Organic lasers: recent developments on materials, device geometries, and fabrication techniques

MCG acknowledges financial support through the ERC Starting Grant ABLASE (640012) and the European Union Marie Curie Career Integration Grant (PCIG12-GA-2012-334407). AJCK acknowledges financial support by the German Federal Ministry for Education and Research through a NanoMatFutur research group (BMBF grant no. 13N13522).Organic dyes have been used as gain medium for lasers since the 1960s, long before the advent of today’s organic electronic devices. Organic gain materials are highly attractive for lasing due to their chemical tunability and large stimulated emission cross section. While the traditional dye laser has been largely replaced by solid-state lasers, a number of new and miniaturized organic lasers have emerged that hold great potential for lab-on-chip applications, biointegration, low-cost sensing and related areas, which benefit from the unique properties of organic gain materials. On the fundamental level, these include high exciton binding energy, low refractive index (compared to inorganic semiconductors), and ease of spectral and chemical tuning. On a technological level, mechanical flexibility and compatibility with simple processing techniques such as printing, roll-to-roll, self-assembly, and soft-lithography are most relevant. Here, the authors provide a comprehensive review of the developments in the field over the past decade, discussing recent advances in organic gain materials, which are today often based on solid-state organic semiconductors, as well as optical feedback structures, and device fabrication. Recent efforts toward continuous wave operation and electrical pumping of solid-state organic lasers are reviewed, and new device concepts and emerging applications are summarized.PostprintPeer reviewe

Nonlinear Optics in Chalcogenide and Tellurite Microspheres for the Generation of Mid-Infrared Frequencies

Le développement de sources optiques émettant au-delà des bandes de télécommunication jusqu’à l’infrarouge moyen est grandissant. Des sources nouvelles et améliorées émettant à des longueurs d’onde allant de 2 μm à 12 μm sont régulièrement rapportées dans la communauté scientifique et quelques sources sont déjà disponibles sur le marché. Divers domaines profitent de ces développements dont l’imagerie, les télécommunications, le traitement des matériaux et l’analyse moléculaire pour n’en nommer que quelques-uns. Parmi ces sources,les lasers basés sur les microcavités à modes de galerie sont de plus en plus présents puisque beaucoup d’efforts sont déployés au transfert de leurs propriétés uniques du proche infrarouge à l’infrarouge moyen. En plus de leurs dimensions micrométriques, les microcavités à modes de galerie sont naturellement adaptées à la génération non linéaire de signaux optiques : elles possèdent de grands facteurs de qualité et de petits volumes modaux. Les processus non linéaires de diffusion Raman stimulée et en cascade sont attrayants puisqu’ils ne requièrent aucune condition de dispersion particulière. De plus, ces processus sont observables sur toute la fenêtre de transmission du matériau. La silice qui est le matériel de choix typiquement utilisé pour la transmission de signal dans le proche infrarouge devient opaque aux longueurs d’onde excédant 2 μm. Pour cette raison, on tirera profit de matériaux moins conventionnels mais transparents dans l’infrarouge moyen, tels que les verres de chalcogénure et de tellure. Parmi les microcavités à modes de galerie basées sur les verres de chalcogénure qui ont été rapportées, aucune démonstration de génération non linéaire n’a été faite. Cela s’explique par des pertes optiques trop élevées qui limitent les puissances de seuil aux dizaines de milliwatts, loin des puissances de seuil de quelques microwatts observées dans les microcavités en silice dans le proche infrarouge. La première contribution de cette thèse répond à ce problème par la fabrication de microsphères de haute qualité en As2S3. Reconnus pour leur transparence entre les longueurs d’onde de 1 μm à 6 μm, les verres en As2S3 peuvent être produits avec une grande pureté et possèdent un gain Raman élevé comparé à la silice. Les microsphères en As2S3 sont produites à partir de fibres optiques de grande pureté et elles démontrent des pertes optiques similaires à celles des fibres. Grâce aux procédés d’usinage par laser, les facteurs de qualité optique sont deux ordres de grandeur supérieurs aux valeurs précédemment rapportées. Les microsphères peuvent être fabriquées avec des diamètres variant de 20 μm à 400 μm. Enfin, leur qualité est conservée par un procédé d’encapsulation.----------Abstract In the recent years, the development of optical sources emitting outside the standard telecommunication bands and in the mid-infrared (mid-IR) region is thriving. New and improved sources with wavelengths spanning from 2 μm to 12 μm are regularly reported in the research community and various sources are already available on the market. Diverse domains including imagery, communication, material processing, and molecular analysis are taking advantage of these sources. Among these, micron-size lasers based on whispering gallery modes (WGM) microcavities are gradually entering the race as more effort is invested to transfer their unique properties from near-infrared to mid-IR regions. Along their compactness,WGM microcavities are naturally suitable for nonlinear signal generation: they possess relatively large Q-factors and small mode volumes. Stimulated and cascaded Raman scattering processes are especially attractive for signal generation as they require no particular dispersion condition. Furthermore, these processes can be observed across the entire transparency window of the host material. Typical near-IR materials such as silica have to be replaced by unconventional ones such as chalcogenide and tellurite glasses. All previously reported WGM microcavities based on chalcogenide and tellurite glasses failed to demonstrate nonlinear interaction. They suffered from large optical losses that push threshold power levels to tens of milliwatts, far from the μW level usually observed in silica microcavities at near-IR wavelengths. The first contribution of this thesis is therefore to solve this issue by fabricating low loss As2S3 WGM microcavities. Known for its 1−6 μm transparency window, As2S3 glass can be produced with high purity and exhibits a large Raman gain compared to silica. Made from high purity optical fibers, As2S3 microspheres demonstrated loss levels similar to the optical fiber attenuation. Thanks to a fabrication technique based on laser shaping, the measured optical Q-factors exceed previously reported values by two orders of magnitude in As2S3. Microspheres can be produced with diameters varying between 20 μm and 400 μm. Their quality is maintained using an encapsulation method. The packaged device additionally includes a tapered optical fiber to couple light in and out of the microcavity. The second thesis contribution is the demonstration of stimulated Raman scattering in As2S3 microspheres. Threshold coupled pump powers of ~ 13 μW with internal power conversion efficiency of 10 % were observed for pump and signal wavelengths of 1550 nm and 1640 nm

