Erbium doped gallium nitride (Er:GaN) bulk crystals have emerged as a promising optical gain material for high energy lasers (HELs) operating at the 1.5 lm "retina-safe" spectral region. Among the many designs of HEL gain medium, the core-cladding planar waveguide (PWG) structure is highly desired due to its abilities to provide excellent optical confinement and heat dissipation. We report the realization of a GaN/Er:GaN/GaN core-cladding PWG structure synthesized by hydride vapor phase epitaxy and processed by mechanical and chemical-mechanical polishing. An Er doping concentration of [Er] ¼ 3 Â 10 19 atoms/cm 3 has been attained in the core layer, as confirmed by secondary ion mass spectrometry measurements. A strong 1.54 lm emission line was detected from the structure under 980 nm resonant excitation. It was shown that these PWGs can achieve a 96% optical confinement in the Er:GaN core layer having a thickness of 50 lm and [Er] ¼ 3 Â 10 19 atoms/cm 3 . This work represents an important step toward the realization of practical Er:GaN gain medium for retina-safe HEL applications.
Erbium nitride (ErN) is a rare-earth metal mononitride with desirable electronic, magnetic, and optical properties. ErN can be incorporated into III-nitride semiconductors to develop new functional materials for optoelectronic and spintronic devices. Here, we report on the optical properties of ErN crystals, grown by sublimation and probed by photoluminescence (PL) spectroscopy. Three transition lines were observed near 1 eV. Theoretically, ErN has a small indirect energy gap of around 0.2 eV with a conduction band minimum at the X-point of the Brillouin zone and a valence band maximum at the Γ-point. The predicted smallest direct energy gap is around 1 eV, with two valence bands at the X-point. Using the PL results together with the reported calculations, a coherent picture for the band structure at the X-point for ErN crystals has been derived. Experimental results revealed that ErN has a minimum direct bandgap of 0.98 eV and a total of two valence bands separated by about 0.37 eV at the X-point.
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.
Erbium-doped gallium nitride (Er:GaN) is a promising gain material for solid-state high-energy lasers operating in the 1.5 μm wavelength window due to the superior optical properties and extremely high thermal conductivity of a GaN host crystal that permit high-power and high-temperature applications. We report the realization of all-crystalline GaN/Er:GaN/GaN embedded waveguide fiber structures using the hydride vapor phase epitaxy growth and re-growth technique, along with chemical–mechanical polishing processes. The Er:GaN core layer possesses an Er doping concentration of [Formula: see text] atoms/cm3, confirmed by secondary ion mass spectrometry measurements. X-ray diffraction measurements confirm, respectively, c-, a-, and m-plane orientations for top/bottom, side, and front/back cross-sectional cladding layers of the fiber structure with good single-crystalline quality. The 1.5 μm Er3+ emission was detected from each surface of the fiber structures via 980 nm resonant excitation. The effect of 1.54 μm light guiding by the fiber structure has been demonstrated. This work laid the foundation toward achieving all-crystalline core-cladding fibers based on GaN wide bandgap semiconductor with potential applications in the harsh environments of high powers, power densities, and temperatures.
Erbium (Er) doped GaN (Er:GaN) bulk crystals are promising as an optical gain material for high energy lasers. Other than the preferred configuration of Er3+ occupying the Ga site with four nearest neighbor N atoms (ErGa), Er can also form a complex with a defect (ErGa-DX) in Er:GaN. A set of Er:GaN semi-bulk crystals were grown by hydride vapor phase epitaxy (HVPE) at different growth temperatures to allow the determination of the formation energies, EF, of Er optical centers in Er:GaN. Photoluminescence (PL) emission spectra near 1.5 μm pumped by a near band edge excitation (λexc = 375 nm) and by a resonant excitation (λexc = 980 nm) were measured, which yielded two different formation energies of EF = 2.8 eV and 3.3 eV, corresponding to the formation of ErGa-DX and ErGa in Er:GaN, respectively. As a gain medium, the formation of ErGa-DX in Er:GaN would not only reduce the pumping efficiency of Er optical centers but also increase the optical loss. Our results provide useful insights into possible strategies for enhancing the fraction of ErGa in Er:GaN and, hence, the pumping efficiency, paving the way for achieving optical gain and lasing in Er:GaN.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.