arXiv subjects

Gabija Kiršanskė

Publications and source records attributed to Gabija Kiršanskė.

6 recordsLinked to original sources

arXiv2021

Carrier-mediated optomechanical forces in semiconductor nanomembranes with coupled quantum wells

In the majority of optomechanical experiments, the interaction between light and mechanical motion is mediated by radiation pressure, which arises from momentum transfer of reflecting photons. This is an inherently weak interaction, and optically generated carriers in semiconductors have been predicted to be the mediator of different and potentially much stronger forces. Here we demonstrate optomechanical forces induced by electron-hole pairs in coupled quantum wells embedded into a free-free nanomembrane. We identify contributions from the deformation-potential and piezoelectric coupling and observe optically driven motion about three orders of magnitude larger than expected from radiation pressure. The amplitude and phase of the driven oscillations are controlled by an applied electric field, which tunes the carrier lifetime to match the mechanical period. Our work opens perspectives for not only enhancing the optomechanical interaction in a range of experiments, but also for interfacing mechanical objects with complex macroscopic quantum objects, such as excitonic condensates.

cond-mat.mes-hall↗

arXiv2018

Quantum optics with near lifetime-limited quantum-dot transitions in a nanophotonic waveguide

Establishing a highly efficient photon-emitter interface where the intrinsic linewidth broadening is limited solely by spontaneous emission is a key step in quantum optics. It opens a pathway to coherent light-matter interaction for, e.g., the generation of highly indistinguishable photons, few-photon optical nonlinearities, and photon-emitter quantum gates. However, residual broadening mechanisms are ubiquitous and need to be combated. For solid-state emitters charge and nuclear spin noise is of importance and the influence of photonic nanostructures on the broadening has not been clarified. We present near lifetime-limited linewidths for quantum dots embedded in nanophotonic waveguides through a resonant transmission experiment. It is found that the scattering of single photons from the quantum dot can be obtained with an extinction of $66 \pm 4 \%$, which is limited by the coupling of the quantum dot to the nanostructure rather than the linewidth broadening. This is obtained by embedding the quantum dot in an electrically-contacted nanophotonic membrane. A clear pathway to obtaining even larger single-photon extinction is laid out, i.e., the approach enables a fully deterministic and coherent photon-emitter interface in the solid state that is operated at optical frequencies.

quant-ph↗

arXiv2017

Indistinguishable and efficient single photons from a quantum dot in a planar nanobeam waveguide

We demonstrate a high-purity source of indistinguishable single photons using a quantum dot embedded in a nanophotonic waveguide. The source features a near-unity internal coupling efficiency and the collected photons are efficiently coupled off-chip by implementing a taper that adiabatically couples the photons to an optical fiber. By quasi-resonant excitation of the quantum dot, we measure a single-photon purity larger than 99.4% and a photon indistinguishability of up to 94+-1% by using p-shell excitation combined with spectral filtering to reduce photon jitter. A temperature-dependent study allows pinpointing the residual decoherence processes notably the effect of phonon broadening. Strict resonant excitation is implemented as well as another mean of suppressing photon jitter, and the additional complexity of suppressing the excitation laser source is addressed. The study opens a clear pathway towards the long-standing goal of a fully deterministic source of indistinguishable photons, which is integrated on a planar photonic chip.

quant-ph↗

arXiv2016

Observation of the exciton Mott transition in the photoluminescence of coupled quantum wells

Indirect excitons in coupled quantum wells have long radiative lifetimes and form a cold quasi-two-dimensional population suitable for studying collective quantum effects. Here we report the observation of the exciton Mott transition from an insulating (excitons) to a conducting (ionized electron-hole pairs) phase, which occurs gradually as a function of carrier density and temperature. The transition is inferred from spectral and time-resolved photoluminescence measurements around a carrier density of $2\times10^{10} \mathrm{cm}^{-2}$ and temperatures of $12-16 \mathrm{K}$. An externally applied electric field is employed to tune the dynamics of the transition via the quantum-confined Stark effect. Our results provide evidence of a gradual nature of the exciton Mott transition.

cond-mat.mes-hall↗

arXiv2015

Soft-mask fabrication of gallium arsenide nanomembranes for integrated quantum photonics

We report on the fabrication of quantum photonic integrated circuits based on suspended GaAs membranes. The fabrication process consists of a single lithographic step followed by inductively-coupled-plasma dry etching through an electron-beam-resist mask and wet etching of a sacrificial layer. This method does not require depositing, etching, and stripping a hard mask, greatly reducing fabrication time and costs, while at the same time yielding devices of excellent structural quality. We discuss in detail the procedures for cleaning the resist residues caused by the plasma etching and present a statistical analysis of the etched feature size after each fabrication step.

physics.optics↗

arXiv2015

Deterministic photon-emitter coupling in chiral photonic circuits

The ability to engineer photon emission and photon scattering is at the heart of modern photonics applications ranging from light harvesting, through novel compact light sources, to quantum-information processing based on single photons. Nanophotonic waveguides are particularly well suited for such applications since they confine photon propagation to a 1D geometry thereby increasing the interaction between light and matter. Adding chiral functionalities to nanophotonic waveguides lead to new opportunities enabling integrated and robust quantum-photonic devices or the observation of novel topological photonic states. In a regular waveguide, a quantum emitter radiates photons in either of two directions, and photon emission and absorption are reverse processes. This symmetry is violated in nanophotonic structures where a non-transversal local electric field implies that both photon emission and scattering may become directional. Here we experimentally demonstrate that the internal state of a quantum emitter determines the chirality of single-photon emission in a specially engineered photonic-crystal waveguide. Single-photon emission into the waveguide with a directionality of more than 90\% is observed under conditions where practically all emitted photons are coupled to the waveguide. Such deterministic and highly directional photon emission enables on-chip optical diodes, circulators operating at the single-photon level, and deterministic quantum gates. Based on our experimental demonstration, we propose an experimentally achievable and fully scalable deterministic photon-photon CNOT gate, which so far has been missing in photonic quantum-information processing where most gates are probabilistic.

quant-ph↗