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Variable
Attenuators for High Power Lasers
Diffractive attenuators control the power of laser radiation
using diffraction gratings. Since phase diffraction gratings
do not absorb light they can be used for high-power laser
radiation (cw, pulsed). Variation of grating parameters
along the substrate results in variable transmission at
a given wavelength.
Diffractive attenuators can be designed for wavelength
from deep UV till IR for laser powers up to 250W/㎠ in
CW and 1000mJ/㎠ in 10ns pulses.
Principle
of operation
Light beam passing through a diffractive grating is partially
deflected into several diffractive orders, which get subsequently
blocked by diaphragm. Thus the zero order beam (does not
change the direction of propagation) is attenuated. The
intensity of output radiation Ioutput
depends on the grating design and wavelength of input
beam. By changing the grating parameters one can control
the power of output radiation1. The transmission coefficient
of such an attenuator is h = Ioutput/Iinput..
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Key features
- High power attenuator: Diffractive attenuators can control
high power laser radiation, either pulsed or continuous
(cw) laser beams due to non-absorbing phase gratings.
- Flexible design of transmission function: The dependence
h(j) of the attenuator transmission on rotation angle
j can be designed by computer according to the customer's
requirements.
- Low cost mass-fabrication: Laser lithographic methods
allow one to produce attenuators by binary optics technology
with significant price decrease for larger quantities.
Applications
- Beam-modulators for high power lasers (Nd:YAG-, Argon-,
Excimer-...) for material processing (e.g. marking, ),
scanner systems, etc.
Beam-splitters with adjustable splitting coefficient and
attenuation. |
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