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arXiv:0907.2620 · PMC Physics B

Effect of biased noise fluctuations on the output radiation of coherent beat laser

Sintayehu Tesfa

Published Dec 1, 2008• 0 citations
arXivHTMLPDF

Abstract

Effect of biased noise fluctuations on the degree of squeezing as well as the intensity of a radiation generated by a one-photon coherent beat laser is presented. It turns out that the radiation exhibits squeezing inside and outside the cavity under certain conditions. The degree of squeezing is enhanced by the biased noise input significantly in both regions. Despite the presence of the biased environment modes outside the cavity, the degree of squeezing outside the cavity can be greater than or equal to or even less than the cavity radiation depending on the initial preparation of the atomic superposition and amplitude of the external driving radiation. But the intensity of the radiation is found to be lesser outside the cavity regardless of these parameters. PACS Codes: 42.50.Dv, 42.50.Ar, 42.50.Gy, 32.80.Bx

DOI
10.1186/1754-0429-1-17

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Effect of biased noise fluctuations on the degree of squeezing as well as the intensity of a radiation generated by a one-photon coherent beat laser is presented. It turns out that the radiation exhibits squeezing inside and outside the cavity under certain conditions. The degree of squeezing is enhanced by the biased noise input significantly in both regions. Despite the presence of the biased environment modes outside the cavity, the degree of squeezing outside the cavity can be greater than or equal to or even less than the cavity radiation depending on the initial preparation of the atomic superposition and amplitude of the external driving radiation. But the intensity of the radiation is found to be lesser outside the cavity regardless of these parameters. PACS Codes: 42.50.Dv, 42.50.Ar, 42.50.Gy, 32.80.Bx
Analysis of the effects of the biased noise fluctuations on the quantum features and statistical properties of the cavity radiation of the two-photon phase-sensitive laser is presented. It turns out that the biased noise fluctuations that enter the cavity via the vibrations of the wall enhance the atomic coherence responsible for the entanglement of the cavity radiation due to the phase sensitivity of the involved cascade transitions. The two-mode squeezing of the superimposed radiation, entanglement of the cavity radiation, and mean number of the photon pairs are found to increase with the rate at which the atoms are injected into the cavity. The two-mode squeezing increases with the intensity of the biased noise fluctuations, but the mean number of the photon pairs decreases. Even then, it is possible to produce quite intense robust continuous variable entanglement in this scheme which is believed to be a motivation for further practical scrutiny. Moreover, the superimposed radiation exhibits super-Poissonian photon statistics with no finite joint probability for getting more photons in mode bbb than mode aaa.
A steady state analysis of the nonclassical features and statistical properties of the cavity radiation of a two-photon coherent beat laser is presented. Results show that the degree of two-mode squeezing, detectable entanglement and intensity of the cavity radiation can increase with the deviation of the phase fluctuations of the laser employed in preparing the atoms, but decrease with the increasing rate at which the induced coherence superposition decays. Although it is found that varying the phase fluctuations and dephasing can lead to modification in the quantum features and statistical properties of the radiation, it does not alter the similarity in the nature of the degree of entanglement detectable by the criteria following from Duan—Giedke—Cirac—Zoller and logarithmic negativity in a perceivable manner. Since the intensity and quantum features can be readily enhanced, this system is expected to be a viable source of a strong robust entangled (squeezed) light under various conditions. Moreover, comparison of the mean number of photon pairs with intensity difference shows that the chance of inciting a two-photon process can be enhanced by changing the rate of dephasing and phase fluctuations.
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A detailed derivation of the master equation and the corresponding time evolution of the cavity radiation of a coherent beat laser when the atoms are initially prepared in a partial coherent superposition is presented. It turns out that the quantum features and intensity of the cavity radiation are considerably modified by the phase fluctuation arising due to the practical incapability of preparing atoms in the intended perfect coherent superposition. New terms having opposite signs than the contribution of the driving radiation emerged in the master equation. This can be taken as an indication of a competing effect between the two in the manifestation of the nonclassical features. This, on the other hand, means that there is a chance to regain the quantum properties that might have been lost due to faulty preparation in engineering the driving mechanism and vice versa. In light of this, quite remarkably, the cavity radiation is shown to exhibit nonclassical features including two-mode squeezing and entanglement when there is no driving and when the atoms are initially prepared in a partial maximum atomic coherence superposition, contrary to earlier predictions for the case of perfect coherence.
A steady state analysis of the nonclassical features and statistical properties of the cavity radiation of a twophoton coherent beat laser is presented.Results show that the degree of two-mode squeezing,detectable entanglement and intensity of the cavity radiation can increase with the deviation of the phase fluctuations of the laser employed in preparing the atoms,but decrease with the increasing rate at which the induced coherence superposition decays.Although it is found that varying the phase fluctuations and dephasing can lead to modification in the quantum features and statistical properties of the radiation,it does not alter the similarity in the nature of the degree of entanglement detectable by the criteria following from Duan-Giedke-Cirac-Zoller and logarithmic negativity in a perceivable manner.Since the intensity and quantum features can be readily enhanced,this system is expected to be a viable source of a strong robust entangled (squeezed) light under various conditions.Moreover,comparison of the mean number of photon pairs with intensity difference shows that the chance of inciting a two-photon process can be enhanced by changing the rate of dephasing and phase fluctuations.
We address the behavior of squeezing in two movable mirrors coupled to a pumped correlated emission laser inside a doubly resonant optomechanical driven cavity in the presence of biased noise fluctuations. Aiming at generating controllable and robust mechanical squeezing that can be utilized in making the quantum features of radiation in the cavity accessible for application, we explore mechanical squeezing that can be induced as a result of the transfer of coherent superposition. We found that a coupled mechanical oscillator mode exhibits squeezing in the good cavity limit and adiabatic regime. It is also shown that the degree of mechanical squeezing is robust for large amplitudes of atomic pumping until maximum squeezing is achieved but weakens afterwards. The squeezing turns out to be powerful mainly for strong atom-field coupling, large atomic injection rates, and intense biased noise fluctuations. In light of the observed possibility of controlling the realizable degree of squeezing, we hope and expect that the considered system could be employed in applications such as quantum metrology.