arXiv subjects

T. Meier

Publications and source records attributed to T. Meier.

At least 19 recordsLinked to original sources

arXiv2023

Phase sensitivity of spatially broadband high-gain SU(1,1) interferometers

Nonlinear interferometers are promising tools for quantum metrology, as they are characterized by an improved phase sensitivity scaling compared to linear interferometers operating with classical light. However, the multimodeness of the light generated in these interferometers results in the destruction of their phase sensitivity, requiring advanced interferometric configurations for multimode light. Moreover, in contrast to the single-mode case, time-ordering effects play an important role for the high-gain regime in the multimode scenario and must be taken into account for a correct estimation of the phase sensitivity. In this work, we present a theoretical description of spatially multimode SU(1,1) interferometers operating at low and high parametric gains. Our approach is based on a step-by-step solution of a system of integro-differential equations for each nonlinear interaction region. We focus on interferometers with diffraction compensation, where focusing elements such as a parabolic mirror are used to compensate for the divergence of the light. We investigate plane-wave and Gaussian pumping and show that for any parametric gain, there exists a region of phases for which the phase sensitivity surpasses the standard shot-noise scaling and discuss the regimes where it approaches the Heisenberg scale. Finally, we arrive at insightful analytical expressions for the phase sensitivity that are valid for both low and high parametric gain and demonstrate how it depends on the number of spatial modes of the system.

quant-ph↗

arXiv2023

Temporal sorting of optical multi-wave-mixing processes in semiconductor quantum dots

Coherent control of ensembles of light emitters by means of multi-wave mixing processes is key for the realization of high capacity optical quantum memories and information processing devices. In this context, semiconductor quantum dots placed in optical microcavities represent excellent candidates to explore strong light-matter interactions beyond the limits of perturbative non-linear optics and control the unitary evolution of optically driven quantum systems. In this work, we demonstrate that a sequence of two optical picosecond pulses can be used to establish coherent control over the phase evolution of the ensemble of trions in (In,Ga)As quantum dots independent of their initial quantum state. Our approach is based on coherent transfer between degenerate multi-wave-mixing signals in the strong field limit where Rabi rotations in multi-level systems take place. In particular, we use the two-pulse photon echo sequence to uncover the coherent dynamics of the trion ensemble, whereas the areas of two additional control pulses serve as tuning knobs for adjusting the magnitude and timing of the coherent emission. Furthermore, we make use of the spin degeneracy of ground and excited state of trions to control the polarization state of the emitted signal. Surprisingly, we reveal that the use of optical control pulses, whose durations are comparable to the dephasing time of the ensemble, lifts the temporal degeneracy between wave-mixing processes of different order. This phenomenon is manifested in a significant modification of the temporal shape of the coherent optical response for strong optical fields. Lifting the temporal degeneracy allows to smoothly trace the transition from the perturbative to the regime of Rabi rotations and opens up new possibilities for the optical investigation of complex energy level structures in so far unexplored material systems.

cond-mat.mes-hall↗

arXiv2022

Multiple Rabi rotations of trions in InGaAs quantum dots observed by photon echo spectroscopy with spatially shaped laser pulses

We study Rabi rotations arising in intensity-dependent photon echoes from an ensemble of self-assembled InGaAs quantum dots. To achieve a uniform distribution of intensities within the excited ensemble, we introduce flattop intensity profiles of picosecond laser pulses. This allows us to overcome the damping of Rabi rotations imposed by the spatial inhomogeneity of Rabi frequencies by a Gaussian laser profile. Using photon echo polarimetry, we distinguish between the coherent optical responses from exciton and trion ensembles. Here, we demonstrate that a photo-induced charging of the quantum dots leads to a significant reduction of the number of neutral quantum dots under resonant excitation with intensive optical pulses with areas exceeding $\frac{\pi}{2}$. The trion ensemble shows robust Rabi rotations when the area of the refocussing pulse is increased up to 5.5$\pi$. We analyze the remaining attenuation of Rabi rotations by theoretical modeling of excitation induced dephasing, inhomogeneity of dipole moments, and coupling to acoustic phonons. The latter is identified as the dominating mechanism resulting in a loss of optical coherence during the action of the involved optical pulses.

