# top hat beam shaping lens fbs operation instructions

```Optical Systems
3. Beam shaper within beam expander (Top Hat size @
1/e² < 90 μm).
Top Hat size is determined by numerical aperture (NA) of focused
beam and is given by:
3.2 µm
≈ 5x diffraction limited @ 1064 nm (10x @ 532 nm)
NA
focusing
lens/objective
nessesary
diameter of
Gaussian
input beam
@1/e2: 3.6 mm
diameter of
Gaussian input beam
@1/e2: <3.6 mm
lens/objective
cylindrical lens
@ focusing optic
homogeneous line profile
distance l
nessesary diameter
of Gaussian input
beam @1/e2: 3.6 mm
z – position of
beam shaper
beam expander
working distance d = ffocusing lens
focal length
A further and even more flexible possibility is to introduce GTH3.6-1.75FA 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-3.6-1.75FA by shifting shaper along z-axis.
It’s just necessary to consider that the beam diameter at the
position of GTH is 3.6 mm @ 1/e². The resulting Top-Hat size
is given by:
≈
beam shaper
lens
input beam
free aperture 2.2x beam
diameter @1/e²
free aperture 2.2x beam
diameter @1/e²
Top-Hat beam
shaper lens
cylindrical lens
3.2 µm
≈ 5x diffraction limited @ 1064 nm (10x @ 532 nm)
NA
FBS
distance l1 > I
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 = 1.8 m.
Top Hat Beam Shaping Lens
Specifications
●New Diffractive Beam Shaping
Concept ! based on Fourier
methods
●Transforming Gaussian TEM00
beam into square or round
homogeneous Top-Hat profile
●Top Hat size is near diffraction
limited and is given by: ~λ /NA
●Achievable Top Hat sizes:
1 μm – 200 μm
Material
fused silica
Diameter
25.4 mm
tolerance ±0.1 mm
Input Beam
TEM00, different models for diameter@1/e²:
2.0 ... 10.0 mm with 0.5 mm step
tolerance ±5%
Necessary Free Aperture
2.2x (or better 2.5x) beam diameter@1/e²
along total beam path
Top Hat Size
1.5x diffraction limited Gaussian spot
square form
(round optional)
Homogenity
+/- 2.5%
rel. to average intensity
within tophat
Wavelength
different models for:
1064 nm, 532 nm or 355 nm
others on request
Transmission
> 99%
AR/AR coating
of input energy within
tophat profile
Efficiency
> 95%
Damage Threshold
4 J/cm² @ 532 nm, 10 ns
Free Aperture
23 mm
Optical Systems
≈
NA represents the numerical aperture of focused beam and is
given by:
NA =
focal length of focusing optic
FBS Operation Instructions
FBS – Top-Hat Fundamental Beam Mode Shaper
Input:
Gaussian profile
Input: Gaussian profile
Focusing system
Focusing system
d
F
F
FBS
Without FBS Beam Shaper: Gaussian-profile at focal plane
With FBS Beam Shaper: Top-Hat-profile at focal plane
– FBS works together with focusing system (FS)
– Top Hat size just depends on wavelength (λ) and numerical
aperture (NA) of focused beam
– Distance d between FBS and FS up to several meters
Visit www.eksmaoptics.com for new products and prices
7.10
Optical Systems
Without FBS shaper: diffraction limited Gaussian profile
2. Beam shaper in front of a beam expander
focusing
lens/objective
FBS beam shaper
free aperture 2.2x beam
diameter @1/e²
– Smallest achievable Top-Hat size: ≈ always 1,5x of
diffraction limited Gaussian-spot @ 1/e²
– Achievable Top Hat profiles: square or round
– Diffraction efficiency: > 95% of energy in Top Hat
– Homogeneity: modulation < ±2.5%
– Depth of focus: similar as for Gaussian beam
– Insensitive to misalignment, ellipticity and input diameter
variation: ±5-10%
free aperture 2.2x beam
diameter @1/e²
Intensity distribution at focal plane
collimated input
beam
@ focusing optic
beam expander
focal length
There is also the possibility to introduce the FBS beam shaper
into the beam path in front of a beam expander. This leads to
a higher numerical aperture of focused beam and to a smaller
Top Hat profile.
Example: A Gaussian beam with a diameter of 5 mm@1/e²
illuminates the FBS beam shaper and is afterwards increased by
a beam expander to a beam diameter of 8 mm. With an focusing optic with f=50 mm the user can generate a Top Hat with a
diameter of 7 μm. The needed free aperture increases with the
expanded beam. For a beam with a diameter of 8 mm the free
aperture have to be at least 18 mm.
3. Beam shaper within a beam expander
focusing
lens/objective
free aperture 2.2x
beam diameter @1/e²
Optical Systems
With FBS shaper: near diffraction limited Top Hat profile
free aperture 2.2x beam
diameter @1/e²
FBS beam shaper
z – position of
beam shaper
beam expander
Optical setup for FBS Top-Hat beam shaper
Independent of optical setup the user has to consider that:
– The free aperture along the total beam path have to be at least
2.2x (better 2.5x) bigger than the beam diameter @ 1/ e²
λ
– The Top Hat size is always given by:
NA
λ is the used wavelength;
NA is the numerical aperture
of focused beam and is given by:
focal length of focusing optic
There are different possibilities to integrate the FBS beam
shaper into an optical setup.