Spin Detection, Amplification, and Microwave Squeezing with Kinetic Inductance Parametric Amplifiers

Superconducting parametric amplifiers operating at microwave frequencies have become an essential component in circuit quantum electrodynamics experiments. They are used to amplify signals at the single-photon level, while adding only the minimum amount of noise required by quantum mechanics. To achieve gain, energy is transferred from a pump to the signal through a non-linear interaction. A common strategy to enhance this process is to place the non-linearity inside a high quality factor resonator, but so far, quantum limited amplifiers of this type have only been demonstrated from designs that utilize Josephson junctions. Here we demonstrate the Kinetic Inductance Parametric Amplifier (KIPA), a three-wave mixing resonant parametric amplifier that exploits the kinetic inductance intrinsic to thin films of disordered superconductors. We then utilize the KIPA for measurements of 209Bi spin ensembles in Si. First, we show that a KIPA can serve simultaneously as a high quality factor resonator for pulsed electron spin resonance measurements and as a low-noise parametric amplifier. Using this dual-functionality, we enhance the signal to noise ratio of our measurements by more than a factor of seven and ultimately achieve a measurement sensitivity of 2.4 x 10^3 spins. Then we show that pushed to the high-gain limit, KIPAs can serve as a `click'-detector for microwave wave packets by utilizing a hysteretic transition to a self-oscillating state. We calibrate the detector's sensitivity to be 3.7 zJ and then apply it to measurements of electron spin resonance. Finally, we demonstrate the suitability of the KIPA for generating squeezed vacuum states. Using a cryogenic noise source, we first confirm the KIPAs in our experiment to be quantum limited amplifiers. Then, using two KIPAs arranged in series, we make direct measurements of vacuum noise squeezing, where we generate itinerant squeezed states with minimum uncertainty more than 7 dB below the standard quantum limit. High quality factor resonators have also recently been used to achieve strong coupling between the spins of single electrons in gate-defined quantum dots and microwave photons. We present our efforts to achieve the equivalent goal for the 31P flip-flop qubit. In doing so, we confirm previous predictions that the superconducting material MoRe would produce magnetic field-resilient resonators and demonstrate that it has kinetic inductance equivalent to the popular material NbTiN

Optics in Our Time

Optics, Lasers, Photonics, Optical Devices; Quantum Optics; Popular Science in Physics; History and Philosophical Foundations of Physic

Intrinsic decoherence in superconducting quantum circuits

Decoherence and parameter fluctuations are two of the mayor obstacles for solid-state quantum computing. In this work, decoherence in superconducting qubits of the transmon type is investigated. For this purpose, a time-multiplexed measurement protocol was developed and applied in long-term measurements. The resulting simultaneous measurement of the qubit\u27s relaxation and dephasing rate, as well as its resonance frequency enables analysis of correlations between these parameters. A spectral noise analysis complements these measurements. Together, the results agree well with the interacting defect model of two-level-systems and yield information about the microscopic origin of the intrinsic decoherence mechanisms in Josephson qubits. Our measurements show inherent correlations between dephasing and fluctuations in qubit frequency on the timescale of seconds to days, which is attributed to the influence of individual defects, located close to conductor edges. Cross-correlation and spectral noise analysis confirm this interpretation and ascribe the source of fluctuation to interactions between thermal fluctuators and surface defects. Single defects reducing the coherence of qubits by up to one order of magnitude are a major challenge for future quantum computers. Non-tunable qubits are intrinsically insensitive to some decoherence channels and thus ideal for this fundamental analysis. However, to widen the focus and contrast the results of different material systems, we pursue the fabrication of voltage controlled gatemon qubits. In the course of this work, the theoretical foundation and technical implementation of transmon qubits based on regular Josephson weak links, and semiconducting nanowires is given. The experimental design and measurement setup are explained in detail. Our findings make continuous re-calibration a necessity in today\u27s solid-state qubits, although new materials or processing techniques might mitigate the problem. However, the results of this work imply that fundamental improvements of qubit parameter stability are necessary in order to realize scalable and coherent qubit circuits