Showing papers on "Amplified spontaneous emission published in 2016"

A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films.

Abstract: Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 μJ/cm2. The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%...

Radiative Monomolecular Recombination Boosts Amplified Spontaneous Emission in HC(NH2)2SnI3 Perovskite Films

Abstract: Hybrid metal-halide perovskites have potential as cost-effective gain media for laser technology because of their superior optoelectronic properties. Although lead-halide perovskites have been most widely studied to date, tin-based perovskites have been proposed as a less toxic alternative. In this Letter, we show that amplified spontaneous emission (ASE) in formamidinium tin triiodide (FASnI3) thin films is supported by an observed radiative monomolecular charge recombination pathway deriving from its unintentional doping. Such a radiative component will be active even at the lowest charge-carrier densities, opening a pathway for ultralow light-emission thresholds. Using time-resolved THz photoconductivity analysis, we further show that the material has an unprecedentedly high charge-carrier mobility of 22 cm2 V–1 s–1 favoring efficient transport. In addition, FASnI3 exhibits strong radiative bimolecular recombination and Auger rates that are over an order of magnitude lower than for lead-halide perovski...

Highly stable solution processed metal-halide perovskite lasers on nanoimprinted distributed feedback structures

Abstract: We report on the performance and stability of distributed feedback lasers based on the solution-processed methylammonium lead iodide perovskite (CH3NH3PbI3). The CH3NH3PbI3 layers are processed via solution-casting in ambient atmosphere onto nanoimprinted second order Bragg gratings. This way, we achieve highly polarized surface-emitted lasing at room temperature with a linewidth of less than 0.2 nm and a laser threshold of 120 kW/cm2. The lasing is stable; no change in the laser emission within 15 h of pulsed excitation with a repetition rate of 1 kHz (corresponding to >5 × 107 pulses) is observed, exceeding the stability achieved for solution processed organic semiconductor lasers. Furthermore, adjustment of the grating period allowed the lasing wavelength to be varied over the entire bandwidth of the amplified spontaneous emission (between 781 and 794 nm). The fabrication process of nanoimprinting followed by solution-casting of the gain material demonstrates that stable CH3NH3PbI3 lasers are compatible with scalable production technologies and offers a route towards electrically pumped diode architectures.

Photovoltaic and Amplified Spontaneous Emission Studies of High-Quality Formamidinium Lead Bromide Perovskite Films

Abstract: This study demonstrates the formation of extremely smooth and uniform formamidinium lead bromide (CH(NH2)(2)PbBr3 = FAPbBr(3)) films using an optimum mixture of dimethyl sulfoxide and N,N-dimethylformamide solvents. Surface morphology and phase purity of the FAPbBr(3) films are thoroughly examined by field emission scanning electron microscopy and powder X-ray diffraction, respectively. To unravel the photophysical properties of these films, systematic investigation based on time-integrated and time-dependent photoluminescence studies are carried out which, respectively, bring out relatively lower nonradiative recombination rates and long lasting photogenerated charge carriers in FAPbBr(3) perovskite films. The devices based on FTO/TiO2/FAPbBr(3)/spiro-OMeTAD/Au show highly reproducible open-circuit voltage (V-oc) of 1.42 V, a record for FAPbBr(3)-based perovskite solar cells. V-oc as a function of illumination intensity indicates that the contacts are very selective and higher V-oc values are expected to be achieved when the quality of the FAPbBr(3) film is further improved. Overall, the devices based on these films reveal appreciable power conversion efficiency of 7% under standard illumination conditions with negligible hysteresis. Finally, the amplified spontaneous emission (ASE) behavior explored in a cavity-free configuration for FAPbBr(3) perovskite films shows a sharp ASE threshold at a fluence of 190 mu J cm(-2) with high quantum efficiency further confirming the high quality of the films.

Optical gain in GaAsBi/GaAs quantum well diode lasers

Abstract: Optical gain, absorption and spontaneous emission spectra for GaAs 0.978 Bi 0.022 /GaAs laser diodes are measured experimentally and compared with theory. Internal optical losses of 10–15 cm−1 and peak modal gain of 24 cm−1 are measured at threshold. The results of calculations showed excellent agreement with the experiment, key for future laser design.

