We report on a process for the fiber-coupling of electrically driven cavity-enhanced quantum dot light emitting devices.The developed technique allows for the direct and permanent coupling of p-i-n-doped quantum dot micropillar cavities to single-mode optical fibers. The coupling process, fully carried out at room temperature, involves a spatial scanning technique, where the fiber facet is positioned relative to a device with a diameter of 2 µm using the fiber-coupled electroluminescence of the cavity emission as feedback parameter. Subsequent gluing and UV curing enables a rigid and permanent coupling between micropillar and fiber core. Comparing our experimental results with finite element method simulations indicate fiber coupling efficiencies of ~46%. The technique presented in this work is an important step in the quest for efficient and practical quantum light sources for applications in quantum information. Solid-state based quantum-light sources are elementary building blocks for photonic quantum technologies [1-3]. Especially the maturity of single-photon sources (SPSs) based on semiconductor quantum dots (QDs) has advanced substantially in recent years [4,5], allowing for the efficient generation of quantum states of light under optical [6-9] or electrical pumping [10,11].As a result, QD-based quantum light sources have been employed for many proof-of-concept experiments on quantum communication [12][13][14] and photonic quantum computing [15]. Most of these experiments, however, suffer from rather complex and bulky setups due to complex light extraction via free-space optics, hindering more widespread applications. On the other hand, the development of user-friendly devices for applications outside shielded lab environments recently attracted much interest [16,17]. A crucial aspect in this context concerns the direct coupling of the quantum light sources to optical single-mode (SM) fibers facilitating a robust packaging of the devices. Pioneering work in this direction utilized fiber-coupled QD samples employing fiber-bundles containing about 600 individual fiber cores to spatially post-select a single emitter [18].More recently, the direct fiber-coupling of optically pumped photonic nanostructures with embedded QDs, such as photonic wires [19] and micropillars with oxide aperture [20], has been reported. The latter scheme has also been used to realize an optically pumped cavity-enhanced single-photon source with gates for spectral tuning of the QD emission [21]. In addition, optically-pumped fiber-integrated microcavities were employed for the generation of coherent acoustic phonons [22].Moreover, schemes for the SM fiber-coupling of QD microlenses are currently under development using two-photon direct
Organic molecules with photoswitchable emission properties are of interest in the optical devices field. We present herein in‐solution studies for two dimethoxydithienylethene‐fluorophore (DTE‐fluorophore) conjugates with a carboxylic acid anchor group attachable to semiconductor surfaces (DTE‐BODIPY and BTD‐DTE, where BTD=benzothiadiazole). Both conjugates show almost quantitative reversible photoisomerization between open (OF) and closed forms (CF). With excitation of the fluorophores, both conjugates emit fluorescence with highly solvent‐dependent OFs (BTD‐DTE>DTE‐BODIPY) and minor solvent‐dependent CFs. In the polar solvent MeCN for BTD‐DTE a TICT state is clearly observed, which will be located in the twisted conjugated structure of the benzoic acid‐BTD‐fluorophore‐methoxy‐thiophene unit. BTD‐DTE shows positive solvatofluorochromism with a decrease of fluorescence quantum yields by increasing the Lippert orientation polarizability function (Δf) verified in Lippert‐Mataga plots. This leads to solvent dependent on‐off/off‐on (CF‐OF) emission modulation by Förster resonance energy transfer (FRET) with well‐separated emission bands for BTD‐DTE.
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