Showing papers by "Tomasz Jakubczyk published in 2022"

A diamond-confined open microcavity featuring a high quality-factor and a small mode-volume

Abstract: With a highly coherent, optically addressable electron spin, the nitrogen-vacancy (NV) center in diamond is a promising candidate for a node in a quantum network. A resonant microcavity can boost the flux of coherent photons emerging from single NV centers. Here, we present an open Fabry–Pérot microcavity geometry containing a single-crystal diamond membrane, which operates in a regime where the vacuum electric field is strongly confined to the diamond membrane. There is a field anti-node at the diamond–air interface. Despite the presence of surface losses, a finesse of [Formula: see text] was observed. The quality ([Formula: see text]) factor for the lowest mode number is [Formula: see text]; the mode volume [Formula: see text] is estimated to be [Formula: see text], where [Formula: see text] is the free-space wavelength. We investigate the interplay between different loss mechanisms and the impact these loss channels have on the performance of the cavity. This analysis suggests that the surface waviness (roughness with a spatial frequency comparable to that of the microcavity mode) is the mechanism preventing the [Formula: see text] ratio from reaching even higher values. Finally, we apply the extracted cavity parameters to the NV center and calculate a predicted Purcell factor exceeding 150.

Luminescent nanoparticles in a shrinking spherical cavity – probing the evaporating microdroplets of colloidal suspension – optical lattices and structural transitions

Abstract: We investigated the possibility of using charged luminescent nanoparticles as nanoprobes for studying the evolution scenarios of surface and internal structure of slowly evaporating free (light-absorbing) microdroplets of suspension. Three concentrations (1, 10 and 50 mg/ml) of luminescent nanoparticles were used. Single microdroplets were kept in a linear electrodynamic quadrupole trap and the luminescence was excited with a CW IR laser with an irradiance of ∼50 W/mm2. Since the microdroplet acted as an optical spherical resonance cavity, the interaction of nanoparticles with light both reflected and modified the internal light field mode structure. Depending on the nanoparticle concentration used, it led, among others, to a very significant increase in modulation depth and narrowing of spherical cavity resonance maxima (morphology dependent resonances – MDRs) observed both in luminescence and scattering, the abrupt changes in the ratio between the luminescence and the scattering and the bi-stability in luminescence signal. The observed phenomena could be attributed to the interaction of optical MDRs with nanoparticle lattice shells forming and changing their structure at the microdroplet surface. In this way, the formation and collapse of such lattices could be detected.

Coherent Dynamics of a Single Mn-Doped Quantum Dot Revealed by Four-Wave Mixing Spectroscopy

Abstract: For future quantum technologies the combination of a long quantum state lifetime and an efficient interface with external optical excitation are required. In solids, the former is for example achieved by individual spins, while the latter is found in semiconducting artificial atoms combined with modern photonic structures. One possible combination of the two aspects is reached by doping a single quantum dot, providing a strong excitonic dipole, with a magnetic ion, that incorporates a characteristic spin texture. Here, we perform four-wave mixing spectroscopy to study the system’s quantum coherence properties. We characterize the optical properties of the undoped CdTe 1 ar X iv :2 20 1. 00 79 2v 1 [ co nd -m at .m es -h al l] 3 J an 2 02 2 quantum dot and find a strong photon echo formation which demonstrates a significant inhomogeneous spectral broadening. Incorporating the Mn2+ ion introduces its spin-5/2 texture to the optical spectra via the exchange interaction, manifesting as six individual spectral lines in the coherent response. The random flips of the Mn-spin result in a special type of spectral wandering between the six transition energies, which is fundamentally different from the quasi-continuous spectral wandering that results in the Gaussian inhomogeneous broadening. Here, the discrete spin-ensemble manifests in additional dephasing and oscillation dynamics. Introduction The incorporation of individual quantum systems into solid-state platforms,1–6 their coherent control, and interfacing them with external degrees of freedom7–10 is a key for implementation of quantum technologies. One of such promising platforms are semiconductor quantum dots (QDs),11 which owing to constant progress in the epitaxial growth12,13 and chemical synthesis,14 have now reached a tremendous structural quality.15 In parallel, processing of this material has been driven virtually to perfection permitting advanced engineering of the light-matter coupling with photonic structures.9 As a result, QDs in photonic microstructures serve as compact sources of single photons for quantum cryptography.16 Conversely, optical or electrical control of single quantum states confined to a QD is challenging, nonetheless intensely pursued in fundamental research.17–20 Over the last decade, a major progress has been achieved in measuring21–23 and controlling24–26 the coherence of optical transitions attributed to the bound electron-hole pair, forming a QD exciton. This was achieved by performing coherent ultrafast nonlinear spectroscopy,27 in particular four-wave mixing (FWM) on photonic devices hosting InGaAs QDs. However, the exciton radiative lifetime T1 lies typically in the nanosecond range, thus setting the upper bound for its coherence time T2 ≤ 2T1. Although an exciton represents an efficient interface between light and matter, its short T2 limits its usage as a qubit. Hence, a promising perspective

