Publications by Alok Rudra | EPFL Graph Search

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Remote coupling between quantum emitters is of great importance for constructing quantum networks. Conventionally, this can be achieved via photon exchange by incorporating the quantum emitters in a waveguide or a large cavity. However, such photonic struc ...

Quantum dots (QDs) of high symmetry (e.g., C3v) have degenerate bright exciton states, unlike QDs of C2v symmetry, making them intrinsically suitable for the generation of entangled photon pairs. Deviations from C3v symmetry are detected in real QDs by pol ...

We demonstrate the self-formation of hexagonal nanotemplates on GaAs (111)B substrates patterned with arrays of inverted tetrahedral pyramids during metal-organic vapor phase epitaxy and its role in producing high-symmetry, site-controlled quantum dots (QD ...

The growth kinetics of vertical III−V nanowires (NWs) were clarified long ago. The increasing aspect ratio of NWs results in an increase in the surface area, which, in turn, enhances the material collection. The group III adatom diffusion from the NW sidew ...

A compact platform to integrate emitters in a cavity-like support is to embed quantum dots (QDs) in a photonic crystal (PhC) structure, making them promising candidates for integrated quantum photonic circuits. The emission properties of QDs can be modifie ...

Radiation properties of a pointlike source of light, such as a molecule or a semiconductor quantum dot, can be tailored by modifying its photonic environment. This phenomenon lies at the core of cavity quantum electrodynamics (CQED). Quantum dots in photon ...

GaInAsN quantum dots (QDs) were grown in inverted pyramids on a patterned (111) B GaAs surface. Incorporation of N in the active structure is attested to by a significant (similar to 80 meV) redshift of the photoluminescence spectrum of the QDs. Influence of the capillarity effect on the N incorporation is evidenced by comparing the redshift in the QD emission to that of its quantum wire (QWR) barriers. The significant increase in the inhomogeneous broadening of the InGaAsN QD arrays as compared to similar

We fabricate and study quantum dot structures incorporating quasi-one-dimensional excited states. The structures are realized by graded bandgap GaAs/AlGaAs quantum wires self-formed inside inverted tetrahedral pyramids. The ground state transitions exhibit ...

The properties of single site-controlled InGaAsN quantum wires (QWRs)-both untreated and irradiated with atomic hydrogen-are probed by micro-magnetophotoluminescence spectroscopy. The strong anisotropy of the diamagnetic shift measured for different orient ...

High symmetry epitaxial quantum dots (QDs) with three or more symmetry planes provide a very promising route for the generation of entangled photons for quantum information applications. The great challenge to fabricate nanoscopic high symmetry QDs is furt ...

An electrically pumped VCSEL (10) and a method of its fabrication are presented. The VCSEL (10) comprises an active cavity material (14) sandwiched between top and bottom DBR stacks (12a, 12b), the top DBR (12b) having at least one n-semiconductor layer. The device defines an aperture region (25) between the structured surface (14b) of the active cavity material (14) and the n-semiconductor layer of the top DBR stack (12b). The structured surface (14b) is formed by a top surface of a mesa (22) that includes

We report on the direct absorption measurement of the polarization selection rules in a V-groove QWR waveguide. Attenuation measurements in a 1 mm long waveguide were performed from 10 K up to room temperature. These measurements yielded the QWR DOS selection rules for lateral (TE) and vertical (TM) confinement directions. 1D heavy-hole like e(n)h(n) subband features were observed in the TE absorption spectra. Effective mass and 4 x 4 k . p models have been used to evaluate the band to band absorption. For

We report on the effects of optical disorder on breaking the symmetry of the cavity modes of H-3 photonic crystal cavities incorporating site-controlled pyramidal quantum dots (QDs) as the internal light source. The high in-plane symmetry of the polarizati ...

investigate the use of MOVPE-grown ordered nanostructures on non-planar substrates for quantum nano-photonics and quantum electrodynamics-based applications. The mastering of surface adatom fluxes on patterned GaAs substrates allows for forming nanostrucutres confining well-defined charge carrier states. An example given is the formation of quantum dot (QD) molecules tunneled-coupled by quantum wires (QWRs), in which both electron and hole states are hybridized. In addition, it is shown that the high degree

We have measured the temperature dependence of the conductance of long V-groove quantum wires fabricated using GaAs/AlGaAs heterostructures, in a wide temperature range (200 mK < T < 4.2 K). We find that for our quantum wires the Fermi velocity can be as l ...

