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Physical Review A

Prediction of inversionless gain in a mismatched Doppler-broadened medium

J. R. Boon, Evangelini Zekou, David McGloin, Malcolm H. Dunn

Published Sep 1, 1998• 18 citations
Publisher

Abstract

Inversionless gain is predicted in a Doppler-broadened $V$ scheme for which the probe laser frequency is approximately twice that of the coupling laser. A comparison is made of inversionless gain achieved via electromagnetically induced transparency in Doppler-broadened matched and mismatched wavelength systems. We show that the presence of Doppler broadening does not preclude inversionless lasing for mismatched wavelengths; importantly, this is shown to hold even for Rabi splittings significantly less than the Doppler width. Our analysis demonstrates that inversionless gain is realizable in Doppler-broadened media, at modest continuous wave laser powers, for a probe frequency well in excess of the coupling field frequency. The presented theory is related to a practical mismatched system in atomic rubidium vapor. Approximately 8% gain is predicted in a 422 nm probe field coherently driven by a 780 nm coupling field, in the presence of a modest level of incoherent excitation.

DOI
10.1103/physreva.58.2560

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Continuous inversionless gain is studied in a Doppler-broadened Λ scheme. The inversionless gain is realizable in Doppler-broadened media for a coupling field wavelength well in excess of probe field wavelength when the laser power is significantly less than the Doppler width, and stronger than that of media for the coupling field wavelength equal to the probe field wavelength. In another scheme for the probe field wavelength well in excess of coupling field wavelength, the inversionless gain doesn't exist. The predictions are explained form the point of electromagneticaly-induced transparency.

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A study of inversionless gain in mismatched, Doppler-broadened systems

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We present a theoretical study of the effects of mismatching wavelengths for the coupling and probe fields in Doppler-broadened media for the three basic energy level configurations commonly used to realize electromagnetically induced transparency (EIT). Three wavelength regimes are considered: mismatched wavelengths for which the coupling frequency is greater than the probe frequency, matched wavelengths for which the coupling and probe frequencies are equal, and mismatched wavelengths for which the probe frequency is greater than the coupling frequency. The transparency that may be induced in these regimes is compared for the cascade-, \ensuremath{\Lambda}-, and Vee-type systems. We show that in the first mismatched regime $({\ensuremath{\lambda}}_{c}<{\ensuremath{\lambda}}_{p})$ EIT is possible in all schemes and is in fact stronger than in the matched case. It is also demonstrated that for the second mismatched regime $({\ensuremath{\lambda}}_{c}>{\ensuremath{\lambda}}_{p})$ EIT can be realized most readily in the Vee-type configuration in the presence of Doppler broadening. These predictions are explained by considering the absorption as a function of both the probe field detuning and the atomic velocity.

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Lasing without inversion in three-level systems without external coherent driving

V. Ahufinger, J. Mompart, R. Corbalán

Summary form only given. We study a model for an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity and producing two laser fields, one of them without population inversion. Each laser field couples to only one of the transitions of the three-level medium. We have studied our model for parameters appropriate to two real atomic systems (i) a cascade scheme in atomic /sup 138/Ba looking for lasing with (without) inversion at /spl lambda//sub /spl beta//=554 nm (/spl lambda//sub /spl alpha//=821 nm), and (ii) a V-scheme in atomic /sup 85/Rb with ordinary lasing at /spl lambda//sub /spl alpha//=780 nm and lasing without inversion (LWI) at /spl lambda//sub /spl alpha//=4216 nm. These two cases are qualitatively different in that two-photon processes are responsible for inversionless gain in case (i) while LWI in case (ii) arises from one-photon processes. Moreover, the frequency up-conversion ratio is R=0.67 for the case of /sup 138/Ba and it is R=1.88 for the case of /sup 85/Rb. In spite of the fact that the frequencies of the two laser fields are relatively different, our results show that dual-wavelength lasing extends up to Doppler broadening values typical for optical transitions of atoms in a vapor cell. In case (i) /spl alpha/-lasing occurs without two-photon inversion only for approximately the lower half of the domain of Doppler-broadening values. However, in case (ii) one has LWI in all the domains. Some considerations for a practical realization of the dual-wavelength inversionless-conventional laser are discussed.

