Mode selection in InAs quantum dot microdisk lasers using focused ion beam technique

TL;DR

This study demonstrates how focused ion beam etching of grooves on InAs quantum dot microdisk lasers can selectively suppress radial modes, enhancing mode spacing and maintaining laser quality, with both experimental and simulation validation.

Contribution

It introduces a method to control mode selection in quantum dot microdisk lasers using focused ion beam surface modification, achieving selective mode suppression.

Findings

Radial grooves suppress specific radial modes depending on their length.

Total suppression of all but the fundamental radial mode is achieved.

Mode spacing increases six-fold from 2.5 nm to 15.5 nm without quality loss.

Abstract

Optically pumped InAs quantum dot microdisk lasers with grooves etched on their surface by a focused ion beam is studied. It is shown that the radial grooves, depending on their length, suppress the lasing of specific radial modes of the microdisk. Total suppression of all radial modes except for the fundamental radial one is also demonstrated. The comparison of laser spectra measured at 78 K before and after ion beam etching for microdisk of 8 $\mu$m in diameter shows a six-fold increase of mode spacing, from 2.5 nm to 15.5 nm, without significant decrease of the dominant mode quality factor. Numerical simulations are in good agreement with experimental results.