Amplified Spontaneous Emission and External Signal Amplification in an Inverted Medium

Allen, L.; Peters, G I

doi:10.1103/physreva.8.2031

Cited by 102 publications

(30 citation statements)

References 40 publications

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“…and, as a result, a complex nomenclature has evolved including the terms superradiance, superfluorescence, amplified spontaneous emission, mirrorless lasing, and random lasing [2, 4,[6][7][8][9], the distinctions among which we will not attempt to summarize here. The problem has recently seen renewed interest in the field of cold atoms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

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confidence: 99%

Second-order coherence of superradiance from a Bose-Einstein condensate

et al. 2014

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We have measured the 2-particle correlation function of atoms from a Bose-Einstein condensate participating in a superradiance process, which directly reflects the 2nd order coherence of the emitted light. We compare this correlation function with that of atoms undergoing stimulated emission. Whereas the stimulated process produces correlations resembling those of a coherent state, we find that superradiance, even in the presence of strong gain, shows a correlation function close to that of a thermal state, just as for ordinary spontaneous emission.PACS numbers: 03.75. Kk, 67.10.Jn, 42.50.Lc Ever since the publication of Dicke's 1954 paper [1], the problem of the collective emission of radiation has occupied many researchers in the fields of light scattering, lasers and quantum optics. Collective emission is characterized by a rate of emission which is strongly modified compared to that of the individual atoms [2]. It occurs in many different contexts: hot gases, cold gases, solids and even planetary and astrophysical environments [3]. The case of an enhanced rate of emission, originally dubbed superradiance, is closely connected to stimulated emission and gain, and as such resembles laser emission [4]. Lasers are typically characterized by high phase coherence but also by a stable intensity, corresponding to a Poissonian noise, or a flat 2nd order correlation function [5]. Here we present measurements showing that the coherence properties of superradiance, when it occurs in an ultracold gas and despite strong amplified emission, are much closer to those of a thermal state, with super-Poissonian intensity noise.Research has shown that the details of collective emission depend on many parameters such as pumping configuration, dephasing and relaxation processes, sample geometry, the presence of a cavity, etc. and, as a result, a complex nomenclature has evolved including the terms superradiance, superfluorescence, amplified spontaneous emission, mirrorless lasing, and random lasing [2,4,[6][7][8][9], the distinctions among which we will not attempt to summarize here. The problem has recently seen renewed interest in the field of cold atoms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. This is partly because cold atoms provide a reproducible, easily characterized ensemble in which Doppler broadening effects are small and relaxation is generally limited to spontaneous emission. Most cold atom experiments differ in an important way from the archetypal situation first envisioned by Dicke: instead of creating an ensemble of excited atoms at a well defined time and then allowing this ensemble to evolve freely, the sample is typically pumped during a period long compared to the relaxation time and emission lasts essentially only as long as the pumping. The authors of reference [10] however, have argued that there is a close analogy to the Dicke problem, and we will follow them in designating this process as superradiance.In the literature on superradiance there has been relatively little discussion...

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confidence: 99%

Second-order coherence of superradiance from a Bose-Einstein condensate

et al. 2014

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“…The minimum laser intensity is found to be The necessary laser intensity depends strongly on the excited-state absorption cross-section a ex . For °ex = 0>^OL -8x 10 9 Wem" 2 is enough to generate fluorescence-pulse durations equal to the pump pulse durations (numerical values of above this were used; compare with dashed curve in Fig. 14).…”

Section: Conditions For Optimum Amplification Of Spontaneous Emissionmentioning

confidence: 99%

“…Amplification of spontaneous emission (superfluorescence) is readily observed in organic dye solutions when the sample is excited with intense light pulses [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The spontaneous fluorescence light is amplified by stimulated emission.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of amplified spontaneous emission with picosecond light pulses in dye solutions

Penzkofer

Falkenstein²

1978

Opt Quant Electron

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The amplified spontaneous emission in dye solutions excited with intense picosecond light pulses is studied theoretically. A multi-level model is applied to take into account the effects of the various dye parameters such as ground-state absorption, stimulated emission, excited-state absorption, reabsorption and relaxations from populated excited levels. The influence of the pump laser duration and intensity and of the dye concentration and sample length is investigated. Optimum situations are derived for the generation of intense picosecond light pulses at new frequencies by amplified spontaneous emission. On the other hand, conditions are found where amplification of spontaneous emission may be neglected. The analysis allows the determination of unknown dye parameters by comparing the calculations with the experiment. IntroductionAmplification of spontaneous emission (superfluorescence) is readily observed in organic dye solutions when the sample is excited with intense light pulses [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The spontaneous fluorescence light is amplified by stimulated emission. When picosecond light pulses are used to excite the dye solutions, the fluorescence signal is shortened in time, increased in intensity, narrowed in spectral extension, and concentrated into a small divergence angle [1-3, 7,8,12,14]. The effect of amplified spontaneous emission allows the generation of picosecond light pulses in new frequency regions. The conventional fluorescence studies are carried out with weak excitation light sources and the amplification effects are negligibly small; but the amplification of spontaneous emission alters the spectroscopic behaviour substantially when iritense pump pulses are used [15,16].The purpose of this paper is to study, theoretically, the influence of various parameters on the fluorescence behaviour of dyes which are excited with intense picosecond light pulses. A model is used that allows the study of the influence of pump pulse absorption, stimulated emission, reabsorption and excited-state absorption as well as of relaxation phenomena in excited states. The effects of the geometrical arrangement, the pump pulse parameters and of the dye concentration are discussed. The analysis allows the determination of unknown dye parameters, such as relaxation rates, by comparing the calculations with the experiment. Optimum situations are found for the generation of picosecond light pulses at new frequencies. Conditions are derived where amplification of spontaneous emission is negligible and conventional fluorescence spectroscopy leads to correct results.

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“…Models based on the rateequation approximation represented a significant portion of past work due to their simplicity [14][15][16][17][18][19][20][21]. Rigorous models included those based on the density matrix formulation [22,23] and the Maxwell-Bloch equations [24]. These models have thus far been mostly limited to relatively simple one-dimensional (1D) applications, and extension to realistic scenarios is not trivial.…”

Section: Introductionmentioning

confidence: 99%

Method to correct the distortion caused by amplified stimulated emission as motivated by LIF-based flow diagnostics

Zhao

2012

Appl. Opt.

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Amplified stimulated emission (ASE) represents a significant issue in two-photon laser-induced fluorescence (TPLIF). The ASE effects are nonlinear and nonlocal, i.e., the ASE effects distort the LIF signal nonlinearly, and the distortion at one location depends on conditions at other locations. In this sense, the ASE effects pose a greater challenge to quantitative TPLIF than quenching and ionization. This work therefore seeks a method to correct such distortion. The method uses two LIF measurements, one with low signal-to-noise ratio (SNR) and negligible ASE distortion and another with high SNR but significant distortion, to generate a faithful measurement with high SNR. Extensive simulations were performed to evaluate the performance of this method for practical applications.

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Amplified Spontaneous Emission and External Signal Amplification in an Inverted Medium

Cited by 102 publications

References 40 publications

Second-order coherence of superradiance from a Bose-Einstein condensate

Second-order coherence of superradiance from a Bose-Einstein condensate

Theoretical investigation of amplified spontaneous emission with picosecond light pulses in dye solutions

Method to correct the distortion caused by amplified stimulated emission as motivated by LIF-based flow diagnostics

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