Publications by Alok Rudra | EPFL Graph Search

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Intraband photocurrent spectroscopy of site-controlled pyramidal quantum dots by inserting them into the intrinsic region of n-i-n like quantum dot infrared photodetector structure is reported. The photovoltaic response is observed in the mid-infrared regi ...

We investigate experimentally and theoretically the impact of valence band mixing and spectrum of confined states on the polarization of light emitted from or absorbed by GaAs/AlGaAs semiconductor quantum dots and quantum wires with tailored heterostructur ...

Optically pumped vertical external cavity surface emitting lasers (VECSELs) based on flip-chip gain mirrors emitting at the 1.55 mu m wavelength range are reported. The gain mirrors employ wafer-fused InAlGaAs/InP quantum well heterostructures and GaAs/AlA ...

The unique properties of transition metal dichalcogenides provide a versatile platform for scalable, room-temperature quantum devices. Their future commercialization will inevitably depend on the development of heterostructures facilitating charge injection into pre-defined areas of 2D components. We showcase here an innovative approach to accurately characterize electrically active nanoscale regions in multidimensional heterostructures made of WSe₂ layers and GaAs, thin films and in-plane one-dimensional n

We report on carrier-induced effects on emission and absorption in forward biased GaAs/AlGaAs V-groove quantum wire (QWR) diodes observed using low-temperature (10 K) photoluminescence (PL), electroluminescence (EL) and PL excitation (PLE) spectroscopy. In the case of simultaneous electron-hole injection we observe a band-gap renormalization (BGR) of at least 5 meV for a carrier density of approximate to 10(6) cm(-1), by comparing high-density EL spectra with low-density PLE spectra. In the case of electron

We demonstrate that the emission characteristics of site-controlled InGaAs/GaAs single quantum dots embedded in photonic crystal slab cavities correspond to single confined excitons coupled to cavity modes, unlike previous reports of similar systems based ...

The effect of surface passivation in BCl3/N-2 inductively coupled plasma reactive-ion etching of GaAs-based photonic crystals (PhCs) was investigated. It is shown that sidewall passivation is crucial for achieving cylindrical, vertical PhC holes, where the ...

We propose and investigate a new type of photonic crystal (PhC) cavity for integrated quantum photonics, which provides tailored optical modes with both confined and extended spatial components. The structures consist of elongated PhC cavities in which the ...

We investigate the embedded interfaces of GaAs/AlGaAs quantum wells grown by metal organic vapor phase epitaxy on slightly (< 1 degrees)-misoriented (001) substrates using selective etching and atomic force microscopy. Depending on the substrate misorienta ...

Two site-controlled quantum dots (QDs) were integrated in a photonic crystal molecule (PCM) formed by L3 nanocavities. A statistical analysis of the coupled cavity modes demonstrated the formation of bonding and anti-bonding delocalized PCM states. Exciton ...

We demonstrate engineering of carrier states in the conduction band (CB) and valence band (VB) of site-controlled InGaAs/GaAs quantum dots (QDs) grown into pyramidal recesses, by controlling their shape, size, and composition. QDs with CB level separation ranging from ∼15 to 70 meV are obtained, useful in applications based on intraband transitions, e.g., QD photodetectors and QD cascade lasers. Moreover, by varying the aspect ratio and composition of the QDs we are able to switch the polarization of the do

We have measured phase modulation in the first chemical beam epitaxy grown InGaAsP/InP barrier, reservoir, and quantum well electron transfer structures. We obtain a negative refractive index change, DELTAn, similar to that found in the InGaAs/InAlAs system. Using new designs to reduce the leakage current in this material system, we obtain a leakage current

Semiconductor quantum-dot (QD) systems offering perfect site control and tunable emission energy are essential for numerous nanophotonic device applications involving spatial and spectral matching of dots with optical cavities. Herein, the properties of ordered InGaAs/GaAs QDs grown by organometallic chemical vapor deposition on substrates patterned with pyramidal recesses are reported. The seeded growth of a single QD inside each pyramid results in near-perfect (

We have studied systems of asymmetric coupled GaAs V-groove quantum wires p-i-n diodes, in which the electrons and holes are injected into different wires. Despite the use of a 7 nm thick AlGaAs tunnel barrier, and although we demonstrate that holes tunnel more slowly than electrons, we observe a very efficient and fast tunneling between the quantum wires (QWR's). We attribute this to the achievement of a resonance between hole levels in the two QWR's. Photoluminescence excitation experiments are compared w

Precise positioning of single site-controlled inverted pyramidal InGaAs quantum dots (QDs) at the antinode of a GaAs photonic crystal cavity with nanometer-scale accuracy holds unique advantages compared to self-assembled QDs and offers great promise for p ...