When a growth interruption is applied to the top interface of a nominally 3 monolayers (ML) thick InAs quantum well (QW), grown on an InP substrate, the InAs layer relaxes by formation of three-dimensional (3D) islands. The emission from the QW is split into at least 8 peaks. Each peak corresponds to an integral number of MLs of InAs. Using cathodoluminescence imaging and photoluminescence excitation spectroscopy, we demonstrate that the emission originates in 3D islands with a lateral extension of less tha

We have studied the capabilities of chemical beam epitaxy (CBE) to produce high-gain media for long-wavelength (1.5 mu m) vertical cavity surface emitting lasers (VCSELs). Using a parameter pair of low growth temperature and small V/III ratio the integration of up to 15 highly strained (1.78%) InAsP quantum wells (QWs) into a periodic gain structure (PGS) is successfully demonstrated. In this work we present data of atomic force microscopy (AFM), X-ray diffraction, reflectivity and electro-luminescence meas

Germanium (Ge) nanowires hold great promise as building blocks for hole spin-based quantum processors. Realizing this potential requires their direct integration onto silicon (Si) wafers. This work introduces V-groove-confined selective epitaxy to enable t ...

Optoelectronic properties of site-controlled AlGaAs/GaAs quasi-one-dimensional structures are investigated. Controllable linear variation of the band gap along the vertical axis of the quantum wire, symmetrical with respect to its center, results in a set ...

Strong optical confinement implemented with 2D photonic-crystal (PhC) microcavities provides a powerful tool for controlling the features of light-matter interaction. Combined with nanostructures such as quantum wells, quantum wires (QVTRs) or quantum dots, the PhC cavities - efficiently controlling spontaneous emission [1] are envisaged to bring superior semiconductor-laser performance [2], which could be exploited for applications in low-power-consumption integrated optoelectronics. Furthermore, inter-cav

Alok Rudra

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Remote excitation between quantum emitters mediated by an optical Fano resonance

Fine structure of exciton complexes in high-symmetry quantum dots: Effects of symmetry breaking and symmetry elevation

Self-formation of hexagonal nanotemplates for growth of pyramidal quantum dots by metalorganic vapor phase epitaxy on patterned substrates

Nucleation-Limited Kinetics of GaAs Nanostructures Grown by Selective Area Epitaxy: Implications for Shape Engineering in Optoelectronics Devices

Spatial quantum-interference landscapes of multi-site-controlled quantum dots coupled to extended photonic cavity modes

Mode Interference Effect in Optical Emission of Quantum Dots in Photonic Crystal Cavities

Dilute-nitride GaInAsN/GaAs site-controlled pyramidal quantum dots

Exciton confinement and trapping dynamics in double-graded-bandgap quantum nanowires

Magneto-optical properties of single site-controlled InGaAsN quantum wires grown on prepatterned GaAs substrates

Spectral signatures of high-symmetry quantum dots and effects of symmetry breaking

Vertical cavity surface emitting laser

Direct observation of new transitions in the absorption spectra of a V-groove quantum wire waveguide

Polarization properties and disorder effects in H-3 photonic crystal cavities incorporating site-controlled, high-symmetry quantum dot arrays

Active Semiconductor Nanophotonics based on Deterministic Quantum Wire and Dot Systems

Experimental evidence for Luttinger liquid behavior in sufficiently long GaAs V-groove quantum wires

Cathodoluminescence investigations of three-dimensional island formation in quantum wells

InAsP/InGaAsP Periodic Gain Structure for 1.5µm Vertical Cavity Surface Emitting Laser Applications

Gate-Tunable Hole Transport in In-Plane Ge Nanowires by V-Groove Confined Selective Epitaxy

Multiexciton dynamics in tailored band-gap quasi-one-dimensional systems

Coupled Photonic-Crystal Cavities and Quantum-Wire Microlasers