Ultrafast parallel laser processing with SLMs for high throughput manufacturing

Laser patterning of organic LEDs is a key industrial process in the manufacturing of OLED displays or solid-state lighting foils [1]. Ultrafast lasers are of particular interest for this application as they enable selective ablative removal of OLED layers with very low energy density requirements on target. Since sufficient laser output from commercial laser sources is currently exceeding single beam process requirements, parallel processing with multiple beams could provide an easy route for up-scaling processing speed and suppress manufacturing costs. In this paper, we propose the use of a reflective liquid crystal on silicon (LCoS) spatial light modulator (SLM), driven by fast computer generated holograms (CGHs) for splitting a parent laser beam to a number of beamlets and digitally manipulate their position and laser intensity on target [2]. With successful blocking of the non-diffracted zero order beam and subsequent delivery of the SLM diffracted beams using a galvanometer scanner and flat-field telecentric lens, we demonstrate high throughput precision patterning of thin film electrodes (ITO anode and metal cathode) on flexible substrates. It is additionally shown that, by careful adjustment of laser intensity in each of the diffracted spots, one can selectively remove one or more layers simultaneously in adjacent locations all within a single scanning step. Microscopic examination with optical profilers and SEM reveals the extent of resolution, process quality and assist quantification of the process speed gain. The benefits and current limitations of this technique are discussed in detail.