Appl. Phys. Lett. 104, 251101 (2014)

Powerful semiconductor sources of broadband light are useful for sensing, spectroscopy and biomedical imaging schemes such as optical coherence tomography. Although LEDs and superluminescent diodes offer broadband emission, their output powers are usually limited, which restricts applications. Now, a team from China and Scotland report that an InGaAs/GaAs quantum well laser could be a more powerful alternative. Their device emits up to 50 mW of pulsed 1.06 μm light with a large spectral bandwidth of 38 nm. The device was fabricated using metal organic chemical vapour deposition and, contrary to conventional laser diodes and LEDs, it features two additional elements above the active layer of the quantum well — a GaAs tunnel junction for electrons and a GaAs heterostructure. These additions help improve the temperature stability and optical gain of the laser. The design may also prove useful for realizing devices that suit mode-locking for short-pulse generation, or offer tunable or multiple wavelength operation. However, the team says that more theoretical modelling and analysis is required.