Fedotov AB, Voronin AA, Serebryannikov EE, Fedotov IV, Mitrofanov AV, Ivanov AA, Sidorov-Biryukov DA, Zheltikov AM. Multifrequency third-harmonic generation by red-shifting solitons in a multimode photonic-crystal fiber.
PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007;
75:016614. [PMID:
17358282 DOI:
10.1103/physreve.75.016614]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Revised: 09/14/2006] [Indexed: 05/14/2023]
Abstract
While the standard scenario of third-harmonic generation (THG) by a dispersive-wave pump involves the emission of light with a frequency 3omega, thrice the frequency omega of the input pump field, solitons undergoing a continuous shift of their central frequency omega due to the Raman effect in a multimode optical fiber can generate the third harmonic in a different fashion. In the experiments reported here, we provide the first direct experimental evidence of THG by a continuously red-shifting soliton pump by studying the third-harmonic buildup in relation to the spectral evolution of the soliton pump field in a silica photonic-crystal fiber (PCF). We show that solitons excited in a PCF by unamplified femtosecond pulses of a Cr:forsterite laser sweep through the spectral range from 1.25 to 1.63 microm , scanning through a manifold of THG phase-matching resonances with 3omega dispersive waves in PCF modes. As a result, intense third-harmonic peaks build up in the range of wavelengths from 370 to 550 nm at the output of the fiber, making PCF a convenient fiber-format multifrequency source of short-wavelength radiation. Time-resolved fluorescence measurements with photoexcitation provided by the third-harmonic PCF output are presented, demonstrating the high potential of PCF sources for an ultrafast photoexcitation of fluorescent molecular systems in physics, chemistry, and biology.
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