High efficiency waveguide-based optical amplifiers and lasers fabricated by femtosecond-laser induced ion migration

The modification of the glass composition by high repetition rate femtosecond (fs) laser pulse irradiation appears as a very attractive method for the production of photonic devices [1]. It has recently been shown that this mechanism enables producing refractive index changes, Δn>10
⁻²
, leading to the production of highly efficient, and controllable passive waveguides in P
2
O
3
-La
2
O
3
-K
2
O-based glasses [2]. The index contrast (An) is caused by the enrichment of La
2
O
3
in the guiding region which is depleted in K
2
O due to cross migration of both elements. Still, it has also been shown [3] that the guiding region is enriched in other lanthanides present in the glass (i.e. Er, Yb). This effect may be detrimental for the production of active devices. In this work we show that fs-laser induced ion-migration can similarly be used to produce high performance waveguide amplifiers and lasers. In fact, we show the feasibility of producing waveguides with different gain in the same glass sample by varying the writing parameters, increasing the flexibility of this technique in integrated photonics applications.