Amplified Spontaneous Emission Output Research Articles

Enhanced Amplified Spontaneous Emission from Perovskite Films by a Multifunctional 4′‐Aminoacetophenone Hydrochloride Additive Assistant Engineering

AbstractMetal halide perovskites are considered as a prospective candidate as optical gain media for stimulated emission, and the advancement of amplified spontaneous emission (ASE) of perovskite materials is gradually becoming the key to realize the commercialization of perovskite lasers. Nonetheless, the ASE of solution‐processed polycrystalline perovskite films still experiences a high threshold and poor optical stability due to their high defect density and poor crystalline quality. In this scenario, a noticeably ameliorated ASE performance with decreased threshold and greater photo‐stability is demonstrated in solution‐processed (FAPbI3)0.85(MAPbBr3)0.15 polycrystalline perovskite films by introducing a neoteric 4′‐Aminoacetophenone hydrochloride (APCl) additive with cost‐effective fabrication. The ASE threshold of the APCl‐embedded perovskite films is prominently curtailed from 12.8 to 5.3 µJ cm−2, with an augmented optical gain, ASE output intensity, and optical durability. The ameliorated ASE performance can be credited to multifunctional effects of the APCl additive in the perovskite films, presenting a low defect density, an unambiguously elevated photoluminescence, a prolonged decay lifetime and thus enabling the easily achieved population inversion caused by the attenuated nonradiative carrier recombination in the optical gain media. These findings provide a significant foundation and pave the way for realizing the electrically excited lasing based on the perovskite materials.

Low Threshold and Ultrastability of One-Step Air-Processed All-Inorganic CsPbX3 Thin Films toward Full-Color Visible Amplified Spontaneous Emission

All-inorganic perovskites (CsPbX3) with the merits of high stability and remarkable optical gain property are attractive for achieving on-chip coherent light sources. Unfortunately, traditional solution-processed CsPbX3 films suffer from inevitable poor surface integrity and pinhole defects, severely hindering their optical properties. Here, from the perspective of precursor solution chemistry, we use an ionic liquid solvent methylammonium acetate (MAAc) to fabricate compact, pinhole-free, and smooth CsPbX3 thin films in a one-step air process without antisolvent treatment. Optically pumped amplified spontaneous emission (ASE) with a straightforward visible spectral tunability (418-725 nm) is achieved under both nanosecond and femtosecond laser excitation. For the representative CsPbBr3 films, the threshold reaches down to 11.4 μJ cm-2 under nanosecond laser pumping, which is comparable to the value under one-photon femtosecond pumping. The long gain lifetime up to 258.2 ps is revealed by transient absorption spectroscopy. Most importantly, the films show excellent optical stability and humidity stability with no obvious degradation under the pulsed laser irradiation for more than 210 min, stable ASE output under 95% high humidity, and conspicuous ASE after 1000 h of storage in air condition without encapsulation. These results demonstrate that the method of fabricating inorganic perovskite films with an ionic liquid solvent is promising in developing high-performance full-color visible lasers.

Phase segregation leading to tunable amplified spontaneous emission in mixed halide perovskites

The amplified spontaneous emission (ASE) of a MAPbI1.5Br1.5 film is studied under continuous wave (CW) and pulsed illumination. The different ASE spectra evolution, especially in the range of 680 nm to 720 nm, indicates the different compositional distribution of bromide in the iodine-rich domains during phase segregation process under different illumination conditions. Furthermore, using light control such as adjusting the repetition rate of pulsed illumination or the duty cycle of Quasi-CW illumination, is of benefit to stabilize the ASE output at any wavelength in the range of ∼ 675 nm to ∼ 775 nm.

Bidirectional GHz bandwidth amplified spontaneous emission generation and high output power single-pass optical amplification through a hot Cs vapor cell

We report the characteristics of GHz bandwidth amplified spontaneous emission (ASE) from a hot Cs atom vapor cell, where the optical feedback was inhibited. When pumped by an 852 nm laser, both forward and backward ASE output near 894 nm showed a nonlinear increase in its power without a pump power threshold. A continual decrease in spectral width down to 4.7 GHz was experimentally observed as the ASE output power increased. Using the same vapor cell, we injected a 1mW signal to configure a single-pass optical amplifier, and we monitored the forward output both in temporal and spectral domains. We found the signal laser efficiently suppressed the ASE and obtained a large amplification factor over 700 at the pump power of 1.2 W.

