Mica Retarders The natural cleavage of mica allows accurate zero-order retarders to be made at much lower cost than in quartz. The mica is laminated between glass plates for ease of handling. The quarter-wave plate converts linear to circular polarisation and is often used with a linear polariser to form an isolator, blocking light reflected from surfaces beyond. The half-wave plate changes the direction of linear polarisation; with a polarising beamsplitter cube or prism it forms a useful variable-ratio beamsplitter. Mica retarders, being zero-order, can be used over a fairly broad wavelength range; e.g. a 5% change of wavelength results in only 0.6% transmittance of light of incorrect polarisation- see box for calculation.
Knight Optical > Retarders > Mica retarders - 1/2 Wave Plate Only UK and EU customers are charged VAT at 17.5%, customers outside the EU and EU customers based outside the UK who have a valid EU VAT number will not be charged VAT Bulk Discounts! Where (B) appears next to a price below, bulk prices are available, click the (B) button to view! PDF Part No. Diameter (mm) Wavelength (nm) Tolerance Price Qty Buy RQM2500 25 442 ±0.02 wave £89.50 RQM2501 25 488 ±0.02 wave £89.50 RQM2502 25 515 ±0.02 wave £89.50 RQM2503 25 532 ±0.02 wave £89.50 RQM2504 25 543 ±0.02 wave £89.50 RQM2505 25 589 ±0.02 wave £89.50 RQM2506 25 633 ±0.02 wave £89.50 RQM2507 25 670 ±0.02 wave £89.50 RQM2508 25 780 ±0.02 wave £89.50 RQM2509 25 830 ±0.02 wave £93.50 RQM2510 25 1064 ±0.02 wave £93.50 RQM2511 25 1510 ±0.02 wave £93.50 Knight Optical > Retarders > Mica retarders - 1/2 Wave Plate
Specification   Retardation Tolerance: Quarter-wave: ± 0.01λ Half-wave: ± 0.02λ Diameter: 25 mm +0 / -0.2 mm Thickness: 3 mm ±0.25 mm
Technical Notes   · The spurious transmittance of a quarter-wave plate in double passage as an isolator, or of a half-wave plate as a 90º rotator, is given by:                                                        Where δλ is the difference between the actual wavelength λ and that for which the retardance is a true half or quarter wave.   · The path-difference (Retardance expressed in nm) of mica is nearly constant with wavelength, so that e.g. a quarter-wave plate for 1064nm has 266nm path-difference and is also a half-wave plate at 532nm.   · The birefringence of mica is about 0.0054, so an unlamented quarter-wave plate for 532nm is about 25 µm thick.   · Tilt of a plate can be used to tune Retardance either upwards or downwards, according as the rotation is about the fast or slow axis. The effect is approximately quadrant with angle, a 10° tilt causing about 9% change in Retardance. Specific requirements We can manufacture Mica retarders to any size at short notice, so if your requirements are not listed please contact us by telephone / fax or email: stockrequirement@knightoptical.co.uk Options available    · Special Wavelengths    · Special Sizes and thickness    · Full-wave and other Retardance    · AR coating    · Mounting