Hydrogenation of buried passive sections in photonic integrated circuits: a tool to improve propagation losses at similar to 1.56 mu m

We demonstrate here that hydrogenation offers a simple and attractive solut ion to fabricate low-loss InGaAsPInP photonic integrated circuits operating at 1.56 mu m. Using InGaAsP/InP buried waveguide test structures closely i mitating the passive sections of photonic circuits, we first demonstrate th at hydrogenation helps to bring down significantly the propagation losses, Secondly, with the aid of modal calculations, as well as the optical and el ectrical measurements on test and control structures, this drop in losses s ubsequent to hydrogenation is principally attributed to a decrease in free hole concentration (and consequently to a reduction of absorption by free h oles) in the upper p(+) InP cladding layer. Lastly, we demonstrated that th e propagation losses improved by hydrogenation are thermally stable up to t emperatures as high as 350 degrees C. (C) 1999 Elsevier Science S.A. All ri ghts reserved.