Self‐Erase Force‐Induced Turn‐On Organic ASE Output Cryptographic Primitive for Advanced Multiple Information Encryption

AbstractThe development of high density and security information encryption system, in particular narrowband luminescence cryptographic primitive, is of notable significance but extremely challenging for anticounterfeiting applications. Herein, a novel piezochromic fluorescent (PCF) molecule 4‐(4‐(4‐methylpiperazin‐1‐yl)styryl)‐N,N‐diphenylaniline (TPIZ) is reported, which features high pressure sensitivity and self‐erase force‐induced amplified spontaneous emission (ASE) output multicolor switching. The remarkable green/cyan photoluminescence emission and blue ASE emission of TPIZ microcrystals can be switched reversibly under pressure and pumping energy. A mechanistic study of X‐ray diffraction analysis reveals that the rotation of the C═C bond under low pressure caused the reduction of the weak intermolecular interaction, which is responsible for its excellent PCF performances with self‐erase features. Moreover, the force‐induced amplification of ASE output behaviors are observed due to the high quality of TPIZ microcrystals. Benefiting from the pressure sensitivity, ASE emission as well as self‐erase behaviors of TPIZ microcrystals, a triple encoding self‐erase system is developed for advanced information encryption. This work can provide a crucial step toward the force‐induced narrowband ASE cryptographic primitive materials for high level security application.

Broadband mid-infrared amplified spontaneous emission from Er/Dy co-doped fluoride fiber with a simple diode-pumped configuration

Er3+/Dy3+ co-doped double-clad ZBLAN optical fiber has been used to obtain amplified spontaneous emission (ASE) broadband light sources cladding-pumped by 980-nm multimode laser diode (LD) sources. It has been demonstrated that mid-infrared broadband emission extending from 2515 to 3735 nm was obtained by energy transfer between Er3+ and Dy3+. We experimentally investigated the optimum design of Er3+/Dy3+ co-doped ZBLAN fiber in terms of ion concentration, fiber length, pumping configuration, and pumping power. The ASE output power was more than 2.5 mW when the LD pump power was set at 5 W. To assess its potential for gas sensing applications, the fabricated ASE light source was used to successfully detect methane gas with concentrations at 1% and 5%. The simple and stable construction of our ASE light source is suitable for practical purposes.

Synergistically Enhanced Amplified Spontaneous Emission by Cd Doping and Cl‐Assisted Crystallization

AbstractOrganic−inorganic hybrid halide perovskite materials have recently been recognized as a promising optical gain medium, and the development of optically pumped amplified spontaneous emission (ASE) of perovskite materials with low threshold and high optical gain will be on the only way to go for realizing its commercial perovskite laser. In this work, enhanced‐performance ASE with lower threshold and higher optical gain is obtained in CdCl2 passivated FA0.9MA0.15Cs0.3PbI2.7Br0.3 (FAMACs) polycrystalline films coated with poly methyl methacrylate (PMMA) layer. The ASE threshold of the FAMACs polycrystalline films with CdCl2 is significantly reduced from 18.7 to 7.9 µJ cm−2, with an enhanced ASE output intensity and stability. The improved ASE performance can be attributed to the synergistic effect of Cd ion doping and Cl‐ion‐assisted crystallization in the FAMACs polycrystalline films, exhibiting remarkably enhanced photoluminescence, a prolonged decay lifetime and a low defect density, and thus leading to easily achieve the population inversion due to the reduction of nonradiative recombination of carriers in the optical gain medium.

The synthesis of a series of fluorescent emitters and their application for dye lasing and cation sensing.

The following paper reported four carbazole-modified fluorescent emitters. Their molecular structure and electronic transition were analyzed via their single crystal and theoretical calculation. Their photophysical parameters, including absorption, emission and quantum yield, were determined and discussed. It was found that the emission performance of benzo-thiazole-based dyes was better than that of benzo-imidazole-based dyes, owing to the electron-donating effect from the S atom. Upon the presence of metal cations, these photophysical parameters were re-measured. Benzo-thiazole-based dyes were found insensitive towards most metal cations, while benzo-imidazole-based dyes showed obvious photophysical variation upon these metal cations, including absorption red shift and emission quenching. Detailed sensing performance of a representative dye was discussed. A linear working curve with good selectivity was finally observed. Its sensing mechanism was confirmed as the coordination between metal cation and deprotonated benzo-imidazole group. Benzo-thiazole-based dyes showed amplified spontaneous emission (ASE) behavior, with threshold energy of ~220μJ. Given the optimal condition, a highest ASE efficiency of ~2% was observed, with FWHM value of 6nm and emission peak of 435nm. The major novelty and advancement of these fluorescent dyes shall be the stable ASE output (dye 4) under UV excitation and the linear sensing curve with good selectivity (dye 3), which was a hard task for emission turn off sensing probes. We attributed its causation to the valent-recognizing sensing mechanism.

