Achromatic Waveplates: Their Manufacturing & Applications

While the last century’s progress was driven by electronics, we are now in the century of photonics. New uses of light are constantly emerging in countless diverse areas including manufacturing, medicine, microscopy, the military, entertainment, telecommunications, and more.
All these applications function by manipulating and analyzing light by its attributes: polarization wavelength, direction, position, and intensity. Waveplates, also known as phase retarders or simply retarders, transform the polarization state of light transmitting through them according to its wavelength, without affecting its direction, position, or intensity. The ability to exchange one
polarization state for another is very useful for manipulating or analyzing light. And waveplates offer high power-handling capability, low wavefront aberrations, and high transmission in a very small package.
Most waveplates work as designed for only one or two specific wavelengths; for many purposes that is exactly what is desired. By manipulating polarization, waveplates may be used to direct or separate beams of light, to maximize their reflection or transmission, and more. Sometimes we might want to do one of these things with one color or wavelength, and something different with another. What makes an achromatic waveplate different is that it does not act differently upon different wavelengths, and sometimes that’s exactly what is required. When a constant phase retardation is desired across a broad range of wavelengths, an achromatic waveplate is required.

How achromatic waveplates are made.

Just as an achromatic lens is made of two types of glass, an achromatic waveplate is made from two different birefringent crystalline materials. The most popular choice is crystal quartz and magnesium
fluoride. While both these materials are birefringent, their birefringence values are slightly different and change at different rates across the spectrum. When properly matched in thickness and orientation using sophisticated optical calculations, they balance each other to produce a combination that can
function well across the entire visible spectrum. Achromatic combinations can also be designed to work over other broad wavelength bands including the near infrared.
After design calculations are performed, the two crystal materials are polished to an exacting thickness (different for each material and each design) with highly parallel faces precisely oriented to their internal axes. Typically, each material type is produced in a batch quantity. During this processing, the retardation of the separate plates is monitored using a purpose-built polarimeter to guarantee that theirtarget values are reached. A hard, durable antireflective coating is applied to reduce all surface reflection and transmission losses to under 0.5% total. Then each individual plate is measured again and paired for best performance with their best-matching mate. Finally the two matched plates are precisely oriented to each other usingoptical methods and placed inside a protective housing.

A specialty

The precision optics field has many fine manufacturers, each with their own set of capabilities and specialties. Waveplates, and especially achromatic waveplates, are not even attempted by most. This is due to the stringent manufacturing methods, specialized testing equipment, and niche design and market knowledge required for success.

Work With A Supplier You Trust

When purchasing waveplates, you should pay heed to the supplier as much as the specifications of the optical device. Partnering with a manufacturer who specializes in such optics and offers years of expertise is your best bet to ensure your unique application needs are met. Tower Optical Corporation has been providing premium quality precision optics to industry experts all over the world for over 40 years. Their commitment to innovation and excellence has helped them garner a stellar reputation as one of the world’s leading manufacturers.
Offering custom, tailor-made solutions to boost industry capabilities, the full service manufacturer also has a wide range of in-stock precision optics. Apart from over 10,000 waveplates, Tower Optical also specializes in optical filters, laser windows, beam expanders, laser mirrors, and prisms. Each product in their inventory is available in-stock and can be made to order according to your
specifications.

Contact Tower Optical at 561 740-2525 or Sales@TowerOptical.com and request a quotation for any custom or stock orders.