Diffractive optical diffuser
Introduction
Beijing HOMOlaser S&T CO., Ltd produces optical Diffuser/Homogenizer (DF/HM) diffractive optical element (DOE) which transforms a single or multi-mode input beam into a well-defined output beam, characterized with a desired shape, and homogenized flat-top intensity (or other intensity profile, see below).
Homolaser’s optical diffuser DOE performs a homogenized spot with accurately defined sharp shaped edges, while enabling high efficiency.
Characteristics
lWorks with single or multi mode input beams
lFused silica mainly, glass or plastic materials available
lAny output shape or symmetry
lUniform/Tailored intensity profile
lExact diffusion angles
Applications
lLaser homogenizing/shaping
lLaser material processing: perforation, ablation, derailing, marking, scribing and welding
llaser test/ detection
lMedical/aesthetic laser treatment
Specifications
General definition
Homolaser is enabled to design an element that will produce any arbitrary shape, intensity profile with precise angle and size of the output, which is obtained in the far field or focal plane if an focusing lens is used. The diffuser performance strongly depends on the incident beam parameters. In general, one can distinguish between two qualities：
1.single mode laser beam with M2<5，highly coherent beam. Best results in terms of intensity profile, uniformity, efficiency and transfer region for single mode lasers can be achieved by using Top Hat (TH) designs like in
page: PRODUCT->TOP-HAT Shaping.
2. Multi-Mode laser beam with M2>5，When the incident beam is more complex to define – by having an arbitrary intensity distribution and not a near-to-perfect Gaussian (higher M2) one, the uniformity performance may be improved at the cost of a sharp edge.
The figure below shows the circular homogenized generated by our diffuser DOE illuminated by a single mode laser beam. The spot border is considerably clear, while the zero order is fairly noticeable due to the high coherence.
Operation principle and design considerations
1.design considerations
uwavelength
uOutput shape and intensity profile
uDivergence angle (of output shape) or image size and EFL
uBeam quality M2
2.The most rudimentary set-up in a beam shaping system consists of a laser, a refractive / diffractive beam shaper element and a focusing lens. See the figure below
θ：diffusion angle
EFL：effective focal length
D：output beam size
The optical parameters of the diffuser can be easily calculated from geometric point of view。
1.The minimum diffusion angle is equivalent to approximately 5-10 times the diffraction-limit. In addition, a larger angle ratio (to a certain level) will increase the performance quality. The formula for the diffraction-limited spot diameter at 1/e2 (D.L.spotsize) follows：
L：working distance
D：output beam size（on the focusing element）
1.According to diffraction theory, The ratio between input divergence angle to diffusion angle, determines our processing difficulty .
2.Additional improvement in the uniformity performance may be achieved by using a high M2 input beam.
3.In addition，the diffractive pattern can be etched on the Plano side of the focusing lens (plano-convex lens). The advantages of this solution include less optical surfaces, compact dimension and low weight.
Beam shaping: single-mode versus multi-mode:
Currently，Homolaser produces a new homogenizer for laser beam with a low M2，effectively reduced the zero order at the cost of energy efficiency.
Refractive optical homogenizer
Introduction
Beijing HOMOlaser S&T CO., Ltd produces refractive optical element(ROE) which transform a laser beam to a well-defined output beam, characterized with a desired shape, and homogenized flat-top intensity and a desired diffusion angle. See the performance of our elements below：
Applications
lLaser display
lMedical laser
lLaser pumping
lLaser lift-off
lLaser communication, etc.
Operation principle
The operation principle of using refractive optical element is fairly simple. All you need to do is to block the laser with the element. See below.
Characteristics
Our refractive homogenizer’s energy efficiency is as high as 99% and more. The diffusion angle（specified byFWHM，that is the spot size in one meter’s distance which can be obtained by calculating the arc tangent of the half diffusion angle）is as big as 41 degrees. The diffusion angle is custom-tailored.
Design consideration
Design considerations according to customers’ demand：laser wavelength，diffusion angle.
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