Temperature activated mirror-less laser action from a hole-transport conjugated-polymer

A plethora of experimental reports and evidences from recent times have collectively taken efforts in developing a novel mirror-less laser. Breakthrough in Conjugated polymer lasers unravel numerous attractive research direction over the last decade. The present study experimentally demonstrated a temperature-activated/controlled amplified spontaneous emission (ASE) in a hole-transport conjugated polymer (HTCP) Poly[N,N’-bis(4-butylphenyl)-N,N’-bis(phenyl)-benzidine] [poly-TDP (4B)]. The poly-TDP (4B) dissolved in toluene under wide range concentration. The solution of different concentration was pumped with an Nd:YAG (355 nm) laser. For temperature lower than 37 °C, the poly-TDP (4B) did not produce ASE, but for the 40 °C, the ASE is observed. Furthermore, the output energy of the ASE is dependent on the temperature of the solution. The ASE output energy attains maximum at a temperature of 78 °C, and then the output falls drastically. The time-resolved spectroscopy studies showed the temperature responsiveness of the HTCP poly-TDP (4B) in the sub-nanosecond time domain. The temperature-dependent laser action is due to reversible dimerization property of the poly-TDP (4B), and it is rare.

Optically Pumped Intensive Light Amplification from a Blue Oligomer.

We demonstrated the time-resolved dynamics of laser action from the conductive oligomer (CO) 1,4-Bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF). Absorption and fluorescence spectra were studied for BECV-DHF in different solvents under a wide range of concentrations. The Fourier-transform infrared spectroscopy (FTIR) spectrum was measured using simulation and experiments. The Ultraviolet-Visible (UV-VIS) spectra of the BECV-DHF were simulated in two different solutions. This CO formed a dimer and had two vibration bands in nonpolar solvents, partially dissolved in polar protic solvents, and created an H-type aggregate in polar aprotic solvents. BECV-DHF produced amplified spontaneous emission (ASE) at 464 nm in many solvents. The high efficiency of ASE is due to the waveguiding and self-assembly nature of the oligomer, which is very rare for optically pumped systems. However, BECV-DHF did not produce ASE in polar protic solvents. BECV-DHF produced ASE in both longitudinal and transverse pumping, and the full-width half maximum (FWHM) was 4 nm and 8 nm respectively for different solvents, such as toluene and acetone. The CO had a very low threshold pump energy (~0.5 mJ). The ASE efficiency was approximately 20%. The time-resolved spectroscopy (TRS) studies showed a temporal Gaussian-shaped ASE output from this CO. BECV-DHF shows remarkably high stability compare to the conjugated polymer (CP) PFO-co-pX.

Numerical investigation on the spectral and temporal characteristics of amplified spontaneous emission in chirped pulse regenerative amplifiers

Accurate characterization of the amplified spontaneous emission (ASE) is greatly important for designing a high-contrast chirped pulse amplifier (CPA). In this paper, we develop a theoretical model based on small signal gain calculation (SSGC) to simulate the temporal and spectral profiles of the ASE output power of a chirped pulse regenerative amplifier. Also, the finite difference time domain (FDTD) is utilized as a robust mathematical method to describe ASE characteristics. Comparison of the two methods introduces the developed SSGC as a fast, greatly efficient and accurate technique to predict and analyze the ASE behavior in a CPA system.

Highly stable enhanced near-infrared amplified spontaneous emission in solution-processed perovskite films by employing polymer and gold nanorods.

Solution-processed organo-lead halide perovskites have emerged as promising optical gain media for tunable coherent light sources. The lasing performance is generally determined by the as-synthesized crystal quality. Noble metal nanostructures have been widely utilized to enhance optical responses due to their unique property of localized surface plasmon resonance. Herein, we report a simple method to enhance the near-infrared amplified spontaneous emission (ASE) performance of MAPbI3 polycrystalline films by solution-processing a PMMA spacer layer and an Au NR-doped PMMA top layer on perovskite thin films. As a result, the ASE threshold of the triple-layer perovskite film was significantly reduced by around 36% and the ASE intensity increased by 13.9-fold, compared to the pristine film. The underlying mechanism was attributed to the combined effects of surface passivation by PMMA and plasmon resonance enhancement of Au NRs. The passivation effect results in suppressing the nonradiative recombination and prolonging excited state decay, which have been investigated by transient absorption and pump-probe measurements. The plasmon effect is systematically studied through distance-dependent and spectra-dependent plasmon enhanced emission. The perovskite films with PMMA and Au NR coating showed great stability for 180 min under intense pulse laser continuous irradiation. The improved ASE performance still remained after leaving the film under the atmosphere for more than one month. We have successfully demonstrated a highly stable and sustained ASE output from MAPbI3 films under pulse laser excitation. This study provides a general approach for exploring plasmonic nanostructures in combination with polymers in the development and application of low-cost solution-processed semiconductor lasers.

