Correlated Spontaneous-emission Laser Research Articles

Generation and Control of Bipartite Entanglement in a Correlated Spontaneous-Emission Laser

Generation and Control of Bipartite Entanglement in a Correlated Spontaneous-Emission Laser

Entanglement in correlated spontaneous emission lasers

Recent studies show that macroscopic entangled states of the radiation field can be generated using correlated spontaneous emission lasers (CEL) even in the presence of cavity losses. Some of the basic schemes based on two-photon CEL and quantum beat laser (QBL) are reviewed in this article.

Steady State Entanglement and Saturation Effects in Correlated Spontaneous Emission Lasers

It has recently been shown that correlated spontaneous emission lasers (CEL) exhibit transient entanglement in the linear regime. Here we re-examine the quantum correlations in two-photon CEL and explore the saturation effects on continuous variable entanglement. It is shown that the steady state entanglement is obtainable in the weak or moderate saturation regime, while is washed out in the deep saturation regime.

Influence of pump-phase fluctuations on entanglement generation using a correlated spontaneous-emission laser

In this paper, we study the effect of phase fluctuations of the pump field upon the entanglement generation in a two-photon correlated emission laser (CEL). We consider initial vacuum and coherent state for the two-cavity modes. In both cases, we find reduction in the entanglement due to the phase fluctuations. However, our results indicate that entanglement generation is highly sensitive to phase fluctuations when we have initial coherent state in the two modes.

THE OPERATION IN THE STEADY STATE AND SQUEEZING OF QUANTUM NOISE IN TWO-MODE TWO-PHOTON CORRELATED-SPONTANEOUS-EMISSION LASERS

Operation in the steady state and squeezing of quantum noise in two-mode two-photon correlated-spontaneous-emission lasers(CEL) are studied via nonliner quantum theory.It is shown that the two-mode two-photon CEL exhibits lasing without inversion and two-mode hysteresis even without triggering.The features of squeezing of quantum noise in the relative amplitude and the average phase are given.

Nonlinear Theory of Many-One-Photon Correlated-Spontaneous-Emission Lasers11The project supported by National Natural Science Foundation of China

Based on the Jaynes-Cummings (JC) model for many -photon correlated-spontaneous-emission lasers (CEL), we give the nonlinear master equation for the matrix elements of the many m-photon CEL field. For many one-photon CEL, by using the Fokker-Planck equation, we discuss the conditions for lasing without inversion and the noise reduction of the laser field.

Influence of Atomic Phase Fluctuations on Field Squeezing and Brightness of Many Two-Photon Correlated-Spontaneous-Emission Lasers11The project supported by National Natural Science Foundation of China

We show in this paper that phase fluctuations of active atoms in many two-photon correlated spontaneous-emission lasers will reduce field squeezings and brightness of the squeezed light. But, under certain conditions of laser operation, the fluctuations of atomic phases between lower almost degenerate atomic levels could increase the squeezings and the brightness. We also show that, even for large phase fluctuations of the active atoms, almost perfect field squeezings and substantial brightness of the squeezed light can be obtained.

Spectrum of squeezing for two-photon correlated-spontaneousemission lasers

We study the spectrum of squeezing for the two-photon correlated-spontaneousemission lasers (CEL's), which consists of coherently pumped, cascade three-level atoms interacting with a single mode of the cavity field. For the resonant two-photon CEL, the spectrum of squeezing is always lorentzian, and more than 80% extra-cavity squeezing has been found in both the phase-and the amplitude-squeezing cases. For the off-resonant two-photon CEL, we use both the exact interaction hamiltonian and an effective two-photon interaction hamiltonian. While the effective hamiltonian always predicts lorentzian spectrum of squeezing in the phase quadrature, the exact hamiltonian gives non-lorentzian one in general, expecially near threshold. Both hamiltonians predict that maximal (over 90%) extracavity phase squeezing is obtained near threshold with large one-photon detunings and equal initial atomic populations between the upper and lower levels. We also find that the effective hamiltonian underestimates the phase variance outside the cavity.

Effect of fluctuation coupling on the spectrum of squeezing

Using a two-photon correlated-spontaneous-emission laser (CEL) as an example, I show that a non-Lorentzian spectrum of squeezing is the result of fluctuation coupling and that the narrow peak at the center of the spectrum is a reflection of the fluctuations in the conjugate quadrature. More than 90% extracavity phase squeezing can be generated by the two-photon CEL near threshold with large one-photon detunings.

