Lasing with well-defined cavity modes in dye-infiltrated silica inverse opals

Abstract

Lasing in dye solution-embedded inverse silica opal structures was investigated. The opal films were prepared by sedimentation of polystyrene microspheres on a cover glass. The polystyrene structures were inverted using sol-gel infiltration of silica and subsequent removal of polystyrene. Photoluminescence of rhodamine (rhodamine B, 6G and sulfo-rhodamine 101) dye solutions embedded into the inverse silica opal structures exhibited clear signatures of the lasing via a distributed feedback (DFB) and gain modulation. The refractive index contrast between the dye and the inverse opal was small enough (approximately 0.03%) for the formation of refractive index coupling between the lasing modes. The lasing spectrum exhibited a highly regular periodic structure of modal peaks, rather than the chaotic superposition of peaks reported in previous studies. Lasing modes having a spectral width of about 0.25 nm and a free spectral range of about 0.75 nm appeared at the position of the maximum gain (the maximum fluorescence of the dye).

Advances in small lasers

“…These materials can be readily prepared as thin films (e.g., with thicknesses << 1 µm) by solution-based processes. In some cases, structures providing optical feedback can even form via self-assembly [33][34][35] . Moreover, the gain spectrum of these materials can be readily tuned by targeted modifications of chemical structure, composition and characteristic dimension (Fig.…”

“…Distributed feedback (DFB) structures can be written into these gain materials directly using electron-beam or interference lithography; for certain materials even in a rewritable fashion, hence allowing a post-fabrication adjustment of the resonant wavelength 41,61 . Organic lasers based on 2D photonic crystal structures 62 and small dye lasers comprising of 3D inverse opal structures 34 have also been demonstrated. Microfluidic lasers also benefit from photonic crystals; circular gratings and photonic band-gap fibers have been used to reduce laser footprint 37,39 .…”

Optical Characterization and Lasing in Three-Dimensional Opal-Structures

“…Here, we demonstrate the formation of well-ordered opals by sedimentation in wet-etched micro-pits in silicon by fast centrifugation (Nishijima, 2009), which the single crystalline fcc opal photonic crystals with large area and short time can be obtained. The resulting three-dimensional structures were characterized by confocal fluorescence and optical diffraction and compared with opal-structures obtained on flat substrates.…”

“…This corroborates that the single pyramidal crystals have better wavelength stability of the lasing modes. This type of lasing is not defined by the photonic band gap because of the low refractive index contrast between silica (1.46) and ethylene glycol (1.42) (Kitamura et al, 2007;Nishijima, 2009;Nishijima et al, 2009a). Rather, it is determined by the distributed feedback (DFB) in the dye as demonstrated recently (Nishijima et al, 2008).…”

“…The Rh6G solution (without SRh) spectra showed lasing with a well-ordered modal structure. The lasing mechanism is due to a gain distributed feedback (DFB) since the refractive index contrast between the silica and dye solution was negligible, and there were no formation of photonic stop gap (Nishijima et al, 2009a). With the addition of SRh (into Rh6G), the lasing of Rh6G changed into amplified spontaneous emission (ASE) while lasing of SRh at the longer wavelength was obtained.…”