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3-ethyl-2-[3-(3-ethyl-2(3H)-benzoxazolylidene)-1-propenyl]benzoxazolium iodide (dye I) and pseudoisocyanine bromide are employed to form H aggregates as donors and J aggregates as acceptors. The energy of an H band of the H aggregates is higher than that of a J band of the J aggregates. It was confirmed that excitation of the H band does not emit fluorescence by comparison of excitation spectra of dye I H aggregates with that of dye I monomer. Absorption, fluorescence, and excitation spectra of spin-coated films of H aggregates mixed with various quantities of J aggregates have been observed. Excitation spectra probed at the J band are found to have a component of the H band. Fluorescence spectra originated from excitation of the H band are extracted and qualitatively analyzed. It is confirmed that excitation of the H band causes to emit fluorescence of a J band of the J aggregates. These phenomena show that exciton energy can transfer from the lowest energy in electronic states of the H aggregate, which state is optically forbidden, to electronic state of the J aggregate.

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We demonstrate an all-optical phase noise mitigation scheme based on the generation, delay, and coherent summation of higher order signal harmonics. The signal, its third-order harmonic, and their corresponding delayed variant conjugates create a staircase phase-transfer function that quantizes the phase of quadrature-phase-shift-keying (QPSK) signal to mitigate phase noise. The signal and the harmonics are automatically phase-locked multiplexed, avoiding the need for phase-based feedback loop and injection locking to maintain coherency. The residual phase noise converts to amplitude noise in the quantizer stage, which is suppressed by parametric amplification in the saturation regime. Phase noise reduction of ∼40% and OSNR-gain of ∼3  dB at BER 10(-3) are experimentally demonstrated for 20- and 30-Gbaud QPSK input signals.

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