Theoretical scheme for lasing without population inversion in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>molecule

Adhya, Lipika; Sanyal, S.; Dastidar, Krishna Rai

doi:10.1103/physreva.52.4078

Cited by 6 publications

(7 citation statements)

References 30 publications

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“…[2]) in a time-dependent parametric calculation for a model system where two AI states are embedded into the same continuum. The present work is an extension of our previous calculation [3] on H 2 molecules, and we have considered here the effect of the second AI state (i.e. the first excited AI state of the 12: g symmetry) embedded into the same continuum.…”

Section: -Results and Discussionmentioning

confidence: 96%

“…ADHYA, S. SANYAL and K. RAJ DASTIDAR In recent years, the feasibility of lasing or amplification of light without population inversion (AWOPI) from an autoionizing (AI) state has been widely investigated in parametric calculations on different model systems [1][2][3][4]. Recent experimental studies [5] have shown that lasing without population inversion (LWOPI) can be obtained in atomic and molecular systems, by choosing proper schemes.…”

Section: -Introductionmentioning

confidence: 99%

“…Actually, in case of resonant (1 + I')-photon autoionization, the absorption profile (Adhya-Rai Dastidar profile [6]) obtained is a modified single-photon autoionization profile (Fano profile [7]) and in our calculation we have utilised this feature to obtain (1 + I')-photon AWOPI from autoionizing states in H 2 molecules. Previously, we have shown [3] that, with moderate coherent pumping of the upper lasing level (i.e. the lowest AI state of the 12: g symmetry), (1 + I)-photon LWOPI can be obtained with short probe pulses (of duration rv 3.45 ps), but by increasing the strength of coherent pumping LWOPI can be obtained for probe pulses of longer duration.…”

Section: -Introductionmentioning

confidence: 99%

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On amplification of radiation emitted from the excited autoionizing state of the H2 molecule in the presence of incoherent pumping to the lowest autoionizing state

1998

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We have shown that the amplification without population inversion (AWOPI) from the first excited autoionizing (AI) state of the lL;g symmetry of the H 2 molecules can be obtained when the lowest AI state of the lL;g symmetry is pumped incoherently. We have considered a resonant two-photon transition scheme from the ground X1L;g(v O,j 1) state to the ionization continuum embracing the two AI states (the lowest and the first excited autoionizing states) of the 1 L;g symmetry via the resonant intermediate B 1 L;u (v 4, j 2) level. The effect of two-photon nearresonant autoionizing channels via the near-resonant rovibrationallevels of the B 1 L;u state has also been considered. We have found that the gain can be obtained in different spectral regions corresponding to the resonances with the lowest and first excited AI states from the intermediate levels of the B 1 L;u state. The inherent coherence between two AI states due to the configuration interaction coupling via the common continuum has been found to have a significant effect on the amplification process, which occurs around all the resonance frequencies connecting this AI state with the intermediate levels. This gain can be significantly modified by increasing the coupling strength of this excited AI state with the continuum. Moreover, the gain from the excited AI state remains unaffected by the damping caused by incoherent pumping to the lowest AI state. It has also been shown that the persistence of inversionless gain from the excited AI state is shorter than that from the lowest AI state. The presence of close-lying near-resonant rovibrationallevels leads to the increase in gain around the resonances with two AI states from the B1L;u (v 4,j 2) level. The advantages of this type of scheme are; i) AWOPI can be obtained from an excited AI state although it has not been pumped and Ii) the amplification obtained from the excited AI state is almost unaffected by the distortion caused by incoherent pumping to the lower AI state.PACS 42.55.Ah -General laser theory. PACS 42.50.Hz -Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift.

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Section: -Results and Discussionmentioning

confidence: 96%

Section: -Introductionmentioning

confidence: 99%

Section: -Introductionmentioning

confidence: 99%

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On amplification of radiation emitted from the excited autoionizing state of the H2 molecule in the presence of incoherent pumping to the lowest autoionizing state

1998

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“…We found that the values of populations and coherences obtained by solving the density matrix equations numerically at large time are in good agreement with the values obtained from the exact expressions in the steady state limit. However, results obtained with first-order approximation agree with the numerical results only when Ω G. AWI were studied theoretically either by choosing different parameters for the process [12,13] or in real systems like atoms [14,15] and molecules [3][4][5][16][17][18]. The presence of rotational and vibrational states makes the study of LWI/AWI fascinating in molecules as these states influence the process of inversionless lasing.…”

Section: Introductionmentioning

confidence: 91%

“…Amplification without inversion (AWI) and lasing without inversion (LWI) have been studied both theoretically [1][2][3][4][5] and experimentally [6,7] in three, four and multilevel systems by choosing different configurations, e.g. ladder, V , Λ etc.…”

Section: Introductionmentioning

confidence: 99%

Control of amplification without inversion in H2 and LiH molecules: Dependence on relative magnitude of probe and coherent field Rabi frequencies in three-level Λ system

Dutta

Dastidar

2006

Pramana - J Phys

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Dependence of amplification without inversion (AWI) on the relative strength of probe and coherent field Rabi frequencies has been studied in H 2 and LiH molecules for three-level Λ configuration. We have derived exact analytical expressions for coherences and populations keeping all the orders of probe field Rabi frequency (G) and coherent field Rabi frequency (Ω) in the steady state limit. Previously, first-order approximation (i.e. keeping only the first-order term in G) was used and hence AWI was studied for the condition Ω G. Here, by using the exact analytical expressions of coherences and populations, we have shown that AWI is maximum when Ω is within the same order of probe field Rabi frequency G irrespective of the choice of different ro-vibrational transitions in both the molecules. However, the shape of the gain profile and the maximum value of gain on the probe field and the absorption on coherent field depend on the choice of different ro-vibrational levels as the upper lasing levels. Effect of bidirectional pumping, homogeneous and inhomogeneous broadening on AWI process has been studied. By solving the density matrix equations numerically it has been shown that both the transient and the steady state AWI can be obtained and the numerical values of coherences and populations at large time are in very good agreement with exact analytical values in the steady state limit. It has been shown that in molecules AWI can be obtained on probe field of smaller wavelength than that of the coherent field which has not been observed in atoms so far.

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