cond-mat.mes-hall↗

arXiv2021

Coherent Contributions to Population Dynamics in a Semiconductor Microcavity

Multidimensional coherent spectroscopy (MDCS) is used to separate coherent and incoherent many-body contributions to the population-time dynamics in a GaAs-based semiconductor microcavity encapsulating a single InGaAs quantum well. In a three-pulse four-wave-mixing scheme, the second delay time is the population time that in MDCS probes excited-state coherences and population dynamics. Nonlinear optical interactions can mix these contributions, which are isolated here for the lower- and upper-exciton-polariton through the self- and mutual-interaction features. Results show fast decays and oscillations arising from the coherent response, including a broad stripe along the absorption energy axis, and longer time mutual-interaction features that do not obey a simple population decay model. These results are qualitatively replicated by Bloch equation simulations for the 1s exciton strongly coupled to the intracavity field. The simulations allow for separation of coherent and incoherent Pauli-blocking and Coulomb interaction terms within the chi^(3)-limit, and direct comparison of each feature in one-quantum rephasing and zero-quantum spectra.

cond-mat.mes-hall↗

arXiv2021

Steady states of $\Lambda$-type three-level systems excited by quantum light in lossy cavities

The interaction between quantum light and matter is being intensively studied for systems that are enclosed in high-$Q$ cavities which strongly enhance the light-matter coupling. However, for many applications, cavities with lower $Q$-factors are preferred due to the increased spectral width of the cavity mode. Here, we investigate the interaction between quantum light and matter represented by a $\Lambda$-type three-level system in lossy cavities, assuming that cavity losses are the dominant loss mechanism. We demonstrate that cavity losses lead to non-trivial steady states of the electronic occupations that can be controlled by the loss rate and the initial statistics of the quantum fields. The mechanism of formation of such steady states can be understood on the basis of the equations of motion. Analytical expressions for steady states and their numerical simulations are presented and discussed.

quant-ph↗

arXiv2021

Non-Degenerate Two-Photon Absorption in ZnSe: Experiment and Theory

We experimentally and theoretically investigate the non-degenerate two-photon absorption coefficient $\beta(\omega_1,\omega_2)$ in the prototypical semiconductor ZnSe. In particular, we provide a comprehensive data set on the dependence of $\beta(\omega_1,\omega_2)$ on the non-degeneracy parameter $\omega_1/\omega_2$ with the total frequency sum $\omega_1+\omega_2$ kept constant. We find a substantial increase of the two-photon absorption strength with increasing $\omega_1/\omega_2$. In addition, different crystallographic orientations and polarization configurations are investigated. The nonlinear optical response is analyzed theoretically by evaluating the multiband semiconductor Bloch equations including inter- and intraband excitations in the length gauge. The band structure and the matrix elements are taken an eight-band k.p model. The simulation results are in very good agreement with the experiment.

cond-mat.mes-hall↗

arXiv2021

Bright correlated twin-beam generation and radiation shaping in high-gain parametric down-conversion with anisotropy

Uniaxial anisotropy in nonlinear birefringent crystals limits the efficiency of nonlinear optical interactions and breaks the spatial symmetry of light generated in the parametric down-conversion (PDC) process. Therefore, this effect is usually undesirable and must be compensated for. However, high gain may be used to overcome the destructive role of anisotropy and instead to use it for the generation of bright two-mode correlated twin-beams. In this work, we provide a rigorous theoretical description of the spatial properties of bright squeezed light in the presence of strong anisotropy. We investigate a single-crystal and a two-crystal configuration and demonstrate the generation of bright correlated twin-beams in such systems at high gain due to anisotropy. We explore the mode structure of the generated light and show how anisotropy, together with crystal spacing, can be used for radiation shaping.

physics.optics↗

arXiv2020

Dark-state and loss-induced phenomena in the quantum-optical regime of $\Lambda$-type three-level systems

The interaction of matter with quantum light leads to phenomena which cannot be explained by semiclassical approaches. Of particular interest are states with broad photon number distributions which allow processes with high-order Fock states. Here, we analyze a Jaynes-Cummings-type model with three electronic levels which is excited by quantum light. As quantum light we consider coherent and squeezed states. In our simulations we include several loss mechanisms, namely, dephasing, cavity, and radiative losses which are relevant in real systems. We demonstrate that losses allow one to control the population of electronic levels and may induce coherent population trapping, as well as lead to a redistribution of the photon statistics among the quantum fields and even to a transfer of the photon statistics from one field to another. Moreover, we introduce and analyze a novel quantity, the quantum polarization, and demonstrate its fundamental difference compared to the classical polarization. Using the quantum polarization and the third level population, we investigate electromagnetically induced transparency in the presence of quantum light and show its special features for the case of squeezed light. Finally, quantum correlations between fields are studied and analyzed in the presence of different types of losses.

