH regarding symmetry breaking where the term containing

Bulk quadrupole and interface dipole contribution for second harmonic generation in Si(111)

r^3

Complex dispersion relation of 1D dielectric photonic crystal with thin metallic layers

in the potential immediately leads to second harmonic generation (SHG).We report a comprehensive study of the fourth rank tensor describing third harmonic generation (THG) and electric field induced second harmonic (EFISH) in centrosymmetric material from two different viewpoints: group theory and the simplified bond hyperpolarizability model (SBHM). We show that the fourth rank tensor related to THG and direct current EFISH can be reduced to two independent elements, whereas SBHM always gives only one, reproducing perfectly well EFISH experimental results in a metal oxide semiconductor. We argue that it is possible to reduce the fourth rank tensor describing EFISH to a third rank tensor and further deliver a classical explanation of EFISH regarding symmetry breaking, where the term containing r3 in the potential immediately leads to second harmonic generation.

The role of Kleinman Symmetry in the Simplified Bond Hyperpolarizability Model

The second harmonic generation (SHG) response was measured for arbitrarily oriented linear input polarization on Si(111) surfaces in rotational anisotropy experiments. We show for the first time, using the simplified bond hyperpolarizability model (SBHM), that the observed angular shifts of the nonlinear peaks and symmetry features—related to changes in the input polarization—help to identify the corresponding interface dipolar and bulk quadrupolar SHG sources, yielding excellent agreement with the experiment. Additionally, we evaluate for the s-in/p-out (sp) and p-in/p-out (pp)-polarization SHG intensities the contributions from the individual Si bonds. Furthermore, a relation between the four parameters arising from SBHM and six coefficients of the phenomenological SHG theory needed to reproduce experimental data is established.

Omnidirectional Reflector in a Ternary Metallo-Dielectric Stack

We have carried out the analytical and numerical analysis of metallic insets embedded in a dielectric photonic crystal (DPC). The corresponding one-dimensional metallo-dielectric photonic crystal (MDPC) is studied in relation to the substratum DPC. We describe the complex MDPC dispersion relation curves and the transmission coefficient at the different propagation regimens trough the finite stack. While in the DPC, the band gap argument corresponds to undefined complex solutions of a real dispersion relation, in a MDPC corresponds to a definite complex solution, function of the metal thickness; and analytic continuation of the dispersion curve on the imaginary K plane. The metal absorption is described by the Drude model, and as a result of the absorption in the inset metallic films, complex Bloch vectors are produced for all frequencies as evanescent waves that differ from the straightforward metal absorption.

Comparison of the Dicke model and the Hamiltonian for n quantum dots

We have shown previously in [J. Opt. Soc. Am. 31, 526-533 (2014)] that Kleinman symmetry plays an important role when comparing the third rank tensor associated with Second Harmonic Generation (SHG) obtained from the Simplified Bond Hyperpolarizability Model (SBHM) and from group theory (GT) for diamond and zincblende lattice. In this work we show that the third rank tensor derived from the SBHM has inherently the assumption of Kleinman symmetry.

Bond Model of Second- and Third-Harmonic Generation in Body- and Face-Centered Crystal Structures

Omnidirectional band gaps are found in a ternary structure, quarter-wave-like, dielectric-dielectric-metal. We plot the band gaps through the analytical dispersion relations, derived using the transfer matrix method, for oblique incidence (transversal electric and magnetic modes).

Facet-dependent electric-field-induced second harmonic generation in silicon and zincblende

CQED has been an active field of research for the last three decades, describing the intimacy of the interaction of radiation and matter in small volumes λ3, and have demonstrated that modifies not only the nature of this interaction, but also atomic characteristic that often were thought intrinsic, such as spontaneous emission or the very quantum nature of the interaction. These conditions have acquired quite an importance for the current activity on Quantum computation and Information. However, most of that activity has been developed in the conceptual and experimental framework of atomic systems. There is evidence that such features also occurs in Quantum Dots. We compare the Dicke and Jaynes Cummings dynamics of atoms described by the Hamiltonian of Quantum Dots, and develop the SU(2) perturbative approach in the regimen where the excitation number (atoms + photons) is larger than the number of atoms L. We exhibit the dynamical detuning produced by the Forster interaction.

Simplified Bond-Hyperpolarizability Model Explanation of the Electric-Field-Induced Second-Harmonic Generation for Different Facets in Si

In this work, we describe the third- and fourth-rank tensors of body- and face-centered cubic systems and derive the s- and p-polarized SHG far field using the simplified bond-hyperpolarizability model. We also briefly discuss bulk nonlinear sources in such structures: quadrupole contribution, spatial dispersion, electric-field second-harmonic generation, and third-harmonic generation, deriving the corresponding fourth rank tensor. We show that all the third- and fourth-rank tensorial elements require only one independent fitting parameter.