arXiv subjects

Martin P. van Exter

Publications and source records attributed to Martin P. van Exter.

At least 19 recordsLinked to original sources

arXiv2026

Simulating frequency splittings and loss in Fabry-Pérot cavities

Finite-element simulations of optical cavities are presented, showing frequency splittings in the resonance spectrum. These can be directly compared to and understood by recent theory and experiments presented in van Exter et al. (2022, Phys. Rev. A 106, 013501), Koks et al. (2022, Phys. Rev. A 105, 063502) and Post et al. (2025, Phys. Rev. A 112, 033537). They provide strong evidence for the nonparaxial theory, but point out limitations of predicted mirror-shape corrections. The simulations also provide model-independent predictions of modal losses for optical cavities.

physics.optics↗

arXiv2025

Optical microcavity characterization via resonance spectra and modes

This paper describes how resonance spectra and mode profiles can be used to characterize and quantify the mode-shaping effects in open-access plano-concave optical microcavities. The presented semi-analytic theory is based on the application of perturbation theory to the roundtrip evolution of the optical field. It includes various mirror-shape and nonparaxial effects and extends the nonparaxial theory presented by van Exter et al. (2022, Phys. Rev. A 106, 013501) and verified by Koks et al. (2022, Phys. Rev. A 105, 063502) to the common case of an anisotropic Gaussian mirror. The presented measurements and analyses of resonance spectra and mode profiles demonstrate how the different mode-shaping effects can be individually distinguished and quantified. Spin-orbit coupling, which is one of the nonparaxial effects, is prominently visible in the intriguing polarization patterns of the resonant modes, while polarization tomography yields the shape-induced birefringence and associated polarization splitting of the fundamental modes.

physics.optics↗

arXiv2024

Confocal polarization tomography of dielectric nanocavities

We employ polarization tomography to characterize the modal properties of a dielectric nanocavity with sub-wavelength mode confinement. Our analysis of reflection spectra shows that the Fano-lineshape depends strongly on the polarization in a confocal configuration, and that the lineshape can be transformed into a Lorentzian-like peak for a certain polarization. For this polarization setting, the background is almost fully suppressed in a finite range of frequencies. This enables us to identify another resonance that has not yet been experimentally reported for these nanocavities. Lastly, we use symmetry-forbidden polarizations and show that, surprisingly, the modal resonance features of the system remain visible.

physics.optics↗

arXiv2024

Probing microcavity resonance spectra with intracavity emitters

We measure the fluorescence spectrum of broadband emitters in an open optical microcavity with radius of curvature R = 17.7(3) um and finesse F ~= 1000. This geometry enables a combined measurement of emission spectra versus cavity length, which has several benefits over measurements at fixed wavelength or fixed cavity length alone. We demonstrate the role of the optical penetration depths on the cavity modes and provide practical working equations for its analysis. Furthermore, we show the ability to measure the coupling of cavity modes within a small scan range of the cavity length. By measuring these cavity emission spectra as a function of cavity length, we thus obtain a rich and complete picture of the optical microcavity.

physics.optics↗

arXiv2016

Experimental investigation of the detection mechanism in WSi nanowire superconducting single photon detectors

We use quantum detector tomography to investigate the detection mechanism in WSi nanowire superconducting single photon detectors (SSPDs). To this purpose, we fabricated a 250nm wide and 250nm long WSi nanowire and measured its response to impinging photons with wavelengths ranging from $λ$ = 900 nm to $λ$ = 1650 nm. Tomographic measurements show that the detector response depends on the total excitation energy only. Moreover, for energies Et > 0.8eV the current energy relation is linear, similar to what was observed in NbN nanowires, whereas the current-energy relation deviates from linear behaviour for total energies below 0.8eV.

cond-mat.mes-hall↗

arXiv2015

Position-Dependent Local Detection Efficiency in a Nanowire Superconducting Single-Photon Detector

We probe the local detection efficiency in a nanowire superconducting single-photon detector along the cross-section of the wire with a spatial resolution of 10 nm. We experimentally find a strong variation in the local detection efficiency of the device. We demonstrate that this effect explains previously observed variations in NbN detector efficiency as function of device geometry.

cond-mat.supr-con↗

arXiv2015

Polarization degenerate solid-state cavity QED

A polarization degenerate microcavity containing charge-controlled quantum dots (QDs) enables equal coupling of all polarization degrees of freedom of light to the cavity QED system, which we explore through resonant laser spectroscopy. We first measure interference of the two fine-split neutral QD transitions and find very good agreement of this V-type three-level system with a coherent polarization dependent cavity QED model. We also study a charged QD that suffers from decoherence, and find also in this case that availability of the full polarization degrees of freedom is crucial to reveal the dynamics of the QD transitions. Our results pave the way for postselection-free quantum devices based on electron spin-photon polarization entanglement.

quant-ph↗

arXiv2015

Quantum dot nonlinearity through cavity-enhanced feedback with a charge memory

In an oxide apertured quantum dot (QD) micropillar cavity-QED system, we found strong QD hysteresis effects and lineshape modifications even at very low intensities corresponding to less than 0.001 intracavity photons. We attribute this to the excitation of charges by the intracavity field; charges that get trapped at the oxide aperture, where they screen the internal electric field and blueshift the QD transition. This in turn strongly modulates light absorption by cavity QED effects, eventually leading to the observed hysteresis and lineshape modifications. The cavity also enables us to observe the QD dynamics in real time, and all experimental data agrees well with a power-law charging model. This effect can serve as a novel tuning mechanism for quantum dots.