quant-ph↗

arXiv2020

Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots

Semiconductor quantum dots are excellent candidates for ultrafast coherent manipulation of qubits by laser pulses on picosecond timescales or even faster. In inhomogeneous ensembles a macroscopic optical polarization decays rapidly due to dephasing, which, however, is reversible in photon echoes carrying complete information about the coherent ensemble dynamics. Control of the echo emission time is mandatory for applications. Here, we propose a novel concept to reach this goal. In a two-pulse photon echo sequence, we apply an additional resonant control pulse with multiple of 2pi area. Depending on its arrival time, the control slows down dephasing or rephasing of the exciton ensemble during its action. We demonstrate for self-assembled (In,Ga)As quantum dots that the photon echo emission time can be retarded or advanced by 5 ps relative to its nominal appearance time without control. This versatile protocol may be used to obtain significantly longer temporal shifts for suitably tailored control pulses.

cond-mat.mes-hall↗

arXiv2019

Generating two-mode squeezing with multimode measurement-induced nonlinearity

Measurement-induced nonclassical effects in a two-mode interferometer are investigated theoretically using numerical simulations and analytical results. We demonstrate that for certain parameters measurements within the interferometer lead to the occurrence of two-mode squeezing. The results strongly depend on the detection probability, the phase inside the interferometer, and the choice of the input states. The appropriate parameters for maximized squeezing are obtained. We analyze the influence of losses and confirm that the predicted effects are within reach of current experimental techniques.

quant-ph↗

arXiv2018

Higher-order contributions and non-perturbative effects in the non-degenerate nonlinear optical absorption of direct-gap semiconductors

The semiconductor Bloch equations for a two-band model including inter- and intraband excitation are used to study the nonlinear absorption of single and multiple light pulses by direct-gap semiconductors. For a consistent analysis the contributions to the absorption originating from both the interband polarization and the intraband current need to be included. In the Bloch equation approach theses contributions as well as different excitation pathways in terms of sequences of inter- and intraband excitations can be evaluated separately which allows for a transparent analysis, the identification of the dominant terms, and analyzing their dependence on the excitation conditions. In the perturbative regime, we obtain analytical expressions for the multi-photon absorption coefficients for continuous-wave excitation. These results are shown to agree well with numerical results for short pulses and/or finite dephasing and relaxation times and we confirm the previously predicted strong enhancement of two-photon absorption for non-degenerate conditions for pulsed excitation. We discuss the dependencies on the light frequencies, initial band populations, and the time delay between the pulses. The frequency dependence of the two-photon absorption coefficient for non-degenerate excitation is evaluated perturbatively in third-order. The higher-order contributions to the optical absorption include three- and four-photon absorption and show a rich frequency dependence including negative regions and dispersive lineshapes. Non-perturbative solutions of the Bloch equations demonstrate a strongly non-monotonous behavior of the intensity-dependent optical absorption for a single incident pulse and in a pump-probe set-up.

cond-mat.mes-hall↗

arXiv2018

Nonlinearity-induced localization in a periodically-driven semi-discrete system

We demonstrate that nonlinearity plays a constructive role in supporting the robustness of dynamical localization in a model which is discrete, in one dimension and continuous in the orthogonal one. In the linear regime, time-periodic modulation of the gradient strength along the discrete axis leads to the usual rapid spread of an initially confined wave packet. Addition of the cubic nonlinearity makes the dynamics drastically different, inducing robust localization of moving wave packets. Similar nonlinearity-induced effects are also produced by combinations of static and oscillating linear potentials. The predicted nonlinearity-induced dynamical localization can be realized in photonic lattices and Bose-Einstein condensates.

nlin.PS↗

arXiv2017

Bloch oscillations and resonant radiation of light propagating in arrays of nonlinear fibers with high-order dispersion

Bloch oscillations of spatio-temporal light wave packets in arrays of nonlinear fibers with high-order dispersion are studied. The light wave experiences discrete spatial diffraction along the waveguide array coordinate together with continuous temporal dispersion including higher order terms. When a gradient in the waveguide light confinement strength is considered, the wave packet features robust long-lived Bloch oscillations with temporal and spatial spreading in the presence of a Kerr nonlinearity. The effect of the spatial Bloch oscillations on the emission of the dispersive radiation by the solitary wave is studied. It is shown that Bloch oscillations result in the generation of new frequencies. The condition of resonant emission of dispersive waves is derived and it is demonstrated that it matches very well with the results of direct numerical simulations.

nlin.PS↗

arXiv2017

Damping of Rabi oscillations in intensity-dependent photon echoes from exciton complexes in a CdTe/(Cd,Mg)Te single quantum well

