Direct laser writing of three-dimensional submicron structures using a continuous-wave laser at 532 nm

Three-dimensional direct laser writing is commonly associated with tightly focused femtosecond laser pulses. Although few reports have used continuous-wave lasers instead, it is unclear whether state-of-the-art three-dimensional submicron structures for photonics can be fabricated along these lines. Here, we systematically investigate the underlying mechanisms using a 532 nm continuous-wave laser operating at power levels of only some 10 mW and three different commercially available photoresists. Body-centered cubic woodpile photonic crystals composed of 24 layers with rod spacings as small as 450 nm serve as a demanding benchmark example for illustrating “state-of-the-art.”