Spatial Extent of Random Laser Modes

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

doi:10.1103/physrevlett.98.143901

Cited by 149 publications

(135 citation statements)

References 31 publications

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“…This phenomenon has been dubbed RL with incoherent feedback (IFRL) because it may be explained in the framework of the diffusion approximation [10] that neglects interference and treats light rays as the trajectories of random walking particles. However this theoretical framework does not explain another kind of RL exhibitting subnanometre sharp spectral peaks [11][12][13] …”

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confidence: 99%

The mode-locking transition of random lasers

2011

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The discovery of the spontaneous mode-locking of lasers, i.e., the synchronous oscillation of electromagnetic modes in a cavity, has been a milestone of photonics allowing the realization of oscillators delivering ultra-short pulses. This process is so far known to occur only in standard ordered lasers with meter size length and only in the presence of a specific device (the saturable absorber). Here we demonstrate that mode-locking can spontaneously arise also in random lasers composed by micronsized laser resonances dwelling in intrinsically disordered, self-assembled clusters of nanometer-sized particles. Moreover by engineering a novel mode-selective pumping mechanism we show that it is possible to continuously drive the system from a configuration in which the various excited electromagnetic modes oscillate in the form of several, weakly interacting, resonances to a collective strongly interacting regime. By realizing the smallest mode-locking device ever fabricated, we open the way to novel generation of miniaturized and all-optically controlled light sources.Random lasers[1] (RLs) are made by disordered highly scattering materials able to amplify light when externally pumped. The simultaneous presence of structural disorder and nonlinearity makes these devices a fertile ground to connect photonics with advanced theoretical paradigms[2] like chaos [3], non Gaussian statistics[4], complexity [5] and also the physics of Bose Einstein condensation [6]. Historically there has been a bridge in the RL interpretation. In pioneering experiments a smooth, single-peaked emission was produced by pumping finely ground laser crystals [7], or titania particles dispersed in a dye-doped solution [8,9]. This phenomenon has been dubbed RL with incoherent feedback (IFRL) because it may be explained in the framework of the diffusion approximation [10] that neglects interference and treats light rays as the trajectories of random walking particles. However this theoretical framework does not explain another kind of RL exhibitting subnanometre sharp spectral peaks [11][12][13] associated with high-Q resonances[14-17] and labeled resonant feedback random laser(RFRL).Standard multimode lasers without disorder and characterized by equispaced resonances may be driven to a synchronous regime through the so called mode-locking transition [18,19], which so far has only been shown to occur spontaneously in the presence of a saturable absorber and allows to generate ultra-short light pulses [20,21]. We show that the same transition occurs in RLs and allows to lock modes of a RFRL casting its emission in the typical IFRL spectrum and demonstrating the inherently coherent nature of the random lasing phenomenon.The system we consider is an isolated micrometer sized cluster of titania nanoparticles immersed in a rhodamine dye solution (see supplementary information (SI)). In our novel setup we use the amplified spontaneous emission (ASE) from the surrounding dye to pump the cluster. The the ASE areas are defined by shaping the beam of an e...

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confidence: 99%

The mode-locking transition of random lasers

2011

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“…First-principle time domain simulations show that modes of a RL arise from electromagnetic states [6][7][8] , that may appear in localized or extended fashion. Several experiments confirmed this view 2,9,10 , and tried to address the connection between the structure 11 pumping condition, or gain and the degree of localization [12][13][14] .…”

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Tunable degree of localization in random lasers with controlled interaction

