Observation of the optical <inline-formula><tex-math><?CDATA ${{\rm{X}}}^{2}{\Sigma }_{{\rm{g}}}^{+}$?></tex-math><mml:math><mml:mrow><mml:msup><mml:mi mathvariant="normal">X</mml:mi><mml:mn>2</mml:mn></mml:msup><mml:msubsup><mml:mo>Σ</mml:mo><mml:mi mathvariant="normal">g</mml:mi><mml:mo>+</mml:mo></mml:msubsup></mml:mrow></mml:math> <inline-graphic xmlns:xlink="https://www.w3.org/1999/xlink" xlink:href="cpb_28_12_123301_ieqn1.gif"/></inline-formula>–A2Πu coupling in <inline-formula><tex-math><?CDATA ${{\rm{N}}}_{2}^{+}$?></tex-math><mml:math><mml:mrow><mml:msubsup><mml:mi mathvariant="normal">N</mml:mi><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:mrow></mml:math> <inline-graphic xmlns:xlink="https://www.w3.org/1999/xlink" xlink:href="cpb_28_12_123301_ieqn2.gif"/></inline-formula> lasing induced by intense laser field<xref rid="cpb_28_12_123301fn1" ref-type="fn">*</xref><fn id="cpb_28_12_123301fn1"><label>*</label>Project supported by the National Natural Science Foundation of China (Grant Nos. 61625501, 11904121, and 61427816), the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM), China, the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT), China (Grant No. 2017TD-21), and Fundamental Research Funds for the Central Universities of China.</fn>

Observation of the optical

X2Σg+

–A²Π_u coupling in

N2+

lasing induced by intense laser field**

Project supported by the National Natural Science Foundation of China (Grant Nos. 61625501, 11904121, and 61427816), the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM), China, the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT), China (Grant No. 2017TD-21), and Fundamental Research Funds for the Central Universities of China.

Wang Siqi¹, Fu Yao¹, Yao Danwen¹, Chen Shanming¹, Zhang Wei¹, Li Helong^{1, 2, †}, Xu Huailiang^{1, 3, ‡}

Schematic of experimental setup based on the pump-coupling-probe scheme. HWP1 and HWP2: half-wave plate of 800-nm laser, HWP3: half-wave plate of 400-nm laser, P: polarizer, BS: beam splitter, DM: dichromic mirror, L1: fused silica lens with f = 40 cm, L2: fused silica lens with f = 30 cm, F: filter, HR1 and HR2: high reflection mirror of 400-nm laser, L3 and L4: fused silica lens with f = 6 cm.