Experimental and theoretical investigations for describing pressure dependence of amplified spontaneous emission output energy, small signal gain and electrical conductivity in nitrogen lasers

An experimental arrangement consists of an oscillator amplifier (OSC-AMP) N2 laser system having electrodes of different lengths, lAMP, was used to measure the amplified spontaneous emission (ASE) output energy extracted from the AMP section at different gas pressure, pAMP, and also the AMP small signal gain, g0 at a constant pAMP. It was observed that the extracted ASE output energy with respect to operational gas pressure has a non-symmetrical character. For explaining the observed behavior two different models for numerical calculations were applied for the results to be compared with each other and also with the experimental observations. The first model, i.e. the model of geometrically dependent gain coefficient (GDGC) was found to explain the pressure dependencies the observed behaviors of threshold and saturation lengths. The second model, which is based on using rate equations for N2 lasers, coupled to the circuit electric discharge was used to calculate the pressure dependences of the ASE output energy and small signal gain. The results showed that ASE output energy versus gas pressure had a symmetrical behavior and within a limited range of gas pressure, small signal gain is a constant value. As geometrically the small signal gain and the electrical conductivity behave similarly, the model was also applied for predicting the pressure dependence of the electrical conductivity. Calculations of g0 vs. lAMP at pAMP = 90 Torr based on applying both models are comparable with the measurements. It is concluded that the GDGC model can be suitably used for predictions of small signal gain, threshold and saturation lengths provided that ASE experimental measurements are available. The modified rate equations, on the other hand, can give appropriate results in absence of experimental measurements.

Investigations of influences of spontaneous emission properties on surface plasmon polariton amplifications with the rate-equation theory

The influences of the position-related spontaneous emission properties of gain media on gain and amplified spontaneous emission (ASE) noise characteristics of surface plasmon polariton (SPP) amplification are investigated with rate-equation theory in this paper. It is found that both the spontaneous emission rate and the probability of spontaneous emission into the SPP mode of the gain media in an SPP waveguide are position related. Based on this, a rate-equation model considering those spontaneous emission properties is presented. With this model, the influences of the position-related spontaneous emission properties on the gain and ASE noise characteristics of a single-mode dielectric-loaded SPP amplifier are discussed. The results show that the spontaneous emission rate of gain media is enhanced near the metal interface and the probability of spontaneous emission into the SPP mode decreases near both the metal and air interfaces of the amplifier. This gives rise to reduced gain and low ASE output power. Moreover, the noise property of the amplifier may be improved because of the great decrease in the output ASE power.

Design and experimental realization of a highly efficient superfluorescent fiber source with flat C-band spectrum

Design and experimental realization of C-band superfluorescent fiber sources using a well-designed high reflector/filter of fiber Bragg grating (FBG) in three configurations, namely double-pass forward (DPF), double-pass backward (DPB), and DPF+DPB , is realized. Using a numerical method, the optimum length and peak absorption coefficient of erbium-doped fiber as well as the optimum specifications of FBG, i.e., its 3-dB bandwidth and central wavelength, are calculated. Our numerical calculations illustrate that an appropriate design may result in a flattened amplified spontaneous emission (ASE) output spectrum with a 3-dB bandwidth of about 22 nm and a central wavelength of 1550 nm. Furthermore, the peak power of the flattened ASE spectrum is 16 dBm larger than the power at a wavelength of 1530 nm that is beneficial for increasing the 3-dB bandwidth. The experimental results show that using an optimum design, there are negligible differences between ASE output spectra acquired by different double-pass configurations. However, the DPB configuration has a higher efficiency as compared with other configurations and can provide a C-band superfluorescent fiber source with a simultaneously good spectral flatness, , high output power of 12 dBm, and maximum 3-dB bandwidth of about 22 nm.

