Principles of Beam Shaper Operation and Lens Shape
Optical Setup for Gauss-to-Top Hat Beam Shaper Lens
If a collimated Gaussian beam is used the Top Hat beam shaper lens delivers at the working distance d= 250 mm a square Top Hat beam profile with the size of (4x4) mm2.
The Top Hat beam shaper lens works also for divergent and convergent Gaussian beams. Important: One has to consider that input beam diameter at beam shaper lens plane must be 5mm@1/e2.
For divergent (or convergent) beams the size of Top Hat and working distance increase (or decrease).
Adjustment of Square Top Hat Size by Additional Spherical Lens
The working distance and the size of the Top Hat profile can be changed (same ratio) by an additional lens. For a convex lens the size of the Top Hat profile and the working distance becomes smaller. For a concave lens the size of the Top Hat profile and the working distance becomes bigger.
The new working distance and the size of the Top Hat profile can be calculated:
for focal length f>0 mm (additional convex lens) respectively focal length f<-250 mm (additional concave lens); s-> 0
Homogeneous Line Generation with Top Hat Beam Shapper Lens and Additional
By introducing an additional cylindrical lens behind the Top Hat beam shaper lens (thereby one has to consider that the distance l between cylindrical lens and working plane must be bigger or same as focal length of cylindrical lens) it‘s possible to generate a line profile at working plane. Along the long axis the intensity profile is homogeneous. Along short axis, which is focused by cylindrical lens, the profile is near Gaussian.
Adjustment of Length of Homogeneous Line by Additional Spherical Lens
Gauss-to-Top Hat Beam Shaping Lens is a special form lens used to distribute energy of Gaussian beam to Top Hat profile.
Material: LF5 Schott glass;
n= 1.5659 @1060 nm;
n= 1.5848 @ 546 nm;
n= 1.6192 @ 365 nm;
Clear aperture: dia 11.0 mm;
Damage threshold (uncoated): >3J/cm2 @ 532 nm, 10 ns;
Mounted in to 1” ring holder;
Square top hat size and correspondingly working distance can be changed by placing extra lens or objective behind beam shaping lens GTH-5-250-4.
Dependence of square size and working distance vs focal length of additional lens or objective:
|Focal length, mm||Top hat square size, mm||Working distance, mm|
|+50||0.67 x 0.67||42|
|+100||1.1 x 1.1||71|
|+200||1.8 x 1.8||111|
|+300||2.2 x 2.2||136|
|-1000||5.3 x 5.3||333|
|-500||8.0 x 8.0||500|
GTH-5-250-4 Operation Specifications
|Recommended operation wavelength range||400-1500 nm|
|Input beam TEM00, diameter (1/e²):||5.0 ± 0.15 mm|
|Output beam|| Top hat size at 250 mm working distance: |
4 × 4 mm² (adjustable with additional lens)
|Working distance||250 mm (adjustable with additional lens)|
|Beam energy distribution efficiency||> 95% of input energy within Top Hat profile|
|Beam homogenity||± 5 % (rel. to average intensity within top hat)|
|Lens diameter||12.0 ± 0.1 mm|
|Thickness||4.0 ± 0.1 mm|