Operation of a degenerate dual-pump phase sensitive amplifier (PSA) is thoroughly numerically investigated using a multi-wave model, taking into account high-order waves associated with undesired four-wave mixing (FWM) processes. More accurate phase-sensitive signal gain characteristics are obtained compared to the conventional 3-wave model, leading to precise optimization of the pump configuration in a degenerate dual-pump PSA. The signal gain for different pump configurations, as well as the phase sensitivity, is obtained and interpreted by investigating the dominant FWM processes in terms of the corresponding phase matching. Moreover, the relation between dispersion slope and the width of the signal gain curve versus the pump-pump wavelength separation is revealed, permitting the application-oriented arbitrary tailoring of the signal gains by manipulating the dispersion profile and pump wavelength allocation.
Electromagnetically induced transparency (EIT) in metastable helium at room temperature is experimentally shown to exhibit light storage capabilities for intermediate values of the detuning between the coupling and probe beams and the center of the atomic Doppler profiles. An additional phase shift is shown to be imposed to the retrieved pulse of light when the EIT protocol is performed at non-zero optical detunings. The value of this phase shift is measured for different optical detunings between 0 and 2 GHz, and its origin is discussed. Since the discovery of coherent population trapping (CPT) [1,2] and electromagnetically induced transparency (EIT) 15 years later [3], different applications of these phenomena were found, ranging from atom cooling [4] to the decrease of group velocities down to a few meters per second [5,6]. This led to the well-known stored light experiments that were performed using EIT in various systems such as cold atoms, gas cells, or doped crystals [7][8][9].The EIT-based storage protocol relies on the long-lived Raman coherence between the two fundamental states of a Λ system, where two ground levels are optically coupled to the same excited level. When a strong coupling beam is applied on one of the two transitions, a narrow transparency window limited by the Raman coherence decay rate is opened along the other leg of the Λ system. Because of the slow-light effect associated with such a dramatic change of the absorption properties of the medium, a weak probe pulse that excites the second transition is compressed when it propagates inside the medium. When it is fully inside this medium, the coupling beam can be suddenly switched off and the signal is then mapped onto the Raman coherences that were excited by the two photon process. Finally, the signal pulse can be simply retrieved by switching on the coupling beam again.Atoms at room temperature in a gas cell are particularly attractive for light storage because of the simplicity of their implementation. However, the significant Doppler broadening has to be considered and might be expected to place a strong limitation. Its effect can nevertheless be minimized using co-propagating coupling and probe beams, and easy-of-use simple gas cells have thus turned out to be attractive for slow or even stopped light experiments [10]. The atoms preferably used for such experiments are alkali atoms, mainly rubidium and sometimes sodium or caesium. Experimental achievements * Electronic address: fabienne.goldfarb@u-psud.fr have shown that squeezing can be preserved after slowing down or storage by EIT at optical resonance in an alkali cell at room temperature [11,12], and the same phenomenon was used to store and retrieve LaguerreGaussian modes [13] [12,14,19].In the present paper we present experimental results obtained not with alkali but with metastable helium atoms at room temperature. We could explore EIT-based light storage in the intermediate detuning regime, i. e., with coupling and probe beams slightly optically detuned from the center of D...
We experimentally investigate the evolution of the direct detection noise figure of a non degenerate phase sensitive amplifier based on nonlinear fiber, as a function of the relative phase between the signal, idler, and pump, all other parameters remaining fixed. The use of a fiber with a high stimulated Brillouin scattering threshold permits to investigate the full range of phase sensitive gain and noise figure without pump dithering. Good agreement is found with theory, both for signal only and combined signal and idler direct detections. arXiv:1812.03708v1 [physics.optics]
In the context of microwave photonics, we experimentally demonstrate the linearity of an optical phase sensitive amplifier by performing third order intermodulation distortion products measurements using two RF tones. Distortionless amplification is achieved.
We numerically simulate the distortion of an analog signal carried in a microwave photonics link containing a phase sensitive amplifier (PSA), focusing mainly on amplitude modulation format. The numerical model is validated by comparison with experimental measurements. By using the well known two-tone test, we compare the situations in which a standard intensity modulator is used with the one where a perfectly linear modulator would be employed. We also investigate the role of gain saturation on the nonlinearity of the PSA. Finally, we establish the conditions, in which the signal nonlinearity introduced by the PSA itself can be extremely small.
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