Laser induced amplified spontaneous emission from the high Rydberg states of diatomic molecules

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Amplified spontaneous emission (ASE) from single rotational levels of 3dσ, π H ィイD12ィエD1ΣィイD1+ィエD1, H' ィイD12ィエD1Π and nf (n = 4-6) Rydberg states of NO has been investigated through optical-optical double resonance excitation via the A ィイD12ィエD1ΣィイD1+ィエD1 state. The H, H'→ 3pσ, π D ィイD12ィエD1ΣィイD1+ィエD1, C ィイD12ィエD1Π (0, 0) systems were rotationally resolved. The mixing of the C ィイD12ィエD1Π(v = 0) state with the valence B ィイD12ィエD1Π(v = 7) state explained the rotational pattern successfully. The degree of polarization of ASE for these transitions was measured and compared with theoretical values of the corresponding resonant fluorescence. As the major ASE relaxation channels from the 4f and 5f (v = 0) states, transitions down to the 3d and 4d (v = 0) Rydberg series were identified,respectively.A new ASE relaxation pathway,6f → 5g,was found in addition to the 6f → 5d band. The ASE from the 7f (v =1) state located above the ionization threshold was observed for the first time.The effect of externally injected radiation on the two-photon laser induced amplified spontaneous emission (LI-ASE) has been stuied. The wave generated via the same LI-ASE process in a seeder cell acts as a seeder field for the inverted medium created in a main cell. A nearly tenfold gain is achieved in the BィイD11ィエD1ΣィイD1+ィエD1 → AィイD11ィエD1Π (0, 3) transition of the CO molecule. We demonstrate that the single rotational transition in the BィイD11ィエD1ΣィイD1+ィエD1 → AィイD11ィエD1Π(0, 4) band is selectively amplified by injection of laser radiation. The polarization effect of the input laser radiation implied that the inverted medium in the main cell serves as an amplifier while maintaining the polarization anisotropy driven by two-photon excitation.