Deep learning reconstruction algorithm for frequency-resolved optical gating.

In general, delay operation is the most time-consuming stage in frequency-resolved optical gating (FROG) technology, which limits the use of FROG for high-speed measurement of ultrashort laser pulses. In this work, we propose and demonstrate the reconstruction of ultrashort optical pulses by employing the sequence-to-sequence (Seq2Seq) model with attention, theoretically. To our knowledge, this is the first deep learning framework capable of accurately reconstructing ultrashort pulses using very partial spectrograms. The root mean squared error (RMSE) of the pulse amplitude reconstruction and phase reconstruction on the overall test dataset are 9.5 × 10-4 and 0.20, respectively. Compared with the classic FROG recovery algorithm based on two-dimensional phase retrieval algorithms, the use of our model can shorten the spectral measurement time to 1/8 of the original time or even less. Meanwhile, the time required for pulse reconstruction using our model is roughly 0.2 s. To our knowledge, the pulse reconstruction speed of our model exceeds all current iteration-based FROG recovery algorithms. We believe that this study can greatly facilitate the use of FROG for high-speed measurements of ultrashort pulses.

Influence of ambient temperature on an Yb:YAG disk laser with anti-Stokes fluorescence cooling.

In general, the operating characteristics of solid-state lasers are significantly impacted by the ambient temperature, especially for Yb:YAG crystal with an anti-Stokes fluorescence cooling effect. In this Letter, the influence of the ambient temperature on the operating characteristics at the zero thermal load (ZTL) state is studied for an Yb:YAG disk crystal with a 1030 nm intra-cavity-pumped scheme. Theoretical analysis indicates that the output power of the laser at the ZTL state is significantly enhanced as the ambient temperature increases. Experimental results show that when the ambient temperature increases to 40°C, the output power of the laser at the ZTL state can reach 1.11 W, which is more than twice than that achieved at an ambient temperature of 25.5°C. This Letter provides a technical pathway for achieving a higher-power radiation-balanced laser (RBL).