徳島大学 教育・研究者情報データベース(EDB)

1. (英) Yusufu Taximaiti / (日) Yusufu Taximaiti

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2. 時実 悠([徳島大学.ポストLEDフォトニクス研究所])

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3. (英) Masaki Yamada / (日) Masaki Yamada

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4. (英) Katsuhiko Miyamoto / (日) Katsuhiko Miyamoto

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5. (英) Takashige Omatsu / (日) Takashige Omatsu

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(英) Tunable milli-joule-level 2µm fractional vortex optical parametric amplifier

(英) Fractional vortex lasers with a fractional topological charge, l, exhibiting a unique fractional radial opening, have been attractive for the optical manipulating of microscopic particles and super-resolution spectroscopy based on stimulated emission depletion. They have also recieved much attention in fundamental physics, including an analogy concerning the quantum flux in the Aharonov-Bohm effect. Such applications of the fractional vortex lasers frequently require wavelength diversity. In particular, tunable fractional vortex lasers in a mid-infrared region, including the eigen frequencies of many molecules originating by the vibration modes, will potentially be attractive for manipulating molecules and molecular spectroscopy with high spatial resolution. Second-order nonlinear frequnecy conversion is a promising method to extend the wavelength range of laser sources. However, the conservation of topological charge, l, in an optical parametric down-conversion process causes a question, i.e., how does the orbital angular momentum of the pump beam divide between the signal and idler outputs? To date, we have demonstrated 2μϖι fractional vortex output with a topological charge l=0.5 from a 1μm vortex pumped optical parametric oscillator (2μϖι fractional vortex OPO) formed by a plane-parallel cavity configuration and a nonlinear crystal KTP [1]. (Such the fractional optical vortex operation is never permitted in a conventional stable laser cavity [2].) However, the pulse energy (<0.5mJ) of the fractional vortex output is limited by severe diffraction loss in the plane-parallel cavity configuration. Also, the lasing wavelength of the fractional vortex output was fixed at 2.128μm.