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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Output Performance of an Incoherently Pumped Random Fiber Laser Dependence on the Pump Bandwidth
摘要： The output performance of an incoherently pumped random fiber laser (RFL) dependence on the pump bandwidth has been investigated. This work could provide a new pumping scheme for the high power RFLs. relatively broad pump bandwidth can also help suppress the spectral broadening while maintaining an ultra-high spectral purity. The results reveal that the increment of pump bandwidth can affect the gain characteristics, nonlinear effects and eventually the output performance. This work could provide a new pumping scheme for the high power RFLs.
关键词： Amplified spontaneous emission,Optical signal-to-noise ratio,Random fiber laser
更新于2025-09-16 10:30:52
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Role of spontaneous emission in the formation of the steady-state optical spectrum of a diode laser
摘要： Based on Maxwell’s equations, we derive a van der Pol-type equation for self-oscillations in the cavity of a diode laser. Its solution is self-oscillations (lasing) even in the absence of spontaneous emission. This solution differs fundamentally from solutions obtained using rate equations containing an additional term in the form of spontaneous emission intensity. Taking into account spontaneous emission in the van der Pol model makes calculation results more realistic and allows one to find parameters characterising diode laser output coherence, including the spectral densities of laser light amplitude and phase fluctuations.
关键词： diode lasers,spontaneous emission,fluctuations in parameters
更新于2025-09-16 10:30:52
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Type-II AlInN/ZnGeN <sub/>2</sub> quantum wells for ultraviolet laser diodes
摘要： We propose a type-II AlInN/ZnGeN2 quantum well (QW) structure serving as the active region for ultraviolet (UV) laser diodes. A remarkably low threshold current density can be achieved using the type-II AlInN/ZnGeN2 QW structure, providing a pathway for the realization of electrically-driven nitride-based semiconductor UV laser diodes. ZnGeN2 has both a very similar lattice constant and bandgap to GaN. Its large band offsets with GaN enable the potential of serving as a hole confinement layer to increase the electron-hole wavefunction overlap in the active region. In this study, we investigate the spontaneous emission and gain properties of type-II AlInN/ZnGeN2 QWs with different ZnGeN2 layer thicknesses. Our findings show that the use of ZnGeN2 layers in the active region provides a significant improvement in hole carrier confinement, which results in ～5 times enhancement of the electron-hole wave function overlap. Such an enhancement provides the ability to achieve a significant increase (～6 times) in the spontaneous emission rate and material gain, along with a remarkable reduction in threshold carrier density compared to the conventional AlGaN-based QW design, which is essential for practical UV laser diodes.
关键词： ultraviolet laser diodes,material gain,AlInN/ZnGeN2,Type-II quantum wells,spontaneous emission
更新于2025-09-16 10:30:52
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Improving the performance of light-emitting diodes via plasmonic-based strategies
摘要： Light-emitting diodes (LEDs), featuring long lifetime, small size, and low energy consumption, are increasingly popular for displays and general light sources. In the past decades, new light-emitting materials and novel device configurations are being continuously investigated to obtain highly efficient LEDs. Nevertheless, the unsatisfying external quantum efficiency severely limits their commercial implementation. Among all the approaches to boost the efficiency of LEDs, the incorporation of plasmonic structures exhibits great potential in increasing the spontaneous emission rates of emitters and improving the light extraction efficiency. In this Perspective, the methods to deal with challenges in quantum-well-based LEDs and organic LEDs by employing plasmonic materials are described, the mechanisms of plasmonic-based strategies to improve the light generation and extraction efficiency are discussed, and the plasmonic control over directional emission of phosphors is introduced as well. Moreover, important issues pertaining to the design, fabrication, and manipulation of plasmonic structures in LEDs to optimize the device performance, as well as the selection roles in finding appropriate plasmonic materials and structures for desired LED devices, are explained. This perspective lists the challenges and opportunities of plasmonic LEDs, with the aim of providing some insights into the future trends of plasmonic LEDs.
