| 摘要 |
<p>PURPOSE:To securely compensate fluctuations of the output power of a light source with a compensation system by providing a beam splitter which splits a beam into a pump beam and a probe beam and detecting the probe beam from a sample. CONSTITUTION:The light from a laser 3 is split by the beam splitter 6 into the pump beam 4 and probe beam 5. The beam 4 is focused by a lens 8 on the sample 7. The beam 5, on the other hand, passes through a delay optical path 9 and focused on the sample 7 by a lens 10 to reach a wide-bad photodetector 1 through a lens 11. A chopper 12 is interposed in the optical path of the pump beam 4 and a chopping frequency (f) which is lower than the pulse laser repetitive frequency f1 is selected. A reference beam 15 is made incident on a wide-band photodetector 2. The photodetectors 1 and 2 have such band width that the chopping frequency (f) is higher, but lower than the pulse laser repetitive frequency f1. The output DC voltages A and B of the photodetectors 1 and 2 are controlled 16 to the same voltage.</p> |