Chemical beam epitaxy (CBE) grown InAsP/InGaAsP edge-emitting laser diodes on GaAs substrates obtained by localised fusion in a nitrogen environment exhibit high quality fused interfaces. A degradation of fused lasers is observed which is attributed to the disordering of quantum wells at fusion temperatures induced by point defects incorporated during low temperature growth.

A terahertz quantum cascade laser design that combines a wide gain bandwidth, large photon-driven transport and good high-temperature characteristics is presented. It relies on a diagonal transition between a bound state and doublet of states tunnel couple ...

The effect of the miscut angle of vicinal substrate on the optical and morphological properties of GaAs/AlxGa1-xAs quantum wells grown by metalorganic vapor phase epitaxy is studied by means of photoluminescence (PL) and atomic force microscopy. Within small changes of the miscut angle, we observe strong variations of the PL linewidth, energy, and lineshape, as well as transitions between the morphology of the sample's surface and interface. The relation between these features is discussed, and the particul

We report on the realization of InGaAs-lnGaAsP separate confinement heterostructure multiple quantum well lasers grown by chemical beam epitaxy. We discuss key growth parameters and characterization by secondary-ion mass spectroscopy, transmission electron microscopy, electron-beam-induced current, and x-ray diffraction. Threshold current densities as low as 450 A/cm(2) are obtained on lasers with five strained InGaAs quantum wells, along with internal quantum efficiencies of 90% and optical losses of 5 cm(

Alok Rudra

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Photocurrent spectroscopy of site-controlled pyramidal quantum dots

Physical origins of optical anisotropy in quantum-confined semiconductors: The roles of valence band mixing, transition broadening, and state filling

Flip-Chip Wafer-Fused OP-VECSELs Emitting 3.65 W at the 1.55-mu m Waveband

Visualizing nanoscale charge flows in multi-dimensional WSe2/GaAs vertical diodes

Visualizing nanoscale charge flows in multi-dimensional WSe2/GaAs vertical diodes

Carrier-induced effects on absorption and emission in V-groove quantum wire diodes

Phonon-Mediated Coupling of InGaAs/GaAs Quantum-Dot Excitons to Photonic Crystal Cavities

Effect of sidewall passivation in BCl3/N2 inductively coupled plasma etching of two-dimensional GaAs photonic crystals

Tilted-potential photonic crystal cavities for integrated quantum photonics

Correlation between optical properties and interfaces morphology of GaAs/AlGaAs quantum wells

Site-controlled quantum dots coupled to a photonic crystal molecule

Engineering conduction and valence band states in site-controlled pyramidal quantum dots

Phase Modulation in Ingaasp Barrier, Reservoir, and Quantum-Well Electron-Transfer Structures, Grown by Chemical Beam Epitaxy

Site-Controlled InGaAs Quantum Dots with Tunable Emission Energy

Electroluminescence and photoluminescence excitation study of asymmetric coupled GaAs/AlxGa1-xAs V-groove quantum wires

Single site-controlled inverted pyramidal InGaAs QD-nanocavity operating at the onset of the strong coupling regime

Characteristics of InAsP/InGaAsP Edge Emitting Laser Diodes Obtained by Localised Fusion on GaAs Substrates

Bound-to-continuum terahertz quantum cascade laser with a single-quantum-well phonon extraction injection stage

Optics, morphology, and growth kinetics of GaAs/Al_{x}Ga_{1-x}As quantum wells grown on vicinal substrates by metalorganic vapor phase epitaxy

Chemical Beam Epitaxy of 1.55-Mu-M Separate-Confinement Heterostructure Multiple-Quantum-Well Laser-Diodes