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3 Enhancement of Er3+ emission at 1.5u by the sensitization of Yb3+ ion. Tetsuro Izumitani and Yeong Lin R&D Center, HOYA Corporation 3-3-1, Musashino, Akishima, Tokyo 196 JAPAN I. INTRODUCTION AND EXPERIMENTS. Erbium laser of 1.5u has become very important in the market because it is in eye-safe wavelength region. However; because of its weak absorption at pumping bands, sensitization ions is generally required of its in order fluorescence by codoping with other donor to improve its lasing efficiency. In this study, we investivgated its sensitization with ytterbium ion and the optimal dopant concentrations. Fluorophosphate glass of FCD1 was selected for host material because of its stable properties and offers a high life time for erbium's excited state of 4I13 /2. Two test melt series were made. In one series, glasses were doped with Er3+ In another series, glasses were doped with Er3+ plus Yb3+. RESULTS AND DISCUSSION. II. The emission intensities versus dopant concentrations are shown in Fig.1. For the glasses doped with erbium only, its emission intensity Io was found to be a function of the square root of erbium ion concentration when the concentration is less than 3cat%.As the erbium concentration became higher than 3.3cat%, its concentration quenching effect appeared and its emission intensity started decreasing. When the ytterbium sensitizer was added to the glass, its emission intensity was found to have peaked at two different combination dopant concentrations One is near 3.45cat% of Er plus 0.55 cat% of Yb and another one is about 0.45cat% of Er plus 3.55cat% of Yb. The variation of emission intensity with dopant concentration(yb3++ Er3+)is discussed on the basis of energy transfer between Yb3+ and Er3+. Fig.1.Er emission intensity at 1.5u versus dopant concentrations."o"from glass doped with Er.`.'from glass duped with Er and Yb with Yb ionic concentration 4-(Er cat%). =

4 13aV4 Enhancement of Er3+ emission at 0.55u and 2.7u by the sensitization of Yb3+ ion. Tetsuro Izumitani and Yeong Lin R&D Center, HOYA Corporatio Musashino Akishima, Tokyo 196 JAPAN I. INTRODUCTION AND EXPERIMENTS. Optimal dopant concentrations in AZF(alumino-zirconium fluoride) glass for Er ion fluorescence at 2.7um and 0.55um have been investigated. For 2.7um fluorescence studies, we used Xe lamp as the pumping source. For 0.55um, we used 800nmd laser diode. One series glasses were doped with various concentrations for Er3+and Yb3+. Another series glasses were only doped with Er3+.In both series, Er3+ concentration was varied between 2-12cat%. 35min. All of these glasses were melted, under argon gas atmosphere, at 950 C for I. RESULTS AND DISCUSSION. For 2.7um emission, under Xe lamp pumping, its intensity was steadily increased as Er ion concentration was increased from 2 to 12cat%(the bottom curve of Fig.1.). No any concentration quenching was observed. When Yb3+ was introduced to these glasses as codopant, its intensity became substantially higher(the top curve of Fig.1.). The optimal dopant concentrations in our investigation range are about 9cat% of Er3+ with 3cat% of Yb3+. The sensitization effect of Yb3+ ions is due to its higher molar absorption coefficient at 0.98um, which involves the excitation from ground state of to 2F5/2. and its ability of performing energy transfer to Er ions. This will cause excitation of ground state Er ion to 4F11/2, from this excited level, it relaxis down to 4I13/2. Its relaxation to 4I13/2 yields the emission of 2.73u m photon. The results of 0.55um emission studies, under 0.8um pumping, are shown in Fig.2. When the glass was only doped with Er ions, a concentration quenching effect was found to have occurred at about 9-10cat%(the bottom curve of Fig.2). Further addition of Yb3+ as codopant caused a considerable improvement of its emission intensity(the top curve of Fig.2). The optimal dopant combination concentrations were found to be about 8cat% of Er3+ and 4cat% of Yb3+. Fig.1.Er2+ ion emission intensity of 2.7u versus the dopant concentration. o; AZF glasses doped with erbium. ; AZF glasses doped with erbium and ytterbimn. Fig.2.Er ion emission intensity of 0.55u versus the dopant concentration. o: AZF glasses doped with erbium. AZF glasses doped with erbium : and ytterbium \6 \

