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

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Nanotechnology

Background:

• Microdisk lasers offer compact and efficient light sources.
• Controlling radial modes in microdisk lasers is crucial for specific applications.
• Indium arsenide (InAs) quantum dots are promising gain media for lasers.

Purpose of the Study:

• To investigate the effect of focused ion beam (FIB) etched radial grooves on InAs quantum dot microdisk lasers.
• To demonstrate the suppression of specific radial modes using surface gratings.
• To analyze the impact on mode spacing and quality factor.

Main Methods:

• Fabrication of InAs quantum dot microdisk lasers.
• Surface modification using focused ion beam (FIB) etching to create radial grooves.
• Optical pumping and spectral analysis at cryogenic temperatures (78 K).
• Numerical simulations for mode analysis.

Main Results:

• Radial grooves effectively suppress specific radial modes of the microdisk laser.
• Complete suppression of higher-order radial modes, leaving only the fundamental mode, was achieved.
• A sixfold increase in mode spacing (from 2.5 nm to 15.5 nm) was observed for an 8 μm diameter microdisk.
• The dominant mode quality factor remained largely unaffected by the etching process.
• Experimental results showed good agreement with numerical simulations.

Conclusions:

• Focused ion beam etching of radial grooves is a viable method for controlling and enhancing mode selectivity in InAs quantum dot microdisk lasers.
• This technique allows for precise tuning of laser output characteristics, including mode spacing and suppression.
• The demonstrated method offers a pathway to developing advanced microcavity laser devices with tailored spectral properties.