Results 1 - 10 of 1196
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[en] We have performed the femtosecond two-pulse self-diffracted four-wave mixing (FWM) experiments for a 500 μm undoped GaAs and a 350 μm undoped InP to have further insight into the FWM singnals in thick semiconductors at far below the band gap. We have observed the third- and fifth-order FWM signals for both samples even in the detuning range of 100-170 meV below the band gap. We have also observed that the pronounced blue-shifts of the spectrally resolved (SR) FWM signals at far below the bands gap, exhibiting that these behaviors do not depend on the material properties and temperature. We have proposed that the FWM signals in thick semiconductors at far below the band gap are contributed by the instantaneously created virtual states by temporal overlap of the excitation laser pulses.
[en] It This paper analyses working status of mixing pad under perfect and imperfect state, and associates with output of intermediate frequency amplifier jumping, finds the relation between mixing pad with output jumping, the problems in mixing pad and puts forward solutions for it. (authors)
[en] Based on the quantum Liouville formalism, a theory of the two-color, triply resonant four-wave mixing is developed for molecules with isotropically oriented angular momenta. The approach allows to strictly incorporate the relaxation matrices Γ(r) (r = 0, 1, 2) into the third-order susceptibility χ(3) whose expression acquires therewith the form of a scalar product in the line space. Thanks to this representation, isolation of all resonance terms from χ(3) becomes a routine task. Some of these terms correspond to the case when a molecule initially interacts with two pump photons of the same frequency. Such interactions give rise to the grating line-space vectors which have the same (zero) eigenfrequency. Due to this degeneracy, the latter are easily mixed by rotationally inelastic collisions which shows up in a state-resolved coherence transfer. The satellite signals induced thereby provide a great scope to study the state-to-state inelastic rates in situ by purely optical means. If the diagonal form of Γ is assumed, the satellites become forbidden and our results reduce to conventional expressions for the main resonances. Polarization configurations are designed for direct measurements of the population (r = 0), orientation (r = 1), and alignment (r = 2) contributions to χ(3). Finally, depending on the photon-molecule interaction sequence, the resonance terms of χ(3) are shown to be differently affected by velocity averaging, the effect which conspicuously manifests itself when Doppler broadening becomes paramount
[en] We demonstrate experimental observation of vacuum Rabi splitting (VRS) of four-wave mixing and six-wave mixing in a collective five-level atomic-cavity coupling system. We study the control of VRS via changing the dressing effect of the vacuum cavity mode; i.e., the cavity mode dressing effect can selectively split the right or left peak when cavity-atom detuning and atom number N are changed. We further report that the cavity window and two electromagnetically induced transparency (EIT) windows induced by the dressing field interfere with each other because of different two-photon conditions they satisfy. Additionally, we investigate the self-dressing field effect on VRS of six-wave mixing (SWM) inside the cavity. Such investigation results can find application in all-optical switches and optical communications. (paper)
[en] We have investigated the temporal and spectral profiles of four-wave mixing (Fm) signals in a 500 μm thick undoped GaAs with detuning from near the excitonic resonance up to 170 MeV below the band gap. The time-integrated (Ti) FWM signals are dominated by exciton states and the dephasing times are larger than the excitation pulse width at small detunings, whereas the instantaneous decay is manifest at large detunings. Furthermore, the central energies of the spectrally resolved (SR) FWM signals with respect to the excitation pulse spectrum far below the band gap are blue-shifted significantly as the time delay moves away from positive to negative. As the detuning increases, the shifts of the central energy and the full width at half maximum (FWHM) of the SR-FWM signals become larger. These phenomena can be explained as due to different group velocities with different frequencies and the instantaneously created virtual states by the two excitation laser pulses.
[en] Loss is a critical roadblock to achieving photonic quantum-enhanced technologies. We explore a modular platform for implementing integrated photonics experiments and consider the effects of loss at different stages of these experiments, including state preparation, manipulation and measurement. We frame our discussion mainly in the context of quantum sensing and focus particularly on the use of loss-tolerant Holland-Burnett states for optical phase estimation. In particular, we discuss spontaneous four-wave mixing in standard birefringent fibre as a source of pure, heralded single photons and present methods of optimizing such sources. We also outline a route to programmable circuits that allows the control of photonic interactions even in the presence of fabrication imperfections and describe a ratiometric characterization method for beam splitters, which allows the characterization of complex circuits without the need for full process tomography. Finally, we present a framework for performing state tomography on heralded states using lossy measurement devices. This is motivated by a calculation of the effects of fabrication imperfections on precision measurement using Holland-Burnett states.
[en] The theoretical framework for the cascaded four waves mixing (CFWM) in gas-filled capillary by fs pulses is constructed. Based on the theoretical framework, the signal-pressure curves (SPC) of the CFWM in gas-filled capillary by fs pulses are calculated. With a comparison between the theoretical and experimental SPC we have discussed the influence of the walk-off and phase modulation on the SPC. At the same time, we have discussed the possible origin of the first three peaks of the SPC.