Recent advances in solid-state organic lasers

Organic solid-state lasers are reviewed, with a special emphasis on works published during the last decade. Referring originally to dyes in solid-state polymeric matrices, organic lasers also include the rich family of organic semiconductors, paced by the rapid development of organic light emitting diodes. Organic lasers are broadly tunable coherent sources are potentially compact, convenient and manufactured at low-costs. In this review, we describe the basic photophysics of the materials used as gain media in organic lasers with a specific look at the distinctive feature of dyes and semiconductors. We also outline the laser architectures used in state-of-the-art organic lasers and the performances of these devices with regard to output power, lifetime, and beam quality. A survey of the recent trends in the field is given, highlighting the latest developments in terms of wavelength coverage, wavelength agility, efficiency and compactness, or towards integrated low-cost sources, with a special focus on the great challenges remaining for achieving direct electrical pumping. Finally, we discuss the very recent demonstration of new kinds of organic lasers based on polaritons or surface plasmons, which open new and very promising routes in the field of organic nanophotonics

A stable, single-photon emitter in a thin organic crystal for application to quantum-photonic devices

Single organic molecules offer great promise as bright, reliable sources of identical single photons on demand, capable of integration into solid-state devices. It has been proposed that such molecules in a crystalline organic matrix might be placed close to an optical waveguide for this purpose, but so far there have been no demonstrations of sufficiently thin crystals, with a controlled concentration of suitable dopant molecules. Here we present a method for growing very thin anthracene crystals from super-saturated vapour, which produces crystals of extreme flatness and controlled thickness. We show how this crystal can be doped with a widely adjustable concentration of dibenzoterrylene (DBT) molecules and we examine the optical properties of these molecules to demonstrate their suitability as quantum emitters in nanophotonic devices. Our measurements show that the molecules are available in the crystal as single quantum emitters, with a well-defined polarisation relative to the crystal axes, making them amenable to alignment with optical nanostructures. We find that the radiative lifetime and saturation intensity vary little within the crystal and are not in any way compromised by the unusual matrix environment. We show that a large fraction of these emitters are able to deliver more than $10^{12}$ photons without photo-bleaching, making them suitable for real applications.Comment: 12 pages, 10 figures, comments welcom

Design and Characterisation of Blue Polymer Lasers

Semiconducting polymers have attracted considerable attention as novel gain materials for laser devices. An important future target in this context is the realisation of a thin- film polymer laser diode. Since inorganic semiconductors are amongst the most important devices in modern optoelectronic technology, there is a lot of interest in achieving electrically pumped laser action in organic semiconductors as a way to broadly tunable lasers covering the whole visible spectrum and producing low-cost laser sources for optical networks. This thesis reports the results of a study on the design and characterisation of optically pumped blue and violet emitting polymer lasers. The laser devices are based on a range of materials belonging to the polyfluorene family of conjugated polymers which generally show efficient, low threshold stimulated emission. For future electrically pumped polymer lasers, a further reduction of the threshold is crucial since a low threshold fluence directly translates into low current densities. The optical properties of in total three polyfluorene copolymers are investigated. Lasers based on one of these copolymers are optically-pumped and emission wavelength tuning is demonstrated by altering both grating period and gain polymer thickness, allowing us to cover a part of the spectral region between the blue and ultra-violet that has not been addressed yet by organic semiconductor lasers. Furthermore, a systematic numerical study of the optical environment on the performance of blue emitting lasers on conducting DFB resonators is presented, which is followed by a demonstration of optically-pumped polymer lasers based on ITO gratings. Finally, the results of a systematic study into optically pumped blue emitting polymer lasers based on circular Bragg (CBR) resonators is reported. An optimised design strategy is implemented and involves matching the grating pro files with the nulls and maxima from the Bessel functions that represent the radial distribution of the fi eld in a circular resonator

