Interference of nonlinear optical signals generated by multimode lasers

Hermann Haken, H. Sauermann

Jasleen Kaur, Yu Mukai, Ryo Okamoto +1 more

Nonlinear quantum interferometry is widely used in photonic quantum sensing applications to perform measurements with undetected photons. While continuous wave (cw) lasers are typically used to generate correlated photon pairs, pulsed laser pumping can enhance the generation efficiency for photon pairs and enable time-resolved measurements. However, the finite spectral linewidth of pulsed lasers leads to imperfect frequency correlation between generated photon pairs, which can affect the sensitivity of nonlinear interferometry. In this work, we investigate the effect of the finite linewidth of a pump laser on the visibility of spectral domain interference in a nonlinear quantum interferometer where signal photons are detected using a dispersive spectrometer. The proposed theory quantitatively predicts the visibility as a function of optical path difference for a pump source with arbitrary spectrum. As a demonstration, we construct an experimental setup to obtain quantum interference using both cw and pulsed laser excitations under the same experimental conditions. At large optical path differences, a fine interference fringe pattern with high contrast is observed with cw laser excitation, whereas with pulsed laser pumping, the visibility decreases as the optical path delay increases, and the interference fringes appear almost washed out. Our quantitative analysis is useful for determining appropriate pulsed laser parameters for designing nonlinear interferometers for quantum sensing applications using a dispersive spectrometer.

Binshuo Luo, Jin Yan, Yaomin jiang +6 more

The nonlinear parametric process is of great significance for achieving high-quality coherent optical signals and quantum correlated photons. With the development of classical and quantum information processing, the study of the properties of parametric processes is evolving in complex scenarios of multimode, which is limited in conventional nonlinear media due to strict phase matching, e.g. nonlinear crystals. Here we study the dressing-energy-level-cascaded four-wave mixing process to generate multimode optical parametric signals. Via cascading double-Λ type configuration of 85 Rb D 1 line, the non-degenerate energy-level-cascaded FWM is constructed to generate multimode self-parametric amplification. Moreover, with the dressing effects based on atomic coherence, the spatial and frequency multimode characteristics of energy-level-cascaded FWM parametric amplification, i.e., the modes number and pattern, are actively modulated by the pump fields detuning. Also, the spatial modes from the coupling of two coexisting spontaneous parametric FWMs can be controlled to reach tremendous scalability via the atomic coherence and Kerr non-linearity. The atomic coherence effects and unique phase-matching symmetry nature allow flexible modulation of the multimode property of the generated parametric signals within a nonlinear device, which paves a way for multimode classical and quantum information processing.

Frank Schlawin

Sascha Wallentowitz, W. Vogel

Raman-type laser excitation of a trapped atom allows one to realize the quantum-mechanical counterpart of phenomena of nonlinear optics, such as Kerr-type nonlinearities, parametric amplification, and multimode mixing. Additionally, huge nonlinearities emerge from the interference of the atomic wave function with the laser waves. They lead to a partitioning of the phase space accompanied by a significantly different action of the time evolution in neighboring phase-space zones. For example, a nonlinearly modified coherent 'displacement' of the motional quantum state may induce strong amplitude squeezing and quantum interferences.

Holger Schmidt