5 WAVELENGTH (um] DNP1040 DYE LASER SPECTRUM NDL112 DYE LASER SPECTRUM

6 1) Y.Hirakawa et al: Opt. Commun. 84 (1991) 365 2) M. Maeda et al.: Pro. Int. Symp. Short-Wavelength Lasers and Appli cations, Osaka, 1987 (Springer, Berlin, 1987) p.345

7 VUV GENERATION BY ANTI-STOKES RAMAN SCATTERING OF KrF LASER RADIATION IN H2 Yunsheng Huo, Kouki Shimizu, and Takashi Yagi Institute of Research and Innovation, Laser Laboratory, 1.Introduction Anti-Stokes Raman scattering in hydrogen gas has been recognized to be an efficient method to generate VUV radiation. In this work, the KrF excimer laser radiation at nm was used to generate up to eleventh-order anti-stokes radiation (ASll) at 116 nm in H2 at room temperature. Rather tight focusing for the pump beam (f<lm) is used in the most anti-stokes experiments to provide phase-matching for the four-wave mixing processes. The pump and Sl beams may be severely depleted by the competing Raman scattering to the second-order and other higherorder Stokes beams. This work also studies how significatly it affects the efficient generation of high-order anti-stokes radiation. 2.Experiments The experimental arrangement is shown in Fig.1. The KrF laser beam was focused by a 100-cm focal-length lens into a H2 Raman cell. An aluminum diffuser was used to reflect the output beams of the Raman cell into a vacuum monochromator to produce more uniform illumination. A Hamamatsu photomultiplier was attached to the output slit of the monochromator to detect AS3 through ASll signals. The pulse energy and pulse shapes from S3 to AS3 (189 nm) radiation were measured by a Joulemeter and Hamamatsu photodiodes respectively. In this case, a quartz prism was used as a dispersion component. 3.Results Up to eleventh-order anti-stokes (116 nm) of the KrF laser radiation (248 nm) was observed in H2 gas at room temperature. The ASll pulse energy was estimated to bƒì l ƒêj, and it corresponds to a conversion efficiency of 5 ~10 for an incident KrF laser energy of 200 mj. The dependences of the AS3, AS6, ASlO, and ASll pulse energy on the H2 pressure are shown in Fig.2. The lower anti-stokes orders show a double-peaks in the H2-pressure dependence. The peaks at the lowerh2 pressure side, observed in our experiment, represent an important region for anti-stokes.conversion, because all the other higher-order anti- Stokes radiation, such as AS10, ASll, have their peaks at about the same H2 pressure. The depletion of the pump and Si beams by the stimulated Raman scattering to S2 and S3 is the main mechanism responsible for the significant decrease in the anti- Stokes efficiency while the H2 pressure is increased from 1-8 atm to 3 atm. 4.Acknowledgment This work. was performed under the Research and Development Program on "Advanced Material Processing and Machining Systems conducted under a program set by New Energy and Industrial Technology Development Organization, which is promoted as a Large-Scale Project undertaken by Agency of Industrial Science and Technology Ministry of International Trade and Industry. Fig.1 Schematic diagram of the experimental arrangement Fig.2 Dependence of anti-stokes energy converge efficiency on hydrogen pressure. \ 17 \

8 [1] A. McPherson, et al., J. Opt. Soc. Am. 84, 595 (1987). [2] X. F. Li, et al., Phys. Rev. A39, 5751 (1989). [3] L. A. Lompre, et al., "Short-wavelength coherent radiation: generation and application," Monterey, CA. MC2-1 (1991) p.25.

9 1) K. Miyazaki and H.Sakai: to be published in Lett. to the Edit., J. Phys. B.

12 1) J.Christiansen and C.Shultheiss, Z. Phys. A290, 35 (1979). 2) J.Christiansen et al., Opt. Commun. 56, 39 (1985). 3) J.Christiansen,Physics and Applications of Pseudosparks, Plenum,1 (1990).

On the Wireless Beam of Short Electric Waves. (VII) (A New Electric Wave Projector.) By S. UDA, Member (Tohoku Imperial University.) Abstract. A new e

On the Wireless Beam of Short Electric Waves. (VII) (A New Electric Wave Projector.) By S. UDA, Member (Tohoku Imperial University.) Abstract. A new electric wave projector is proposed in this paper. The