Excitation and emission mechanisms of Er:GaN gain medium in 1.5 μ m region

Zhao

et al. 2019

Appl. Phys. Express

Erbium-doped GaN (Er:GaN) possesses superior optical, mechanical and thermal properties and is a very promising material as a gain medium for solid-state high-energy lasers. We report here the optical properties of GaN/Er:GaN/GaN core-cladding planar waveguides (PWGs). Optical confinement in the core layer has been investigated. The measured optical loss coefficients of Er:GaN PWGs at 1.54 μm are 1.0 cm −1 for the TE polarization mode and 1.2 cm −1 for the TM polarization mode. Approaches to further reduce optical loss and the optimal configuration for resonantly pumped GaN/Er:GaN/GaN PWGs for achieving amplification near 1.5 μm have been identified.

mentioning

confidence: 99%

Optical properties of GaN/Er:GaN/GaN core–cladding planar waveguides

Zhao

et al. 2019

Appl. Phys. Express

Resonant excitation cross-sections of erbium in freestanding GaN bulk crystals

Applied Physics Letters

Zhao

et al. 2018

Self Cite

Erbium doped GaN (Er:GaN) is a promising candidate as a new gain medium for high energy lasers. The excitation and emission mechanisms as well as the transition cross sections of the pump and laser wavelength are of paramount importance for understanding the performance of lasers and amplifiers made of Er:GaN materials. We report here the results of direct measurements of resonantly excited photoluminescence emission, photoluminescence excitation, and optical absorption spectroscopy in the 1.5 lm "retina-safe" spectral region performed on freestanding Er:GaN bulk crystals synthesized by hydride vapor phase epitaxy. The results established that 1514 nm and 1538 nm are the most appropriate resonant pump wavelengths for achieving gain and lasing, which differs from Er in YAG and glass hosts. The absorption coefficients (a) and absorption cross-sections (r exc) of Er in GaN in the 1.5 lm window have been directly measured, providing r exc ¼ 1.4 Â 10 À20 cm 2 and 2.7 Â 10 À20 cm 2 for 1514 nm and 1538 nm pump wavelengths, respectively. These values are considerably higher than those of Er ions in glass and YAG hosts.

Polarization-resolved Er emission in Er doped GaN bulk crystals

Gong

Journal of Applied Physics

et al. 2020

Erbium-doped GaN (Er:GaN) quasi-bulk crystals are emerging as a promising novel gain medium for high energy lasers emitting at the retina-safe wavelength window of 1.5 μm. We report the polarization-resolved photoluminescence (PL) emission spectroscopy studies, which revealed that the pumping efficiency with the excitation polarization parallel to the c-axis of GaN (E⇀||c⇀) is significantly higher than that with the excitation polarization perpendicular to the c-axis of GaN (E⇀⊥c⇀). This phenomenon is a direct consequence of the inherent polar wurtzite GaN lattice, giving rise to a net local field, surrounding each Er ion, along the c-axis of GaN. The temperature dependent behaviors of the PL emission spectra were explained in terms of the Boltzmann population distributions among sublevels within the 4I15/2 ground state and the 4I13/2 first excited state of Er3+ in GaN, thereby providing an improved understanding regarding the origin of the dominant emission lines observed near 1.5 μm. The results suggested that the polarization field in GaN can be exploited to enhance the effective Er excitation cross section by manipulating the polarization of the excitation light source.