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Improving the photon collection efficiency in light-sensitive devices is crucial for next-generation photodetectors and solar cells. A valid strategy consists of placing a microlens or microlens array (MLA) on top of the active area of these devices, with sustained gains of up to 50% in their quantum efficiency. However, current technologies for micro-optics fabrication can be limited in throughput, attainable geometries, fill-factor (FF), or range of suitable substrates. In this talk, I will show how the combination of additive manufacturing with photopolymer materials can help fill this void and produce customized microlenses and MLA over planar, curved, and flexible substrates. Specifically, I will focus on two different strategies. The first one uses laser pulses to print liquid pre-polymer droplets on targeted locations of a substrate [1,2]. After a UV-curing step, the droplets become solid microlenses that exhibit almost perfectly smoothness. In the second strategy, termed laser catapulting (LCP), irradiation of a cross-linked photopolymer film results in the delamination and ejection of microdisks that are collected on a substrate of interest [3]. Following a thermal reflow process, the discs are converted into high-quality microlenses whose focusing power and geometry depend on the initial laser parameters [4,5]. I will present an in-depth experimental characterization of the two strategies, discuss their advantages and pitfalls, and illustrate their suitability in several applications, including enhancing the performance of single-photon avalanche diode (SPAD) arrays for super-resolution microscopy.
1. C. Florian, S. Piazza, A. Diaspro, P. Serra, and M. Duocastella, "Direct Laser Printing of Tailored Polymeric Microlenses," ACS Appl. Mater. Interfaces 8, 17028–17032 (2016).
2. S. Surdo, A. Diaspro, and M. Duocastella, "Microlens fabrication by replica molding of frozen laser-printed droplets," Appl. Surf. Sci. 418, (2017).
3. S. Surdo, R. Carzino, A. Diaspro, and M. Duocastella, "Single-Shot Laser Additive Manufacturing of High Fill-Factor Microlens Arrays," Adv. Opt. Mater. 6, 1701190 (2018).
4. S. Surdo, A. Diaspro, and M. Duocastella, "Geometry-controllable micro-optics with laser catapulting," Opt. Mater. Express 9, (2019).
5. S. Surdo, A. Diaspro, and M. Duocastella, "Printability conditions for an all-solid-state laser transfer," Appl. Surf. Sci. 506, (2020).
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