Automatic Power Control

Schematic of the CCVA-TL-KT kit.

The computer controlled closed loop attenuator sets and maintains the power by positioning the ½ wave-plate based on a feedback signal from a photo detector which can exhibit a strong dependence on wavelength. This chromaticity becomes significant when the tuning range is large. Consequently, a spectrometer is incorporated into the setup which provides real-time information about the wavelength of the laser, thus taking advantage of the precise wavelength calibration of the photo-detector. This is especially important when the laser power needs to be held constant while scanning wavelength. The algorithm used to control power operates in a closed loop with PID (proportional, integral, derivative) feedback, compensating for slow changes in output power within the bandwidth of the device greater than 500 ms.

Attenuate Light by a Factor of 1000

This device is capable of attenuating light by a factor of 1000 while still maintaining an error of less than 10%. Depending on the choice of components the attenuator is suitable for laser wavelengths ranging from 400 nm to 1100 nm, and average powers from 1nW up to 20 Watts (500 Watts/cm2 damage threshold).

Reference Software

The software included with this product is for reference only. It has been tested in the experimental setup described in the application note. The software will need to be customized by the user for additional experimental requirements. At the present time, Newport provides limited support for this software and any concern should be discussed with Newport before purchasing the product.


Applications for this variable attenuator kit include:

  • Multiphoton Microscopy
  • Supercontinuum Generation
  • Terahertz Generation
  • Ultrafast Spectroscopy
  • Optical Coherence Tomography

Please see Application Note 30 for more information.