Dominant factors limiting the optical gain in layered two-dimensional halide perovskite thin films

Abstract: Semiconductors are ubiquitous gain media for coherent light sources. Solution-processed three-dimensional (3D) halide perovskites (e.g., CH3NH3PbI3) with their outstanding room temperature optical gain properties are the latest members of this family. Their two-dimensional (2D) layered perovskite counterparts with natural multiple quantum well structures exhibit strong light–matter interactions and intense excitonic luminescence. However, despite such promising traits, there have been no reports on room temperature optical gain in 2D layered perovskites. Herein, we reveal the challenges towards achieving amplified spontaneous emission (ASE) in the archetypal (C6H5C2H4NH3)2PbI4 (or PEPI) system. Temperature-dependent transient spectroscopy uncovers the dominant free exciton trapping and bound biexciton formation pathways that compete effectively with biexcitonic gain. Phenomenological rate equation modeling predicts a large biexciton ASE threshold of ∼1.4 mJ cm−2, which is beyond the damage threshold of these materials. Importantly, these findings would rationalize the difficulties in achieving optical gain in 2D perovskites and provide new insights and suggestions for overcoming these challenges.

Excitation Wavelength Independence: Toward Low-Threshold Amplified Spontaneous Emission from Carbon Nanodots.

Abstract: Carbon nanodots (CDs) are known to be a superior type of lasing material due to their low cost, low toxicity, high photostability, and photobleaching resistance. Significant attention has been paid to synthesizing CDs with high fluorescence quantum yields (FLQYs) to achieve higher optical gains. In this report, we reveal that excitation wavelength-independent (λex-independent) photoluminescence (PL) characteristics, rather than high FLQYs, should be given priority to realize CD-based light amplification. CDs with excitation wavelength-dependent (λex-dependent) PL characteristics and FLQYs as high as 99% and 96% were found not to exhibit amplified spontaneous emission (ASE), while those with λex-independent PL characteristics and FLQYs of only 38% and 82% realized ASE with low thresholds. The difficulty of achieving ASE using CDs with λex-dependent PL characteristics is likely attributable to their high contents of C–O–H or C–O–C groups. These groups can induce numerous localized electronic states within t...

A Highly Crystalline and Wide-Bandgap Polydiarylfluorene with β-Phase Conformation toward Stable Electroluminescence and Dual Amplified Spontaneous Emission.

Abstract: Bulky conjugated polymers with high crystallinity is the prerequisite for the overall improvement of performance in wide-bandgap semiconductors, including charge transport, photoluminescence quantum yield, processing reliability, and stability. Herein, we report a stable β-phase film of bulky polydiarylfluorene (PODPF) preparing by thermal annealing at ∼220 °C. The β-phase conformation and regular molecular packing are confirmed by UV-vis, photoluminescence (PL), Raman spectra, and grazing incidence X-ray diffraction (GIXD), respectively. Polymer light-emitting diodes (PLEDs) with crystalline and β-phase film serving as the active layer exhibit higher current efficiency of 1.8 cd/A (6.0 V) and more stable electroluminescence over the amorphous one. Surprisingly, mixed conformations in PODPF film produce dually tunable amplified spontaneous emission (ASE) at 463 and 482 nm. Polydiarylfluorenes with quasi-planar conformation will be a promising candidate for the next-generation gain medium toward a broadly ...

Two-Dimensional Organic Single Crystals with Scale Regulated, Phase-Switchable, Polymorphism-Dependent, and Amplified Spontaneous Emission Properties

Abstract: The successful preparation of two-dimensional (2D) single crystals can promote the development of organic optoelectronic devices with excellent performance. A Schiff base compound salicylidene(4-dimethylamino)aniline with aggregation induced emission (AIE) property was employed as the building block to fabricate 2D thin single crystal plates with scales from around 50 μm to 1.5 cm. Yellow and red emissive polymorphs were concomitantly obtained during crystallization. The single-crystal-to-single-crystal (SC-to-SC) transformation from yellow polymorph to red one was demonstrated. Furthermore, both polymorphs exhibited amplified spontaneous emission (ASE) properties. Interestingly, the red polymorph displayed size-dependent ASE characteristics. The larger red polymorph showed near-infrared ASE with maximum at 706 nm, whereas the smaller one presented red ASE with maximum at 610 nm. These results suggest that the different scale single crystalline thin films with perfect optoelectronic properties may be fabr...

