Single-mode laser action in quantum cascade lasers with spiral-shaped chaotic resonators

Abstract

The authors have fabricated and characterized quantum cascade lasers with spiral-shaped microresonators. The lasers operate in pulsed mode at room temperature with peak optical power greater than 20mW and in continuous wave at temperatures up to 125K. They exhibit single-mode emission in both pulsed mode and continuous wave operation, with a 30dB side-mode suppression ratio at injection currents well above threshold. Subthreshold spectral measurements indicate that the spiral cavities support whispering-gallery-like modes. Single-mode lasing occurs on one of these modes. Far-field profiles reveal enhanced directionality compared to microdisk lasers.