2.1 µm holmium based ultrafast lasers for material processing

Ultrafast lasers at 2 µm wavelength have strong potential for material processing. For example, the long wavelength enables in-volume modification and backside-machining using the transparency window of semiconductors. While research laboratories have conventional access to SWIR via optical parametric amplifier systems, these remain impractical for industrial application demanding simple and robust sources. Such sources can be obtained from Thulium (Tm)- or Holmium (Ho)-based lasers emitting around 1.9 µm and 2.1 µm wavelength, respectively. Tm-doped fiber lasers excel at low energy and high average power, while Ho-doped bulk lasers offer high energy scaling potential and high average power. The higher pulse energies accessible in a bulk laser architecture are beneficial for compensation of the substantial losses of beam shaping and high-NA focusing. In this contribution, we first present a holmium-based ultrafast bulk lasers for scientific and industrial users and then discuss first material processing tests with such an amplifier system translating the benefits of SWIR lasers from the laboratory to the factory floor.