III-V nanowires with quantum dots: MBE growth and properties

We demonstrate growth of AlGaAs NWs with GaAs QDs and InP NWs with InAsP QDs on silicon substrates. Results of GaAs QDs optical properties study have shown that these objects are sources of single photons. In case of InP NWs with InAsP QDs, the results showed that ~ 100% of homogeneously oriented NWs were formed with good optical quality of this system on a Si(111). PL spectrum peak near 1.3 μm indicates that such system is promising for optoelectronic devices.

Simulations of Decentration and Tilt of a Supplementary Sulcus-Fixated Intraocular Lens in a Polypseudophakic Combination Using Ray-Tracing Software

This study aimed to assess image quality after the tilt and decentration of supplementary intraocular lenses (IOLs) in a two-lens configuration. One was designed for sulcus fixation with a nominal power range of 1D–10D and was combined with a capsular fixation 20D IOL. The optical performance of a ray-tracing model was tested under IOL misalignment through the area under the modulation transfer function (MTFa) and wave aberrations. Tilting by 10° resulted in a 4% reduction of the MTFa for a 10D IOL as compared to 9% for the 20D lens. The two models demonstrated good tolerance to a 1 mm decentration; as for the 10D sulcus-fixated lens, the MTFa loss was 2%, and 4% for the capsular fixation lens. Coma and astigmatism increased three- and four-fold, respectively, after a 10° tilt compared to the aberration level induced by the 1 mm decentration. Both analyses showed a trend towards a lower MTF impact and fewer optical errors with decreasing nominal power. In conclusion, when misaligned, low-power sulcus-fixated IOLs might retain their good optical quality. An extreme tilt of 10° has a more detrimental effect on the IOL performance than a 1 mm decentration. The proper alignment of a high-power capsular fixation lens is important in achieving a desirable postoperative outcome.

Fabrication and performance evaluation of novel transparent ceramics RE:Tb3Ga5O12 (RE = Pr, Tm, Dy) toward magneto-optical application

Transparent ceramics are at the heart of modern magneto-optical materials providing promising opportunities for Faraday isolators. 1.0 at% RE:Tb3Ga5O12 (rare earth (RE) = Pr, Tm, Dy) transparent ceramics were successfully prepared by air sintering and sequential HIP technique using the coprecipitated powders as the raw material. All the powders have shown to be a pure cubic terbium gallium garnet (TGG) phase and exhibit good dispersion. Additionally, a change could not be observed in particle shape with the different doped ions. After the two-step sintering, all the obtained ceramics have good optical quality, and the in-line transmittances at 1070 nm are higher than 80%. Moreover, no secondary phase can be detected from the microstructures. However, the pores which remain entrapped in the ceramics can be noted. The Verdet constant of ceramic samples is optimized by RE doping, and the Verdet constant at 632.8 nm is about −143 rad·T−1·m−1, which is about 5% higher than that of TGG ceramics. Finally, the thermo-optical properties of 1.0 at% RE:TGG transparent ceramics are compared. The annealed TGG ceramic showed the best thermo-optical properties, and the thermally induced depolarization of 1.0 at% Ce:TGG and 1.0 at% Tm:TGG was inferior to that of annealed TGG ceramic.

Electronic Confinement in the Continuum: Leaky Bragg Mirror for Electrons

In this work we present an InGaAs/InAlAs heterostructure lattice matched with InP that holds two leaky electronic states in the continuum. An optical analogy with Bragg mirrors is used to explain the origin and the desired characteristics of the leaky electronic state. Multipass waveguide absorption measurements were performed and theoretical calculations used to determine the energy levels involved in the optical transitions. The comparison between the theoretical and experimental oscillator strength shows the good optical quality of the sample.

Synthesis, Growth and Optical Properties of 2-Aminopyridine Potassium Di-hydrogen Orthophosphate Crystal in Additive of Cadmium Chloride and Lithium Chloride

A good optical quality crystal of 2-aminopyridine (2AP) metal complex crystals was grown by slow evaporation technique at room temperature. The transparent and defect less bulk size of 2-aminopyridine potassium dihydrogen orthophosphate metal complex crystals have been grown by solution growth method. The molecular structure and morphology of grown crystals was drawn and planes are indexed using WINXMORPH software. A optical absorption spectrum, the UV cut-off wavelength, Band gap (Eg), Reflectance (R), Refractive Index (n), Extinction coefficient (K) and Electrical susceptibility (χc) are calculated for 2AP metal complex crystals.

