High-power high-efficiency 0.98-μm wavelength InGaAs-(In)GaAs(P)-InGaP broadened waveguide lasers grown by gas-source molecular beam epitaxy

We describe the design and experimental results for high-power, high-efficiency, low threshold current, 0.98-μm wavelength, broadened waveguide (BW) aluminum-free InGaAs-(In)GaAs(P)-InGaP lasers. The decrease in the internal losses with an increase in the width of the waveguide layer for a separate-confinement heterostructure multiple-quantum-well (SCW-MQW) structure is attributed to lower free-carrier absorption due to the reduced overlap of the optical mode with the highly doped cladding regions. The BW lasers grown with both InGaAsP and GaAs waveguides show lower internal losses and similar threshold currents than those designed for an optimum optical confinement factor within the QW region. We report a record-low internal loss of 1.8±0.2 cm^-2 for (In)GaAs(P)-InGaP lasers grown by gas-source molecular beam epitaxy (GSMBE). The temperature dependence of internal loss suggests that optical loss from free-carrier absorption in the waveguide dominates at T>40°C, while near room temperature, the residual loss is attributed to scattering and free-carrier absorption in the QW´s. The relative insensitivity of internal loss near room temperature has enabled the use of a simplified InGaAs-GaAs-InGaP BW structure to achieve very high CW and quasi-CW (QCW) power operation. We report the highest CW output power of 6.8 W for a GaAs-InGaP laser, and the highest quasi-continuous output power of 13.3 W measured for a single 100-μm-wide aperture, 0.8-0.98-μm wavelength Al-free laser diode grown by GSMBE