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, ‡}

Forward probe (seed) spectra when the pump laser is turned on without (blue short dash) and with the coupling laser whose polarization direction is parallel (pink dash) and perpendicular (red solid) to that of the pump. The signs || and ⊥ represent the laser polarization direction parallel and perpendicular to the horizontal direction, respectively.