Conference on Lasers and Electro-Optics•Aug 29, 2005•1 citation
Inversionless gain is predicted in a Doppler-broadened VVV scheme for which the probe laser frequency is approximately twice that of the coupling laser. A comparison is made of inversionless gain achieved via electromagnetically induced transparency in Doppler-broadened matched and mismatched wavelength systems. We show that the presence of Doppler broadening does not preclude inversionless lasing for mismatched wavelengths; importantly, this is shown to hold even for Rabi splittings significantly less than the Doppler width. Our analysis demonstrates that inversionless gain is realizable in Doppler-broadened media, at modest continuous wave laser powers, for a probe frequency well in excess of the coupling field frequency. The presented theory is related to a practical mismatched system in atomic rubidium vapor. Approximately 8% gain is predicted in a 422 nm probe field coherently driven by a 780 nm coupling field, in the presence of a modest level of incoherent excitation.
Continuous inversionless gain is studied in a Doppler-broadened Λ scheme. The inversionless gain is realizable in Doppler-broadened media for a coupling field wavelength well in excess of probe field wavelength when the laser power is significantly less than the Doppler width, and stronger than that of media for the coupling field wavelength equal to the probe field wavelength. In another scheme for the probe field wavelength well in excess of coupling field wavelength, the inversionless gain doesn't exist. The predictions are explained form the point of electromagneticaly-induced transparency.
Recently it was predicted, and shown experimentally, that a cw coherently induced transparency feature could be observed in a Doppler-broadened cascade medium even when the probe and coupling fields had a wavelength mismatch of several hundred nanometers.1 This observation is significant since it removes the requirement for finding wavelength-matched systems to carry out cw atomic coherence experiments within an inhomogeneously broadened medium.2,3 The explanation of this transparency lies with the fact that both E.I.T. and Autler-Townes splitting4 are velocity group dependent. Each velocity group experiences its own Doppler-shift and hence detuning from the probe and coupling field transitions. Therefore, there exists a variation in the frequency position of maximum E.I.T. and of the Autler-Townes split components for each velocity groups. It is the integration of both of these effects over all of the velocity groups that produces the overall probe absorption.
We present a theoretical study of the effects of mismatching wavelengths for the coupling and probe fields in Doppler-broadened media for the three basic energy level configurations commonly used to realize electromagnetically induced transparency (EIT). Three wavelength regimes are considered: mismatched wavelengths for which the coupling frequency is greater than the probe frequency, matched wavelengths for which the coupling and probe frequencies are equal, and mismatched wavelengths for which the probe frequency is greater than the coupling frequency. The transparency that may be induced in these regimes is compared for the cascade-, \ensuremath{\Lambda}-, and Vee-type systems. We show that in the first mismatched regime $({\ensuremath{\lambda}}_{c}<{\ensuremath{\lambda}}_{p})$ EIT is possible in all schemes and is in fact stronger than in the matched case. It is also demonstrated that for the second mismatched regime $({\ensuremath{\lambda}}_{c}>{\ensuremath{\lambda}}_{p})$ EIT can be realized most readily in the Vee-type configuration in the presence of Doppler broadening. These predictions are explained by considering the absorption as a function of both the probe field detuning and the atomic velocity.
An experimental observation of transparency on a transition in the blue spectral region, induced by a continuous-wave (cw) infrared coupling field in a Doppler-broadened medium, is presented. This experimental result is supported by extensive theoretical modeling of the system, a V-type scheme in atomic rubidium vapor. Transparency is observed by a 422-nm probe field on the transition between the hyperfine split ground state 5S1/2{5S}_{1/2}5S1/2​ and the excited state 6P1/2.{6P}_{1/2}.6P1/2​. The coupling laser is employed on the linked transition ${5S}_{1/2}{\ensuremath{-}5P}_{3/2},$ inducing significant levels of transparency (>70(>70%)(>70 nondissipatively and in the absence of optical pumping effects.
Summary form only given. We study a model for an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity and producing two laser fields, one of them without population inversion. Each laser field couples to only one of the transitions of the three-level medium. We have studied our model for parameters appropriate to two real atomic systems (i) a cascade scheme in atomic /sup 138/Ba looking for lasing with (without) inversion at /spl lambda//sub /spl beta//=554 nm (/spl lambda//sub /spl alpha//=821 nm), and (ii) a V-scheme in atomic /sup 85/Rb with ordinary lasing at /spl lambda//sub /spl alpha//=780 nm and lasing without inversion (LWI) at /spl lambda//sub /spl alpha//=4216 nm. These two cases are qualitatively different in that two-photon processes are responsible for inversionless gain in case (i) while LWI in case (ii) arises from one-photon processes. Moreover, the frequency up-conversion ratio is R=0.67 for the case of /sup 138/Ba and it is R=1.88 for the case of /sup 85/Rb. In spite of the fact that the frequencies of the two laser fields are relatively different, our results show that dual-wavelength lasing extends up to Doppler broadening values typical for optical transitions of atoms in a vapor cell. In case (i) /spl alpha/-lasing occurs without two-photon inversion only for approximately the lower half of the domain of Doppler-broadening values. However, in case (ii) one has LWI in all the domains. Some considerations for a practical realization of the dual-wavelength inversionless-conventional laser are discussed.