Multidimensional Coherent Spectroscopy of a Semiconductor Microcavity

Rephasing and non-rephasing two-dimensional coherent spectra map the anti-crossing associated with normal-mode splitting in a semiconductor microcavity. For a 12-meV detuning range near zero detuning, it is observed that there are two diagonal features related to the intra-action of exciton-polariton branches and two off-diagonal features related to coherent interaction between the polaritons. At negative detuning, the lineshape properties of the diagonal intra-action features are distinguishable and can be associated with cavity-like and exciton-like modes. A biexcitonic companion feature is observed, shifted from the exciton feature by the biexciton binding energy. Closer to zero detuning, all features are enhanced and the diagonal intra-action features become nearly equal in amplitude and linewidth. At positive detuning the exciton- and cavity-like characteristics return to the diagonal intra-action features. Off-diagonal interaction features exhibit asymmetry in their amplitudes throughout the detuning range. The amplitudes are strongly modulated (and invert) at small positive detuning, as the lower polariton branch crosses the bound biexciton energy determined from negative detuning spectra.Comment: 13 pages, 4 figure

Effect of atomic layer deposition on the quality factor of silicon nanobeam cavities

In this work we study the effect of thin-film deposition on the quality factor (Q) of silicon nanobeam cavities. We observe an average increase in the Q of 38±31% in one sample and investigate the dependence of this increase on the initial nanobeam hole sizes. We note that this process can be used to modify cavities that have larger than optimal hole sizes following fabrication. Additionally, the technique allows the tuning of the cavity mode wavelength and the incorporation of new materials, without significantly degrading Q

Arrays of Ag split-ring resonators coupled to InGaAs single-quantum-well gain

We study arrays of silver split-ring resonators operating at around 1.5-{\mu}m wavelength coupled to an MBE-grown single 12.7-nm thin InGaAs quantum well separated only 4.8 nm from the wafer surface. The samples are held at liquid-helium temperature and are pumped by intense femtosecond optical pulses at 0.81-{\mu}m center wavelength in a pump-probe geometry. We observe much larger relative transmittance changes (up to about 8%) on the split-ring-resonator arrays as compared to the bare quantum well (not more than 1-2%). We also observe a much more rapid temporal decay component of the differential transmittance signal of 15 ps for the case of split-ring resonators coupled to the quantum well compared to the case of the bare quantum well, where we find about 0.7 ns. The latter observation is ascribed to the Purcell effect that arises from the evanescent coupling of the split-ring resonators to the quantum-well gain. All experimental results are compared with a recently introduced analytical toy model that accounts for this evanescent coupling, leading to excellent overall qualitative agreement

TEM EDS analysis of epitaxially-grown self-assembled indium islands

International audienceEpitaxially-grown self-assembled indium nanostructures, or islands, show promise as nanoantennas. The elemental composition and internal structure of indium islands grown on gallium arsenide are explored using Transmission Electron Microscopy (TEM) Energy Dispersive Spectroscopy (EDS). Several sizes of islands are examined, with larger islands exhibiting high (>94%) average indium purity and smaller islands containing inhomogeneous gallium and arsenic contamination. These results enable more accurate predictions of indium nanoantenna behavior as a function of growth parameters. 1. Background As the field of plasmonic nanostructures develops, there is increasing demand for epitaxially-grown metallic nanostructures. Metal-on-semiconductor nanoantennas, which operate at optical and near-infrared wavelengths, have a wide range of potential applications, from low-cost photodetectors1 to higher-efficiency solar cells.2 Currently, nanoantenna fabrication is often performed separately from substrate preparation;3-8 this discontinuity can adversely affect the finished product through contamination and impurities introduced during fabrication. One method for avoiding these issues is to epitaxially grow both the substrate and plasmonic nanostructure, with the structure self-assembling from a uniformly-deposited metal layer such as silver or indium.9,10 Self-assembled nanostructures can additionally benefit from a better contact interface between structure and substrate compared to other fabrication methods. Epitaxially-grown nanostructures may also have applications in quantum computing.11,12 Majorana fermions, a candidate for qubit construction, have been observed in InSb nanowires coupled to superconducting NbTiN.13 Other s-wave superconductor-1D semiconductor systems are also expected to generate Majorana fermions; InAs and indium have been identified as a potential semiconductor and superconductor, respectively.14,15 InAs nanowires can be grown epitaxially, suggesting that self-assembled indium islands may allow for the epitaxial growth of entire Majorana fermion-generating heterostructures. While epitaxially-grown self-assembled indium islands show promise as nanoantennas,16 the internal structure of these islands has not been thoroughly explored. Prior work has indicated that these structures may contain impurities unique to the epitaxial growth process.17 This paper seeks to describe and analyze the internal structure of indium islands grown under three different sets of growth conditions, in order to better predict the behavior and future applications of these plasmonic nanostructures. 2. Experimen