Gb/s One-Time-Pad Data Encryption With Synchronized Chaos-Based True Random Bit Generators

Abstract: Ultrafast physical random bit generators based on broadband optical signals have been presented lately at astounding speeds. Some of the most popular mechanisms to obtain such random sequences are through signals that emerge from the coherence collapse operation of semiconductor lasers or from the photodetection signal beating of amplified spontaneous emission optical noise. Especially in the first case, the potential of chaotic signals to synchronize offers a great potential for secure communications. In this paper, we combine two unique properties of semiconductor lasers that operate at a chaotic regime: Their potential to become highly synchronized when optically coupled through appropriate configurations and their ability to seed ultrafast true random bit generators. The concurrent fulfillment of both conditions is shown in this paper and is used to demonstrate experimentally the one-time-pad encryption communication protocol. We report an error-free operation of such an encryption system, exceeding for the first time the Gb/s rate. Forward-error-correction coding is applied on the encryption scheme, in order to drastically reduce the errors of the synchronized true random bit sequences and optimize the decoding performance of the system, while securing the distribution of the random seed.

Low Threshold Two-Photon-Pumped Amplified Spontaneous Emission in CH3NH3PbBr3 Microdisks.

Abstract: Two-photon-pumped amplified spontaneous emission (ASE) of CH3NH3PbBr3 microdisks (MDs) were investigated by using femtosecond laser system. Low threshold at 2.2 mJ cm–2 was obtained. Also, emission spectral tunability from 500 to 570 nm was demonstrated by synthesis the mixed halide perovskite MDs. The spatial effect of photoluminescence (PL) properties under one-photon and two-photon excitation were also studied by means of two-photon laser scanning microscope (TPLSM) and time-resolved PL spectroscopy. It was found that the band to band emission of near-surface regions and photocarriers’ diffusion from near-surface regions to interior regions is significant for one-photon excitation. By contrast, reabsorption of emission under two-photon excitation plays a major role in the emission properties of the MDs. These results will give a more comprehensive understanding of the nonlinear effect of CH3NH3PbBr3 single crystals.

High-speed 405-nm superluminescent diode (SLD) with 807-MHz modulation bandwidth.

Abstract: III-nitride LEDs are fundamental components for visible-light communication (VLC). However, the modulation bandwidth is inherently limited by the relatively long carrier lifetime. In this letter, we present the 405 nm emitting superluminescent diode (SLD) with tilted facet design on semipolar GaN substrate, showing a broad emission of ~9 nm at 20 mW optical power. Owing to the fast recombination (τe<0.35 ns) through the amplified spontaneous emission, the SLD exhibits a significantly large 3-dB bandwidth of 807 MHz. A data rate of 1.3 Gbps with a bit-error rate of 2.9 × 10−3 was obtained using on-off keying modulation scheme, suggesting the SLD being a high-speed transmitter for VLC applications.

Generation of Light with Multimode Time-Delayed Entanglement Using Storage in a Solid-State Spin-Wave Quantum Memory.

Abstract: Here, we demonstrate generating and storing entanglement in a solid-state spin-wave quantum memory with on-demand readout using the process of rephased amplified spontaneous emission (RASE). Amplified spontaneous emission (ASE), resulting from an inverted ensemble of Pr^{3+} ions doped into a Y_{2}SiO_{5} crystal, generates entanglement between collective states of the praseodymium ensemble and the output light. The ensemble is then rephased using a four-level photon echo technique. Entanglement between the ASE and its echo is confirmed and the inseparability violation preserved when the RASE is stored as a spin wave for up to 5 μs. RASE is shown to be temporally multimode with almost perfect distinguishability between two temporal modes demonstrated. These results pave the way for the use of multimode solid-state quantum memories in scalable quantum networks.

