Abstract

Tunable lasers that cover a large wavelength range are important devices in wavelength division multiplexing applications. One promising structure is based on grating-assisted codirectional coupling [1] between two waveguides and has recently been fabricated [2]. This paper reports on the calculation of the threshold characteristics. An analytical expression has been derived, from which the threshold gain can be calculated. It turns out that lasing occurs at the wavelength of maximum coupling, only for not too large κl-values. This paper explains this behaviour. Furthermore the influence of the facet reflectivities is studied with respect to the threshold gain and the emission wavelength.

© 1992 Optical Society of America