Low-cost fabrication of microlasers based on polymeric micropedestals

Abstract

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 ∼ 53 µ m and a height of ∼ 40 µ m , 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 ∼ 5 µ J c m − 2 . The observed free spectral range associated with the lasing peaks of ∼ 1.3 n m 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.

Single‐Step 3D Printing of Micro‐Optics with Adjustable Refractive Index by Ultrafast Laser Nanolithography

“…This is essential for the active micro-optics, where the exact refractive index for the pump and emission wavelengths is critical and must be considered designing the microlaser cavities. [29] This opens the possibility of the design and fabrication of 4D printing (freedom in 3D shape and on-demand refractive index) of free-form micro-optical elements and stacked components out of a single hybrid organic-inorganic pre-polymer material. That is offering next step for free-form morphology and inhomogenuous refractive index distribution.…”

Supplementary document for Studies of transition between amplified spontaneous emission and optical lasing in ultrahigh-Q polymeric micro-pedestals - 6257453.pdf

“…The multiple resonances achieved by our devices (based on WGM) can be calculated by solving Equation S5 [7][8][9]:…”

“…Due to the dimensions of our cavities, attributing a single mode to each peak becomes a complicated task, instead, we decide to present a comb for multiple q, l, R mode-variation solutions where q is associated with the radial mode, m to the Azhimutal mode and R with the cavity radius [7][8][9][10]. Figure S2 (b).…”

Microfluidic system manufacturing by direct laser writing for the generation and characterization of microdroplets

“…However, the high economical cost of the equipment and the maintenance to operate has limited its use. Novel fabrication techniques based on 'direct laser writing' (DLW) are nowadays increasingly used [28][29][30][31][32]. DLW is among the photopolymerization techniques, and it stands up from stereolithography [33,34] and selective laser sintering [35,36] due to superior resolution and it does not require re-coating or layer by layer fabrication, neither specialized and, most of the times, expensive equipment [37].…”

“…DLW manufacturing protocol face problems associated with the convectional photolithography procedures and offer shorter fabrication times and higher flexibility for complex master mask designs. DLW fabrication method is based on 'Low One-Photon Absorption' (LOPA) [30], 'One-Photon Absorption' (OPA) [28] and 'Two-Photon Absorption' (TPA) [38]. The increasing importance of LOPA method lies in the convenience of using a CW laser set up, which operates in an ultra-low optical absorption regime and allows the fabrication of 3D microstructures by a high light intensity at the tight focusing spot with few milliwatts [28].…”