关键词： spontaneous emission rates,light-emitting diodes,light extraction efficiency,external quantum efficiency,plasmonic structures
更新于2025-09-16 10:30:52
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Optical Fiber Communications (Principles and Applications) || Optical Sources and Transmitters
摘要： An optical source provides the electrical–optical signal conversion efficiently that enables the optical output to be effectively coupled and launched into the optical fiber. It is an active device that requires external power supply for operation in optical fiber communications. This chapter begins with the major requirements or desirable properties for the optical source in general. Light emitting diodes (LEDs) and injection laser diodes (ILDs) {which are simply known as laser diodes (LDs)} are the most popular semiconductor optical sources. LED is an incoherent optical source. It can support many propagation modes of light within its structure. This is the reason why is it employed as a multimode optical source. Whereas, ILD is a highly coherent optical source that has a very narrow spectrum and fast response time. Thus, it is mostly used as a single-mode optical source in single-mode propagation requirements. In this chapter the basic principle of operation of both these optical sources along with their major structures and configurations are described. For producing the light signal, the emission can be a spontaneous emission, as in the case of LED, or a stimulated emission as in the case of ILD. The spontaneous emission takes place when electrons are brought to a very high energy level, and an unstable state. The electrons will return spontaneously (within few picoseconds) to a stable state, and will consequently emit photons.. The optical wavelength is determined by the amount of energy the electron releases. A laser diode operates with stimulated emission in which the electrons enters and stays in a high-energy state for a few microseconds. Then it changes its state spontaneously. During this state, the photon stimulates so as to emit the energy in the form of another photon. Thus, the laser produces the light signal. Finally, a typical functional block schematic including features and operations of optical transmitter is covered to assess the utility of optical sources.
关键词： LED,spontaneous emission,optical transmitter,optical sources,stimulated emission,laser diode,optical fiber communications
更新于2025-09-12 10:27:22
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Rate equations for the diode laser and their applicability area
摘要： Taking into account spontaneous emission by adding its intensity in the form of a constant term to the laser emission intensity in rate equations is shown to be an inadequate approach. The use of rate equations without equations for phases of waves is limited to problems in which light is characterised by its total intensity, without its spectral composition. Such equations are incapable of adequately modelling the emission spectrum of diode lasers.
关键词： diode lasers,spontaneous emission,rate equations
更新于2025-09-12 10:27:22
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Polarized Species in an Organic Semiconductor Laser
摘要： Meeting the challenge of direct electrically driven organic semiconductor lasers (OSLs), the design of OSL materials is under concern. Polarized species generally exist in conjugated organic materials and play an important role in the photophysics procedure; therefore, understanding these species is beneficial to designing novel OSL materials. Here, we use the amplified spontaneous emission effect as a medium to reveal a carbazole-benzothiadiazole-based polarized species that induced by charge transfer process. Spectroscopic analysis confirms that this polarized species that acted as a CT pair defect brings negative influence to both the ASE stability and solid state fluorescent quantum yield. It inspires us to be cautious for some specific molecular group combinations when designing OSL materials.
关键词： polaron,organic laser,carbazole,amplified spontaneous emission,charge transfer
更新于2025-09-12 10:27:22
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D‐A Type Pendant Conjugated Molecules based on Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers
摘要： A set of fluorene-capped pendant conjugated molecules (T-m and T-p), which consist of triazine center with three carbazole substituents as the donor-acceptor (D-A) type pendant structure, were designed, synthesized and investigated as gain media for organic semiconductor lasers (OSLs). Particularly, varying the capping positions of the fluorene units onto the pendant core structures results in obviously different intramolecular charge transfer (ICT) properties, whereas T-m manifested depressed ICT characteristic and high fluorescence quantum yield. The lowest ASE threshold in neat films was recorded of 1.9 μJ/cm2 for T-m and 83.8 μJ/cm2 for T-p, respectively, which indicated that depressed ICT characteristic in the case of T-m helps to enhance the ASE properties. Remarkably, the ASE threshold remained almost unchanged and the ASE spectra showed very small shifts (within 1 nm) for T-m with film samples annealed up to 180°C in open air. In contrast, its linear counterpart 2FEtCz-m showed obviously increased ASE threshold upon annealing above 100°C. The results suggest that the selective construction of conjugated pendant molecules with depressed ICT characteristics is beneficial for finely modulating the optical and electrical properties as well as improving the thermostability and photostability, which manifests the great potentials as robust gain media for OSLs.
