Ultrafast fiber laser delivers high energy and long-term reliability

Abstract

Conventional lasers used for materials processing often introduce undesirable side effects. Those operating at visible to near-IR wavelengths typically leave behind thermal damage, such as rough edges or changes to the material structure.1 UV lasers induce unwanted alterations in the basic chemistry of target materials.2 By contrast, ultrashort-pulse (USP) lasers—for which the pulse duration is shorter than the heat-diffusion time of the target material—can produce extremely fine features in almost any material without side effects.3 USP lasers that are cost-effective, reliable, and easy to use will enable commercial production of advanced medical implants (see Figure 1), lowcost solar panels,1 and many other devices. Researchers have demonstrated compelling applications for USP lasers using large and cumbersome systems based on solid-state-crystal amplification (i.e., titanium sapphire). These systems employ many free-space optical components4 and therefore require regular maintenance by a highly skilled technician or researcher. Commercially available systems use optical-fiber-based technology to bringmore compact but lowerpulse-energy USP lasers to the market place.5 Still, none of the existing laser architectures provide hands-off operation (i.e., no laser tuning or maintenance) with sufficient pulse energy and average power output. To address this technology gap, we have combined robust, uniquely configured fiber-optic telecom technology with microprocessors and embedded stabilization software to produce high-performance, reliable, and cost-effective USP lasers. In our platform, the software operating system does all of the monitoring and adjusting functions normally performed by a person. Our use of fiber to route the beam through the system largely avoids optical misalignment associated with using free-space components like mirrors and lenses. Scaling this platform to high energy requires expanding the mode-field area in the Latter amplifier stages, reducing losses in the Figure 1. Microscope image of the uniformmaterial structure and welldefined edge of a biodegradable stent (a wire-mesh tube) made with an ultrashort-pulse laser. The device was not subjected to any postprocessing.