Erbium-doped GaN (GaN:Er) epilayers were synthesized by metal organic chemical vapor deposition. GaN:Er waveguides were fabricated based on four different GaN:Er layer structures: GaN:Er/GaN/Al2O3, GaN:Er/GaN/AlN/Al2O3, GaN:Er/GaN/Al(0.75)Ga(0.25)N/AlN/Al2O3, and GaN/GaN:Er/GaN/Al2O3. Optical loss at 1.54 μm in these waveguide structures has been measured. It was found that the optical attenuation coefficient of the GaN:Er waveguide increases almost linearly with the GaN (002) x-ray rocking curve linewidth. The lowest measured loss was ~6 dB/cm.

Er-doped GaN (Er:GaN) is a promising candidate as a gain medium for solid-state high energy lasers (HELs) at the technologically important and eye-safe 1.54 μm wavelength window, as GaN has superior thermal properties over traditional laser gain materials such as Nd:YAG. However, the attainment of wafer-scale Er:GaN bulk or quasi-bulk crystals is a prerequisite to realize the full potential of Er:GaN as a gain medium for HELs. We report the realization of freestanding Er:GaN wafers of 2-in. in diameter with a thickness on the millimeter scale. These freestanding wafers were obtained via growth by hydride vapor phase epitaxy in conjunction with a laser-lift-off process. An Er doping level of 1.4 × 1020 atoms/cm3 has been confirmed by secondary ion mass spectrometry measurements. The freestanding Er:GaN wafers exhibit strong photoluminescent emission at 1.54 μm with its emission intensity increasing dramatically with wafer thickness under 980 nm resonant excitation. A low thermal quenching of 10% was measured for the 1.54 μm emission intensity between 10 K and 300 K. This work represents a significant step in providing a practical approach for producing Er:GaN materials with sufficient thicknesses and dimensions to enable the design of gain media in various geometries, allowing for the production of HELs with improved lasing efficiency, atmosphere transmission, and eye-safety.

Cubic boron nitride (c-BN) thin films are deposited on p-type Si wafers using radio frequency (RF) sputtering and then doped by implanting S ions. The implantation energy of the ions is 19 keV, and the implantation dose is between 10 15 ions/cm 2 and 10 16 ions/cm 2 . The doped c-BN thin films are then annealed at a temperature between 400 • C and 800 • C. The results show that the surface resistivity of doped and annealed c-BN thin films is lowered by two to three orders, and the activation energy of c-BN thin films is 0.18 eV.

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.

Er doped GaN (Er:GaN) is a very promising gain medium for realizing high energy lasers (HELs) operating in the relatively eyesafe 1.5 lm spectral region due to its high thermal conductivity, low thermal expansion coefficient, low temperature coefficient of the refractive index, and high atmospheric transmittance. We report the results of optical absorption and resonantly excited photoluminescence emission spectroscopy studies performed on Er:GaN freestanding quasi-bulk crystals grown by hydride vapor phase epitaxy. Fine features resulting from the transitions between Stark sublevels in the 4 I 13/2 first excited state and 4 I 15/2 ground state manifolds enabled the construction of energy level diagrams pertaining to the excitation and emission mechanisms of Er:GaN eyesafe HELs. Our results suggest that the most appropriate pump lines in Er:GaN are 1514 nm and 1539 nm, whereas the lasing emission lines are most likely to occur at 1569 nm and 1581 nm, conforming to the requirements of an extremely small quantum defect lasing system. In contrast to the more established HEL gain medium of Er:YAG, the well-known absorption (or pump) line near 1470 nm is absent in Er:GaN. Er:GaN HELs are expected to outperform those based on Er:YAG in terms of average power, power density, and beam quality. Published by AIP Publishing.