Noise-mediated Casimir-like pulse interaction mechanism in lasers

Abstract: Strongly pumped mode-locked lasers often form pulse bunches. Although several mechanisms of pulse interaction are known, none yields the experimentally observed long-range attraction. Here we demonstrate theoretically and experimentally a new pulse interaction mechanism mediated by the continuum noise floor that is a universal feature in multipulse passively mode-locked lasers. Long-range attraction is facilitated by the depletion of the gain by the pulses, leading to an inhomogeneous noise floor that biases the timing jitter of the pulses and produces an effective interpulse potential with stable pulse bunch configurations. The pulses attract by suppressing electromagnetic fluctuations, as do conductors in the Casimir effect of quantum electrodynamics. This enables manipulation and design of multipulse waveforms to ultimately make them useful for application of mode-locked lasers.

A naked eye colorimetric sensor for alcohol vapor discrimination and amplified spontaneous emission (ASE) from a highly fluorescent excited-state intramolecular proton transfer (ESIPT) molecule

Abstract: A highly fluorescent HPI-based excited-state intramolecular proton transfer (ESIPT) molecule is designed and adopted as a naked-eye colorimetric sensor to distinguish methanol, ethanol and isopropanol vapors. Amplified spontaneous emission was also observed for the C1-form single crystal of the molecule attributed to its intrinsic four-level energy states.

Core/Alloyed-Shell Quantum Dot Robust Solid Films with High Optical Gains

Abstract: We report high optical gain from freestanding, optically stable, and mechanically robust films that are loaded with cross-linked CdSe/Cd1–xZnxSe1–ySy core/alloyed shell quantum dots (QD). These solid films display very high net optical gain as high as 650 cm–1 combined with a low pump excitation gain threshold of 44 μJ/cm2. The functionalization of the QDs using short-chain bifunctional cross-linkers not only significantly improves the net optical gain by allowing for a nearly 2-fold increase in QD loading but also provides stable passivation of the QDs which imparts excellent thermal stability, mechanical robustness, and stability under harsh chemical environments. The gain achieved here is up to 3-fold higher than that typically reported for traditional drop-cast QD films. Moreover, stable photoluminescence over long shelf storage time is a distinguished characteristic of the films. The QD films fabricated here span large areas (several cm2), can be readily micropatterned and sustain multiple harsh chem...

Reversible Laser-Induced Amplified Spontaneous Emission from Coexisting Tetragonal and Orthorhombic Phases in Hybrid Lead Halide Perovskites

Abstract: The photoluminescence in a lead halide perovskite is measured for different temperatures (5-300 K) and excitation fluences (21-1615 mu J cm(-2)). It is found that amplified spontaneous emission (ASE) is observed for an excitation density larger than about 1 x 10(18) cm(-3) for both the tetragonal phase above 163 K and the orthorhombic phase below about 163 K. The fluence that is required to obtain this excitation density depends on temperature and phase since the nonradiative decay of excitations is temperature activated with different activation energies of 85 +/- 20 and 24 +/- 5 meV for the tetragonal and orthorhombic phase, respectively. The ASE from the tetragonal phase-usually prevailing at temperatures above about 163 K-can also be observed at 5 K, in addition to the ASE from the orthorhombic phase, when the sample is previously exposed to a fluence exceeding 630 mu J cm(-2) at a photon energy of 3.68 eV. This additional ASE can be removed by mild heating to 35 K or optically, by exposing the sample by typically a few seconds with a fluence around 630 mu J cm(-2). The physical mechanism underlying this optically induced phase transition process is discussed. It is demonstrated that this phase change can, in principle, be used for an all-optical "write-read-erase" memory device.

Experimental demonstration of change of dynamical properties of a passively mode-locked semiconductor laser subject to dual optical feedback by dual full delay-range tuning.

Abstract: In this contribution we experimentally demonstrate the change and improvement of dynamical properties of a passively mode-locked semiconductor laser subject to optical feedback from two external cavities by coupling the feedback pulses back into the gain segment. Hereby, we tune the full delay-phase of the pulse-to-pulse period of both external cavities separately and demonstrate the change of the repetition rate, timing jitter, multi-pulse formation and side-band suppression for the first time for such a dual feedback configuration. In addition, we thereby confirm modeling predictions by achieving both a good qualitative and quantitative agreement of experimental and simulated results. Our findings suggest a path towards the realization of side-band free all-optical photonic oscillators based on mode-locked lasers.

