RESUMO
In this work, we demonstrate the properties of Rhodamine B-doped polymeric cylindrical microlasers to perform either as gain amplification devices through amplified spontaneous emission (ASE) or as optical lasing gain devices. A study based on different %wt concentrations of microcavity families with distinct geometrical features demonstrates the characteristic dependence on either gain amplification phenomena. Principal component analysis (PCA) discriminates the relationship between the main ASE and lasing properties and the geometrical aspects of the cavity families. ASE and optical lasing thresholds were found, respectively, as low as 0.2 µJcm-2 and 0.1 µJcm-2 passing the best-reported microlaser performances in literature for cylindrical cavities, even in comparison with those based on 2D patterns. Moreover, our microlasers showed ultrahigh Q-factor of â¼3 × 106, and for the first time, to the best of our knowledge, a visible emission comb constituted by above a hundred peaks at 40 µJcm-2 with a registered free spectral range (FSR) of 0.25 nm corroborated through the whispery gallery mode (WGM) theory.
RESUMO
Our current work exploits direct laser writing (DLW) and low one-photon absorption (LOPA) in a low-cost three-dimensional optical fabrication system designed to print micrometric polymeric structures. Micropedestals were obtained by focusing a laser beam on a photoresist layer deposited on a silica glass substrate. Subsequent coating with rhodamine 6G dye allows these pedestals to function as microlasers upon optical excitation at 532 nm. Our microlasers, with a diameter of â¼53µm and a height of â¼40µm, exhibit a broad fluorescence peak in the spectral range 540-600 nm, in addition to narrow lasing peaks, exhibiting quality factors Q exceeding 2000 and a lasing threshold of â¼5µJcm-2. The observed free spectral range associated with the lasing peaks of â¼1.3nm is consistent with simulations, which we include in this paper. In addition, we present simulations for the longitudinal shift of the patterning laser spot, which occurs particularly for relatively thick photoresist layers, coupled with a large index contrast at the photoresist top surface. Such a shift could introduce errors in the resulting microfabricated structures if left unaccounted for. We hope that our work will contribute to the development of microlasers for various photonic applications, particularly if dimensions can be reduced, for on-chip optical communications and data processing.