Gauss-To-Top Hat Beam Shaping Lens GTH-3.6-1.75FA

Gauss-to-Top Hat Beam Shaping Lens is a special form lens used to distribute energy of Gaussian beam to Top Hat profile.

 

Lens Specifications: 

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.

 

Working distance is given by focal length of additional lens which is always needed. Top Hat appears always at focal plane of additional lens.
For instance if an additional lens f=100 is used, Top Hat appears at 100 mm behind additional lens. So GTH-3.6-1.75FA could be easily put in front of objectives for example.
The distance between GTH-3.6-1.75FA and additional lens is not critical (up to several tens of centimeters).
The full fan angle of Top-Hat generation for GTH-3.6-1.75FA is 1.75 mrad. This leads to Top-Hat sizes:
- 88x88 µm for lens with f=50 at 50 mm distance
- 175x175 µm for lens with f=100 at 100 mm distance
- 1.75x1.75 mm for lens with f=1000 at 1000 mm distance


GTH-3.6-1.75FA Operation Specifications:

 

Recommended operation wavelength range450-1550 nm
Necessary free aperturealways 2.2x beam diameter @ 1/e2, along total beam path
Input beamTEM00 , diameter @ 1/e2: 3.6 mm ± 0.15 mm
Achievable Top Hat size @ 1/e25x diffraction limited @ 1064 nm, 10x diffraction limited @ 532 nm
Full fan angle of Top-Hat generation1.75 mrad
Beam energy distribution efficiency>95% of input energy within Top Hat profile
Beam homogenity±5 % (rel. to average intensity within Top Hat)
Lens diameter12.0 ± 0.1 mm
Lens thickness2.0 ± 0.1 mm

 

 

Delivery

Estimated delivery time: from 4 - 5 days

Description
Code Description Price Delivery Add to cart
GTH-3.6-1.75FA uncoated 791 $ Request To cart
GTH-3.6-1.75FA-IR IR coated lens (700-1300 nm (R<1% per face)) 868 $ 4 - 5 days To cart
GTH-3.6-1.75FA-VIS VIS coated lens (400-700 nm (R<1% per face)) 868 $ 4 - 5 days To cart
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 General function of Top-Hat beam shaper GTH-3.6-1.75FA
 

 

The Top-Hat beam shaper GTH-3.6-1.75FA generating a square Top-Hat profile with a full fan angle of 1.75 mrad. To get best results it is necessary to use a Gaussian TEM00 input beam with a diameter of 3.6 mm@1/e².
For all setups using GTH beam shaper the user have to consider that the free aperture along the total beam path have to be at least 2.2 (better2.5) times bigger than the beam diameter@1/e².

 

Optical setup for Top-Hat beam shaper GTH-3.6-1.75FA
-Setup overview -

 

There are different possibilities to integrate the GTH-3.6-1.75FA beam shaper into an optical setup:

 

a. Beam shaper directly in front of focusing optic/objective (Top Hat size @1/e² > 90µm):
Top Hat size is determined by focal length (f) of focusing optic/objective and can be calculated as follows: (1.75/1000)*f

 

b. Beam shaper in front of beam expander (Top Hat size @1/e² < 90μm):
Top Hat size is determined by numerical aperture (NA) of focused beam and is given by:
 ≈3.2 µm/NA -> ≈ 5 x diffraction limited @ 1064 nm (10x@532 nm)

 

c. Beam shaper within beam expander (Top Hat size @1/e² < 90μm):
Top Hat size is determined by numerical aperture (NA) of focused beam and is given by:
 ≈3.2 µm/NA -> ≈ 5 x diffraction limited @ 1064 nm (10x@532 nm)

 

Optical setup for Top-Hat beam shaper GTH-3.6-1.75FA
- beam shaper in front of focusing optic -

 

 

By introducing the GTH-3.6-1.75FA into the beam path in front of a lens/objective the initial diffraction limited Gaussian spot will be transformed into a square homogeneous Top-Hat profile.

 

The necessary beam diameter at the position of GTH-3.6-1.75FA is 3.6mm@1/e².

 

The resulting Top-Hat size is given by: (1.75/1000)*focal length for example with f= 50mm => 87.5μm.

 

Optical setup for Top-Hat beam shaper GTH-3.6-1.75FA
- beam shaper in front of beam expander -

 

 

 

 

To realize Top Hat sizes smaller than 90μm it’s recommended to introduce the GTH-3.6-1.75 into the beam path in front of a beam expander. Initially the necessary input beam diameter of 3.6mm@1/e² is passing the GTH. Afterwards the beam is expanded and focused on working plane. The initial diffraction limited Gaussian spot at focal plane will be transformed into a square homogeneous Top-Hat profile.

 

The resulting Top-Hat size is given by: ≈3.2 µm/NA => ≈ 5x diffraction limited @1064 nm(10x@532 nm)

 

NA represents the numerical aperture of focused beam and is given by: NA=beam radius@focusing optics/focal length of focusing optics.

 

Optical setup for Top-Hat beam shaper GTH-3.6-1.75FA
- beam shaper within beam expander -


 

 

A further and even more flexible possibility is to introduce GTH-3.6-1.75 into the beam path within a beam expander. The user has the possibility for an easy “fine tuning” of beam diameter at the position of GTH-3.6-1.75 by shifting shaper along z-axis. It’s just necessary to consider that the beam diameter at the position of GTH is 3.6mm@1/e².

 

The resulting Top-Hat size is given by: ≈ 3.2µm/NA => ≈ 5x diffraction limited @ 1064 nm (10x@532 nm)

 

NA represents the numerical aperture of focused beam and is given by: NA=beam radius @ focusing optics/ focal length of focusing optics.

 

Homogeneous line generation with additional cylindrical lens

 

 

If an additional cylindrical lens is used, one can generate homogeneous line profiles. By varying the distance   l the width of line profile (short axis) can be changed from near diffraction limited size to several millimeters. We recommend the use of a cylindrical lens or lens system with a focal length of = 1.8m.


 

 

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