Meadowlark Optics specializes in precision polymer retarders for the visible to near-infrared region. Our Precision Retarders have the highest optical quality and tightest retardance tolerance of all polymer retarders. These true zero-order Precision Retarders consist of a birefringent polymer cemented between two precision polished, optically flat BK 7 windows. The retarder fast axis is conveniently marked for quick and easy reference. Precision Retarders are supplied with a broadband antireflection coating. Optical transmittance of a Precision Retarder is typically greater than 97%. The retardance δ at a wavelength λ that is different from the center wavelength λc is given by: δ ≈ δc(λc /λ) where δc is the retardance at λc.

This relationship is very important when using sources which vary in wavelength from their nominal value. The two graphs show the retardance behavior as a function of relative wavelength for a quarter and half‐wave retarder, respectively. The Mueller calculus can be used to calculate the transmitted polarization state based on the retardance differences from the ideal case.

Since polymer retarders are true zero‐order devices, they offer the significant advantage of improved angular performance. You can expect less than 1% retardance change over ±10°incidence angle.

Meadowlark Optics has developed precision ellipsometric techniques that can measure retardance to λ/1000. Our metrology for these measurements is the best in the industry. You can have absolute confidence that the calibration measurements supplied with your retarder are of the highest accuracy obtainable.

COMMON SPECIFICATIONS

• Retarder Material: Birefringent Polymer
• Substrate Material: N‐BK7
• Retardance Accuracy: ≤ λ/350
• Transmitted Wavefront Distortion: ≤ λ/5
• Surface Quality: (scratch‐dig) 40 –20
• Beam Deviation: ≤ 1 arc‐min
• Reflectance (per surface): ≤ 0.5% at normal incidence
• Laser Damage Threshold: 500 W/cm², CW 600 mJ/cm², 20 ns, visible 4 J/cm², 20 ns, 1064 nm
• Operating Temperature: 20˚C to 50˚C

Prolonged exposure to strong ultraviolet radiation may damage these retarders.