5mm long broad-area lasers at 976nm with 65 wall-plug efficiency

摘要

Especially for pump applications there is a strong demand for broad-area (BA) diode lasers with high-brightness. Brightness is proportional to output power divided by near and far field widths in both directions. Therefore to achieve a high-brightness broad-area laser, high output power together with high wall-plug efficiencies and a strong reduction of the beam waists in both directions is essential. Whereas fast axis far fields show mostly a current independent behaviour, near- and far-fields in the slow axis suffer from a strong current and temperature dependence, limiting the brightness of broad-area lasers. To fulfill these issues, we have realized MBE grown InGaAs/AlGaAs high-brightness broad-area diode lasers with a resonator length of 5mm and a stripe width of 90μm to guarantee good heat dissipation. The emitting wavelength is 976nm. Single emitters have been mounted p-side down. An output power of 10W has been achieved at 9.8A. A wall-plug efficiency of 65% has been measured. To our knowledge, for a 5mm long device, this is the highest wall-plug efficiency reported so far. To evaluate the brightness of these broad-area lasers, near-fields and far fields in both directions have been carefully investigated. The design of the vertical structure of the broad-area lasers results in a far field angle of 45° in the fast axis (95% power inclusion). In the slow-axis values of 6.5° at 8.5W and 8° at 10W have been demonstrated, which results in a brightness doubled in comparison to state-of-the-art broad-area diode lasers.