Amplified spontaneous emission

About: Amplified spontaneous emission is a research topic. Over the lifetime, 6827 publications have been published within this topic receiving 118931 citations.

Low-temperature solution-processed wavelength-tunable perovskites for lasing

Abstract: Low-temperature solution-processed materials that show optical gain and can be embedded into a wide range of cavity resonators are attractive for the realization of on-chip coherent light sources. Organic semiconductors and colloidal quantum dots are considered the main candidates for this application. However, stumbling blocks in organic lasing include intrinsic losses from bimolecular annihilation and the conflicting requirements of high charge carrier mobility and large stimulated emission; whereas challenges pertaining to Auger losses and charge transport in quantum dots still remain. Herein, we reveal that solution-processed organic-inorganic halide perovskites (CH 3 NH 3 PbX 3 where X = Cl, Br, I), which demonstrated huge potential in photovoltaics, also have promising optical gain. Their ultra-stable amplified spontaneous emission at strikingly low thresholds stems from their large absorption coefficients, ultralow bulk defect densities and slow Auger recombination. Straightforward visible spectral tunability (390-790 nm) is demonstrated. Importantly, in view of their balanced ambipolar charge transport characteristics, these materials may show electrically driven lasing. © 2014 Macmillan Publishers Limited.

Principles of Lasers

Abstract: 1 Introductory Concepts.- 1.1 Spontaneous and Stimulated Emission, Absorption.- 1.1.1 Spontaneous Emission.- 1.1.2 Stimulated Emission.- 1.1.3 Absorption.- 1.2 The Laser Idea.- 1.3 Pumping Schemes.- 1.4 Properties of Laser Beams.- 1.4.1 Monochromaticity.- 1.4.2 Coherence.- 1.4.3 Directionality.- 1.4.4 Brightness.- Problems.- 2 Interaction of Radiation with Matter.- 2.1 Summary of Blackbody Radiation Theory.- 2.2 Absorption and Stimulated Emission.- 2.2.1 Rates of Absorption and Stimulated Emission.- 2.2.2 Allowed and Forbidden Transitions.- 2.2.3 Transition Cross Section, Absorption and Gain Coefficient.- 2.3 Spontaneous Emission.- 2.3.1 Semiclassical Approach.- 2.3.2 Quantum Electrodynamic Approach.- 2.3.3 Einstein Thermodynamic Treatment.- 2.3.4 Radiation Trapping, Superradiance, Superfluorescence, and Amplified Spontaneous Emission.- 2.4 Nonradiative Decay.- 2.5 Line Broadening Mechanisms.- 2.5.1 Homogeneous Broadening.- 2.5.2 Inhomogeneous Broadening.- 2.5.3 Combined Effect of Line Broadening Mechanisms.- 2.6 Saturation.- 2.6.1 Saturation of Absorption: Homogeneous Line.- 2.6.2 Gain Saturation: Homogeneous Line.- 2.6.3 Inhomogeneously Broadened Line.- 2.7 Degenerate Levels.- 2.8 Relation between Cross Section and Spontaneous Radiative Lifetime.- 2.9 Molecular Systems.- 2.9.1 Energy Levels of a Molecule.- 2.9.2 Level Occupation at Thermal Equilibrium.- 2.9.3 Radiative and Nonradiative Transitions.- Problems.- References.- 3 Pumping Processes.- 3.1 Introduction.- 3.2 Optical Pumping.- 3.2.1 Pumping Efficiency.- 3.2.2 Pump Light Distribution.- 3.2.3 Pumping Rate.- 3.3 Electrical Pumping.- 3.3.1 Electron Impact Excitation.- 3.3.2 Spatial Distribution of the Pump Rate.- 3.3.3 Pumping Efficiency.- 3.3.4 Excitation by (Near) Resonant Energy Transfer.- Problems.- References.- 4 Passive Optical Resonators.- 4.1 Introduction.- 4.2 Plane-Parallel Resonator.- 4.2.1 Approximate Treatment of Schawlow and Townes.- 4.2.2 Fox and Li Treatment.- 4.3 Confocal Resonator.- 4.4 Generalized Spherical Resonator.- 4.4.1 Mode Amplitudes, Diffraction Losses, and Resonance Frequencies.- 4.4.2 Stability Condition.- 4.5 Unstable Resonators.- Problems.- References.- 5 Continuous Wave and Transient Laser Behavior.- 5.1 Introduction.- 5.2 Rate Equations.- 5.2.1 Four-Level Laser.- 5.2.2 Three-Level Laser.- 5.3 CW Laser Behavior.- 5.3.1 Four-Level Laser.- 5.3.2 Three-Level Laser.- 5.3.3 Optimum Output Coupling.- 5.3.4 Reasons for Multimode Oscillation.- 5.3.5 Single-Line and Single-Mode Oscillation.- 5.3.6 Two Numerical Examples.