消色差波片是一种特殊的零级波片，由两个波片组成，每个波片分别由两种不同的双折射材料（例如石英和氟化镁）制成。色散的存在会显著影响材料的折射率。构成消色差波片的两种双折射材料具有互补的双折射特性，可以衰减色散效应，从而使第一个波片中延迟随波长变化而产生的过度偏移可以被第二个波片抵消。这会导致在很宽的波长带（通常为数百纳米）上相位延迟的响应几乎平坦，因此消色差波片是可调谐激光源、飞秒激光系统、光谱仪和其他涉及宽带光源的系统等应用的绝佳选择。
两个最常见的相位延迟值是 lambda/2 和 lambda/4 延迟，半波片可用于将垂直偏振旋转为水平偏振，反之亦然，而四分之一波片可用于线性和圆偏振的转换。
Shalom EO 提供带 AR 镀膜的消色差半波片和消色差四分之一波片。 两片组成波片，一片由单晶石英制成，另一片由氟化镁 (MgF2) 制成，两者之间要么使用 NOA61（诺兰光学胶 61，一种光学级粘合剂）粘合在一起，要么采用气隙结构。NOA61 是一种高性能粘合剂，具有高粘合强度、高耐热性和出色的清晰度，可支持各种工作条件下的光学应用，Shalom EO 仅将胶水涂抹在波片的通光孔径之外。采用空气隙设计的消色差波片在所有面上均镀膜，然后安装在垫片的相对两侧，并放置在一个单元内，以在石英波片和 MgF2 波片之间形成气隙。空气隙模块具有出色的损伤阈值，大于 500 MW/cm^2，适用于高功率激光器。
Shalom EO 提供现成的消色差波片在线购买。标准消色差波片具有二分之一或四分之一延迟，提供三个可选波长范围：450-650nm、690-1200nm 和 900-2000nm，覆盖可见光和部分红外光谱。我们保证快速发货和经济实惠的价格。如果您有任何其他特殊要求，Shalom EO 还提供定制服务，所有参数均可根据您的需求进行定制。
常见问题解答：
以下是一些关于波片的典型问题和解答，希望对买家有所帮助。以下内容为总结版，如需了解更多，请参阅我们的波片和延迟器简介。您还可以找到有关四分之一波片和半波片简介的相关资源。
波片的工作原理是什么？
波片和延迟器是操纵和改变激光偏振态的重要光学元件。
波片通常由双折射晶体（例如石英和氟化镁）制成。 （还有由非双折射材料制成的延迟器。菲涅尔菱形延迟器就是一个很好的例子，它通常由 BK7、紫外熔融石英或 ZnSe 制成，利用全内反射实现相位延迟。菲涅尔菱形产生的延迟实际上完全取决于折射率和棱镜的几何形状。）
这些晶体材料的各向异性导致一束光线在到达界面时分离成两束。两条分裂的光线会遇到不同的折射率：一束称为寻常光线，由寻常折射率控制；另一束称为非常光线，由方向敏感的非常折射率控制。这两条光线的偏振方向始终彼此垂直。
波片被特意切成薄片，使其光学表面与光轴平行。寻常光线和非常光线将具有不同的折射率，因此以不同的相速度传播。极化电矢量以较大速度（Vfast=c/Nfast）沿其传播的轴被定义为快轴。电矢量以较低速度（Vslow=c/Nslow）沿其传播的轴被定义为慢轴。这两个轴始终正交。
当光束垂直投射到波片表面时，两个分量的不同相速度自然会在快分量和慢分量之间引入相位延迟，其中慢分量将滞后于快分量几个相位（或相位的一小部分）。相位延迟的幅度称为延迟。波片的延迟量可以用以下公式计算：
延迟量=2πL(Nslow-Nfast)/λ
式中，L 为入射光行进的距离（波片的厚度），Nfast 和 Nslow 分别为快轴和慢轴的折射率。
延迟量的值可以写成多种形式，例如，“半波”延迟量相当于 π 弧度或 lambda/2 的延迟量。
从上面的公式中，可以很容易地推断出，通过精心设计波片的厚度，可以获得所需的延迟量。然而，除了波片的厚度之外，其他外部因素也会影响延迟值，例如入射光的波长、工作环境的温度、入射角等等。外部因素引起的延迟变化通常令人不安且有害，这也是制造商竭力避免的。
如何找到快轴？
找到每个波片的快轴是使用波片时的关键步骤。Shalom EO 提供的已安装波片均设计为在安装座上以直光形式指示快轴。而未安装版本的快轴均直接标记在波片上。但是，如果没有指示快轴或指示模糊，有一种简单的方法可以帮助您找到适用于所有延迟值波片的快轴。首先，在激光器前方放置一个偏振片，倾斜偏振片直至光完全消失；然后将波片置于激光器和偏振片之间，旋转波片，使最终输出的光仍然保持消失状态——瞧！您已经成功找到了光轴。
需要调整吗？
此外，您可能会发现购买的波片产生的延迟量与设计值不完全一致。原因有很多：例如，波片并非根据您的目标波长设计，或者存在温度等外部因素影响延迟量。可以通过将偏振平面旋转至波片的快轴或慢轴来调整这些细微的偏差。旋转至快轴会降低延迟量，而旋转至快轴会增加延迟量。尝试两个方向，并使用偏振片持续检查延迟量的变化。
规格:
450-650nm，
690-1200nm,
900-2000nm
延迟曲线：
下图展示了消色差波片在以下波长范围内的延迟情况。
1. 450-650nm 消色差四分之一波片和二分之一波片
2. 690-1200nm消色差四分之一波片和半波片
3. 900-2000nm消色差四分之一波片和半波片
Understanding different types of Waveplates and Retarders are equally as important as figuring out their working principle, especially for buyers. Don’t worry, Shalom EO edited a brief guide for you, after reading that you might have a much clarified and profound understanding of waveplates.
