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Coherence and Ultrashort Pulse Laser Emission Part 8

Tham khảo tài liệu 'coherence and ultrashort pulse laser emission part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 272 Coherence and Ultrashort Pulse Laser Emission Fig. 13. a DOG harmonic spectra taken with the CE phase scanned from On to 8n b Line out of the normalized integrated spectrum. The integration range is from 48 nm to 20 nm. The 2n periodicity is consistent with the asymmetric electric field of DOG Chen et al. 2009 . 3. Isolated attosecond pulse generation with CE phase stabilized high-power laser As mentioned in the previous section one of the important applications of CEP stabilized laser is to generate isolated attosecond pulses. Attosecond pulse generation is usually interpreted in the semi-classical re-collision model three-step model Corkum 1993 Corkum Chang 2008 . Briefly as a strong near infrared NIR laser pulse strikes an atom a free electron wave packet is produced by ionization. Once freed the wave packet moves away from the atom. However when the oscillating laser electric field reverses direction half of the packet is driven back towards the parent ion. This return electron can recombine with the parent ion emitting an extreme ultraviolet XUV photon which is the origin of attosecond XUV pulses. In general a multi-cycle laser will produce an attosecond XUV pulse every half of a laser cycle. The result is a train of attosecond pulses. It is obvious that the CEP is critical in the isolated attosecond pulse generation with a gating technique. It is preferred that the CEP of the NIR laser pulse is stabilized so that the center of the gate always overlaps with a single attosecond XUV pulse in the pulse train. If the CEP is not optimized the pulse energy of the single attosecond pulse would be reduced or in the worst scenario multiple attosecond pulses will be generated instead of an isolated attosecond pulse. To study the relation between the CE phase and attosecond pulse generation the isolated attosecond pulse generation and characterization experiments were performed in the KLS lab Feng et al. 2009 Gilbertson et al. 2010 . Carrier-Envelope Phase .