Er:YGG planar waveguides grown by pulsed laser deposition for LIDAR applications

Abstract

Er:YGG planar waveguide amplifiers (PWAs) are promising candidates to meet the needs of greenhouse-gas differentialabsorption LIDAR applications. We report pulsed-laser-deposition growth of this doped crystal and net-gain performance (internal gain ~2 dB/cm for 0.7-at.% Er-doping) in a 0.9-cm-long uncoated single-pass PWA. Rapid fabrication is also demonstrated with optimized parameters, where crystal growth rates approaching 20 microns/hour have been realized. We compare Er-doping concentrations ranging from 0.5 at.% -4 at.%, and report on their spectroscopic properties. Furthermore, we show the ability to tailor the deposited crystal properties, controlling the waveguide and gain characteristics. Finally, we discuss the spectroscopy and potential performance of this relatively unstudied material for PWAs in the eye-safe regime.

1.6-micron Er:YGG waveguide amplifiers

“…With the bi-directional PLD protocol, an order of magnitude lower defect density in the grown crystal films was obtained, when compared with the classic uni-directional ablation method. This manifests itself in reduced propagation losses as realized in the channeled samples detailed herein, some better than -0.3 dB/cm, compared with similar planar films reported in [5] of -0.8 dB/cm. Channels were fabricated with widths ranging from ~13 µm to ~19 µm, with ductile-dicing leading to optical quality surface roughness and the low propagation losses along the waveguide.…”

“…In the simplified schematic of Fig.1 it is clear that the incident UV laser beam is fixed at a unique angle. In our previous Er:YGG work [5] we employed a target-motion scheme that provided an epitrochoidal path across the surface, sweeping out a broad ablation path after many iterations of the target movement. At the same time the system maintains a static point of incidence so that the plume is originating from the same place.…”

“…In this paper we present the latest developments in the fabrication of low-loss planar waveguides comprising Er-doped YGG via pulsed laser deposition (PLD), expanding on our previous work [5]. A further process step, involving precision dicing in the ductile regime, was then used to produce ridge channel waveguides, with optical quality side-and end-facets.…”

Methane optical density measurements with an integrated path differential absorption lidar from an airborne platform

“…Using Er:YAG for CH 4 detection dates back to 1972 55 and recent successful demonstration and commercialization of high-power and high spectral brightness pump sources have afforded the realization of resonant pumping of Er:YAG [56][57][58][59] and Er:YGG. 60,61 The emission cross section of Er:YAG crystal is centered near 1645.3 nm and falls off rapidly at 1650.96 nm. It is near the MERLIN lines at 1645.55 nm, which are relatively wide (∼56 pm).…”

The challenges of measuring methane from space with a lidar

“…Chania, Greece 9 -12 October 2018 1972 50 . In recent years, successful demonstrations and commercialization of high power and high spectral brightness pump sources at 1470 nm and 1532 nm, driven in large part by the various industries including defense, telecommunications and medical, have afforded the realization of resonant pumping of of Er:YAG [51][52][53][54] and Er:YGG 55,56 lasers. The emission cross-section of Er:YAG crystal is centered near 1645.3 nm and falls off rapidly at 1650.96 nm.…”