Crystal Planar Waveguides, a Power Scaling Architecture for Low-Gain Transitions

Abstract

In this paper, we present the underlying advantages that make the crystalline planar waveguide (PW) the key ingredient in power-scaling difficult or "weak" laser transitions, especially those which are extremely challenging to operate in other gain medium configurations. The planar waveguide architecture is shown to enable efficient laser operation of low-gain and/or quasi-four-level transitions that suffer reabsorption losses. Exemplar configurations are reported to make this case, for example, 1.4 W at 1.8 μm from a Nd:YAG double-clad planar waveguide laser (PWL), in addition to 0.5 W at 2.7 μm from a similar highly doped Er:YAG PWL. New laser performance levels from sesquioxide PWs fabricated by pulsed laser deposition are also presented for the first time, with >1 W obtained from a Yb:Y 2 O 3 PWL. Current performance and future prospects are discussed for this laser architecture.

Universal Quasi-Level Parameter for the Characterization of Laser Operation

“…The sums in the enumerator and denominator correspond to the expressions for the so-called spectroscopic absorption and emission cross sections σ a and σ e , i.e., the quantities that are accessible to direct external measurements [18]. Thus ( 16) can simply be written as γ = 1 + σ a /σ e in agreement with literature [19].…”

Characterisation and laser performance of a Yb:LuAG double-clad planar waveguide grown by pulsed laser deposition

“…For a double-clad PW design, where the core mode(s) interact with the outer-cladding interfaces [4], mode selection can be achieved via gain saturation effects through tailoring the doping profile [2,19], which can be crucially important for power scaling PWL [20]. In many cases, simply restricting the doping to the central portion (< 60%) of the full waveguide aperture robustly selects fundamentalmode operation [2].…”

An 115 W Yb:YAG planar waveguide laser fabricated via pulsed laser deposition

“…They also have the advantage of allowing confinement of the pump and laser modes [4], significantly lowering laser thresholds in comparison to bulk lasers, provided propagation losses remain modest [5]. A planar waveguide laser, with appropriate control over the oscillating spatial mode, can thus be used as an efficient device to increase brightness over a wide range of wavelengths [6], though due to difficulties in their fabrication, practical implementation has been limited.…”