Simple Approach to Improving the Amplified Spontaneous Emission Properties of Perovskite Films.

Abstract: Organo-lead halide perovskite has emerged as a promising optical gain media. However, continuous efforts are needed to improve the amplified spontaneous emission (ASE) even lasing properties to evade the poor photostability and thermal instability of the perovskites. Herein, we report that simply through the coating of polymer layer, the CH3NH3PbBr3 polycrystalline films prepared by a modified sequential deposition process show remarkably enhanced photoluminescence and prolonged decay lifetime. As a result, under nanosecond pulse pumping, the ASE threshold of the perovskite films is significantly reduced from 303 to 140 μJ/cm2. Furthermore, the light exposure stability is improved greatly after the polymer coating. We confirmed that the polymer layer plays the roles of both surface passivation and symmetric waveguides. Our results may shed light upon the stable and sustained output of laser from perovskite materials.

Polymorphism and Amplified Spontaneous Emission in a Dicyano-Distyrylbenzene Derivative with Multiple Trifluoromethyl Substituents: Intermolecular Interactions in Play

Abstract: Intermolecular interactions are decisive in controlling optoelectronic properties of molecular materials. Polymorphism in one and the same material gives a unique opportunity to gain a direct insight into the intermolecular contributions. Here, stimulated emission properties in two polymorphs of a dicyanodistyrylbenzene derivative with multiple trifluoromethyl groups in the terminal rings are investigated, and are correlated to the intermolecular arrangement and resulting excitonic coupling. The polymorphs have distinctly different emission behavior with one emitting in the blue, while the other emits in the green. Only the blue polymorph exhibits light amplification with an apparent threshold of spectral narrowing about 100 μJ cm−2. The green polymorph fails to exhibit any gain even at two orders of magnitude higher excitation fluence. Pump–probe studies indicate a more extended excited state absorption toward the emission region in the green polymorph compared to the blue, allowing net gain only on a subpicosecond (ps) time scale, too short for the observation of amplified spontaneous emission. This is attributed to intermolecular breathing/shearing modes coupled to the electronic transition due to strong π–π overlap in the green polymorph. These observations emphasize the significance of intermolecular interactions in controlling the optical properties as well as light amplification processes in organic conjugated materials.

Investigation of stimulated Raman scattering effect in high-power fiber amplifiers seeded by narrow-band filtered superfluorescent source.

Abstract: In this paper the stimulated Raman scattering (SRS) effect in high-power fiber amplifiers seeded by the narrow-band filtered superfluorescent source (SFS) is firstly analyzed both theoretically and experimentally. Spectral models for the formation of the SFS and the spectral evolution in high-power fiber amplifiers seeded by filtered SFS are proposed. It is found that the SRS effect in high-power fiber amplifiers depends on the spectral width of the filtered SFS seed. The theoretical predictions are in qualitative agreements with the experimental results.

Star-Shaped Single-Polymer Systems with Simultaneous RGB Emission: Design, Synthesis, Saturated White Electroluminescence, and Amplified Spontaneous Emission

Abstract: A three-armed star-shaped single-polymer system comprising tris(4-(3-hexyl-5-(7-(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)phenyl)amine (TN) as red emissive cores, benzothiadiazole (BT) as green emissive dopants, and polyfluorene (PF) as blue arms was successfully developed, in which the construction of the star-shaped architectures can depress intermolecular interactions and concentration quenching. The thermal, photophysical, electrochemical, electroluminescent, and amplified spontaneous emission (ASE) properties of the synthesized polymers are systematically investigated. The modulation of the doping concentration of TN and BT can guarantee the partial energy transfer in a star-shaped single-polymer system, further achieving saturated white emission. Consequently, a current efficiency of 2.41 cd A–1 and Commission Internationale d’Eclairage (CIE) coordinates of (0.34, 0.35) were recorded for TN-R3G4 with 0.03 mol % red core and 0.04 mol % green dopants. The saturated white emiss...

The generation of amplified spontaneous emission in high-power CPA laser systems.

Abstract: An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high-intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations ≤350 fs . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high-intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high-contrast front-end design are derived regarding the necessary contrast improvement and the amplified "clean" output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high-intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model.