We study Rabi oscillations detected in the coherent optical response from various exciton complexes in a 20~nm-thick CdTe/(Cd,Mg)Te quantum well using time-resolved photon echoes. In order to evaluate the role of exciton localization and inhomogeneous broadening we use selective excitation with spectrally narrow ps-pulses. We demonstrate that the transient profile of the photon echo from the localized trion (X$^-$) and the donor-bound exciton (D$^0$X) transitions strongly depends on the strength of the first pulse. It acquires a non-Gaussian shape and experiences significant advancement for pulse areas larger than $\pi$ due to non-negligible inhomogeneity-induced dephasing of the oscillators during the optical excitation. Next, we observe that an increase of the area of either the first (excitation) or the second (rephasing) pulse leads to a significant damping of the photon echo signal, which is strongest for the neutral excitons and less pronounced for the donor-bound exciton complex (D$^0$X). The measurements are analyzed using a theoretical model based on the optical Bloch equations which accounts for the inhomogeneity of optical transitions in order to reproduce the complex shape of the photon echo transients. In addition, the spreading of Rabi frequencies within the ensemble due to the spatial variation of the intensity of the focused Gaussian beams and excitation-induced dephasing are required to explain the fading and damping of Rabi oscillations. By analyzing the results of the simulation for the X$^-$ and the D$^0$X complexes we are able to establish a correlation between the degree of localization and the transition dipole moments determined as $\mu($X$^-$)=73~D and $\mu($D$^0$X)=58~D.

cond-mat.mes-hall↗

arXiv2017

Modified Two-Photon Interference Achieved by the Manipulation of Entanglement

In this theoretical study we demonstrate that entangled states are able to significantly extend the functionality of Hong-Ou-Mandel (HOM) interferometers. By generating a coherent superposition of parametric-down-conversion photons and spatial entanglement in the input channel, the coincidence probability measured at the output changes from a typical HOM-type dip (photon bunching) into much richer patterns including an anti-bunching peak and rapid oscillation fringes with twice the optical frequency. The considered system should be realizable on a single chip using current waveguide technology in the $LiNbO_3$ platform.

quant-ph↗

arXiv2017

Bloch oscillations sustained by nonlinearity

We demonstrate that nonlinearity may play a constructive role in supporting Bloch oscillations in a model which is discrete, in one dimension and continuous in the orthogonal one. The model can be experimentally realized in several fields of physics such as optics and Bose-Einstein condensates. We demonstrate that designing an optimal relation between the nonlinearity and the linear gradient strength provides extremely long-lived Bloch oscillations with little degradation. Such robust oscillations can be observed for a broad range of parameters and even for moderate nonlinearities and large enough values of linear potential. We also present an approximate analytical description of the wave packet's evolution featuring a hybrid Bloch oscillating wave-soliton behavior that excellently corresponds to the direct numerical simulations.

nlin.PS↗

arXiv2017

Toolbox for the design of $LiNbO_3$-based passive and active integrated quantum circuits

We present and discuss perspectives of current developments on advanced quantum optical circuits monolithically integrated in the lithium niobate platform. A set of basic components comprising photon pair sources based on parametric down conversion (PDC), passive routing elements and active electro-optically controllable switches and polarisation converters are building blocks of a toolbox which is the basis for a broad range of diverse quantum circuits. We review the state-of-the-art of these components and provide models that properly describe their performance in quantum circuits. As an example for applications of these models we discuss design issues for a circuit providing on-chip two-photon interference. The circuit comprises a PDC section for photon pair generation followed by an actively controllable modified Mach-Zehnder structure for observing Hong-Ou-Mandel (HOM) interference. The performance of such a chip is simulated theoretically by taking even imperfections of the properties of the individual components into account.

quant-ph↗

arXiv2017

Transient photon echoes from donor-bound excitons in ZnO epitaxial layers

The coherent optical response from 140~nm and 65~nm thick ZnO epitaxial layers is studied using transient four-wave-mixing spectroscopy with picosecond temporal resolution. Resonant excitation of neutral donor-bound excitons results in two-pulse and three-pulse photon echoes. For the donor-bound A exciton (D$^0$X$_\text{A}$) at temperature of 1.8~K we evaluate optical coherence times $T_2=33-50$~ps corresponding to homogeneous linewidths of $13-19~\mu$eV, about two orders of magnitude smaller as compared with the inhomogeneous broadening of the optical transitions. The coherent dynamics is determined mainly by the population decay with time $T_1=30-40$~ps, while pure dephasing is negligible in the studied high quality samples even for strong optical excitation. Temperature increase leads to a significant shortening of $T_2$ due to interaction with acoustic phonons. In contrast, the loss of coherence of the donor-bound B exciton (D$^0$X$_\text{B}$) is significantly faster ($T_2=3.6$~ps) and governed by pure dephasing processes.

cond-mat.mtrl-sci↗