@ focusing optic
focal length
A further and even more flexible possibility is to introduce the
FBS beam shaper 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 FBS beam shaper by shifting shaper
along z-axis.
Scribing of CIGS-solar cells
P2
P3
1. Beam shaper directly in front of a focusing optic/objective
ITO
free aperture 2.2x beam
diameter @1/e²
FBS beam shaper
collimated input
beam
lens/objective
CdS
Cu(InGa)Se2
@ focusing optic
Mo
focal length
Polymer substrate
By introducing the FBS beam shaper into the beam path in front
of a lens/objective the initial diffraction limited Gaussian spot will
be transformed into a homogeneous Top-Hat profile.
When a Gaussian TEM00 input beam with a diameter of 5 mm@
1/e² is used the diameter of the free aperture along the total beam
path have to be at least 11 mm (better 13 mm).
If for example a wavelength with 532 nm, a Gaussian TEM00
input beam with a diameter of 5 mm@1/e² and a focusing lens
with f=160 mm is used, ones will get a homogeneous Top Hat
profile with a diameter of 34 μm.
7.11
P1
– Wasted area, reducing efficiency → need of smallest
scribing lines
– Cut quality influence efficiency → need of small HAZ,
no debris, smooth edges
– High scanning speed for high throughput → need of small
pulse overlap
EKSMA OPTICS • Tel.: +370 5 272 99 00 • Fax: +370 5 272 92 99 • info@eksmaoptics.com • www.eksmaoptics.com
Optical Systems
P1 – „Scribing“
P3 – „Scribing“
Gaussian Profile
FBS-Top-Hat Profile
small overlap, smooth edges
Removal of a front contact in ZnO(1 μm)/CIGS/Mo/PI structure.
Laser PL10100/SH, 10 ps, 370 mW, 100 kHz, 532 nm; scanning
speed 4.3 m/s, single pass.
Gaussian Profile
FBS-Top-Hat Profile
small HAZ, smooth edges
Tilted SEM pictures of the P3 scribe in ZnO(1 μm)/CIGS/ Mo/PI
structure. Laser PL10100/SH, 10 ps, 370 mW, 100 kHz, 532 nm;
scanning speed 60 mm/s, single pass.
Raciukaitis et. al, JLMN-Vol. 6, No. 1, 2011
Recommended Accessories
Zoom Beam
Expander
Two Axes Translation
Polarizer Holder
840-0240
See page 7.4
See page 8.98
precision opto-mechanical holder 8400197. Variable attenuator/beamsplitter
incorporates a high-performance Polarizing Cube Beamsplitter which reflects
s-polarized light at 90° while transmitting
p-polarized light.
A rotating λ/2 waveplate is placed in the
incident polarized laser beam. The intensity ratio of those two beams may be continuously varied without alteration of other
beam parameters by rotating the waveplate. The intensity of either exit beam, and
their intensity ratio, can be controlled over
a wide dynamic range. Pure p-polarization
could be selected for maximum transmission, or pure s-polarization for maximum
attenuation of the transmitted beam.
● Divides laser beam into two
intensity ratio
●Convenient 90° angle between
reflected and transmitted beams
●Negligible beam deviation
● Large dynamic range
● Weight – 0.16 kg
Continuously Variable Attenuator/Beamsplitter is designed for down to 100 fs laser
pulses. It consists of 2 high-performance
polarizing optics components placed in
Multiple Order Half Waveplate and Cube
Polarizing Beamsplitters
Achromatic Air-Spaced Waveplate and
Glan Laser Polarizing Prism
Specifications
Specifications
mJ/cm2
Damage threshold
200
Damage threshold
0.5 J/cm2 10 ns, 10 Hz at 1064 nm
Antireflection coating
R < 0.25% all entrance and exit surfaces
pulsed at 1064 nm, typical
Antireflection coating
R < 1% all entrance and exit surfaces
Extinction ratio
Ts/Tp < 1:200
Extinction ratio
Ts/Tp < 1:10000
Optical Systems
Continuously Variable
Attenuator / Beamsplitter
990-0060
Catalogue
number
Central
wavelength, nm
Clear
aperture, mm
Price,
EUR
990-0061-10
1064
9
465
Catalogue
number
Central
wavelength, nm
Clear
aperture, mm
Price,
EUR
1290
990-0061-15
1064
14
495
990-0060-10VIS
450-680
9
990-0061-20
1064
17
515
990-0060-12VIS
450-680
11
1395
990-0064-10
532
9
465
990-0060-10IR
700-1000
9
1290
990-0064-15
532
14
495
990-0060-12IR
700-1000
11
1395
990-0064-20
532
17
515
990-0060-10FIR
950-1300
9
1290
990-0065-10
355
9
596
990-0060-12FIR
950-1300
11
1395
990-0065-15
355
14
656
990-0065-20
355
17
706
Visit www.eksmaoptics.com for new products and prices
7.12
```