Generation of 7W nanosecond pulses with 670nm ridge-waveguide lasers

The aim of this paper is to present detailed experimental and theoretical investigations of the behavior of ridge-waveguide (RW) lasers emitting at 670 nm under injection of sub-ns current pulses with high amplitudes. The RW lasers are based on strained GaInP double quantum wells embedded in an asymmetric AlGaInP/AlInP waveguide structure. The width of the ridge is 15 μm and the cavity length 3 mm. The laser diode is mounted on an in-house developed laser driver with a final stage based on GaN transistors, which generates nearly rectangular shaped current pulses with amplitudes up to 30 A and widths down to 300 ps. The pulse width can be varied electronically between 300 ps and 1.2 ns with a repetition frequency up to 1 MHz, which results in a variation of the pulse width of the emitted optical pulses between 200 ps and 1.2 ns. The maximum pulse power depends on the electrical pulse width and reaches 7.2 W for a ridge width of 15 μm. At high pulse current amplitudes the pulse power saturates. Time-dependent simulations with the drift-diffusion simulator WIAS-TeSCA reveal that accumulation of excess electrons under the ridge is the root cause for the power saturation, limiting the maximum achievable output power.