Mie resonances to tailor random lasers

P. D. García, M. Ibisate, R. Sapienza, D. S. Wiersma, and C. López

Phys. Rev. A 80, 013833 – Published 29 July 2009

Abstract

In this paper, we present an optical characterization of photonic glass-based random lasers. We show how the resonant behavior of diffuse light transport through such systems can tailor the lasing emission when a gain medium is added to the glass. A DNA-based organic dye is used as gain medium. The resonances in the transport mean-free path influence the lasing wavelength of the random laser. The laser wavelength is therefore controlled by the sphere diameter. Furthermore, the existence of Mie resonances reduces the necessary pump energy to reach the lasing threshold.

Received 2 March 2009

DOI:https://doi.org/10.1103/PhysRevA.80.013833

Authors & Affiliations

P. D. García^1,*, M. Ibisate¹, R. Sapienza¹, D. S. Wiersma², and C. López¹

¹Instituto de Ciencia de Materiales de Madrid (CSIC) and Unidad Asociada CSIC–UVigo, Cantoblanco, 28049 Madrid, Spain
²European Laboratory for Nonlinear Spectroscopy and INFM–BEC, Sesto Fiorentino, 50019 Florence, Italy

^*Present address: DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, rsteds Plads 343, DK-2800 Kgs. Lyngby, Denmark; dgar@fotonik.dtu.dk

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Issue

Vol. 80, Iss. 1 — July 2009

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Images

Figure 1
(Color online) Schematic diagram for the gain medium. (a) Representation of DNA helices. (b) Inclusion of DCM organic dye into the helices of the DNA.Reuse & Permissions
Figure 2
(Color online) (a) Emission intensities below (dashed curve) and above (continuous curve) the threshold in the case of DCM@DNA embedded in a ${TiO}_{2}$ matrix. The lasing mode is defined by the gain maximum. (b) Emission intensity and its full width at half maximum (FWHM) as a function of pumping energy. A clear threshold appears at a $500 μ J$ per pulse. Pumping spot size is 2 mm.Reuse & Permissions
Figure 3
(Color online) (a) Random laser emission from photonic glasses with different sphere diameter compared to the pure dry dye fluorescence and a reference sample made with ${TiO}_{2}$ powder doped with DCM@DNA. The pump energy for every sample is around 10 mJ. [(b) and (c)] Emission intensity and total transmission for photonic glasses, respectively, with $d = 0.9 μ m$ and $d = 1.0 μ m$ . Lasing occurs close to the transmission minimum.Reuse & Permissions
Figure 4
(Color online) Real image of the lasing mode from $d = 0.9 μ m$ and $d = 1.0 μ m$ photonic glasses doped with DCM@DNA with a pump energy around 10 mJ in both cases. The spectral difference between both lasing emissions $(\sim 30 nm)$ is distinguishable by naked eye.Reuse & Permissions
Figure 5
(Color online) (a) Total integrated transmission for a photonic glass with $d = 1 μ m$ (continuous curve) and from a colloidal suspension of the same spheres ( $5 vol %$ of concentration) in ethanol (dashed curve). The refractive index of the host medium increases, respectively, from 1 (air) to 1.36 (ethanol). (b) Random laser emission for different spheres suspension in ethanol with DCM@DNA as optical active medium, with an external pump energy fixed at 10 mJ. In this case, the total spectral separation of the emission maxima for the different suspensions is only 7 nm.Reuse & Permissions
Figure 6
Threshold for various photonic glasses: a standard sample with $d = 0.2 μ m$ $(d / λ_{lasing} = 0.3)$ which does not sustain Mie resonances in the visible, two photonic glasses with $d = 0.9 μ m$ $(d / λ_{lasing} = 1.45)$ and $d = 1.0 μ m$ $(d / λ_{lasing} = 1.6)$ which sustain Mie resonances within the gain curve and a polydisperse arrangement $(\sim 42 %)$ of PS spheres for which a threshold appears at 3.9 mJ. This plot points out how the existence of scattering resonances for light within the gain spectral range reduces the pump energy necessary to achieve gain larger than losses.Reuse & Permissions

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