- 5.3.7 Frequency Pulling and Limit to Monochromaticity.- 5.3.8 Lamb Dip and Active Stabilization of Laser Frequency.- 5.4 Transient Laser Behavior.- 5.4.1 Spiking Behavior of Single-Mode and Multimode Lasers.- 5.4.2 Q-Switching.- 5.4.2.1 Methods of Q-Switching.- 5.4.2.2 Operating Regimes.- 5.4.2.3 Theory of Q-Switching.- 5.4.2.4 A Numerical Example.- 5.4.3 Mode Locking.- 5.4.3.1 Methods of Mode Locking.- 5.4.3.2 Operating Regimes.- 5 5 Limits to the Rate Equations.- Problems.- References.- 6 Types of Lasers.- 6.1 Introduction.- 6.2 Solid-State Lasers.- 6.2.1 The Ruby Laser.- 6.2.2 Neodymium Lasers.- 6.3 Gas Lasers.- 6.3.1 Neutral Atom Lasers.- 6.3.2 Ion Lasers.- 6.3.2.1 Ion Gas Lasers.- 6.3.2.2 Metal Vapor Lasers.- 6.3.3 Molecular Gas Lasers.- 6.3.3.1 Vibrational-Rotational Lasers.- 6.3.3.2 Vibronic Lasers.- 6.3.3.3 Excimer Lasers.- 6.4 Liquid Lasers (Dye Lasers).- 6.4.1 Photophysical Properties of Organic Dyes.- 6.4.2 Characteristics of Dye Lasers.- 6.5 Chemical Lasers.- 6.6 Semiconductor Lasers.- 6.6.1 Photophysical Properties of Semiconductor Lasers.- 6.6.2 Characteristics of Semiconductor Lasers.- 6.7 Color-Center Lasers.- 6.8 The Free-Electron Laser.- 6.9 Summary of Performance Data.- Problems.- References.- 7 Properties of Laser Beams.- 7.1 Introduction.- 7.2 Monochromaticity.- 7.3 First-Order Coherence.- 7.3.1 Complex Representation of Polychromatic Fields.- 7.3.2 Degree of Spatial and Temporal Coherence.- 7.3.3 Measurement of Spatial and Temporal Coherence.- 7.3.4 Relation between Temporal Coherence and Monochromaticity.- 7.3.5 Some Numerical Examples.- 7.4 Directionality.- 7.5 Laser Speckle.- 7.6 Brightness.- 7.7 Higher-Order Coherence.- Problems.- References.- 8 Laser Beam Transformation.- 8.1 Introduction.- 8.2 Transformation in Space. Gaussian Beam Propagation.- 8.3 Transformation in Amplitude: Laser Amplification.- 8.4 Transformation in Frequency: Second-Harmonic Generation and Parametric Oscillation.- 8.4.1 Physical Picture.- 8.4.1.1 Second-Harmonic Generation.- 8.4.1.2 Parametric Oscillation.- 8.4.2 Analytical Treatment.- 8.4.2.1 Parametric Oscillation.- 8.4.2.2 Second-Harmonic Generation.- Problems.- References.- 9 Applications of Lasers.- 9.1 Introduction.- 9.2 Applications in Physics and Chemistry.- 9.3 Applications in Biology and Medicine.- 9.4 Material Working.- 9.5 Optical Communications.- 9.6 Measurement and Inspection.- 9.7 Thermonuclear Fusion.- 9.8 Information Processing and Recording.- 9.9 Military Applications.- 9.10 Holography.- 9.11 Concluding Remarks.- References.- Appendixes.- A Space-Dependent Rate Equations.- B Physical Constants.- Answers to Selected Problems.

Low-threshold amplified spontaneous emission and lasing from colloidal nanocrystals of caesium lead halide perovskites

Abstract: Metal halide semiconductors with perovskite crystal structures have recently emerged as highly promising optoelectronic materials. Despite the recent surge of reports on microcrystalline, thin-film and bulk single-crystalline metal halides, very little is known about the photophysics of metal halides in the form of uniform, size-tunable nanocrystals. Here we report low-threshold amplified spontaneous emission and lasing from ∼10 nm monodisperse colloidal nanocrystals of caesium lead halide perovskites CsPbX3 (X=Cl, Br or I, or mixed Cl/Br and Br/I systems). We find that room-temperature optical amplification can be obtained in the entire visible spectral range (440–700 nm) with low pump thresholds down to 5±1 μJ cm−2 and high values of modal net gain of at least 450±30 cm−1. Two kinds of lasing modes are successfully observed: whispering-gallery-mode lasing using silica microspheres as high-finesse resonators, conformally coated with CsPbX3 nanocrystals and random lasing in films of CsPbX3 nanocrystals. Lead halide perovskite colloidal nanocrystals have promising optoelectronic properties, such as high photoluminescence quantum yields and narrow emission linewidths. Here, the authors report low-threshold amplified spontaneous emission and two kinds of lasing in nanostructured caesium lead halide perovskites.

