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Coherence and Ultrashort Pulse Laser Emission Part 7

Tham khảo tài liệu 'coherence and ultrashort pulse laser emission part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 232 Coherence and Ultrashort Pulse Laser Emission length drifts thermal and temperature fluctuation random polarization change pump instability and so on. As affected by the perturbations the initially co-propagated laser-1 may go behind or ahead of the laser-2 as shown in Fig. 2-1. In the case that the laser 1 goes behind the laser 2 the rising-edge of laser-1 will cross with the falling-edge of laser-2. Because the slope of intensity I2 is negative in its falling-edge for laser-1 the spectrum of laser-1 will be blue-shifted Aờ 0 while laser-2 will be red-shifted Âffl2 0 due to the positive intensity slope of I1 according to relation 5 and 6 . Thus in a medium with negative group dispersions for the two lasers the blue-shifted light will go Fig. 2-1. The propagation schematic diagram of Laser-1 a behind and b ahead Laser -2. faster than the red-shifted one and therefore the delayed pulse laser-1 can catch up with the advancing pulse laser-2 . In the case that laser-1 is ahead of laser-2 the XPM will lead laser-1 to be red-shifted and laser-2 to be blue-shifted in spectrum which may eventually make both pulses be maximally overlapped in the time domain. Once the pulses are maximally overlapped the spectral shifts for both pulses will be reduced to zero since the laser intensity profile is supposed to be temporally symmetric. In this situation the two lasers operate at a synchronization state with the same round-trip frequency. For evaluating a passive synchronization system there are two crucial parameters 1 the ability for the system compensating for environmental perturbations which is estimated by the value of cavity mismatch tolerance and 2 the precision for the synchronization which is defined as timing jitter between the two laser pulses Shelton el at. 2002 . Besides the synchronization stability is also an important factor to decide how long lasers are operated at synchronization state. Recently experimental results have shown that the jitter for two .