Line length (Top Hat) | approximately 2 * λ * f / d, with f = focal length, d = beam diameter @1/e2 |
Line width (Gaussian) | similar to the diameter of the Gaussian spot in the same optical configuration |
Efficiency | up to 92.5% |
Homogeneity | ca. ± 2.5% (rel. to average intensity of the Top Hat plateau) |
Side modes (strongest) | ~15x weaker than line plateau (< 1.7% of input energy) |
Depth of focus (DOF) | ~50% 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 2x larger than the beam diameter @ 1/e² |
Alignment |
Alignment in lateral direction (translation) is necessary. Recommended mount: 840-0240 X-Y translation 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 FBSL
230.63 kB |
FBSL series Top Hat beam shapers are single-piece optical elements designed for the generation of square Top Hat profiles. FBSL 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 FBSL lens is designed for a fixed input beam diameter (@1/e²) and specific operation wavelength. FBSL 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.
FBSL generate Top Hat spots with long depth of focus (DOF), which is about 50% 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 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 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.