Top Hat width | approximately 2 * λ * f / d, with f = focal length, d = beam diameter @1/e2 |
Efficiency | up to 95% |
Homogeneity | ca. ± 2.5% (rel. to average intensity of the Top Hat plateau) |
Side modes (strongest) | ~70x weaker than line plateau (< 1.5% of input energy) |
Depth of focus (DOF) | ~30% of the Rayleigh length |
Material | Fused silica |
Transmission | >99% |
Damage threshold @ 10 ns | 10 J/cm² @ 1064 nm 5 J/cm² @ 532 nm 3 J/cm² @ 355 nm |
Dimensions | ⌀25.4 x 3 mm |
Input beam | Gaussian beam TEM00, M² of 1.4 or better |
Apertures within the optical setup | Clear aperture along the whole beam path should be at least 2.2x larger than the beam diameter @ 1/e² |
Alignment |
Alignment in lateral direction (translation) is necessary. Recommended mount: 990-0051 X-Y positioner. |
Optical equipment | Required: focusing optics. Top Hat is generated in the focal plane of this optic. Useful: beam expander for adjustment of the beam diameter (effective beam diameter to the FBS2 design input beam diameter) and for adjustment of the beam diameter to the desired spot size. Helpful: beam profiler to check the profiles while aligning. |
EKSMA Optics Top Hat Beam Shaping Lenses FBSR
230.63 kB |
FBSR series Top Hat beam shapers are single-piece optical elements designed for the generation of round Top Hat profiles. FBSR beam shapers are so-called focal beam shapers and can generate a Top Hat profile in the focal plane of nearly any focusing optics. Each FBSR lens is designed for a fixed input beam diameter (@1/e²) and specific operation wavelength. FBSR beam shaper can be combined with any objective or F-Theta lens, it can be integrated into the beam path at nearly any position, even in front of or within a beam expander / telescope.
FBSR generate Top Hat spots with long depth of focus (DOF), which is about 30% of the Rayleigh length compared to a Gaussian spot in a similar optical setup. Within this range the Top Hat profile doesn’t change and shows nearly constant peak intensity.
The width of the Top Hat spot generated by FBSR is approximately 1.5 times larger than the diffraction-limited Gaussian spot size. The size of the Top Hat size depends on the focal length of the focusing optics (f), the beam diameter @1/e² (d), and the operation wavelength (λ). The achieved Top Hat size is typically smaller than 100 µm, and can easily be scaled by using different additional focusing optics.
The approximate size of the Top Hat can be calculated by the formula:
2 * λ * f / d or λ / NA, where NA is the numerical aperture of the focused beam.