Nano-lasing from Zn-doped GaAs nanowires on Iron (Fe) substrate*

We investigated optically pumped lasing from highly zinc-doped GaAs nanowires (NWs) on an iron (Fe) substrate at 5 K cryostat temperature. The conically shaped GaAs NWs possess an 8 nm thick Al₂O₃ layer around it to reduce Schottky band-banding. The NWs were optically excited with 150 fs laser pulses generated from Ti-Sapphire centered at a wavelength of 720 nm. The lasing output versus excitation power (L-L) of the lasing NWs shows the characteristic S shaped curve. Lasing NWs on Fe have a length of more than 4 µm with tip and base diameters of ~300 and~500 nm, respectively. Shorter NWs did not provide sufficient modal gain to exceed the plasmonic losses in the Fe film. The emission spectrum reveals two or three longitudinal modes, which resonate within the gain spectrum. The threshold power for NW lasers on Fe substrate were higher than for NWs on Au or glass due to significantly higher losses in the Fe film. FDTD simulations reveal that the hybrid plasmonic mode of lasing NWs on Fe has a predominantly photonic character. In a further step, we will investigate if an applied magnetic field influences the lasing behavior in GaAs NWs on Fe substrate.