High Power Attenuator Using Glan Taylor Polarisers
Variable attenuators are frequently configured using a combination of a half wave retardation plate and a linear polarizer. Light is input through the retardation plate, a rotation of which produces a rotation in the angle of the plane of polarization as seen entering the polarizer. By Malus' law, the relative transmission of this combination (ignoring other loss mechanisms) is given by the square of the cosine of the relative angle between the plane of the input polarization state and that of the transmission state of the polarizer. This approach relies on the input light being in a well defined linear polarized state and the maximum attenuation will be dictated by the purity of the input polarization state. It is also wavelength dependent by definition as it relies on the retardation plate providing a half wave retardation which of course it will do only for certain wavelengths
This alternative design of optical attenuator uses a pair of high quality Glan-Taylor polarizers and therefore can be used at wavelengths between 0.35-2.0µm (subject to variations in transmission of the AR coatings). Maximum continuous rating is 200W/cm2 and peak power handling is up to 500MW/cm2 for q-switched pulses (1064nm). If the attenuator is used with plane polarised light the maximum transmission is ~90% and with unpolarised light the maximum transmission is ~40 (lower if un-coated prisms are used for maximum transmission uniformity).
The input polariser is rotated through up to 90o and energy in the side exit beam is dumped onto a light absorbing block. If required the block can be removed and the side exit beam allowed to leave the attenuator. The output polarization state remains fixed for any degree of attenuation as only the input polarizer rotates.
Specification
| Dimensions | 60mm dia. x 72mm long |
| Mounting | 6mm threaded holes at 90o |
| Aperture | 10, 12 or 15mm |
| Maximum Continuous Rating | 200W/cm2 |
| Maximum Peak Power | 500MW/cm2 |
| Operating Range | 0.35 - 2.0µm |
| Attenuation Range | 0.4 - 60dB |
| Beam Deviation | <3 minutes of arc |
| Wavefront Distortion | <1/4 |
| Input Polarisation State | Any |
| Output Polarisation | Plane Polarised |
