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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Two-photon absorption studies in rare-earth-doped fibers for sensing infrared radiation

Bommareddi Rami Reddy

Published Feb 14, 2003• 0 citations
Publisher

Abstract

Two-photon absorption phenomena are useful for the generation of short wavelength radiation. When the same atom absorbs IR and visible photons it generates uv/visible energy. Such two-photon absorption phenomena in certain rare-earth ion doped materials have been implemented in our laboratory. The importance of these studies in fibers will be discussed. Infrared quantum counter studies in Eu, Tb, Ho, Er, and Pr doped fibers are proposed for future work.

DOI
10.1117/12.456326

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Two-photon absorption phenomena are useful for the generation of short wavelength radiation. When the same atom absorbs IR and visible photons it generates uv/visible energy. Such two-photon absorption phenomena in certain rare-earth ion doped materials have been implemented in our laboratory. The importance of these studies in fibers will be discussed. Infrared quantum counter studies in Eu, Tb, Ho, Er, and Pr doped fibers are proposed for future work.
This paper reviews the results of a program of experimental work on infrared quantum counter action in trivalent rare earth doped CaF2, SrF2, BaF2, and LaF3lattices. The action has been found in eight of the nine possible ions that could give an output in the visible region. While the strengths of the various schemes at a 1 percent doping level are consistant with a low concentration theory, the strengths of the schemes at a 10 percent doping level indicate that there are ion-ion interactions influencing the systems. These ion-ion couplings are so effective that three photon addition schemes have been identified.
The realization of single-photon generation is important for implementing various quantum information technologies. The use of rare-earth ions in an optical fiber is a promising single-photon generation method due to its ability to operate at room temperature as well as the low cost involved. Neodymium ions are especially interesting because the ions are one of the most commercially affordable rare-earth materials in the current industry. The neodymium ion also has the advantage of having a rich energy level structure, which offers several possible wavelengths for emitted single photons from visible to near-telecommunication wavelengths. In this paper, we experimentally demonstrated single-photon generation using an isolated single neodymium ion in tapered silica fiber at room temperature. Our results have significant implications as a platform for low-cost wavelength-selectable single-photon sources and photonic quantum applications.
Doubly-resonant two-photon-absorption-induced four-wave mixing has been observed for the first time in a rare earth insulator.The generation of the nonlinear signal exhibits strong intermediate and two-photon resonances in crystalline Tb (OH)3 and LiTbF4 This provides a novel method for high resolution measurements of intermediate 4f^n configurations and excited configurations of rare earth ions.The intermediate resonance showed spectral line narrowing up to ten times narrower than the corresponding inhomogeneously broadened absorption.In LiTbF4, laser-limited line widths were obtained and in Tb(OH)3, a homogeneous limit corresponding to T2 = 50 psec may have been reached.The qualitative behavior of the narrowing is explained by the dispersion of the anamalous index of refraction and its effect on phase matching.Direct measurement of the anamalous dispersion was made to test the model.Results indicate nonlinear contributions to the refractive index may have been present.The two-photon resonance in Tb(OH)3 was measured to be a 230 cm^-1 wide crystal field component of the broad 4f^n 5d excited configuration.Thus high resolution UV spectroscopy with tunable visible lasers is demonstrated.Applications are discussed including the extraction of homogeneous line widths from inhomogeneously broadened spectra, coherent transient measurements, and UV and VUV spectrosocpy.The latter uses different selection rules than linear absorption methods and allows study of transitions between excited states.DOUBLY-RESONANT TWO-PHOTON-AB^ORPTION-INDUCED EOUR-WAVB MIXPNQ IN, .T b .(DR) 3 . .
A fiber-coupled single-photon source is an essential component for the implementation of optical quantum communication technologies. Using the rare-earth ion doped in an optical fiber as an emitter is a significant method to construct such a photon source at room temperature, as well as achieving high coupling and channeling efficiency. In this study, we experimentally demonstrated the generation of single photons at room temperature by selectively exciting a sole rare-earth ion isolated within a tapered silica fiber. The key advantages of our method are the ability to manipulate a purely single ion and the efficient collection of photons from the guided mode of the fiber, owing to the single ion's emission of photons directly within the fiber. These features make our system a promising building block for realizing all-fiber-integrated optical quantum networks. We have also measured the optical lifetime of a single neodymium ion in the tapered fiber, and the result supports that the single-photon correlation time is practically determined by the absorption time of the ion.
In this thesis, we study the single-photon source using a rare-earth (RE) ion doped in a tapered fiber.Single-photon sources are key components for various optical quantum information technologies, and the development of low-cost single-photon sources has been desired for their implementation.A wide variety of emitters for single-photon sources have been studied.Among these emitters, RE ions have attracted much attention as single-photon emitters due to their high stability of luminescence and the sharpness of the emission spectrum with 4f transitions.In our single-photon source, we obtain spatially isolated single RE ions, which are separated from each other beyond the diffraction limit by tapering a commercially available RE-ion-doped silica fiber.RE ions doped in the silica fiber can be optically activated at room temperature.Therefore, our single-photon source does not need cryogenic systems.In addition, the emission wavelength can be selected based on the type of RE ions doped in the fiber.These features of our single-photon source enable the development of a low-cost and wavelength-selectable source.We performed the autocorrelation measurements using a neodymium (Nd 3+ ) ion in the tapered fiber, and showed the generation of single photons from the ion.In addition, we proposed a method to selectively excite a single RE ion in the tapered fiber, which can directly generate single photons within the tapered fiber, and collect them through the tapered fiber with high collection and channeling efficiencies.Generating single photons with this excitation method is proved by the autocorrelation measurements.We also observed the optical properties of the single photon emitted from the single Nd 3+ ion in the tapered fiber, such as the fluorescence lifetime, saturation intensity and polarization states.The fluorescence lifetime is one of the most important parameters for a single-photon source because this parameter is closely related to the emission rate.We observed the fluorescence lifetime of the single Nd 3+ ion in the tapered silica fiber and an 1 ensemble of the Nd 3+ ion in the unstructured silica fiber.The saturation power of the excitation laser and the saturated fluorescence intensity tell us the appropriate excitation power for generating single photons with high signal-to-noise ratio.Here, we measured the relationship between the fluorescence intensity from the single Nd 3+ ion and the power of the excitation light.In addition, the polarization state of the single photons emitted from the single Nd 3+ ion in the tapered fiber was observed.Our results will lead to the implementation of the low-cost and wavelength-selectable single-photon source to realize various optical quantum information technologies.
The fiber-coupled single-photon source, which can operate at room temperature, is an essential component for implementing optical quantum communication technologies such as quantum internet and quantum key distribution. Here, we experimentally demonstrated the generation of single photons at room temperature from a single Rare-Earth (RE) ion isolated in the optical tapered fiber. Our single photon source is fabricated based on commercially available RE ion doped fibers, which can be prepared at low cost. To investigate the characteristics of our single-photon source, several optical properties were also observed such as saturation intensity of the single RE ion. Our results will lead to the realization of various photonic quantum information technologies such as optical quantum communication networks.