2012

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We show that the degree of localization for the modes of a random laser (RL) is affected by the inter mode interaction that is controlled by shaping the spot of the pump laser. By experimentally investigating the spatial properties of the lasing emission we infer that strongly localized modes are activated in the low interacting regime while in the strongly interacting one extended modes are found lasing. Thus we demonstrate that the degree o localization may be finely tuned at the micrometer level.PACS numbers: 42.25.Dd 07.05.Fb Keywords: Light localization, Random lasing RL are among the most complex systems in photonics, encompassing structural disorder and nonlinearity, 1 and ranging from micron sized optical cavities 2 to kilometerlong fibers 3 . Attention on this systems has been constantly growing as the number of potential applications, ranging from object coding 4 to speckle-free illumination 5 .First-principle time domain simulations show that modes of a RL arise from electromagnetic states [6][7][8] , that may appear in localized or extended fashion. Several experiments confirmed this view 2,9,10 , and tried to address the connection between the structure 11 pumping condition, or gain and the degree of localization 12-14 . The The pulsed laser (532 nm, repetition frequency 10 Hz and fluence 0.1nJ/µm 2 ), whose spot is shaped by a SLM in amplitude configuration (by using the two crossed polarizers P1 and P2), pumps a single titanium dioxide cluster (diameter between 5 and 12 µm). The RL emission is collected by a microscope objective (OBJ) to be imaged by using a beamsplitter (BS) in two different image planes. In one of them lies a fiber controlled by translators with nanometric resolution that allows the measurement of the spatio-spectral map. In this way it is possible to scan a magnified (50×) image of the sample and measure the spectra emitted from a single point. The fibre core (50 µm in diameter) collects spectra originating in an area of 1µm of diameter of the sample. The other light path allows imaging the sample on a CCD. presence of many modes may give rise to unique phenomena: in a linear system extended necklace states spread over the sample via multiple (localized) resonances 15 while in a system with gain the inter-mode coupling affects the whole spectrum generating mode repulsion 16 directly connected to the nonlinear interaction 17 .On the other hand it has been recently demonstrated that the inter-mode coupling plays a critical role in the onset of two fundamentally different RL regimes, distinguished by the shape of the emission: a "resonant feedback random laser" (RFRL) 18 , which appears as a set of sharp peaks oscillating independently at fixed spectral positions, and the "intensity feedback random laser" (IFRL) 19 , characterized by a smooth single line narrowed spectrum. By using a tailored spatial shape of the pump area 20,21 , a switching between the two can be achieved. In fact a RFRL is observed when activating a set of weakly interacting resonances while IFRL is produced un...

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“…There is a large literature on RLs motivated by the interest in a deeper understanding of the fundamental properties of RLs [33][34][35][36], as well as reports on their possible application in sensing [37], optofluidics [38,39], and imaging [40], among other fields [41]. Moreover, although from the fundamental point of view there are many reports focusing on the basic characteristics of RLs and their operation, the analogies between RLs and other complex systems have been investigated by experiments only recently.…”

Section: Introductionmentioning

confidence: 99%

Lévy Statistics and Glassy Behavior of Light in Random Fiber Lasers

Araújo¹,

Gomes²,

Raposo³

2017

Preprint

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Abstract:The interest in random fiber lasers (RFLs), first demonstrated one decade ago, is still growing and their basic characteristics have been studied by several authors. RFLs are open systems that present instabilities in the intensity fluctuations due to the energy exchange among their non-orthogonal quasi-modes. In this work, we present a review of the recent investigations on the output characteristics of a continuous-wave erbium-doped RFL, with emphasis on the statistical behavior of the emitted intensity fluctuations. A progression from the Gaussian to Lévy and back to the Gaussian statistical regime was observed by increasing the excitation laser power from below to above the RFL threshold. By analyzing the RFL output intensity fluctuations, the probability density function of emission intensities was determined, and its correspondence with the experimental results was identified, enabling a clear demonstration of the analogy between the RFL phenomenon and the spin-glass phase transition. A replica-symmetry-breaking phase above the RFL threshold was characterized and the glassy behavior of the emitted light was established. We also discuss perspectives for future investigations on RFL systems.

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Spatial Extent of Random Laser Modes

Cited by 149 publications

References 31 publications

The mode-locking transition of random lasers

The mode-locking transition of random lasers

Tunable degree of localization in random lasers with controlled interaction

Lévy Statistics and Glassy Behavior of Light in Random Fiber Lasers

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Spatial Extent of Random Laser Modes

Cited by 149 publications

References 31 publications

The mode-locking transition of random lasers

The mode-locking transition of random lasers

Tunable degree of localization in random lasers with controlled interaction

L&eacute;vy Statistics and Glassy Behavior of Light in Random Fiber Lasers

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Lévy Statistics and Glassy Behavior of Light in Random Fiber Lasers