Theoretical study of amplified spontaneous emission intensity and bandwidth reduction in polymer

Amplified spontaneous emission (ASE), including intensity and bandwidth, in a typical example of BuEH-PPV is calculated. For this purpose, the intensity rate equation is used to explain the reported experimental measurements of a BuEH-PPV sample pumped at different pump intensities from Ip = 0.61 MW/cm2 to 5.2 MW/cm2. Both homogeneously and inhomogeneously broadened transition lines along with a model based on the geometrically dependent gain coefficient (GDGC) are examined and it is confirmed that for the reported measurements the homogeneously broadened line is responsible for the light–matter interaction. The calculation explains the frequency spectrum of the ASE output intensity extracted from the sample at different pump intensities, unsaturated and saturated gain coefficients, and ASE bandwidth reduction along the propagation direction. Both analytical and numerical calculations for verifying the GDGC model are presented in this paper. Although the introduced model has shown its potential for explaining the ASE behavior in a specific sample it can be universally used for the ASE study in different active media.

有机材料EnBOD的放大自发发射性能研究

Amplified spontaneous emission( ASE) properties of organic material En BOD were studied under ultraviolet pulse laser pumping. En BOD sample in dilute toluene solution shows narrowband absorption and PL spectra,with the maximum peak located at 508 nm and 527 nm,respectively.The ASE efficiency changes with the solution concentration. The maximum ASE efficiency of 22. 6%was obtained when the En BOD sample concentration is 0. 008 mol·L- 1,in which the ASE threshold is 29. 5 k W·cm- 2,ASE peak is 542 nm and full width at half maximum is about 12. 4 nm.The ASE output intensity attenuated to 61. 2% of the initial strength under the pulse pump frequency of 200 000. The results indicated that En BOD is a kind of laser material with low ASE threshold and good light stability.

High-power single-stage thulium-doped superfluorescent fiber source

In this paper, we report a high-power thulium (Tm)-doped superfluorescent fiber source (SFS) in the 2-μm spectral region. The SFS is based on double angle-cleaved facet operation and uses a simple single-stage geometry. The copropagating amplified spontaneous emission (ASE) yields a maximum output of 20.7 W at a center wavelength of 1,960.7 nm, with a full width at half maximum (FWHM) of ~45 nm. The counterpropagating ASE yields a maximum output of 25.2 W at a center wavelength of 1,948.2 nm, with a FWHM of ~50 nm. The maximum combined output of the SFS is as much as 45.9 W, which corresponds to a slope efficiency of 38.9 %. In addition, a model of the ~2 μm SFS in Tm-doped silica fibers pumped at ~790 nm is developed, and the influence of fiber length and end-facet reflectivity on the ASE output performance and the parasitic lasing threshold are studied numerically.

A high flattening C + L band broadband source based on single pump and the same erbium-doped fiber

In order to realize a high flattening C+L band amplified spontaneous emission (ASE) light output, a broadband source using just one 976nm laser diode (LD) and two stages erbium-doped fibers (EDF) with the same concentration is proposed theoretically and demonstrated experimentally, and the theoretical analysis and experimental verification are presented in details. Firstly, based on the energy level of Er3+, the methods of realizing C+L band ASE output is presented. Then, the system configuration is designed. One 976nm LD is used for pumping, and the pump light, which is divided into two parts by one coupler, is pumped into two EDFs by wavelength division multiplexer (WDM). A fiber loop mirror (FLM) is used to improve working efficiency. Meanwhile, an optical isolator is used to avoid the effect of reflected wavelength from output facet. Finally, based on the mathematical model of the ASE gain, the length of EDF is discussed as well. In the experiment, by optimizing the length of EDF1 and EDF2, a 0.12m EDF1 and 16m EDF2 are adopted. In the end, the flatness of the spectra from 1540nm to 1610nm is ±0.91dB, and the flatness is ±1.65dB during 1520–1610nm without any filter. The high flattening C+L band ASE output is achieved by just one 976nm LD, which can optimize system and reduce the cost as well.

Theoretical study of amplified spontaneous emission using a model based on a geometrically dependent gain coefficient

It is shown that a model based on a geometrically dependent gain coefficient (GDGC), which is characterized by gain parameters (m′, , b), introduces a powerful method to describe amplified spontaneous emission (ASE) intensity behavior and its bandwidth reduction when the ASE is propagating along the z-direction. The model also gives correct predictions for unsaturated and saturated gain coefficients and the frequency dependence of the ASE output intensity in a given laser system. For the calculation, the GDGC model in saturated and unsaturated conditions along with the intensity rate equation were applied, and for verification of the model the reported ASE intensity measurements and the measured bandwidth reduction in KrF lasers were utilized. The present model will have applications in any type of pulsed laser system of different active media and different dimensions without going through complicated analysis or utilizing heavy computer numerical computations. Details of the present approach will be given and the excellent agreement with the available and typical experimental measurements for KrF lasers confirms the validity of the proposed GDGC model.