Creation of low-charge-noise nitrogen-vacancy centers in diamond with solid-immersion lens-assisted laser writing

Abstract: The negatively charged nitrogen-vacancy (NV) center in diamond is among the most promising solid-state systems implementations of a quantum bit. However, integration of the NV center into any efficient photonic environment requires microstructuring the diamond at below-micrometer scale. Preserving the low NV zero-phonon line inhomogeneous broadening during this process is a major challenge with standard NV creation methods. This issue severely limits practical applications of NV centers. Initial studies on pulsed-laser assisted creation of NVs yielded promising results by creating NVs with low inhomogeneous broadening at desired spatial locations in diamond [1]. Crucially, the lattice damage resulting from implantation of energetic ions was avoided. However, the method relied on a narrow window of parameters for successful writing. We widen this window by using a solid immersion lens (SIL), which facilitates laser writing over a broad range of pulse energies and allows for vacancy formation close to a diamond surface without inducing surface graphitization. We operate in the previously unexplored regime where lattice vacancies are created following tunneling breakdown rather than multiphoton ionization [2]. We present NV arrays that have been created between 1 and 40 µm from a diamond surface, all presenting optical linewidth distributions with means as low as 61.0±22.8 MHz [2], including spectral diffusion induced by off-resonant repump for charge stabilization. This emphasizes the exceptionally low charge-noise environment of laser-written NVs. Such high-quality NV centers are excellent candidates for practical applications employing two-photon quantum interference with separate NV centers. Finally, we propose a model for disentangling power broadening from inhomogeneous broadening in the NV zero-phonon line optical linewidth [2]. [1] Y.-C. Chen, P. S. Salter, S. Knauer, … and J. M. Smith, Nat. Photonics 11, 77 (2017). [2] V. Yurgens, J.A Zuber, S. Flågan, M. De Luca, B.J. Shields, I. Zardo, P. Maletinsky, R.J. Warburton, and T. Jakubczyk, ACS Photonics 8, 1726–1734 (2021)

A chiral one-dimensional atom using a quantum dot in an open microcavity

Abstract: Abstract In a chiral one-dimensional atom, a photon propagating in one direction interacts with the atom; a photon propagating in the other direction does not. Chiral quantum optics has applications in creating nanoscopic single-photon routers, circulators, phase-shifters, and two-photon gates. Here, we implement chiral quantum optics using a low-noise quantum dot in an open microcavity. We demonstrate the non-reciprocal absorption of single photons, a single-photon diode. The non-reciprocity, the ratio of the transmission in the forward-direction to the transmission in the reverse direction, is as high as 10.7 dB. This is achieved by tuning the photon-emitter coupling in situ to the optimal operating condition ( β = 0.5). Proof that the non-reciprocity arises from a single quantum emitter lies in the photon statistics—ultralow-power laser light propagating in the diode’s reverse direction results in a highly bunched output ( g (2) (0) = 101), showing that the single-photon component is largely removed.