quant-ph↗

arXiv2014

Polarization degenerate micropillars fabricated by designing elliptical oxide apertures

A method for fabrication of polarization degenerate oxide apertured micropillar cavities is demon- strated. Micropillars are etched such that the size and shape of the oxide front is controlled. The polarization splitting in the circular micropillar cavities due to the native and strain induced bire- fringence can be compensated by elongating the oxide front in the [110] direction, thereby reducing stress in this direction. By using this technique we fabricate a polarization degenerate cavity with a quality factor of 1.7*?10^4 and a mode volume of 2.7 u?m3, enabling a calculated maximum Purcell factor of 11.

physics.optics↗

arXiv2013

Fine tuning of micropillar cavity modes through repetitive oxidations

Repetitive wet thermal oxidations of a tapered oxide aperture in a micropillar structure are demonstrated. After each oxidation step the confined optical modes are analyzed at room temperature. Three regimes are identified. First, the optical confinement increases when the aperture oxidizes towards the center. Then, the cavity modes shift by more than 30 nm, when the taper starts to oxidize through the center, leading to a decrease in the optical path length. Finally, the resonance frequency levels o?f, when the aperture is oxidized all the way through the micropillar, but confined optical modes with a high quality factor remain. This repetitive oxidation technique therefore enables precise control of the optical cavity volume or wavelength.

physics.optics↗

arXiv2013

Universal Response Curve for Nanowire Superconducting Single-Photon Detectors

Using detector tomography, we investigate the detection mechanism in NbN-based superconducting single photon detectors (SSPDs). We demonstrate that the detection probability uniquely depends on a particular linear combination of bias current and energy, for a large variation of bias currents, input energies and detection probabilities, producing a universal detection curve. We obtain this result by studying multiphoton excitations in a nanodetector with a sparsity-based tomographic method that allows factoring out of the optical absorption. We discuss the implication of our model system for the understanding of meander-type SSPDs.

quant-ph↗

arXiv2013

Monitoring the formation of oxide apertures in micropillar cavities

An imaging technique is presented that enables monitoring of the wet thermal oxidation of a thin AlAs layer embedded between two distributed Bragg reflector (DBR) mirrors in a micropillar. After oxidation we confirm by white light reflection spectroscopy that high quality optical modes confined to a small volume have been formed. The combination of these two optical techniques provides a reliable and efficient way of producing oxide apertured micropillar cavities for which the wet thermal oxidation is a critical fabrication step.

physics.optics↗

arXiv2012

H1 photonic crystal cavitites for hybrid quantum information protocols

Hybrid quantum information protocols are based on local qubits, such as trapped atoms, NV centers, and quantum dots, coupled to photons. The coupling is achieved through optical cavities. Here we demonstrate far-field optimized H1 photonic crystal membrane cavities combined with an additional back reflection mirror below the membrane that meet the optical requirements for implementing hybrid quantum information protocols. Using numerical optimization we find that 80% of the light can be radiated within an objective numerical aperture of 0.8, and the coupling to a single-mode fiber can be as high as 92%. We experimentally prove the unique external mode matching properties by resonant reflection spectroscopy with a cavity mode visibility above 50%.

physics.optics↗

arXiv2012

Optical modes in oxide-apertured micropillar cavities

We present a detailed experimental characterization of the spectral and spatial structure of the confined optical modes for oxide-apertured micropillar cavities, showing good-quality Hermite-Gaussian profiles, easily mode-matched to external fields. We further derive a relation between the frequency splitting of the transverse modes and the expected Purcell factor. Finally, we describe a technique to retrieve the profile of the confining refractive index distribution from the spatial profiles of the modes.

cond-mat.mes-hall↗

arXiv2012

Tomography and state reconstruction with superconducting single-photon detectors

We perform quantum state reconstruction of coherent and thermal states with a detector which has an enhanced multiphoton response. The detector is based on superconducting nanowires, where the bias current sets the dependence of the click probability on the photon number; this bias current is used as tuning parameter in the state reconstruction. The nonlinear response makes our nanowire-based detector superior to the linear detectors that are conventionally used for quantum state reconstruction.

quant-ph↗

arXiv2012

Far-field emission profiles from L3 photonic crystal cavity modes

We experimentally characterize the spatial far-field emission profiles for the two lowest confined modes of a photonic crystal cavity of the L3 type, finding a good agreement with FDTD simulations. We then link the far-field profiles to relevant features of the cavity mode near-fields, using a simple Fabry-Perot resonator model. The effect of disorder on far-field cavity profiles is clarified through comparison between experiments and simulations. These results can be useful for emission engineering from active centers embedded in the cavity.

cond-mat.mes-hall↗

arXiv2012

Schmidt modes generated in parametric downconversion

This paper presents the general Schmidt decomposition of two-photon fields generated in spontaneous parametric down-conversion (SPDC). It discusses in particular the separation of the radial and azimuthal degrees of freedom, the role of projection in modal analysis, and the benefits of collinear phase mismatch. The paper is written in a review style and presents a wealth of numerical results. It aims at emphasising the physics beyond the mathematics, through discussions and graphical representations of key results.

quant-ph↗

arXiv2011

Strain-tuning of quantum dot optical transitions via laser-induced surface defects

We discuss the fine-tuning of the optical properties of self-assembled quantum dots by the strain perturbation introduced by laser-induced surface defects. We show experimentally that the quantum dot transition red-shifts, independently of the actual position of the defect, and that such frequency shift is about a factor five larger than the corresponding shift of a micropillar cavity mode resonance. We present a simple model that accounts for these experimental findings.

cond-mat.mes-hall↗