关键词： Organic semiconductors,Amplified spontaneous emission (ASE),Organic semiconductor lasers,Pendant conjugated molecules,Intramolecular charge transfer (ICT)
更新于2025-09-12 10:27:22
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Enhanced Energy Transfer in Doped Bifluorene Single Crystals: Prospects for Organic Lasers
摘要： Organic single crystals with long-range molecular order ensure enhanced carrier mobility and stability as well as emission outcoupling, which makes them attractive as gain medium for electrically pumped organic lasers. Unfortunately, effects of excitonic coupling introduce losses degrading optical performance in crystals, hence higher lasing thresholds are observed compared to amorphous films. Here, crystal doping strategy is investigated as a method to avoid pronounced reabsorption and annihilation losses associated with J-type excitonic coupling, while taking advantage of enhanced exciton transport for efficient energy transfer. Bifluorene-based derivatives linked with acetylene and ethylene rigid bridges are suitable as host and dopant system forming high-quality crystals doped at various concentrations (0.5–11.0%). Enhanced exciton transport in host crystal mediates picosecond host–dopant energy transfer enabling 100% transfer efficiency at lower doping concentrations compared to amorphous films. Amplified spontaneous emission threshold of 1.9 μJ cm?2 in 3.5% doped crystal is enabled by minimized exciton annihilation and emission reabsorption losses at optimal doping concentration.
关键词： long-range energy transport,organic single crystals,organic laser gain materials,amplified spontaneous emission,F?rster resonant energy transfer
更新于2025-09-12 10:27:22
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Low‐Threshold Amplified Spontaneous Emission and Lasing from Thick‐Shell CdSe/CdS Core/Shell Nanoplatelets Enabled by High‐Temperature Growth
摘要： Colloidal semiconductor nanoplatelets (NPLs) have recently emerged as highly promising optical gain medium because of their superior optical properties. Here, the shell-thickness-dependent optical gain properties of CdSe/CdS core/shell NPLs synthesized by high-temperature growth are systematically investigated for the first time. The core/shell NPLs show the increased quantum yields and enhanced photostability as well as clear reduced emission blinking, thanks to the preferable passivation of nonradiative surface defects by the growth of the high-quality CdS shells under high reaction temperature. Meanwhile, the amplified spontaneous emission (ASE) performance of CdSe/CdS NPLs indicates a nonmonotonic dependence on the shell thickness. The ASE threshold is achieved as low as ≈4.4 μJ cm?2 for thick-shell NPLs with six monolayer CdS shells, and exhibiting ultrafast transient dynamics process (≈11 ps). Besides, an extremely long lifetime (>800 ps) and large bandwidth (>140 nm) of optical gain are observed by employing ultrafast transient absorption spectroscopy. Finally, a thick-shell NPLs vertical cavity surface-emitting laser is developed, which demonstrates spatially directional single-mode operation with an ultralow lasing threshold of ≈1.1 μJ cm?2. These excellent results are attributed to the remarkable optical gain performance of core/shell NPLs and represent an important step toward practical NPL laser devices.
关键词： CdSe/CdS,amplified spontaneous emission,nanoplatelets,vertical cavity surface-emitting laser,optical gain
更新于2025-09-12 10:27:22