Controlled Modification of Erbium Lifetime in Silicon Dioxide Film with Chromium or Titanium Coatings
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1055-GG12-01
Controlled Modification of Erbium Lifetime in Silicon Dioxide Film with Chromium or Titanium Coatings Nanfang Yu1, Jiming Bao1, Alexey Belyanin2, Thomas Mates3, Mariano Troccoli4, and Federico Capasso1 1 School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138 2 Department of Physics, Texas A&M University, College Station, TX, 77843 3 Materials Department, University of California, Santa Barbara, Santa Barbara, CA, 93106 4 Argos Tech, LLC, Santa Clara, CA, 95051 ABSTRACT We report systematic measurements of the lifetime of the 1.54 µm transition of erbium implanted at different energies in SiO2 films coated with titanium or chromium. The lifetime shows a strong reduction up to a factor of 20 with decreasing distance between the erbium and the metal coating. Our experiments combined with rigorous theoretical modeling demonstrate that a high degree of control over the radiative properties of erbium can be achieved in erbiumimplanted materials. INTRODUCTION Erbium is a rare-earth element of paramount technological importance for photonics. Its 4I13/2 – 4I15/2 optical transition falls into the silica fiber transmission window near 1.5 µm. Er-doped fiber amplifiers are widely used in optical communications [1]. Er-doped thin films and nanostructures are increasingly being investigated for applications such as solid-state lasers, modulators, and other optoelectronics devices [2,3]. In bulk SiO2, the lifetime of Er is determined by its radiative lifetime, due to spontaneous emission, as well as by its non-radiative interactions with the neighboring lattice structure. In lattice relaxed SiO2 at a low Er concentration, the lifetime of the 1.54 µm transition is of the order of 15 ms and is mainly determined by radiative spontaneous emission [1,3]. It is well known that both the lifetime and the separation between energy levels of atoms are affected by the presence of interfaces with other materials that change the electromagnetic (EM) modes, see, e.g., references 4-8, and references therein. If the interface is located in the near zone of an atom, i.e. at a distance much less than the optical transition wavelength, the influence of the interface on the lifetime is mainly due to a semiclassical London-van-der-Waals interaction rather than to EM vacuum fluctuations. Therefore, it can be adequately described by the change in the total EM reaction field acting on the atom. This approach was shown to provide accurate quantitative results [9-11]. In the case of a finite imaginary part ε2 of the dielectric constant of the medium adjacent to an atom, the dominant physical mechanism of the lifetime modification is the surface plasmon-mediated energy transfer between the atom and the dissipative medium [9,12-15]. This dissipative energy transfer becomes more effective the smaller the separation between the atom and the medium, thus leading to a shorter lifetime and smaller photoluminescence (PL) intensity. Recently, Kalkman et al. demonstrated enhanced PL decay rate for the Er/silica glass/silv
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