The 935 variable attenuators have a large dynamic range, broadband transmission, and high damage threshold, with negligible beam deviation. Three aperture sizes are available: 3, 5, and 10 mm diameter. These attenuators are based on the principle of Fresnel reflection from four uncoated, counter-rotating UV fused silica wedged plates.
The 3 and 5 mm aperture versions accommodate micrometer-style actuators to control the system attenuation. These models can easily be motorized with micrometer replacement actuators such as the CMA-25CC or the new LTA. The 10 mm aperture version is available only with an adjustment knob.
The peak power rating of these attenuators is determined purely by the damage threshold of fused silica, while average power is limited by the power dissipation characteristics of the mechanical housing.
The 935-B and 935-LB 90° mounting brackets allow the attenuators to be mounted so the input beam polarization can be effectively rotated 90°.
How does it work?
A collimated beam incident on a wedged optical plate experiences Fresnel reflection which varies with incident angle θτ. A single wedged plate is unsatisfactory as an attenuator because the output beam deviation varies with angle and the dynamic attenuation range is small. However, with careful design, a symmetric arrangement of two pairs of counter-rotating wedges can be employed to produce an attenuator, with negligible output beam deviation and dynamic range proportional to the fourth power of the transmission of a single wedge. For small wedge angles an input beam polarized in the plane of incidence can experience near zero attenuation when θτ equals the Brewster angle θβ. The attenuation for both polarizations increases as θ approaches the critical angle for total internal reflection.
The graph shows the large dynamic range as a function of angle measured from the critical angle.
Reference: K. Bennett and R.L. Byer. Appl. Opt. pp 2408-12, Vol. 19. 15 July, 1980.
Actuator Options
|
Model |
Motion |
Minimum Incremental Motion, Linear
(µm) |
Option Code
(OPT) |
HR-1
HR-1 Series |
Manual |
0.25 |
04 |
SM-25
SM Series |
Manual |
1 |
02 |
AJS100-2
AJS Series |
Manual |
0.6 - 0.75 |
03 |
CMA-25CC
CMA Series |
Motorized |
<0.5 |
01 |
LTA-HS
LTA Series |
Motorized |
0.1 |
07 |
Note: For motorized actuators, a motion controller must be specified separately.
HR-1 Series Lockable High-Resolution Micrometer Heads
SM Series Vernier Micrometer Heads
AJS Series High-Precision Adjustment Screws
CMA Series Compact Motorized Actuators
LTA Series Precision Motorized Actuators
