The authors report systematic measurements of the lifetime of the 1.54μm transition of erbium implanted at different energies in SiO2 films coated with different metals (titanium and chromium). The lifetime shows a strong reduction (up to a factor of 20) with decreasing distance between the erbium and the metal overlay. Their experiments combined with rigorous theoretical modeling demonstrate that a high degree of control over the radiative properties of erbium can be achieved in erbium-implanted materials in a wide range of implantation energies.
The authors report systematic measurements of the lifetime of the 1.54μm transition of erbium implanted at different energies in SiO2 films coated with different metals (titanium and chromium). The lifetime shows a strong reduction (up to a factor of 20) with decreasing distance between the erbium and the metal overlay. Their experiments combined with rigorous theoretical modeling demonstrate that a high degree of control over the radiative properties of erbium can be achieved in erbium-implanted materials in a wide range of implantation energies.
The active modulation of optical response of quantum emitters at the nanoscale is of paramount importance to realize tunable light sources for nanophotonic devices. Herein, a thin film of phase‐change material (VO2) is coupled to a 20 nm‐thick silica layer embedding Er3+ ions, and it is demonstrated how the active tuning of the local density of optical states near the erbium emitters provided by the thermally induced semiconductor‐to‐metal transition of VO2 can be used to dynamically control the Er3+ emission lifetime at telecom wavelength (1.54 μm). A decay rate contrast of a factor 2 is obtained between high temperature (90 °C), when VO2 is metallic, and room temperature, when VO2 is semiconductor, in agreement with calculations performed with the classical dipole oscillator analytical model. A hysteretic behavior is observed by measuring the Er3+ lifetime as a function of the temperature, whose parameters are consistent with those of grazing incidence X‐ray diffraction and optical transmittance measurements. The fractions of Er3+ ions that couple with VO2 in each phase at the different temperatures are determined by the analysis of the temporal decays. The results make the investigated system an optimal candidate for the development of tunable photon sources at telecom wavelength.
Erbium implanted sodalime silicate glass was covered with a range of transparent liquids. The spontaneous emission rate of Er3+ around 1.54 $\ensuremath{\mu}$m shows clear changes depending on the liquid refractive index and Er depth. A rigorous quantum mechanical calculation shows that the effect of the interface on the spontaneous emission rate is fully described by the classical density of optical modes as a function of distance from the interface. The data provide the first direct determination of the radiative transition rate $(45{s}^{\ensuremath{-}1})$ at 1.54 $\ensuremath{\mu}$m of Er3+ which is widely used in optical amplifiers.
Since the advent of vertical cavity surface-emitting lasers, a renewed interest has also emerged for the spontaneous emission from Fabry-Pérot microcavities. Changes in spontaneous emission characteristics in a 1D microcavity were predicted long ago,1 but have been demonstrated only recently in the optical domain for solid-state, e.g. semiconductor, structures where changes in spectral purity, lifetime, and emission intensity were observed.2 However, the interpretation of these effects is somewhat obscure, because these structures are highly absorbing and often involve band-to-band, rather than atomic, transitions. In the present study, we use optically transparent Si/SiO2 cavities, consisting of two coplanar Si/SiO2 distributed Bragg reflectors (DBR) around a (λ/2) SiO2 active region, which was doped with ~0.2 at.% Er3+ ions through MeV ion implantation. The Er3+ ions in SiO2 exhibit a sharp, atomic-like, intra-4f transition around λem=1.54 μm, which is effectively shielded by the outerlying filled 5s2 and 5p6 shells. Recently, we reported on the considerable enhancement of the spontaneous emission intensity out of such an Er-doped microcavity.3 In this paper, we present a more detailed study of the modified spontaneous emission, including fluorescence decay measurements to study the effect of the cavity on the spontaneous emission rate.
Erbium is a rare-earth metal that, when incorporated in a solid, can emit light at a wavelength of 1.5 μm. It plays a key role in current day telecommunication technology as the principle ingredient of optical fiber amplifiers. In this thesis the control of the Er spontaneous emission in three different types of microphotonic materials is described. Part I of this thesis focuses on the effect of a metallo-dielectric interface on the spontaneous emission of optical emitters in silica glass. It is shown that Er ions near a Ag interface can couple to surface plasmons (SPs) via a near-field interaction. By coupling SPs out into the far field, large changes in the Er photoluminescence emission distribution, spectra, and polarization can be observed. The excitation of SPs also results in an increase of the Er photoluminescence decay rate. The observed decay rates are in good agreement with calculations based on a classical dipole oscillator model. From the change in photoluminescence decay rate of Si nanocrystals near a Ag interface it is shown that Si nanocrystals can efficiently excite SPs and have an internal quantum efficiency of 77 %. Part II focuses on the effect of a microcavity on the spontaneous emission of Er and describes how ion implantation can be used to dope dielectric microresonators with optically active Er ions. The fabrication and characterization of an Er ion-implanted silica microsphere resonator is described that shows lasing at 1.5 μm when pumped above its lasing threshold. Ion implantation is also used to dope toroidal microcavities on a Si chip with Er. The microtoroids are doped by either pre-implantation into the SiO2 base material, or by post-implantation in a fully fabricated microtoroid. The optical activation of Er ions in the microtoroid is investigated and Er lasing at 1.5 μm is observed for both types of microcavities with the lowest threshold (4.5 μW) for the pre-implanted microtoroids. Part III describes the fabrication of an Er-doped Si-inverse opal photonic crystal. These photonic crystals can potentially have a photonic bandgap that can fully inhibit the spontaneous emission of on optical emitter. Fabrication criteria are derived for such a photonic crystal, based on the lattice parameter, filling fraction, and Si refractive index. In the opal photonic crystal composed of both Si and SiO2 we show that Er ions can be selectively excited in both the Si and SiO2 part of the photonic crystal by changing the excitation wavelength and/or the measurement temperature.
We have fabricated a series of thin (~50 nm) erbium-doped (by ion implantation) silicon-rich oxide films in the configuration that mitigates previously proposed mechanisms for loss of light emission capability of erbium ions. By combining the methods of optical, structural and electrical analysis, we identify the erbium ion clustering as a driving mechanism to low optical performance of this material. Experimental findings in this work clearly evidence inadequacy of the commonly employed optimization procedure when optical amplification is considered. We reveal that the significantly lower erbium ion concentrations are to be used in order to fully exploit the potential of this approach and achieve net optical gain.
Successful incorporation of both erbium and ytterbium in alumina by ion implantation is reported. Some evidence for indirect pumping of erbium through the transfer of energy from ytterbium has been observed. Both plasma-enhanced CVD deposited alumina thin films and sapphire crystals were employed as substrates. Yb3+ and Er3+ concentrations ranged from 2.4 At% to 8 At% and from 0.4 At% to 0.8 At%, respectively. The samples show strong, broad, room-temperature photoluminescence at λ = 1.53 µm corresponding to the intra-4f transitions between the 4I13/2 (first excited) and the 4I15/2 (ground) state of Er3+. The full width at half maximum of the emission spectrum is as high as 67 nm for the Al2O3 thin films; for the sapphire crystals it is 45 nm. The fluorescence lifetime of the samples has been measured to be as high as 4.2 ms at 50 mW pump power.