Medical Device Link.

PRECISION TECHNOLOGY

If short pulses produce better results—smaller features and better edge quality—why stop at 10 ns? Why not use even shorter pulses? Indeed, in many micromachining applications, thermal effects become insignificant at pulse widths of less than 1 ns. Nanosecond laser pulses are created by a process called Q-switching. Unfortunately, at power levels that are practical for micromachining, it is very difficult to produce highly stable Q-switched DPSS lasers with pulses much shorter than 10 ns.

An alternative pulsing approach, called mode locking, has long been used in scientific lasers to produce laser pulses as short as picoseconds and femtoseconds (1 picosecond = 10–12 seconds; 1 femtosecond = 10–15 seconds). However, these so-called ultrafast lasers have been limited in two ways. Either their pulse energy or overall power were too low for commercial micromachining, or they did not offer the reliability and turnkey simplicity necessary for 24/7 manufacturing operations.

In the past year, industrial-grade picosecond lasers have finally become available, driven in part by the demands of the microelectronics industry. These lasers use a novel fiber-laser architecture that was originally developed for high-reliability telecommunications applications. The picosecond pulses will benefit micromachining in two ways. First, they eliminate thermal effects. Second, their extreme peak power means they remove material by a nonlinear optical process whose cross section is narrower than the full spot size of the focused laser, so they can produce smaller features.

At this early stage, the higher cost of these lasers compared with ns lasers will limit their use to high-value applications where these benefits are critically enabling factors. As the technology matures, their use will definitely expand into commodity products that include some medical disposables.