Optimized WDM Transmission Impairment Mitigation by Multiple Phase Conjugations

Abstract: Multiple phase conjugations within a transmission-optimized fiber link enable significant nonlinearity cancellation in the wavelength division multiplexed (WDM) systems. In particular, we demonstrate the fiber impairment mitigation of WDM $24\times 48$ Gb/s dual-polarization quadrature phase shift keying (DP-QPSK) signals using 12 optical phase conjugations (OPC). The power excursion and dispersion-tailored transmission line in which the phase conjugations acted periodically, enabled an 8-dB higher nonlinearity threshold for the WDM 1.1-Tb/s DP-QPSK signals. With the nearly perfect nonlinearity cancellation, large input powers per span became available. Under these circumstances, we also present a first approach to the analysis of the impact of multiple phase conjugations in a distributed Raman amplified link. The analysis considers the performance of the experimentally measured OPC subsystem within an optimized transmission line limited only by an amplified spontaneous emission noise. This raw estimate gives insight into the linear noise performance limit of the employed phase conjugator when inserted multiple times in such a transmission system.

Correlated photon pair generation in AlGaAs nanowaveguides via spontaneous four-wave mixing.

Abstract: We demonstrate a source of correlated photon pairs which will have applications in future integrated quantum photonic circuits. The source utilizes spontaneous four-wave mixing (SFWM) in a dispersion-engineered nanowaveguide made of AlGaAs, which has merits of negligible two-photon absorption and low spontaneous Raman scattering (SpRS). We observe a coincidence-to-accidental (CAR) ratio up to 177, mainly limited by propagation losses. Experimental results agree well with theoretical predictions of the SFWM photon pair generation and the SpRS noise photon generation. We also study the effects from the SpRS, propagation losses, and waveguide lengths on the quality of our source.

54 J pulses with 18 nm bandwidth from a diode-pumped chirped-pulse amplification laser system.

Abstract: We report on results from the fully diode-pumped chirped-pulse amplification laser system Polaris. Pulses were amplified to a maximum energy of 54.2 J before compression. These pulses have a full width at half-maximum spectral bandwidth of 18 nm centered at 1033 nm and are generated at a repetition rate of 0.02 Hz. To the best of our knowledge, these are the most energetic broadband laser pulses generated by a diode-pumped laser system so far. Due to the limited size of our vacuum compressor, only attenuated pulses could be compressed to a duration of 98 fs containing an energy of 16.7 J, which leads to a peak power of 170 TW. These pulses could be focused to a peak intensity of 1.3×1021 W/cm2. Having an ultra-high temporal contrast of 1012 with respect to amplified spontaneous emission these laser pulses are well suited for high-intensity laser–matter experiments.

Lasing dynamics of neutral nitrogen molecules in femtosecond filaments

Abstract: We investigate the dynamics of cavity-free lasing from neutral nitrogen molecules in femtosecond laser filaments. An important difference of intensity and temporal duration is observed between backward and forward lasing, in both amplified spontaneous emission and seed-amplification regimes. Numerical simulations based on a nonadiabatic Maxwell-Bloch model reproduce well the observations, and attribute these differences to the finite gain lifetime and the traveling excitation nature of this gas laser.

Tm^3+ doped lead silicate glass single mode fibers for 20 μm laser applications

Abstract: Tm3+ doped lead silicate glasses with good thermal stability were prepared by the melt-quenching method. Based on the absorption and emission spectra, Judd-Ofelt intensity parameters, absorption and emission cross sections, gain spectra, and σe × FWHM were calculated and analyzed. These results suggest that Tm3+ doped lead silicate glasses are promising as mid-infrared laser materials. Tm3+ doped lead silicate glass single mode (SM) fibers with cladding diameter of 125 μm and core diameter of 8.5 μm were then fabricated by the rod-in-tube technique. The Tm3+ doping concentration reached as high as 4.545 × 1020 ions/cm3. ~2.0 μm amplified spontaneous emission (ASE) was realized in a 3.5-cm-long as-drawn SM fiber when pumped by a homemade single mode 1560 nm fiber laser. The results indicate that these Tm3+ doped lead silicate glass single mode fibers are promising fiber material for 2.0 μm fiber laser applications.