FTIR and UV-Visible Absorbance Studies of Hydrothermally Grown ZnO Coated with Polyvinylpyrrolidone

Hydrothermally grown hexagonal wurtzite ZnO microrods coated with polyvinylpyrrolidone (PVP) via an ex-situ method, was successfully synthesized without using complex procedure or experimental setup. FTIR results confirm the presence of different functional groups of PVP at the ZnO surface and the chemical interaction of ZnO with the C=O ligand of the PVP molecule. The presence of PVP molecules prevents the absorption of atmospheric CO2 by the Zn2+ ions since PVP chemically interacts with ZnO by attaching to the exposed cations. The coating concentration doesn’t induce a frequency shift in the vibrations of the PVP functional groups. The ZnO microrods possess good optical quality as indicated by the high UV absorption and pronounced excitonic peak at room temperature, even after coating with higher PVP concentrations.

Organic Lanthanide Crystals for Nano-Optics Studies

ABSTRACTSingle crystals of Ln(NO3)3·Bpy2 where Ln = Eu, Gd, Nd, Tm, Er, La and Yb were fabricated and characterized. Materials have good optical quality, can be excited at UV or the rare earth ion transitions, demonstrate efficient luminescence and are suitable for thin film fabrication. Fabrication approaches and possible applications are discussed.

FABRICATION OF GaN HOMO-JUNCTION ON Si (111) SUBSTRATE FOR SENSOR APPLICATIONS

In this paper, we investigated growth of GaN pn-homo junction layers on silicon (111) by plasma-assisted molecular beam epitaxy (PA-MBE) system and its application for photo-sensors. Silicon (Si) and magnesium (Mg) were used in this study as n- and p-dopants, respectively. Structural and optical analysis of the GaN homo-junction samples were performed by using reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), Raman spectroscopy and photoluminescence (PL) to analyze the crystalline quality of the samples. Surprisingly, the Raman analysis has revealed that there is no quenching of the A1 (LO) peak, with the presence of Si - and Mg -dopants in sample. The pn-junctions sample has good optical quality as measured by the PL system. Electrical characterization of the photo-sensors was carried out by using current–voltage (I–V) measurements.

Synthesis and Properties of New Glassy Molecular and Oligomer Azocompounds Suitable for Holographic Recordings

Molecular diphenylamine derivative containing two azochromophores has been synthesized. Compound showed formation of stable amorphous glassy phase with good optical quality. Functionalization with bulky trityl- group was carried to further improve physical properties of material. Two types of azochromophore containing polymeric materials, azochromophore in side chain containing aromatic polyether and azochromophores in both, main and side chain, containing polyester were also synthesized. Samples for holographic recording were prepared using spin coating technique from saturated chloroform solution. Holographic recording experiments have been made using 532 and 633 nm lasers. All compounds showed ability of forming laser induced diffraction gratings.

A STUDY ON THE INDIUM-INDUCED VARIATIONS IN PHOTOLUMINESCENCE PROPERTIES OF INDIUM-DOPED ZINCOXIDE NANORODS

In doped ZnO nanorods ( ZnO : In NRs) were grown on Si (111) substrates by using AuGe as a catalyst. In-concentration was controlled as high as 0.33 at.%. The length L to diameter D relationship of NRs revealed that the growth mechanism should be explained in terms of not a simple vapor–liquid–solid (VLS) mechanism but a diffusion-induced growth model. In-induced changes have been investigated from the viewpoint of photoluminescence (PL) property. At room temperature, an increase of extrinsic carrier concentration and interaction with excitons were estimated from the blueshift of peak position and decrease of luminescence intensity. Also, narrow linewidth of low-temperature PL spectra characterized the high structural quality of ZnO : In NRs. We have assigned several PL lines and confirmed the assignment by using excitation power and temperature dependence PL. Considerable evidence of crystal quality degradation was not observed from both measurements; however, we could observe that a defect and donor-bound-exciton complex dominate the PL spectrum. ZnO : In NRs shows good optical quality within our experimental range, and this result strongly supports the feasibility of In -doping to enhance the electrical property of ZnO -based nanostructure.