In sintering and welding spots of different sizes are often processed in sequence. Solutions for changing beam spot size requiring external moving bulk optics, such as zoom collimators, are slow, expensive, result in energy losses and are prone to optics contamination. The YLR-AM laser allows user to rapidly change beam spot size from single-mode to ~3-5× larger in diameter from the same laser without any bulk moving external optics. Rapid switching between two spot sizes at approximately constant fluence results in up to 10× faster printing, reductions of capital cost and factory floor area. The single-mode core enables copper printing with a low-cost infrared laser.