“…Thanks to its unique 3D structuring capabilities, FLW has enabled many innovative geometries for the fabrication of integrated photonic devices like directional couplers and Y-splitters [5], complex multipaths interferometers [6], 3D waveguide lattices [7,8], polarization rotators [9,10], and Bragg reflectors [11]. This versatility, in addition to low-cost and rapid prototyping, has allowed the fabrication of FLW-based devices for waveguide-assisted applications in several fields like astrophotonics [12], telecommunications [13], high-order harmonic generation in gases [14], optical [15,16] and NV center-based sensing [17]. Most notably, FLW-based optofluidic and microfluidic lab-on-chip techniques, in which three-dimensional microchannels and optical waveguides are monolitically integrated within the same substrate, [18,19] are now a mature technology used world-wide for chemical analysis [20,21], biosensors [22] and single-cell processing tools [23][24][25].…”