研究目的
Investigating the emissions from N2+ pumped with ultrafast filaments using high-resolution pump probe to understand the phase relation between transition lines and the gain mechanism beyond coherence loss.
研究成果
The study demonstrates that gain on transition lines of N2+ extends beyond the time when coherence is lost, suggesting that coherence in the system plays a crucial role in the gain mechanism. The findings highlight the importance of phase relations between rotational states in achieving stimulated emission.
研究不足
The study is limited by the spectral resolution of the spectrometer and the temporal resolution determined by the precision of the delay between pump and seed pulses. The interpretation of gain mechanisms is complex due to the interplay of stimulated emission and Raman processes.
1：Experimental Design and Method Selection:
The study uses high-resolution pump-probe spectroscopy to analyze emissions from N2+ pumped with ultrafast filaments. The methodology involves ultrafast laser pulses to ionize nitrogen molecules and a delayed seed pulse to probe the emissions.
2：Sample Selection and Data Sources:
The experiment is conducted in a nitrogen-filled cell at pressures ranging from 100–760 Torr. The emissions are measured with high spectral resolution.
3：List of Experimental Equipment and Materials:
A Ti:sapphire oscillator-regenerative amplifier (Coherent-Hidra) generates 50 fs pulses at 795 nm. A second harmonic beam is used as a seed pulse. The setup includes dichroic mirrors, wave plates, and a high-resolution spectrometer.
4：Experimental Procedures and Operational Workflow:
The pump and seed pulses are focused into the nitrogen cell. The delay between them is varied, and the emission spectrum is recorded at each delay with a high-resolution spectrometer.
5：Data Analysis Methods:
The time-dependent gain is analyzed by comparing the emission spectra at different delays. Fourier transform analysis is used to study the rotational wave packet dynamics.
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