Low Order Waveplates or Multiple Order Waveplates
Due to difficulties in the manufacturing stage, it could be hard to churn out large quantities of waveplates that are ultra-thin and which produce exactly the desired fractional retardance. The Low Order Waveplates, Or Multiple Order Waveplates are relatively thick and generate the desired retardation with several additional wavelengths of phase delay. Because light waves repeat themselves periodically, a low order half waveplate, which produces a phase delay of lambda/2 plus 3 additional lambdas could also function as a half waveplate. The word “Order” here refers to the number of additional wavelengths generated. In this text, a low order waveplate is better than multiple order waveplates because it produces less addition phase delay and its retardation is more precise. However, the surplus of retardation also implies that they are much more sensitive to changes in wavelengths, temperature, or the AOI than their zero order counterparts.
Generally speaking, if you are looking for cheap buying-in-bulk waveplates for single wavelength applications, then Low Order Waveplates are just right for you. Shalom EO offers Low Order Waveplates of two material options (Quartz for Visible to Near-IR spectral or MgF2 for greater wavelengths up to 7000nm).
Zero Order Waveplates
Zero Order Waveplates are essentially comprised of two multiple order or low order waveplates with their axes orthogonally aligned (aligning the fast axis of one waveplate to the slow axis of the another), the resulting retardation is the difference between two individual retardations produced by respectively by the two constituent waveplates. By combining two single waveplates together, Zero Order Waveplates effectively offset the impacts of external factors (wavelength change, ambient temperature) on the retardation, which means the retardation will be much more constant compared to the low order waveplates, making them competent for applications involving broadened wavelength. Nevertheless, they might still have rather susceptive responsiveness to variations of the angle of incidence.
Shalom EO offers three types of Zero Order Waveplates: Air spaced Zero Order Waveplates, Optically Contacted Zero Order Waveplates and NOA61 Cemented Zero Order Waveplates. While the cemented zero order waveplates are the common alternative, for high energy operations, consider Air spaced zero order waveplates and optically contacted zero order waveplates, since the two types have relatively higher damage threshold than the cemented versions.
True Zero Order Waveplates
True Zero Order Waveplates are waveplates of single-plate structure and provide exactly the required retardation, therefore its thickness is usually only several micrometers. Although requiring relatively strict processing, the contracted thickness contributes to more superior retardation constancy against wavelength variations or climate changes than conventional Zero Order Waveplates. Shalom EO offers True Zero Order Waveplates made from Quartz (for 532-3000nm) or MgF2 (for long-wavelength applications from 3000-7000nm), the single plate versions are relatively fragile but are of high damage threshold, while the versions cemented with BK7 substrates are much easy to handle, but are of lower damage threshold.
Achromatic Waveplates
Achromatic Wavepltes are constructed by one MgF2 Waveplate and one Quartz Waveplates with their axes orthogonally aligned, of which the birefringent properties are complementary, achieving the required focal length while minimizing chromatic dispersion. Through this approach the intrinsic influence of wavelength shifts on the retardation is drastically reduced, making achromatic waveplates even more retardation-constant than zero order waveplates, thus eminent for various Broadband applications spanning wide spectral ranges (e.g. from 900-2000nm). Two application examples are Tunable laser sources, Femtosecond laser systems, etc.
Super Achromatic Waveplates
Super Achromatic Waveplates are virtually an upgraded version of achromatic waveplates. The operation principle of super achromatic waveplates is the same as that described of achromatic waveplates. Super achromatic waveplates are also compounded by two crystal materials (e.g. quartz and magnesium fluoride), but instead of two as in the case of achromatic waveplates, they consists of six single waveplates (three of Quartz, three of MgF2), the result is exceedingly flat retardation over even wider wavelength ranges.
Fresnel Rhomb Retarders
Fresnel Rhomb Retarders operates upon an entirely different principle other than exploiting the birefringence. A Fresnel Rhomb introduces phase difference between the components of light using total internal reflection. When light is projected on the interface, the electric field of the light wave splits into two perpendicular components, the s component, and the p component. The rhombs are strategically processed into the shape of a right parallelepiped, so that with the angle of incidence cautiously chosen, the p component will proceed lambda/8 relative to the s component at each total internal reflection underwent. When light emerges, after experiencing two total internal reflections, the p component will eventually be lambda/4 ahead of the s component, thus realizing the same function of a Quarter Waveplate. When constructing a Half Wave Fresnel Rhomb Retarder, two rhombs are cemented in tandem to avert reflections at the interface.
The Fresnel Rhombs are usually made from glass materials, which are non-birefringent, the typical three being BK7, UV Fused Silica or ZnSe. Because the retardation introduced by the rhomb is related to the refractive index, which only varies slightly over a wide wavelength range, the Fresnel Rhomb Retarders have even broader wavelength capabilities than other broadband waveplates such as achromatic waveplates.
Dual Wavelength Waveplates
Dual Wavelength Waveplates introduce two retardation values for two wavelengths through the fitting of the refractive index at different wavelengths. Dual Wavelength Waveplates are particularly useful when used in conjunction with other polarization-sensitive components to separate coaxial laser beams of different wavelengths or elevate and promote the conversion efficiency of Solid State SHG Lasers. Additionally, Dual Wavelength Waveplates could also be applied to THG Systems. Triple Wavelength Waveplates could also be customized by Shalom EO at your request.