an introduction to polarization directed flat lenses

AN INTRODUCTION TO POLARIZATION
DIRECTED FLAT LENSES
CONTENTS
•  Background/Technology
•  Product Info
•  FAQ’s
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PRINCIPLE OF OPERATION
Technology Basics
Using Liquid Crystal Polymers (LCP), Linear Photo Polymeriza:on (LPP) and a variety of dopants, three-­‐dimensional pa?erns of liquid crystals are created and captured within a thin film.
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PRINCIPLE OF OPERATION
Dynamic Phase
•  The “normal” phase delay
•  For example,
–  Prisms
–  Lenses
–  Phase Gratings
–  Spatial Light Modulators
(computer generated holograms)
•  All optical path length difference
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GEOMETRIC PHASE
(Reference, wave in vacuum) n, d
ne, no , d, φ
(Isotropic media) “normal” phase delay called dynamic phase due to op:cal path length difference (Anisotropic media) “extra” phase delay called geometric phase PROPRIETARY - Property of Edmund Optics, Inc. | 2016 Copyright© Edmund Optics, Inc.
2π
δ =n
d
λ
Dynamic phase ⎛ n + n ⎞ 2π
δ =⎜ e o⎟
d ± 2φ
⎝ 2 ⎠ λ
Geometric Phase POLARIZATION DIRECTED FLAT LENS
Principle: Ø  Structure is nonlinear orienta:on angle Ø  Phase = Ø  Phase can be aspheric, off-­‐axis, or any func:on Ø  Polariza:on selects ± focal length PROPRIETARY - Property of Edmund Optics, Inc. | 2016 Copyright© Edmund Optics, Inc.
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POLARIZATION DIRECTED FLAT LENS
Principle: Ø  Structure is nonlinear orienta:on angle Ø  Phase = Ø  Phase can be aspheric, off-­‐axis, or any func:on Ø  Polariza:on selects ± focal length PROPRIETARY - Property of Edmund Optics, Inc. | 2016 Copyright© Edmund Optics, Inc.
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STANDARD PRODUCT SPECIFICATIONS
Dimensions Dimensional Tolerance Thickness Thickness Tolerance Lens Aperture Coa:ng Specifica:on Surface Quality Design Wavelength Substrate PROPRIETARY - Property of Edmund Optics, Inc. | 2016 Copyright© Edmund Optics, Inc.
25 x 25mm ±0.25mm 0.45mm ±0.25mm 24.5mm Diameter Rabs <0.5% @ 450 -­‐ 650nm 60-­‐40 550nm D263 8
STANDARD PRODUCT AVAILABILITY
Effec:ve Focal Length Size 45mm 25 x 25mm 50mm 25 x 25mm 75mm 25 x 25mm 100mm 25 x 25mm PROPRIETARY - Property of Edmund Optics, Inc. | 2016 Copyright© Edmund Optics, Inc.
f/# 1.8 2 3 4 Stock Number #33-­‐463 #33-­‐464 #33-­‐465 #33-­‐466 9
FREQUENTLY ASKED QUESTIONS
Q: What is a Polarization Directed Flat Lens?
A: A Polarization Directed Flat Lens is a thin (0.45mm) flat window with a
complex photo-aligned liquid crystal polymer (LCP) film deposited on the
surface. By varying the geometrical phase shift spatially, the LCP achieves
near perfect diffraction efficiency of the holographically recorded lens
wavefront. Essentially, a Polarization Directed Flat lens is a thin film
equivalent of a geometric optic with very little volume, yielding significant
reductions in weight and thickness.
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FREQUENTLY ASKED QUESTIONS
Q: How does polarization affect the performance?
A: The Polarization Directed Flat Lenses are sensitive to circular polarization.
The lenses have the unique property that one circular polarization will focus or
converge through the lens (positive focal length) and the orthogonal circular
polarization will defocus or diverge (negative focal length).
•  When the lens is oriented with the LCP surface facing the light source:
Left-Hand Circular Polarization (LHCP) light will focus with the stated
positive focal length of the lens. Right-Hand Circular Polarization (RHCP)
light will diverge with the negative stated focal length of the lens.
•  When the lens is oriented with the LCP surface away from the light source:
RHCP light will focus with the stated positive focal length of the lens. LHCP
light will diverge with the negative stated focal length of the lens.
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FREQUENTLY ASKED QUESTIONS
Q: Will the lens focus unpolarized light?
A: With unpolarized light, the Polarization Directed Flat Lens will act as a
positive lens for 50% of the light (one of the circular polarizations) and it will
act as a negative lens for the other 50% of the light (the orthogonal
polarization).
Q: What happens with linear polarized light?
A: Linear polarized light will act the same as unpolarized – 50% of the light
will be focused, and 50% of the light will be diverged with a negative focal
length.
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FREQUENTLY ASKED QUESTIONS
Q: What are the advantages of Polarization Directed Flat Lenses?
A: Polarization Directed Flat Lenses are a thin film equivalent of a geometric
optic. Thus, they have significantly less volume than an equivalent spherical
optic, yielding significant reduction in weight and thickness. The technology
used to create them is also well suited to create gratings and other
polarization optics, allowing for multiple optical technologies to be designed
into a single optical component.
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FREQUENTLY ASKED QUESTIONS
Q: Are there any disadvantages to Polarization Directed Flat Lenses?
A: To operate as efficiently as possible, the lenses require the incoming light
to be circularly polarized. This requires extra care in the setup, and potentially
additional polarization optics in the optical design. Also, the lenses function as
a grating, and thus have significant chromatic aberration when used with
broadband illumination. Care should be taken to limit the spectral bandwidth
of the illumination for optimum results.
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FREQUENTLY ASKED QUESTIONS
Q: How can I specify a custom Polarization Directed Flat Lens?
A: To create a custom Polarization Directed Flat Lens, the following
information is required:
•  Lens Size (Diameter, Square, etc)
•  Clear Aperture
•  Maximum Thickness
•  Desired Focal Length
•  Operating Wavelength Range
•  Wavefront Characteristics (aspheric, etc)
•  AR Coating Specs (wavelength, reflectance, etc.)
•  Wavefront Accuracy
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FREQUENTLY ASKED QUESTIONS
Q: How should I clean my Polarization Directed Flat Lens?
A: Polarization Directed Flat Lenses can be cleaned with the same methods
used for other anti-reflection coated optics. Visit our application note on
Cleaning Optics for more information.
Q: How can I mount my Polarization Directed Flat Lens?
A: All of our standard Polarization Directed Flat Lenses are 25 x 25mm. Our
25mm Square Rectangular Bar Clamp, #54-994, is a good choice for bench
mounted applications.
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