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Amplification and cross-Kerr nonlinearity in waveguide quantum electrodynamics
摘要： We explore amplification and cross-Kerr nonlinearity by a three-level emitter (3LE) embedded in a waveguide and driven by two light beams. The coherent amplification and cross-Kerr nonlinearity were demonstrated in recent experiments, respectively, with a V and a ladder-type 3LE coupled to an open superconducting transmission line carrying two microwave fields. Here, we consider (cid:2), V, and ladder-type 3LE, and compare the efficiency of coherent and incoherent amplification as well as the magnitude of the cross-Kerr phase shift in all three emitters. We apply the Heisenberg-Langevin equations approach to investigate the scattering of a probe and a drive beam, both initially in coherent states. We particularly calculate the regime of the probe and drive powers when the 3LE acts most efficiently as a coherent amplifier and derive the second-order coherence of amplified probe photons. Finally, we apply the Kramers-Kronig relations to correlate the amplitude and phase response of the probe beam, which are used in finding the coherent amplification and the cross-Kerr phase shift in these systems.
关键词： waveguide quantum electrodynamics,three-level emitter,cross-Kerr nonlinearity,amplification,Heisenberg-Langevin equations,Kramers-Kronig relations
更新于2025-09-23 15:21:01
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Multilayer plasmonic photonic structures embedding photochromic molecules or optical gain molecules
摘要： We study the optical properties of different functional molecular systems in order to embed them in properly designed photonic structures for photochromic switching and lasing. We study the light absorption of two photochromic molecules and of 4,4’-bis[(N-carbazole)styryl]biphenyl (BSB-Cz) with density functional theory. For the photochromic diarylethene we derivate the refractive index with Kramers-Kronig relations and we design multilayer photonic structures alternating diarylethene with either poly vinyl carbazole or fluorine indium co-doped cadmium oxide (FICO) nanoparticle-based layers. For BSB-Cz we design a one-dimensional photonic crystal alternating BSB-Cz layers wit SiO2 layers and a microcavity embedding BSB-Cz between indium tin oxide (ITO) / FICO nanoparticle-based multilayers.
关键词： multilayer plasmonic photonic structures,photochromic molecules,density functional theory,Kramers-Kronig relations,optical gain molecules
更新于2025-09-23 15:19:57
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Radiation pressure and electrostriction induced enhancement for Kerr-like nonlinearities in a nanoscale silicon pedestal waveguide
摘要： We report an enhancement of effective nonlinear-index coefficient from the combination of radiation pressure and electrostriction in an air-cladding silicon pedestal waveguide. The effective nonlinear-index coefficient was experimentally measured by characterizing spectral broadening with incident pulses in the pedestal waveguide. Larger spectral broadening was observed in the pedestal waveguide compared to a conventional silicon waveguide. Theoretically, the primary enhancement of the effective nonlinear-index coefficient can be calculated by using Kramers-Kronig relations, which is associated with the change in absorption from stimulated Brillouin scattering in the pedestal waveguide. The calculations were consistent with experimental results. By tailoring the pillar width of the pedestal waveguide, about 27.6% enhancement in the effective nonlinear-index coefficient of the pedestal waveguide was possible at the center wavelength of 1555 nm.
关键词： Kramers-Kronig relations,nonlinear-index coefficient,stimulated Brillouin scattering
更新于2025-09-23 15:19:57
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Identification of Chemical Compounds by the Reflected Spectra in the Range of 5.3–12.8 μm Using a Tunable Quantum Cascade Laser
摘要： We have considered the technique and experimental laboratory setup that allow the recording of the specular and diffuse reflectance spectra of the infrared radiation of substances in solid and liquid aggregate states on various surfaces. A quantum cascade laser, tunable in the wavelength range of 5.3–12.8 μ m with a spectral resolution of 2 cm–1 and an average power of 15 mW, was used as a probing radiation source. The experimental setup made it possible to record the spectra of the diffusely reflected radiation of the substances. Methods for the identification of substances based on the scattered radiation spectra are proposed. It is shown that the use of the Kramers–Kronig integral transform increases the degree of selectivity of the spectra and, as a consequence, the reliability of identification.
关键词： quantum cascade laser,infrared spectroscopy,Kramers–Kronig relations,identification
更新于2025-09-16 10:30:52
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On the Kramers-Kronig relations
摘要： We provide a new derivation of the Kramers-Kronig relations on the basis of the Sokhotski-Plemelj equation with detailed mathematical justifications. The relations hold for a causal function, whose Fourier transform is regular (holomorphic) and square-integrable. This implies analyticity in the lower complex plane and a Fourier transform that vanishes at the high-frequency limit. In viscoelasticity, we show that the complex and frequency-dependent modulus describing the stiffness does not satisfy the relation but the modulus minus its high-frequency value does it. This is due to the fact that despite its causality, the modulus is not square-integrable due to a non-null instantaneous response. The relations are obtained in addition for the wave velocity and attenuation factor. The Zener, Maxwell, and Kelvin-Voigt viscoelastic models illustrate these properties. We verify the Kramers-Kronig relations on experimental data of sound attenuation in seabottoms sediments.
关键词： Viscoelasticity,Causality,Zener model,Kramers-Kronig relations,Waves,Sokhotski-Plemelj equation
更新于2025-09-09 09:28:46