Waveplates
Principle of Waveplate
Waveplates (retardation plates or phase shifters) are made from materials which exhibit birefringence. The velocities of the extraordinary and ordinary rays through the birefringent materials vary inversely with their refractive indices. The difference in velocities gives rise to a phase difference when the two beams recombine. In the case of an incident linearly
modulatepolarized beam this is given by α=2πd(n e-n o)/l(α-phase difference;
d-thickness of waveplate; n e,n o-refractive indices of extraordinary and
ordinary rays respectively; λ-wavelength). At any specific wavelength the phase difference is governed by the thickness of the retarder.
Half Waveplate
The thickness of a half waveplate is such that the phase difference
is 1/2-wavelength (ture-zero order) or some multiple of 1/2-wavelength (multiple order).
A linearly polarized beam incident on a
half waveplate emerges as a linearly
polarized beam but rotated such that its
angle to the optical axis is twice that
of the incident beam. Therefore,
half-waveplates can be used as
continuously adjustable polarization
rotators. Half-waveplates are used in
rotating the plane of polarization, electro-optic modulation and as a variable ratio beamsplitter when used in conjunction with a polarization cube.
Quarter Waveplate
The thickness of the quarter waveplate is such that the phase difference is 1/4 wavelength (ture-zero order) or some multiple of 1/4 wavelength (multiple order).
If the angle θ (between the electric
field vector of the incident linearly
polarized beam and the retarder
principal plane) of the
quarter-waveplate is 45, the emergent
beam is circularly polarized. When a
quarter waveplate is double passed, i.e.
by mirror reflection, it acts as a half waveplate and rotates the plane of polarization to a certain angle. Quarter waveplates are used in creating circular polarization from linear or linear polarization from circular, ellipsometry, optical pumping, suppressing unwanted reflection and optical isolation.
Dual-wavelength Waveplate
The THG-PR polarization rotator is an example of dual-wavelength waveplates and used to manage the polarizations of laser beams to obtain maximum conversion efficiency of third harmonic generations (THG), i.e., 1064 nm + 532 nm -> 355 nm.
Generally, type I frequency-doubler(oo-> e) + type II
frequency-tripler( oe-> e) will be the best design for THG which needs no polarization rotator. However, when a type II KTP crystal is used as frequency-doubler and type II LBO as frequency-tripler (see the Figure), the laser polarizations coming out from KTP are not optimized for THG. How to change it into its optimum? CASIX's THG-PR polarization rotator can do it!
Commoν 1/2 ωαϖε πηασε ρεταρδατιον πλατε χουλδ ονλψ ροτατε τηε πολαριζατιον οφ 532 νµ το α σ
πεχιφιχ ανγλε. Ηοωεϖερ, τηε λινεαρ πολαριζατιον οφ 1064 νµ ωιλλ βε διστορτεδ το βε ελλιπτιχαλ. Τηε ΤΗΓ−ΠΡ ροτατορ ισ σπεχιαλλψ δεσιγνεδ το µαινταιν τηε λινεαρ πολαριζατιον οφ 1064 νµ (λ plate) and change simultaneously 532 nm (λ/2 plate) to the angle you need. The THG-PR can be
applied to:
1. Type II (SHG) + Type II
(THG)
2. Type I (SHG) + Type I
(THG)
3. Type II (SHG) + Type I (THG)
Waveplate Designer
In order to assist customers in
effectively selecting waveplates
for their application, CASIX's
engineers have complied Waveplate
Designer software to calculate the
main properties of waveplate, such
as thickness, orders, spectral
bandwidth, temperature bandwidth
and angular bandwidth. The
interface of the Waveplate Designer
is enclosed for your reference.
Dual-wavelength waveplate and archomatic waveplate can be also calculated.  Ask us for more information about Waveplate Designer if needed.You can download it from here.
Ture-Zero, Low, Multi, Zero order waveplates
In practice, the thickness required to produce true-zero order waveplate is about tens of micron according to the wavelength, which is too thin to manufacture. For this reason, multiple order waveplate often provides a convenient means of producing the required retardation. CASIX provides two kinds of multiple orders waveplates- low order and multi order which are classified by the thickness. The retardation value of a multiple order waveplate is strongly dependent on temperature,
wavelength, angle of incidence and degree of collimation. Zero order waveplates do not have this dependency. A zero order waveplate is constructed of two multiple order waveplates (optically contacted, cemented or airspaced) with their axes crossed. Thus, the effect of the first plate is canceled by the second, except for the residual difference between them. The following Table based on 532 nm, λ/4 waveplates with retardation tolerance <λ/100 gives you a rough idea of the comparison among all the orders waveplates.
Zero Order of Waveplate Multi Low Ture-Zero
Cemented Air-spaced Thickness(mm)=10.3<0.1 Spectral bandwidth(nm)0.5  1.530
Temperature 1038735
bandwidth(c)
Angular bandwidth  2.5  4.52033 Damage
>500>500>10>10>500 threshold(MW/cm2)
CASIX's Waveplates, including octadic-wave (λ/8), quarter-wave (λ/4), half-wave (λ/2) and full-wave (
λ) plates, are widely used in synthesis and analysis of light in various states of polarization. The standard specification of CASIX's waveplates are listed following for your reference.
The standard waveplate wavelengths (nm) of CASIX's waveplates
248266308325331337
347251354363413441
457476488510514530
532543557573589594
612682.8647694752780
8008308508709051050
106411521300131015502020
Other wavelengths within the ranger of 200-2300nm are also available upon requirment.
The standard specification of CASIX's waveplates
Material Crystal Quartz
Dimension+0.0, -0.2mm
Wavefront distortion<λ/8@632.8
Retardation tolerance<λ/500
Parallelism<1 arc second
Surface quality20/10 scratch and dig
Clear aperture>80%
AR coating R<0.2% at central wavelength
CASIX's Waveplate series:
Low-Order
Multi-Order
Cemented Zero-Order
Airspaced Zero-Order
True Zreo-Order
Dual Wavelength
Polarization Rotators
Fresnel Rhomb
Mounts and Holders for Waveplates
Low-Order Waveplate
•Thickness: 0.2-0.4 mm
•High Damage Threshold
•Better Temperature
Bandwidth
•Low Cost
Uncoated AR/AR coated φ(mm)
Part No.Part No.
10.0WPL1110WPL1210
12.7WPL1112WPL1212
15.0WPL1115WPL1215
20.0WPL1120WPL1220
25.4WPL1125WPL1225
Multi-Order Waveplate
•Thickness:1 mm
•Single plates
•High Damage Threshold
•Low Cost
φ(mm)Uncoated AR/AR coated

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