Michael Gehl

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.

Spectroscopic studies of resonant coupling of silver optical antenna arrays to a near-surface quantum well

The coupling of radiation emitted on semiconductor inter-band transitions to resonant optical-antenna arrays allows for enhanced light–matter interaction via the Purcell effect. Semiconductor optical gain also potentially allows for loss reduction in metamaterials. Here we extend our previous work on optically pumped individual near-surface InGaAs quantum wells coupled to silver split-ring-resonator arrays to wire and square-antenna arrays. By comparing the transient pump-probe experimental results with the predictions of a simple model, we find that the effective coupling is strongest for the split rings, even though the split rings have the weakest dipole moment. The effect of the latter must thus be overcompensated by a smaller effective mode volume of the split rings. Furthermore, we also present a systematic variation of the pump-pulse energy, which was fixed in our previous experiments.

Characterization of 1D Photonic Crystal Nanobeam Cavities Using Curved Microfiber

We investigate high-Q, small mode volume photonic crystal nanobeam cavities using a curved, tapered optical microfiber loop. The strength of the coupling between the cavity and the microfiber loop is shown to depend on the contact position on the nanobeam, angle between the nanobeam and the microfiber, and polarization of the light in the fiber. The results are compared to a resonant scattering measurement.

Multidimensional Coherent Spectroscopy of a Semiconductor Microcavity

Multidimensional coherent spectroscopy maps the detuning dependence of the upper (UP) and lower (LP) excitonpolariton branches1 in a wedged microcavity with a single InGaAs quantum well at 5 K. Features on the diagonal correspond to intra-action coherences of the UP and LP branches. Off-diagonal peaks are interaction coherences between the UP and LP branches. With increasing detuning (Δ), all peaks move to higher energy, the exciton-like (EEX) and cavity-like (Eγ) modes swap position and have maximum intensity near the anti-crossing at Δ=0. An isolated biexciton (B) is only seen at Δ<0, separated by a binding energy of approximately 2 meV. For Δ>0, the spectral weight of the off-diagonal features swap, as the LP and B come into resonance. This indicates that the off-diagonal features are sensitive to the interactions including two-quantum contributions and that a situation similar to a Feshbach resonance exists.2 Polarization of two-quantum contributions show spin sensitive two-polariton and new biexciton correlations. The latter likely influence the Feshbach resonance between biexcitons and two-polariton states. The two-quantum signatures also demonstate that biexcitons perturb the light-matter coupling in the microcavity to reduce the mixed two-polariton contributions. Detuning dependence of zero-quantum contributions show Raman-like coherences that are enhanced near zero detuning. Asymmetry of the Raman coherences are indicative of many-body interactions, which also grow stronger as the light-matter interactions are enhanced near zero deuning.

Superconductivity in epitaxially grown self-assembled indium islands: progress towards hybrid superconductor/semiconductor optical sources

Currently, superconducting qubits lead the way in potential candidates for quantum computing. At the same time, transferring quantum information over long distances typically relies on the use of photons as the elementary qubit. Converting between stationary electronic qubits in superconducting systems and traveling photonic qubits is a challenging yet necessary goal for the interface of quantum computing and communication. One promising path to achieving this goal appears to be the integration of superconductivity with optically active semiconductors, with quantum information being transferred between the two by means of the superconducting proximity effect. Obtaining good interfaces between superconductors and semiconductors is the next obvious step for improving these hybrid systems. Here, we report on our observation of superconductivity in a 2.3 μm diameter self-assembled indium structure grown epitaxially on the surface of a semiconductor material.

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

Air Force Office of Scientific Research (AFOSR) [FA9550-13-1-0003, 12RY05COR]; National Science Foundation Atomic, Molecular and Optical Physics [NSF-AMOP 1205031]; Engineering Research Center for Integrated Access Networks (NSF ERC-CIAN) [EEC-0812072]; Arizona Technology and Research Initiative Funding (TRIF); Department of Defense through the National Defense Science and Engineering Graduate (NDSEG) Fellowship Program; Department of Energy (DOE) through the Office of Science Graduate Fellowship (SCGF), [DE-AC05-06OR23100]; French technology network RENATECH

Progress of the quantum nano-optics of semiconductors group at Optical Sciences

The history of semiconductor quantum optics group in the College of Optical Sciences will be discussed. The work from planar microcavities including VCSELs, photonic crystal cavities leading to the observation of strong-coupling between an L3 cavity and a quantum dot, and now metallic cavities coupled to quantum wells and quantum dots will be described.

In Situ Growth of Self-assembled Indium Islands in Close Proximity to Semiconductor Quantum Emitters

Self-assembled indium islands on III-V quantum dot (QD) samples with a 7nm cap show a 4x enhancement in the peak intensity of the PL offering a bottom-up platform for studying the resonant coupling between plasmonic structures and semiconductor quantum emitters.

Effect of Metallic Antenna Shape on the Near-Field Coupling to a Semiconductor Quantum Well

Arrays of metallic antennae with wire, square and split-ring shapes are fabricated on a near-surface quantum well. The hybrid system is investigated using photoluminescence, transmission and transient pump-probe experiments.