Abstract

The development of Wavelength Division Multiplexing (WDM) telecommunications systems has driven the rapid development of Erbium doped fiber amplifier and very narrow band lasers [1] Recently, new efficient waveguide amplifier on phosphate glass has been demonstrated [2]. In this paper, we present the first steps of fabrication and analysis of 10 monolithically integrated DFB lasers on a chip. The starting point of our work is a Er/Yb co-doped phosphate, on which buried channel waveguides have been realized using ion exchanged techniques [2] Recent progress in that technology has led to a gain of 3dB/cm. The waveguides present a mean index variation of 2 10^-2 above substrate refractive index value of 1 52. For operation at 1 55 µm, the grating period predicted by the Bragg phase matching condition is d=λ/2n_e=0 505 µm related to the mean effective index n_e of the waveguides In this work, a corrugate 1 cm long grating was made on the top of the wafer. Interferometric exposure of photoresist with an Ar⁺ laser operating at 488 nm was used to print the grating After development, the grating pattern is transferred on the glass surface through a Reactive Ion Etching process. The glass is etched sufficiently to get more than 60 % of reflectivity at Bragg wavelength. Under pumping at 980 nm, single longitudinal mode operation around 1 55 µm is demonstrated for all the ten waveguides of the chip.

© 2000 IEEE