Modeling erbium-doped fiber amplifiers

Abstract: Erbium-doped fiber amplifiers are modeled using the propagation and rate equations of a homogeneous two-level laser medium. Numerical methods are used to analyze the effects of optical modes and erbium confinement on amplifier performance, and to calculate both the gain and amplified spontaneous emission (ASE) spectra. Fibers with confined erbium doping are completely characterized from easily measured parameters: the ratio of the linear ion density to fluorescence lifetime, and the absorption of gain spectra. Analytical techniques then allow accurate evaluation of gain, saturation, and noise in low-gain amplifiers (G >

Laser Diode Modulation and Noise

Abstract: 1 Introduction.- 2 Basic Laser Characteristics.- 2.1 Double heterostructure characteristics.- 2.2 Direct and indirect semiconductors.- 2.2.1 Energy- and momentum conservation.- 2.2.2 Semiconductor materials for direct and indirect semiconductors.- 2.3 Emission and absorption.- 2.3.1 Density of photon oscillation states.- 2.3.2 Principal mechanisms of radiative transitions.- 2.3.3 Carrier lifetime and lifetime of spontaneous emission.- 2.3.4 Gain and stimulated emission.- 2.4 Lasing characteristics of Fabry-Perot-type lasers.- 2.4.1 Lasing conditions.- 2.4.2 Dynamic characteristics of laser operation.- 2.4.3 Light current characteristics, threshold current and quantum efficiency.- 2.4.4 Basic laser structures.- 2.4.5 Modifications for the spontaneous emission term.- 2.5 Dynamic single-mode laser structures.- 2.5.1 DFB laser characteristics.- References.- 3 Longitudinal Mode Spectrum of Lasing Emission.- 3.1 Multimode rate equations.- 3.2 Spectral envelope for Fabry-1 Introduction.- 2 Basic Laser Characteristics.- 2.1 Double heterostructure characteristics.- 2.2 Direct and indirect semiconductors.- 2.2.1 Energy- and momentum conservation.- 2.2.2 Semiconductor materials for direct and indirect semiconductors.- 2.3 Emission and absorption.- 2.3.1 Density of photon oscillation states.- 2.3.2 Principal mechanisms of radiative transitions.- 2.3.3 Carrier lifetime and lifetime of spontaneous emission.- 2.3.4 Gain and stimulated emission.- 2.4 Lasing characteristics of Fabry-Perot-type lasers.- 2.4.1 Lasing conditions.- 2.4.2 Dynamic characteristics of laser operation.- 2.4.3 Light current characteristics, threshold current and quantum efficiency.- 2.4.4 Basic laser structures.- 2.4.5 Modifications for the spontaneous emission term.- 2.5 Dynamic single-mode laser structures.- 2.5.1 DFB laser characteristics.- References.- 3 Longitudinal Mode Spectrum of Lasing Emission.- 3.1 Multimode rate equations.- 3.2 Spectral envelope for Fabry-Perot-type lasers (linear gain).- 3.3 Influence of nonlinear gain on the spectral characteristics.- 3.3.1 Symmetric nonlinear gain.- 3.3.2 Asymmetric nonlinear gain.- 3.3.3 Nonlinear gain, conclusions.- References.- 4 Intensity-Modulation Characteristics of Laser Diodes.- 4.1 Modulation characteristics by studying single-mode rate equations.- 4.1.1 Turn-on delay.- 4.1.2 Rate equations, small signal analysis.- 4.1.3 Relaxation oscillation damping.- 4.1.4 Upper limits for the modulation bandwidth of laser diodes.- 4.2 Influence of lateral carrier diffusion on relaxation oscillation damping.- 4.3 Modulation bandwidth limits due to parasitic elements.- 4.4 Examples for high speed modulation of laser diodes.- 4.5 Modulation and longitudinal mode spectrum.- 4.5.1 Transient spectra of laser diodes.- 4.5.2 Lasing spectra under high speed modulation.- 4.5.3 Dynamic single-mode condition.- 4.6 Modulation with binary signals.- 4.7 Harmonic and intermodulation distortions (without fibre interaction).- 4.7.1 Harmonic and intermodulation distortions for low modulation frequencies.- 4.7.2 Harmonic and intermodulation distortions for high modulation frequencies.- References.- 5 Frequency-Modulation Characteristics of Laser Diodes.- 5.1 Relation between intensity-modulation and frequency modulation.