A comparison between degenerate paramagnetic oscillators and two-photon correlated-spontaneous-emission lasers

The degenerate parametric oscillator (DPO) is analyzed with the nonlinear material treated quantum mechanically. The source of squeezing in the DPO is the same as in the two-photon correlated-spontaneous-emission laser (CEL) — the level coherence. In this sense, they are similar. The amount of squeezing in DPO is the same as in the two-photon CEL at two-photon resonance, but the gain in DPO is usually much smaller than that in the two-photon CEL at two-photon resonance.

Noise-color-induced quenching of fluctuations in a correlated spontaneous-emission laser model.

We show via (1) an approximate, analytical technique, (2) a formally exact matrix continued-fraction analysis, and (3) an analog simulation of the classical Langevin equation of a correlated spontaneous-emission laser (CEL) that noise of nonzero correlation time leads to an enhancement of the characteristic CEL noise quenching.

Quantum theory of a two-mode two-photon correlated spontaneous-emission laser.

A quantum theory of a two-mode two-photon correlated spontaneous-emission laser is developed. It is shown that the quantum-noise quenching and even nonclassical effects can occur in both the average phase and relative amplitude of the two fields. Near threshold we find a maximum of 50% intracavity squeezing in the two-photon transition limit, with each of the average phase and the relative amplitude contributing 25% squeezing.

Nonlinear theory of a two-photon correlated-spontaneous-emission laser: A coherently pumped two-level–two-photon laser

We develop a nonlinear theory of a two-photon correlated-spontaneous-emission laser (CEL) by using an effective interaction Hamiltonian for a two-level system coupled by a two-photon transition. Assuming that the active atoms are prepared initially in a coherent superposition of two atomic levels involved in the two-photon transition, we derive a master equation for the field-density operator by using our quantum theory for coherently pumped lasers. The steady-state properties of the two-photon CEL are studied by converting the field master equation into a Fokker-Planck equation for the antinormal-ordering Q representation of the field-density operator. Because of the injected atomic coherence, the drift and diffusion coefficients become phase sensitive. This leads to laser phase locking and an extra two-photon CEL gain. The laser field can build up from a vacuum in the no-population-inversion region, in contrast to an ordinary two-photon laser for which triggering is needed. We find an approximate steady-state solution of the Q representation for the laser field, which consists of two identical peaks of elliptical type. We calculate the phase variance and, for any given mean photon number, obtain the minimum variance in the phase quadrature as a function of the initial atomic variables. Squeezing of the quantum noise in the phase quadrature is found and it exhibits the following features: (1) it is possible only when the laser intensity is smaller than a certain value; (2) it becomes most significant for small mean photon number, which is achievable in the no-population-inversion region; and (3) a maximum of 50% squeezing can be asymptotically approached in the small laser intensity limit. As a by-product we also study the ordinary two-photon laser and find, e.g., photon-number variance and laser linewidth.

Quantum-noise quenching in the correlated spontaneous-emission laser as a multiplicative noise process. II. Rigorous analysis including amplitude noise.

An analytical steady-state distribution for the phase difference \ensuremath{\psi} in a correlated spontaneous-emission laser (CEL) is derived based on the amplitude and phase equations of a CEL. This distribution is shown to be an excellent approximation to that obtained from a numerical simulation of the complete set of CEL equations. In particular, the effects of amplitude noise on CEL operation are considered and it is shown that fluctuations in the relative amplitude are also noise quenched.

Quantum-noise quenching in the correlated spontaneous-emission laser as a multiplicative noise process. I. A geometrical argument.

We show, via simple geometrical arguments, the quantum-noise quenching in a correlated (spontaneous) emission laser (CEL). This noise quenching is a consequence of the correlation between noise sources which results in a multiplicative noise process. The steady-state distribution for the phase difference between the two electric fields in a CEL is compared and contrasted to that of a standard phase-locked laser. Noise quenching is shown to occur in the case of the CEL via an explicit solution of the Fokker-Planck equation.

Dynamically correlated spontaneous-emission laser: theory and comparison with experiment

A higher-order correlated-emission laser (CEL) effect is found theoretically in a Doppler-broadened medium. A full quantum-mechanical account of the CEL in the nonlinear regime shows a large reduction in the beat-signal linewidth. This behavior is confirmed by a recent experiment.

Correlated spontaneous-emission lasers: Quenching of quantum fluctuations in the relative phase angle.

In quantum-beat and Hanle-effect experiments, spontaneous-emission events from two coherently excited states are strongly correlated. A doubly resonant laser cavity driven by such atomic configurations can have vanishing diffusion coefficient for the relative phase angle.