Organic lasers and nanostructred organic films for hybrid integration

Light emitting polymers (LEPs) are a promising category of organic materials for photonic applications owing to their potential for simple fabrication and availability of materials emitting across the whole visible spectrum. LEPs are already exploited commercially in the case organic light emitting diodes and their interesting properties for colour conversion and as laser gain material are under investigation. To keep the LEPs' benefit of simple and low-cost fabrication, integration onto inorganic semiconductor devices such as in particular gallium nitride light emitting diodes (LEDs) is an important research topic. In this thesis, developments towards integration of organic devices onto micro-pixellated ip-chip LEDs are presented. This particular format may be beneficial for applications such as displays, various sensing schemes and data transmission owing to spatio-temporal control, high modulation bandwidths and potential for simple integration with complementary metal oxide semiconductor electronics. The properties of LEP films as optical gain medium were assessed on smooth and corrugated substrates. In the former case, random laser action (RL) was observed which is attributed to the high optical gain delivered by these materials. Arguments are presented suggesting that RL may be very common in high gain media. In the latter case, mechanically flexible distributed feedback lasers were fabricated in a very simple way and their properties including operational lifetime were characterised. Nano-patterned LEP films for colour conversion of LED light exhibited strong modification of the LEP emission due to the photonic crystal (PhC) effect of the periodic pattern. PhCs allow tailoring of the emission properties by appropriate design of the nano-pattern and they can be created relatively easy in organic films. Furthermore, the modulation bandwidth of an organic PhC film excited by micro-LEDs was measured to be 168 MHz and was mainly limited by the inorganic LED. This underpins the potential of LEPs for communications applications. The suitability of micro-LEDs in flip-chip format as pump source for organic semiconductor lasers was investigated. For this purpose, stripe-shaped arrays of micro-LEDs were developed that were employed for the demonstration of the first micro-LED pumped polymer laser.Light emitting polymers (LEPs) are a promising category of organic materials for photonic applications owing to their potential for simple fabrication and availability of materials emitting across the whole visible spectrum. LEPs are already exploited commercially in the case organic light emitting diodes and their interesting properties for colour conversion and as laser gain material are under investigation. To keep the LEPs' benefit of simple and low-cost fabrication, integration onto inorganic semiconductor devices such as in particular gallium nitride light emitting diodes (LEDs) is an important research topic. In this thesis, developments towards integration of organic devices onto micro-pixellated ip-chip LEDs are presented. This particular format may be beneficial for applications such as displays, various sensing schemes and data transmission owing to spatio-temporal control, high modulation bandwidths and potential for simple integration with complementary metal oxide semiconductor electronics. The properties of LEP films as optical gain medium were assessed on smooth and corrugated substrates. In the former case, random laser action (RL) was observed which is attributed to the high optical gain delivered by these materials. Arguments are presented suggesting that RL may be very common in high gain media. In the latter case, mechanically flexible distributed feedback lasers were fabricated in a very simple way and their properties including operational lifetime were characterised. Nano-patterned LEP films for colour conversion of LED light exhibited strong modification of the LEP emission due to the photonic crystal (PhC) effect of the periodic pattern. PhCs allow tailoring of the emission properties by appropriate design of the nano-pattern and they can be created relatively easy in organic films. Furthermore, the modulation bandwidth of an organic PhC film excited by micro-LEDs was measured to be 168 MHz and was mainly limited by the inorganic LED. This underpins the potential of LEPs for communications applications. The suitability of micro-LEDs in flip-chip format as pump source for organic semiconductor lasers was investigated. For this purpose, stripe-shaped arrays of micro-LEDs were developed that were employed for the demonstration of the first micro-LED pumped polymer laser

Highly efficient polaritonic light-emitting diodes with angle-independent narrowband emission

