Random lasing in ballistic and diffusive regimes for macroporous silica-based systems with tunable scattering strength
Random lasing in ballistic and diffusive regimes for macroporous silica-based systems with tunable scattering strength
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DOI：
10.1364/oe.18.012153
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发表时间：
2010-06-07
期刊：
影响因子：
3.8
通讯作者：
Tanaka, Katsuhisa
中科院分区：
文献类型：
--
作者：
Meng, Xiangeng;Fujita, Koji;Tanaka, Katsuhisa
我们系统地研究了由浸泡在染料溶液中的大孔二氧化硅圆盘组成的弱散射系统中的随机激光特性，其中溶剂是两种醇的混合物。通过控制混合溶剂的折射率，我们可以在很大范围内改变散射强度。我们发现在发射光谱中出现线宽小于1.0 nm的尖峰的两种不同的散射区，即具有相干反馈的随机激光。当溶剂和二氧化硅之间的折射率对比度很小时，虽然系统看起来几乎是透明的，但观察到了相干反馈的随机激光。当折射率对比度增大到某一临界值时，相干反馈消失，而折射率对比度进一步增大，相干反馈恢复。我们认为，微腔的存在在很弱的散射区(弹道)中起着重要的作用，而当散射强度增加时，其他机制，如放大的扩展模，可能会导致激光振荡的相干反馈。(C)2010年美国光学学会
We have systematically investigated random lasing properties in weakly scattering systems composed of a macroporous silica disk immersed in a dye solution where the solvent is a mixture of two alcohols. Controlling the refractive index of the mixed solvent allows us to vary the scattering strength over a wide range. We have found two different scattering regimes where sharp spectral spikes with linewidth less than 1.0 nm, i.e., random laser with coherent feedback, appear in emission spectra. When the refractive index contrast between the solvent and the silica is very small, random lasing with coherent feedback is observed although the system appears nearly transparent. The coherent feedback vanishes when the refractive index contrast is increased up to a critical value, while further increase in the refractive index contrast results in the revival of the coherent feedback. We suggest that the existence of underlying microcavities plays an important role in the very weakly scattering regime (ballistic) while other mechanisms such as amplified extended modes may lead to the coherent feedback in lasing oscillation when the scattering strength increases. (C)2010 Optical Society of America