Galvanometer scanners are widely used in micromaching, marking and similar applications. Every scanner consists of rotary motors, board of electronics and laser scanning mirror. The mirror is crucial optical component in every 2D or 3D galvanometric system, thus we pay extra attention to optical and mechanical properties.
Low inertia is crucial for laser beam steering systems to attain the highest possible accelerations. On the other hand high stiffness of mirrors is required to achieve stability of servo scanner. Balancing between the two, thin substrates for mirrors are made of standard materials like silicon and fused silica. Despite thickness ranging from 1,5 mm up 2,0 mm mirrors should not introduce additional wavefront distortion therefore the substrates are polished to feature reflected λ/10 - λ/20 @ 633 nm wavefront distortion.
Many different mirror coating configurations can be applied on scanning mirror substrates: protected aluminum, gold, silver and dielectric coatings for wavelengths ranging from 250 nm to 10,6 μm. Typically coatings come with a secondary reflectivity band for guiding laser beam, typically HeNe (633 nm). Most popular coatings are design for 343 nm - 355 nm, 515 nm - 532 nm and 1030 nm - 1064 nm wavelengths. Special coating technology lets us to deposit stress free layers and maintain initial flatness of the substrate. Femtosecond lasers storm into micromachining applications rapidly, hence customers aiming for optimized performance with ultrashort pulses we offer mirrors made of fused silica and compensated group delay dispersion (GDD) coatings. Due to extreme peak power high laser induced damage threshold is also critical in applications where ultrafast pulses are used. That is why we developed coatings which can handle energy densities scaling from 10 J/cm2 up to 30 J/cm2.
Requirements for design of laser scan mirrors are dictated by laser characteristics such as wavelength, power, beam diameter, pulse width, frequency. This means either one has to select the best alternative from a large array of existing designs or create a mirror which matches ones performance requirements.