Authors acknowledge funding by the Volkswagen Foundation (no. 93404; M.C.G.), the Leverhulme Trust (RPG-2017-213; M.C.G), the European Research Council under the European Union Horizon 2020 Framework Programme (FP/2014-2020)/ERC grant agreement no. 640012 (ABLASE; M.C.G) and the Alexander von Humboldt Foundation (Humboldt Professorship; M.C.G.). A.M. acknowledges funding through an individual fellowship of the Deutsche Forschungsgemeinschaft (404587082; A.M.) and from the European Union’s Horizon 2020 research and innovation programme under Marie Skłodowska-Curie grant agreement no. 101023743 (PolDev; A.M.).Angle-independent narrowband emission is required for many optoelectronic devices, ranging from high-definition displays to sensors. However, emerging materials for electroluminescent devices, such as organics and perovskites, show spectrally broad emission due to intrinsic disorder. Coupling this emission to an optical resonance reduces the linewidth, but at the cost of inheriting the severe angular dispersion of the resonator. Strongly coupling a dispersionless exciton state to a narrowband optical microcavity could overcome this issue; however, electrically pumped emission from the resulting polaritons is typically hampered by poor efficiencies. Here we present a universal concept for polariton-based emission from organic light-emitting diodes by introducing an assistant strong coupling layer, thereby avoiding quenching-induced efficiency losses. We realize red- and green-emitting, narrowband (full-width at half-maximum of less than 20 nm) and spectrally tunable polaritonic organic light-emitting diodes with up to 10% external quantum efficiency and high luminance (>20,000 cd m−2 at 5 V). By optimizing cavity detuning and coupling strength, we achieve emission with ultralow dispersion (<10 nm spectral shift at 60° tilt). These results may have wide-reaching implications for on-demand polariton emission and demonstrate the practical relevance of strong light–matter coupling for next-generation optoelectronics, particularly display technology.Publisher PDFPeer reviewe

Quantum Dot-Based Light Emitting Diodes (QDLEDs): New Progress

In recent years, the display industry has progressed rapidly. One of the most important developments is the ability to build flexible, transparent and very thin displays by organic light emitting diode (OLED). Researchers working on this field try to improve this area more and more. It is shown that quantum dot (QD) can be helpful in this approach. In this chapter, writers try to consider all the studies performed in recent years about quantum dot-based light emitting diodes (QDLEDs) and conclude how this nanoparticle can improve performance of QDLEDs. In fact, the existence of quantum dots in QDLEDs can cause an excellent improvement in their efficiency and lifetime resulted from using improved active layer by colloidal nanocrystals. Finally, the recent progresses on the quantum dot-based light emitting diodes are reviewed in this chapter, and an important outlook into challenges ahead is prepared

Simple and scalable growth of AgCl nanorods by plasma-assisted strain relaxation on flexible polymer substrates

Implementing nanostructures on plastic film is indispensable for highly efficient flexible optoelectronic devices. However, due to the thermal and chemical fragility of plastic, nanostructuring approaches are limited to indirect transfer with low throughput. Here, we fabricate single-crystal AgCl nanorods by using a Cl 2 plasma on Ag-coated polyimide. Cl radicals react with Ag to form AgCl nanorods. The AgCl is subjected to compressive strain at its interface with the Ag film because of the larger lattice constant of AgCl compared to Ag. To minimize strain energy, the AgCl nanorods grow in the [200] direction. The epitaxial relationship between AgCl (200) and Ag (111) induces a strain, which leads to a strain gradient at the periphery of AgCl nanorods. The gradient causes a strain-induced diffusion of Ag atoms to accelerate the nanorod growth. Nanorods grown for 45 s exhibit superior haze up to 100% and luminance of optical device increased by up to 33%. ? The Author(s) 2017.114Ysciescopu

量子ドット太陽電池とペロブスカイト太陽電池における界面エンジニアリングと界面電荷移動ダイナミクス

電気通信大学201

An account on structure, synthesis and application of polythiophene and swelling behaviour of non-conducting polymers

Polymer matrixes are studied extensively due to their unique chemical and mechanical properties and a wide field of applications. Conducting polymers are utilized as the active materials for solid-state devices viz. batteries, LED and sensors. The present article discusses the application of polythiophene as an active material for energy active devices. In addition, the authors have worked on enhancing the ionic conduction of non-conducting polymers like poly[ethylene oxide]. Solvent diffusion mechanism of non-conducting polymer–salt composite is nonlinear in nature. Swelling tendency of polymer composite can be influenced to physical, chemical and morphological behaviour. Ionic conductivity phenomena of polymer–salt composite are also influenced by the solvent