Fig. 1. (a) Schematic of the SLM-assisted spatially shaped fs laser microfabrication system. The dashed blue rectangle indicates the phase diagram loaded onto the SLM. (HWP: half-wave plate; P: pinhole; OBJ: objective lens; M: metal mirror; D: dichroic mirror; BE: beam expander; L1 and L2 represent lenses with different focal lengths.) (b) Top-view and (c) side-view optical micrographs of the laser-written tracks inside the fused silica. The dashed line in (c) indicates the glass surface. The image below the dashed line in (c) shows the actual structure of the laser-written tracks, while the one above the dashed line is a virtual image created by optical microscopy.

Fig. 2. Relationship between the etching rate and Ep under different θ and N values: (a) N=40  pulses μm−1 and (b) N=10  pulses μm−1. Top-view optical micrographs of 2 h etched microchannels under different θ, Ep, and N values: (c) N=40  pulses μm−1 and (d) N=10  pulses μm−1. Ep gradually increased from the top to the bottom in each micrograph in (c) and (d). The etching of laser-written tracks began at the open ports indicated by arrows.

Fig. 3. Top-view SEM images of fs-laser-modified regions in fused silica under different θ and N values: (a) N=40  pulses μm−1 and (b) N=10  pulses μm−1. Ep was set at 1.6 μJ.

Fig. 4. Relationship between the etching rate and Ep under different θ and N values: (a) N=5  pulses μm−1, (b) N=20  pulses μm−1, and (c) N=25  pulses μm−1. (d) Etching rate versus θ under different laser processing parameters (N and Ep).

Fig. 5. Top-view SEM images of fs-laser-modified regions (N=5  pulses μm−1) in fused silica under different θ and Ep: (a) 1.3 μJ and (b) 2.1 μJ.

Fig. 6. Centimeter-length curved microchannels fabricated by laser-assisted etching in fused silica. (a) A fabricated microchannel structure including a circular-shaped microchannel and two straight microchannels. (b) Four parallel and concentric racetrack microchannels. In (a) and (b), the left panels (i) show photographs of the channels (N=10  pulses μm−1), respectively. The middle (ii) and right (iii) panels present optical micrographs of the channels within the dashed rectangles indicated in (i) and the fabricated channels (N=40  pulses μm−1) for comparison, respectively. The pulse energy was 1.6 μJ. The inset in the middle panel (ii) in (b) shows the circular cross-section of the microchannel enabled by slit-assisted beam shaping.

Fig. 7. (a) Photograph of a curved microchannel structure used for fabricating a bending optofluidic waveguide in glass. The microchannels indicated within the dashed yellow rectangles were used to fill the liquid-core solutions. (b) Insertion loss of the bending optofluidic waveguide versus mixing decane and liquid paraffin proportions. The inset in (b) illustrates the schematic of the experimental layout used to measure waveguide loss. (c) Mode field profiles of the optofluidic waveguides with different liquid-core solutions. The mixing proportions of decane and liquid paraffin (Vd/Vp) were 1:3, 1:4, 1:5, and 1:6 from left to right. The insets in (c) show the near-field mode images of the waveguide at the output port for each condition.

Fig. 8. Fabrication of 1×2 and 1×4 optofluidic waveguide beam splitters in glass. (a) Photograph of the fabricated microchannels for the waveguide beam splitters in glass. (b) and (c) are the optical micrographs of the 1×2 and 1×4 splitting parts of the microchannels shown in (a), respectively. The black arrows in (b) and (c) indicate the typical locations of extra-access ports. The bottom-left insets in (b) and (c) are near-field mode images of the formed waveguide beam splitters at the output port. The top-right insets in (b) and (c) are the top-view optical micrographs of the microchannels filled with liquid-core solutions.

Fig. 9. Flowchart of the fabrication process for optofluidic waveguides in fused silica. The fabrication procedure consists of four steps. First, the fs laser beam spatially shaped by the SLM is utilized for 3D direct writing in fused silica to inscribe the programmed micropatterns of curved microchannels. Second, hollow microchannels and extra-access ports are formed by selective chemical etching of the laser-processed fused silica samples in 10 mol/L KOH solution at 90°C. Third, the ports are sealed to create closed and smooth channels by defocusing CO2 laser irradiation. Finally, optofluidic waveguides are formed within the channels using vacuum-assisted liquid-core filling.

Fig. 10. Schematic of the defocusing CO2 laser irradiation for port sealing. The average power and defocusing distance of the CO2 laser beam were approximately 30.7 W and 21.9 cm, respectively.

Fig. 11. Schematic of SLM-enabled dynamic slit-assisted laser writing for creating micropatterns of curved microchannels. During laser processing, the slit orientation remained parallel to the laser writing direction. The black and yellow arrows indicate the laser writing direction and the orientation of the SLM-enabled slit at specific positions, respectively.

Fig. 12. (a) Photograph of a ∼51  mm long microchannel with a turning radius of 2 mm for forming a multi-mode bending optofluidic waveguide. The inset shows a near-field mode image of the optofluidic waveguide at the output port. (b), (c) Microscope images of the corresponding sections of the optofluidic waveguide constructed from the microchannels shown in (a). The black arrows in (b) and (c) indicate the specific extra-access ports of the microchannels. The microchannel consists of four semicircular channels with radii of 2 mm each and five straight channels. The optofluidic waveguide was formed within the channel by filling it with a mixture of decane and liquid paraffin in a 1:3 ratio.