Features

• High Energy Air-Spaced Design
• Operates as a Quarter-Wave Plate at One Wavelength and a Half-Wave Plate at a Second Wavelength

Thorlabs' dual wavelength, multi-order wave plates are made from high-quality crystalline quartz and are available at quarter-wave or half-wave retardance. The wave plates are designed to be used in dual wavelength setups (1064 nm and 532 nm) and operate as a quarter-wave plate at one wavelength and as a half-wave plate at the second wavelength. Two models are available: λ/4 @ 532 nm and λ/2 @ 1064 nm or a λ/4 @ 1064 nm and λ/2 @ 532 nm.

Multi-order refers to the fact that the retardance of a light path will undergo a certain number of full wavelength shifts (also referred to as the order, or m) in addition to the fractional design retardance. Compared to their zero-order counterparts, the retardance of multi-order wave plates are more sensitive to wavelength and temperature changes, however, they are less expensive and find use in many applications where the increased sensitivities is not an issue.

Our wave plates are mounted in a Ø1" housing with the fast axis of the wave plate clearly marked with a straight line on the housing's front panel. The wave plates are easily removed from their mounts for use in custom or OEM applications (see the Specs tab for the unmounted wave plate thickness). The unmounted waveplates have a small flat to indicate the polarization axis (see image on the right). Available as either λ/2, for rotating the polarization or λ/4, for converting linearly polarized light into circular polarization and vice versa. For further information on using and selecting a wave plate please visit our Selection Guide tab.

Operating Principal of Wave Plates

Optical wave plates are constructed from birefringent material that introduces a phase difference between the fast and slow principal axis of the wave plate. The birefringent properties of the material create a difference in refractive index between the two axis. This in return creates a difference in the velocity between the two orthogonal components. The fast principal axis of the wave plate has a lower refractive index resulting in faster wave velocity. The slow axis has a higher refractive index with slower velocity. The actual phase shift created depends on the properties of the material, the thickness of the wave plate and the wavelength of the signal, and can be described as:

where n₁ is the refractive index of the principal plane, n₂ is the refractive index of the orthogonal plane and d is the thickness of the wave plate.

Using a Wave Plate

Wave plates are typically available as λ/4 or λ/2 meaning a phase shift of quarter of a wavelength or half a wavelength (respectively) is created.

Half-Wave

Quarter-Wave

A quarter-wave plate is designed such that the phase shift created between the fast and slow axis is quarter of a wavelength (λ/4) or a multiple of λ/4. When applying a linearly polarized beam with the polarization plane aligned at 45° to the wave plate’s principal plane, the output beam will be circularly polarized. Similarly when applying a circularly polarized beam to a λ/4 wave plate the output beam will be linearly polarized. Accordingly quarter wave plates are used in Optical Isolators, Optical pumps and EO modulators.

Choosing a Wave Plate

Thorlabs offers achromatic, zero-order (both unmounted wave plates and mounted wave plates) and multi-order wave plates (single wavelength and dual wavelength) with either λ/4 or λ/2 phase shift.

While our Achromatic Wave Plates provide phase retardance over a large spectral range, zero-order and multi-order wave plates provide a phase shift that is wavelength dependent. Our achromatic wave plates are available with four AR coatings: 260-410 nm, 400-800 nm, 690-1200 nm, and 1100-2000 nm.

Zero-order waveplates are designed such that the phase shift created is exactly one quarter or one half of a wave. They offer substantially lower dependence on temperature and wavelength than multi-order wave plates. Our Zero-Order Quartz Wave Plates are composed of two wave plates stacked together with the fast axis of one aligned to the slow axis of the other to achieve zero-order performance. Thorlabs' zero-order wave plates are available for a number of discrete wavelengths ranging from 266 nm to 2020 nm. Our Economy Zero-Order Quarter-Wave Plates consist of a thin layer of liquid crystal polymer retarding material sandwiched between two glass plates and are available at discrete wavelengths between 405 nm and 1053 nm. Our quartz zero-order wave plates provide better retardance accuracy and lower reflectance (see table), while our LCP zero-order wave plates produce a smaller decrease in retardance at larger AOIs. In addition, Thorlabs also offers unmounted true Zero-Order Telecom Wave Plates for WDM applications.

Multi-Order Wave Plates are made such that the retardance of a light path will undergo a certain number of full wavelength shifts (also referred to as the order, or m) in addition to the fractional design retardance. Compared to their zero-order counterparts, the retardance of multi-order wave plates is more sensitive to wavelength and temperature changes. Multi-order wave plates are, however, a more economical solution for many applications where increased sensitivities are not an issue. Our multi-order wave plates are available for a number of discrete wavelengths ranging from 266 nm to 1550 nm. Thorlabs also offers Dual-Wavelength Multi-Order Wave Plates designed for use at both 532 nm and 1064 nm.