| 摘要 |
A device for source compensating a fiber optic coupler output automatically compensates for changes in light intensity at the output end of the fiber caused by changes in light intensity from the source, beam walking at the input of the fiber and mode changes in the fiber. Laser light enters a frequency doubler and exits as a doubled frequency output which is focused onto the input face of a fiber optic cable by a lens. The lens is selected so that the spot size of the focused light on the face of the fiber is smaller than the diameter of the fiber and that the entry angle of the light cone is within the acceptance angle of the fiber. The fiber is tightly wound into a mode scrambler to provide a uniform intensity distribution of the light exiting the fiber. The light leaving the fiber is collimated and directed to additional optical elements. The collimated beam is directed to a beam splitter which reflects 8% of the incident beam to a calibrated photodiode that is terminated with a transimpedance amplifier. The light that transmits through the beam splitter can be focused onto the sample. To compensate for light fluctuations, the signal from the transimpedance amplifier is divided into the signal from the sample.
|
