(Phys.org)—It has taken more than 20 years, but researchers have demonstrated for the first time that femtosecond lasers can be used to structurally manipulate bulk silicon for high-precision applications. Since the late ’90s, researchers have been using the ultrashort pulses of femtosecond lasers to write into bulk materials with wide band gaps, which are typically insulators. But until now, precise ultrafast laser writing has not been possible for materials with narrow band gaps, such as silicon and other semiconductors.