A feedback insensitive laser is a prerequisite for a desirable laser source for silicon photonic integration, as it is not possible to include an on-chip optical isolator. This work investigates the feedback insensitivity of an InAs/GaAs quantum dot laser epitaxially grown on an Si (001) substrate by operating in a sole excited state. The experimental results show that the sole excited-state lasing InAs quantum dot lasers on Si are less sensitive to external optical feedback than both Fabry-Perot and distributed-feedback quantum-well lasers. By comparing the laser behavior under different feedback levels, sole excited-state InAs quantum dot lasers on Si exhibit at least a 28 dB stronger feedback tolerance than quantum-well lasers. This result proposes a possible route for a high feedback insensitive laser as an on-chip light source towards Si waveguide integration with the absence of an optical isolator.
Lasing due to the excited state in quantum dot lasers
