A New Platform for Compact Solid-State Yellow Lasers: Waveguides in Dy,Tb:LiLuF₄

Laser sources emitting in the yellow range are of great interest for medical and industrial application. In addition, the metrological line of Yb atomic clock lies at 578 nm, within the yellow band of the visible spectrum. This spectral region lacks of semiconductor-based coherent sources and the availability of laser sources operating in the yellow range involve complex nonlinear optical systems to perform sum frequency generation or second harmonic generation [1]. Concerning direct emission from solid-state sources, D<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</inf>3+ ions showed laser emission in the 560–580 nm band and can be effectively pumped with InGaN based laser diodes due to the presence of an absorption transition at about 450 nm. The main drawbacks of employing Dy-doped materials are the low absorption and emission cross-sections, both of the order of 10–<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, and the presence of cross relaxation processes that limits the doping to a few percent [2]. This reflects in the necessity of using active media with a length of about 20–30 mm, corresponding to a poor overlap between the pump beam and the mode inside the laser cavity.