Light amplification without population inversion: Time-dependent study of (1+1)-photon emission from autoionizing states

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

doi:10.1103/physreva.49.5135

Cited by 12 publications

(12 citation statements)

References 26 publications

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“…u (v = 4, j = 2) level (E a = 136) and iv) from the excited AI state to the B1I:.u(v = 4,j = 0) level (E a = 137.2) and hence the wavelengths for the resonant transitions are 315 nm, 314 nm, 234 nm and 233.5 nm, respectively The gain profiles obtained (figs. 2a and b) are quite similar to our previous (Adhya and Rai Dastidar [2]) parametric calculation, where, contrary to the present system, the two autoionization states were embedded in different continua. In that calculation also, the gain peaks (see fig.…”

Section: -Results and Discussionsupporting

confidence: 75%

“…(3) of ref. [2] (Adhya and Rai Dastidar)) were obtained about the resonance frequencies with la) (i.e. E a = 0) and with Ib) (i.e.…”

Section: -Results and Discussionmentioning

confidence: 99%

“…It is to be mentioned here that by formally solving for G c from eq. (21) and substituting it in other equations, one can write down a set of equations in terms of ionization widths li(= 21TID ic I 2 ) and Im(= 21TID mc I 2 ), autoionization widths r a (= 21TlVacI 2 ) and r b (= 21TI%cI 2 ), the coupling strength between two AI states via common continuum, two-photon coupling strength between two intermediate levels via continuum, the detunings from these AI levels (8 a and 8 b ) and from the intermediate levels (8 i and 8 m ) and the Fano q-parameters qia, qib, qma and qmb for transitions from Ii) and 1m) to la) and Ib), respectively. The damping factor '\, due to incoherent pumping, has been added to r a phenomenologically to consider the effect of distortion due to this pumping on the evolution of the system.…”

Section: -Theorymentioning

confidence: 99%

“…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%

“…It has been shown that when the lowest AI state is pumped incoherently, transfer of population from the lower AI state to the excited AI state occurs due to the configuration interaction coupling between these two levels via continuum and hence gives rise to an emission which dominates over damped absorption. In a parametric calculation [2], it was found that positive gain can be obtained when the probe laser frequency is around the resonance with the excited AI state, in the absence of direct pumping to this level. But the present study gives the results of more detailed investigations and demonstrates the feasibility of this type of amplification without population inversion in a real system like H 2 molecules for the first time.…”

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 Discussionsupporting

confidence: 75%

“…(3) of ref. [2] (Adhya and Rai Dastidar)) were obtained about the resonance frequencies with la) (i.e. E a = 0) and with Ib) (i.e.…”

Section: -Results and Discussionmentioning

confidence: 99%

Section: -Theorymentioning

confidence: 99%

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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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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Amplification without population inversion in molecules

Bhattacharjee

Sanyal²,

Dastidar

2005

Journal of Molecular Spectroscopy

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Light amplification without population inversion: Time-dependent study of (1+1)-photon emission from autoionizing states

Abstract: In a time-dependent dressed-state calculation we have studied the time development of (1+1)-photon

Cited by 12 publications

References 26 publications

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

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

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

Amplification without population inversion in molecules

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