Quasi-Two-Dimensional Diffusive Random Laser Action

Gottardo, S.; Cavalieri, Stefano; Yaroshchuk, O.; Wiersma, Diederik S.

doi:10.1103/physrevlett.93.263901

Cited by 173 publications

(95 citation statements)

References 29 publications

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“…The large interaction volume can exploit several feedback paths through scattering, support many coupled lasing modes [44] and their competition/thermalization [45], producing smoother spectrum and spatial profile as compared to "standard" random lasers. Furthermore, owing to anisotropic light scattering in uniaxials [46], the spontaneous as well as the stimulated emissions in NLC doped with pyrromethene-dye tend to be polarized in the plane of the director alignment [10,43]; hence, the generated photons are co-polarized with the reorientational soliton and can be trapped in the light-induced waveguide, the nematicon. At variance with a standard one-beam configuration (see Fig.…”

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confidence: 99%

Soliton-assisted random lasing in optically-pumped liquid crystals

Perumbilavil

Piccardi

Buchnev

et al. 2016

Applied Physics Letters

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We demonstrate a novel random laser configuration by exploiting the coexistence of optical gain and light self-localization in a reorientational nonlinear medium. A spatial soliton launched by a near-infrared beam in dye-doped nematic liquid crystals enhances and confines stimulated emission of visible light in the optically-pumped gain-medium, yielding random lasing with enhanced features.In random lasers, a disordered distribution of scattering centers provides the required feedback for oscillations in optically amplifying media. In recent years they have attracted a great deal of attention, mainly due to the versatility stemming from cavity-less geometries and the ease of realization [1][2][3][4][5][6][7][8][9]. In liquid crystals, suitable dopants can provide the gain action through optical pumping, while optical birefringence in conjunction with intense fluctuations of the dielectric tensor yield the required recurrent multiple scattering for random resonances to occur [10][11][12][13][14][15][16][17]. In the nematic phase, moreover, liquid crystals are positive uniaxial materials subject to optic axis reorientation under the action of electric fields, either at low or optical frequencies [18]. The latter response provides a low-power mechanism for nonlinear optics [19] and light localization into self-confined lightbeams, the so-called "nematicons" [20]. Nematicons are bright spatial solitons (solitary waves) which are stable in two transverse dimensions due to the nonlocal response associated with the elastic intermolecular links in the liquid state [21,22]; they support graded-index waveguides able to confine additional (incoherent) signals/beams of different wavelengths as well as powers and profiles [23][24][25][26][27][28][29][30], are robust against refractive index perturbations [31-35] and collisional interactions [36][37][38]. Aided by nematicons, reorientational and electronic nonlinear responses, characterized by distinct time-and power-scales, can synergystically be combined [39,40]. Owing to their large numerical aperture [41], nematicon waveguides solitons have also been employed in experiments involving incoherent light generation by fluorescence [42] or amplified spontaneous emission [43], offering a means to better collect and couple the emitted light into optical fibers.In this Letter we demonstrate a novel example of synergy between diverse nonlinear responses: the combination of spatial solitons and random lasing into a "nematicon random laser", whereby a low-power self-confined beam provides a guided-wave landscape for the stimu- * assanto@uniroma3.it lated emission induced by collinear optical pumping of dye-doped nematic liquid crystals (NLC).Several benefits can be expected from adopting such light-induced guided-wave configuration for random lasing. At variance with standard thin film geometries, the thick NLC cell provides an extended volume where optical pumping can produce fluorescence and, in turn, stimulated emission and lasing action via random scattering and feedback. The la...

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confidence: 99%

Soliton-assisted random lasing in optically-pumped liquid crystals

Perumbilavil

Piccardi

Buchnev

et al. 2016

Applied Physics Letters

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“…Prospective of random lasing is however strongly hindered by the absence of emission control: random lasers are highly multimode with unpredictable lasing frequencies and polydirectional output. Manipulation of the underlying random structure [14][15][16][17][18][19][20][21][22][23] and recent work constraining the range of lasing frequencies [24,25] have resulted in significant progress toward possible control. However, the ability to choose a specific frequency in generic random lasing systems has not yet been achieved.…”

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confidence: 99%

Taming Random Lasers through Active Spatial Control of the Pump

et al. 2012

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Active control of the pump spatial profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable singlemode operation of a random laser.PACS numbers: 42.55. Zz,42.25.Dd Multiple scattering of light in random media can be actively manipulated through spatial shaping of the incident wavefront [1]. This technique has allowed advances in focusing [2][3][4], and imaging [5,6], paving the road to actual control of light transport in strongly scattering media [7][8][9]. Introducing gain in disordered media allows amplification of multiply scattered light, leading to the observation of random lasing [10]. The broad range of systems where it has been studied [11] and the fundamental questions it has raised [12,13] has captivated the community for this last decade. Prospective of random lasing is however strongly hindered by the absence of emission control: random lasers are highly multimode with unpredictable lasing frequencies and polydirectional output. Manipulation of the underlying random structure [14][15][16][17][18][19][20][21][22][23] and recent work constraining the range of lasing frequencies [24,25] have resulted in significant progress toward possible control. However, the ability to choose a specific frequency in generic random lasing systems has not yet been achieved. The spatial profile of the pump is an interesting degree of freedom readily available in random laser (e.g., [26,27]). In a regime of very strong scattering where the modes of the random system are spatially localized [28], local pumping allows selection of spatially non-overlapping modes [29,30]. In weaker scattering media however (e.g., [31][32][33]), several hurdles appear toward achieving fine control. Selecting modes is complicated by a narrow distribution of lasing thresholds [34,35] and spatial mode overlap. Increased pumping required in these lossy systems begins to alter the random laser itself. Moreover, modifying the shape of the pump introduces changes to both the spatial and spectral properties of lasing modes [33,[36][37][38]. Such difficulties are typically absent in more conventional lasers, which have employed pump shaping, both electrically [39][40][41][42] and optically [43], to select favorable lasing modes. The question is, can shaping of the incident pump field achieve taming of random lasers?In this letter, we exercise control over the distribution of lasing thresholds via the pump geometry to choose the random laser em...

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“…10,11 Instead the emission appears to collapse into a broader extended mode, synonymous with diffusive materials. 12 It is important to note that due to the polydispersity of our sample, scattering is considered to be nonresonant, in contrast to the resonance-driven random lasing observed by Gottardo et al 13 from monodisperse particulates.…”

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confidence: 99%

Band-edge and random lasing in paintable liquid crystal emulsions

Hands

Gardiner

Morris

et al. 2011

Applied Physics Letters

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Lasing mechanisms within paintable dye-doped chiral liquid crystal emulsions are investigated. Evidence shows that by variation in liquid crystal droplet size, by simple control of mechanical mixing speeds, a change in the lasing mechanism from band-edge lasing (large droplets) to diffuse nonresonant random lasing (small droplets) can be facilitated. This approach represents a facile technique for the variation in lasing mechanism, within a self-organizing, flexible, and conformable system, and offers the opportunity of developing controllable linewidth laser sources.

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Quasi-Two-Dimensional Diffusive Random Laser Action

Cited by 173 publications

References 29 publications

Soliton-assisted random lasing in optically-pumped liquid crystals

Soliton-assisted random lasing in optically-pumped liquid crystals

Taming Random Lasers through Active Spatial Control of the Pump

Band-edge and random lasing in paintable liquid crystal emulsions

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