IMRA America Inc.

The development of a "temporally tailored" laser source that produces a rectangular pulse shape with real-time tunable pulse duration between 4 and 20 ns at 20-kHz rates was made possible by combining three technical innovations: preshaped nanosecond diode seeders, fiber optic devices and femtosecond amplifier technologies.

IMRA America Inc. of Ann Arbor, Mich., developed the GX Pulsar industrial laser at the request of the semiconductor industry for a proprietary application. The design is based on ytterbium-doped fiber amplifier technology that was originally developed for a femtosecond amplified system. A special property of this fiber is that it is made from a large-core fiber, allowing extraction of higher energy than is possible with typical single-mode fibers. By using patented techniques developed at IMRA, this large-core fiber amplifier produces high-quality single-mode output. The seed for this amplifier is a directly modulated, 1-µm-wavelength nanosecond laser diode. The combination of this seed and amplifier allows sharp rise/fall times, resulting in nearly rectangular temporal pulse shape.

The system has output pulse energy of >15 µJ, which can be maintained over the full time and repetition rate tuning range. Users can preselect the pulse duration and adjust it in real time using the laser controller. The TEM₀₀ beam from the amplifier is coupled into a polarization-maintaining fiber with collimated output for ease of integration into the user's application.

The company says that, with this new design, laser energy deposition and its dosage can be optimized online for real-time measured structures on a 300-mm silicon wafer. Submicron-scale thin structures can be removed without damage to the underlying or neighboring structures.