Purpose: The purpose of this paper is to explore the possibility of an enhanced continuous liquid interface production (CLIP) with a porous track-etched membrane as the oxygen-permeable window, which is prepared by irradiating polyethylene terephthalate membranes with accelerated heavy ions. Design/methodology/approach: Experimental approaches are carried out to characterize printing parameters of resins with different photo-initiator concentrations by a photo-polymerization matrix, to experimentally observe and theoretically fit the oxygen inhibition layer thickness during printing under conditions of pure oxygen and air, respectively, and to demonstrate the enhanced CLIP processes by using pure oxygen and air, respectively. Findings: Owing to the high permeability of track-etched membrane, CLIP process is demonstrated with printing speed up to 800 mm/h in the condition of pure oxygen, which matches well with the theoretically predicted maximum printing speed at difference light expose. Making a trade-off between printing speed and surface quality, maximum printing speed of 470 mm/h is also obtained even using air. As the oxygen inhibition layer created by air is thinner than that by pure oxygen, maximum speed cannot be simply increased by intensifying the light exposure as the case with pure oxygen. Originality/value: CLIP process is capable of building objects continuously instead of the traditional layer-by-layer manner, which enables tens of times improvement in printing speed. This work presents an enhanced CLIP process by first using a porous track-etched membrane to serve as the oxygen permeable window, in which a record printing speed up to 800 mm/h using pure oxygen is demonstrated. Owing to the high permeability of track-etched membrane, continuous process at a speed of 470 mm/h is also achieved even using air instead of pure oxygen, which is of significance for a compact robust high-speed 3D printer.

We firstly propose the integration of heterogeneous Tm:YAG and Ho:YAP crystals into a single bulk structure for a compact, diode-pumped passively Q-switched (PQS) Ho laser. Efficient 2129 nm laser, with maximum CW power of 6.67 W was obtained from the Tm:YAG/Ho:YAP gain medium, with slope efficiency of 38.3% and optical conversion efficiency of 27.4% by considering the incident diode power at 785 nm. Modulated by a Cr:ZnSe saturable absorber inside a hybrid cavity, characteristic self-pulsing of the integrated Ho laser can be suppressed for a stable PQS process, where average output power of 743 mW at 2053.3 nm was obtained with shortest pulse duration of 123 ns at 14.2 kHz. As the maximum thermal stress of 48.2 MPa is far below the fracture limits of each integrated section (~160 MPa), higher laser power can be expected. The results pave the way to explore the integration of other existing Tm-doped and Ho-doped hosts for an accessible 2.1 m source.