- 5.2 Current/frequency-modulation characteristics.- 5.3 Chirp effects in directly modulated laser diodes.- 5.3.1 Spectral line broadening due to laser chirping.- 5.3.2 Chirp-reduction by proper pulse shaping.- 5.3.3 Time-bandwidth product of chirped pulses.- 5.3.4 Transmission of chirped pulses over single-mode fibres.- 5.4 Possibilities of modifying the chirp parameter ?.- 5.4.1 Dispersion of the chirp parameter ?.- 5.4.2 Chirp of laser diodes, coupled to optical cavities.- References.- 6 Instabilities and Bistability in Laser Diodes.- 6.1 Repetitive self-pulsations due to lateral instabilities.- 6.2 Instability and bistability in laser diodes with segmented contacts.- References.- 7 Noise Characteristics of Solitary Laser Diodes.- 7.1 Relative intensity noise (RIN).- 7.1.1 Basic properties of noise signals.- 7.1.2 Definition and measurement of RIN.- 7.1.3 Requirement of RIN for intensity modulated systems.- 7.2 Introduction of the spontaneous emission noise.- 7.3 Intensity noise of laser diodes.- 7.3.1 Intensity noise of laser diodes by studying single-mode rate equations.- 7.3.2 Mode partition noise.- 7.3.3 Mode partition noise analysis for nearly single-mode lasers.- 7.3.4 Mode-hopping noise.- 7.3.5 1/f-intensity noise.- 7.4 Statistics of intensity noise.- 7.4.1 Statistics of amplified spontaneous emission.- 7.4.2 Probability density distribution for the total laser light output.- 7.4.3 Statistics of mode partition noise.- 7.4.4 Turn-on jitter in laser diodes.- 7.5 Mode partition noise for the transmission of pulse-code modulated (PCM)-signals.- 7.5.1 Multimode lasers.- 7.5.2 The mode partition coefficient k.- 7.5.3 Nearly single-mode lasers.- 7.6 Phase and frequency noise.- 7.6.1 Phase and frequency noise characterization in general.- 7.6.2 Spectral line shape for white frequency noise.- 7.6.3 Spectral line shape for 1/f-frequency noise.- 7.6.4 Frequency noise and spectral linewidth for single-mode laser diodes.- 7.6.5 Power-independent contribution to the linewidth of laser diodes.- 7.6.6 Correlation between FM-noise and AM-noise.- References.- 8 Noise in Interferometers Including Modal Noise and Distortions.- 8.1 Noise in interferometers.- 8.1.1 Complex degree of coherence.- 8.1.2 Interferometric noise analysis for single-mode lasers.- 8.1.3 Interferometric set-ups for measuring the linewidth and the degree of coherence.- 8.1.4 Interferometric noise analysis for multimode lasers.- 8.2 Modal noise.- 8.2.1 Modal noise for monochromatic light sources.- 8.2.2 Modal noise for single-mode lasers with finite spectral linewidth.- 8.2.3 Modal noise for multimode laser diodes.- 8.2.4 Modal distortions.- 8.3 Modal noise and distortions in single-mode fibres.- References.- 9 Semiconductor Lasers with Optical Feedback.- 9.1 Amplitude and phase conditions for laser diodes with external cavities.- 9.1.1 Short external reflectors for longitudinal mode stabilization.- 9.1.2 Emission frequency shifts due to optical feedback.- 9.1.3 Single external cavity mode condition.- 9.1.4 Spectral linewidth for laser diodes with external optical feedback.- 9.2 Dynamics of laser diodes with external reflections.- 9.2.1 Derivation of the time-dependent electric field.- 9.2.2 Modulation characteristics of external-cavity lasers.- 9.3 Laser diodes with distant reflections.- 9.3.1 Classification of feedback regimes.- 9.3.2 Phase and frequency noise of laser diodes with distant reflectors.- 9.3.3 Intensity noise in laser diodes with distant reflectors.- 9.3.4 Coherence collapse.- 9.3.5 Tolerable feedback levels.- References.- 10 Laser Diodes with Negative Electronic Feedback.- 10.1 Modulation characteristics of laser diodes with negative electronic feedback.- 10.2 Linewidth narrowing and phase noise reduction with negative electronic feedback.- References.- 11 Circuitry for Driving the Laser Diode.- 11.1 Schemes for stabilizing the bias current.- 11.2 Laser drivers with optoelectronic integration.- References.