Intrinsic intensity fluctuations in random lasers

Molen, K.L. van der; Mosk, Allard; Lagendijk, Ad

doi:10.1103/physreva.74.053808

Cited by 67 publications

(60 citation statements)

References 19 publications

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“…-focus area A of the pump beam on the sample, as it provides information of the size and shape (together with ℓ and ℓ a ) of the amplified volume -wavelength of the pump laser λ p -duration of the pump pulse t p , as studies have shown that pulse duration is an important parameter [4,20] -repetition rate of the pump laser -pump fluence I for every published spectrum -integration time for every published spectrum Before we list the required experimental data, we briefly elaborate on two key criteria: the occurrence of spikes and gain narrowing. The occurrence of spikes in an emission spectrum of a random laser is a central issue.…”

Section: Pacs Numbersmentioning

confidence: 99%

Quantitative analysis of several random lasers

Molen¹,

Mosk²,

Lagendijk

2007

Optics Communications

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We prescribe the minimal set of experimental data and parameters that should be reported for random-laser experiments and models. This prescript allows for a quantitative comparison between different experiments, and for a criterion whether a model predicts the outcome of an experiment correctly. In none of more than 150 papers on random lasers that we found these requirements were fulfilled. We have nevertheless been able to analyze a number of published experimental results and recent experiments of our own. Using our method we determined that the most intriguing property of the random laser (spikes) is in fact remarkably similar for different random lasers.

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Section: Pacs Numbersmentioning

confidence: 99%

Quantitative analysis of several random lasers

Molen¹,

Mosk²,

Lagendijk

2007

Optics Communications

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“…In this paper, we address the question whether the lasing modes are the quasimodes of passive random systems. The answer to this question determines whether the statistical distribution of the decay rates of quasimodes can be used to predict the lasing threshold and the number of lasing modes for random laser 12,13,14,15,16,17,18,19 .…”

Section: Introductionmentioning

confidence: 99%

Effect of local pumping on random laser modes in one dimension

Wu¹,

Andreasen²,

Cao³

et al. 2007

J. Opt. Soc. Am. B

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We have developed a numerical method based on the transfer matrix to calculate the quasimodes and lasing modes in one-dimensional random systems. Depending on the relative magnitude of the localization length versus the system size, there are two regimes in which the quasimodes are distinct in spatial profile and frequency distribution. In the presence of uniform gain, the lasing modes have one-to-one correspondence to the quasimodes in both regimes. Local excitation may enhance the weight of a mode within the gain region due to local amplification, especially in a weakly scattering system.

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“…From the solution of the diffusion equation, the mean value of the cavity-decay time t c can be derived 27 and found to depend on D(l), t c ¼ L 2 /8D(l). From equation (1) it is then evident that the threshold and laser process can be controlled by modifying D(l) and hence ' t (l).…”

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confidence: 99%

“…In previous work 9, 27 , spheres or particles have always been dispersed in a solvent plus laser dye, making the refractive index contrast very low. This meant that at the given values of polydispersity it was impossible to resolve any Mie resonances.…”

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confidence: 99%

Resonance-driven random lasing

Sapienza

García

Gottardo³

et al. 2008

Nature Photon

273

183

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A random laser is a system formed by a random assembly of elastic scatterers dispersed into an optical gain medium 1 . The multiple light scattering replaces the standard optical cavity of traditional lasers and the interplay between gain and scattering determines the lasing properties. All random lasers studied to date have consisted of irregularly shaped or polydisperse scatterers, with a certain average scattering strength that was constant over the frequency window of the laser [2][3][4] . In this letter we consider the case where the scattering is resonant. We demonstrate that randomly assembled monodisperse spheres can sustain scattering resonances over the gain frequency window, and that the lasing wavelength can therefore be controlled by means of the diameter and refractive index of the spheres. The system is therefore a random laser with an a priori designed lasing peak within the gain curve.In recent years the interest in random lasing has grown very rapidly, particularly following the observation of this phenomenon in powdered laser crystals 5 , ceramics 6 , organic composites 7 , and even biological tissue 8 . The necessary condition for a random laser is that the material is multiply scattering light, which means that the transport mean free path (the average distance over which the scattered light direction is randomized) ' t ( L, where L is the sample size. The other fundamental quantity is the gain length ' g , which represents the path length over which the intensity is amplified by a factor e þ1 . The interaction between gain and scattering determines the unique properties of the random laser and, in particular, defines the critical thickness for the sample (in slab geometry) to lase,. Unlike in ordinary lasers, the resulting light emission is multidirectional, but the threshold behaviour 3 , the photon statistics 10,11 and relaxation oscillations 12,13 are very similar to those of standard lasers. The spectral output of a random laser system contains narrow emission spikes 4 , which for large spectral width can merge into a smooth peak with an overall narrowing of the spectrum in most experimental configurations 3,14 , like the one considered in this paper.Wavelength tunability is a crucial property of lasing devices. In regular lasers this is easily achieved by tuning the resonance frequency of the resonator. The same principle has also been applied in more complex cavity structures, such as distributed feedback lasers and photonic crystals lasers, in which the cavity modes are the Bloch modes associated with the periodic structure. Tuning the lattice constant then provides a simple tool to tune the laser for high-quality photonic crystals 15,16 or with localized periodicity 17,18 . These tricks do not work in random structures due to the absence of periodicity. Here we will show, however, that even in a completely random system with no periodicity, resonant tunability can be achieved based on singleparticle resonances.A random system, composed of particles of arbitrary shape and size, has a...

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Intrinsic intensity fluctuations in random lasers

Cited by 67 publications

References 19 publications

Quantitative analysis of several random lasers

Quantitative analysis of several random lasers

Effect of local pumping on random laser modes in one dimension

Resonance-driven random lasing

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