Raw material properties
The optical and mechanical properties of silicon are described in section M4.0.
Silicon mirrors are manufactured using ‘mirror-grade’ (non-transmissive) monocrystalline silicon.
Silicon lenses are manufactured using monocrystalline ‘optical grade’ (transmissive) material.
Standard ULO Optics products are made to the following specifications and tolerances:
Diameter : +0 / -0.1mm
Thickness : ± 0.1mm
Flatness : Within λ/40 over any 25mm test dia.
Parallelism : Within 0.05mm ETV
Si mirrors are available with the following coating options:
PMR .. max R% for pulsed CO2 lasers, with R>99.5%. A dielectric stack deposited over a metal
underlayer, designed for max LIDT (pulsed TEA lasers). Usual use is for rear mirrors in TEA lasers.
See data section 15.20
DUAL .. enhanced silver coatings, with max R for both visible and CO2 laser beams at 45° incidence. Used
in articulated arms in (eg.) medical laser systems. Data section 15.20.
SUPERMAX .. a new zero-phase coating for highest performance Si mirrors. Measured reflectivity at
10.6μm is usually 99.9% at normal incidence, and 99.85% average at 45° incidence. (guaranteed >99.8%,
99.7% respectively). Used on ULO Optics Si scanner mirrors (data section 10).
PFM .. Polarization-forcing mirrors, used for in-cavity forcing of one specific direction of
polarization. In general R(s) is maximized, and the coating is designed so that R(p)<<R(s). See data
Si lenses are custom-made only. AR/AR coatings for all options (single wavelength, broad-band,
dual-band) are available over the useful range of wavelengths for Si (approx 2μm to 10μm).
CO laser optics
Umicore Laser Optics are experienced in the manufacture of Si optics for CO laser systems, generally
operating in the wavelength region 5 – 6 μm.
High reflectivity (low absorption) is offered over this relatively broad band. These components are
Standard Si mirrors: see data section 15.10