Thin Solid Films 453 – 454 (2004) 150–153 0040-6090/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2003.11.089 (110)Nd:KGW waveguide films grown on CeO y Si substrates by 2 pulsed laser deposition P.A. Atanasov *, T. Okato , R.I. Tomov , M. Obara a,b, a b a Department of Electronics and Electrical Engineering, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama-shi 223-8522, Japan a Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose Boulevard, Sofia 1784, Bulgaria b Abstract Textured (110)Nd:KGW optical waveguides are grown on CeO ySi substrates by pulsed laser deposition. Ceria buffer layer 2 is prepared on (100)Si substrates by KrF excimer laser ablation of Ce Gd O ceramic target. The (100) or (111) orientation 0.9 0.1 2 of CeO depends on the deposition conditions. The Nd:KGW films are prepared by ablation of K-rich ceramic targets in O or 2 2 Ar. The influence of the synthesis conditions (O or Ar pressure and substrate temperature) and the orientation of the CeO 2 2 buffer layer on the crystallinity of the Nd:KGW films are studied. Better results are obtained when deposited on (100)CeO y 2 (100)Si. The as-grown films are optically active. The crystallinity improves and the intensity of the emission spectra increases upon annealing at 700 8C in air. The emission spectra of Nd:KGW films are demonstrated for the main Nd transitions in 0.85– 1.45 mm spectral range. Waveguide loss as low as 3.3 dB cm is measured. y1  2003 Elsevier B.V. All rights reserved. PACS: 81.15.Fg; 42.70.Hj Keywords: Pulsed laser deposition; Nd-doped potassium gadolinium tungstate; Ceria buffer layer; Structural and optical properties; Ceramic target 1. Introduction In the last few years, increasing attention has been paid to the preparation of passive and active waveguides that are of great interest as components for integrated optics and optoelectronics. Among the materials with high potential for light generation or amplification, potassium gadolinium tungstate wKGd(WO ) or KGWx 42 doped with rare-earth ions such as Nd, Er or Yb is of special interest w1–6x. Nd:KGW operates both in c.w. and Q-switched modes, provides an excellent match for diode pumping w6,7x, has lower threshold and more than a factor of 2 higher slope efficiency than Nd:YAG lasers w2,8x. Moreover, it offers very efficient and ultra-low- threshold stimulated Raman scattering and thus allows simultaneous generation of the common Nd lines at 1.06, 1.35 and 0.89 mm together with several Stokes and Anti-Stokes lines w9,10x. Frequency doubling and *Corresponding author. Tel.: q359-2-714-4382; fax: q359-2-975- 3201. E-mail address: paatanas@ie.bas.bg (P.A. Atanasov). mixing provides laser emission at numerous wavelengths in the range from 500 to 700 nm. Nd-doped YAG w11x and GGG w12x optical thin films and active waveguide were successfully grown by pulsed laser deposition. Recently, thin Nd:KGW films have been grown for the first time w13x. They were deposited on sapphire and exhibit photoluminescence (PL) at 1.068 mm. Although some progress has been made w14– 18x, the growth of high quality Nd:KGW film is still a challenge. Deposition of these active materials on Si substrates is highly desirable to build integrated devices. The aim of the present work is to demonstrate the feasibility of growth of Nd:KGW films with good luminescent and optical properties on Si using ceria (CeO ) as buffer layer. CeO is used widely as a buffer 2 2 layer or optical coating w19–21x. We chose it because its lattice parameters match well with those of Si and its index of refraction is lower than Nd:KGW, allowing for waveguide propagation. The growth conditions have been varied in order to achieve the optimum structural and optical properties of both—buffer and Nd:KGW thin films.