Linewidth enhancement in spasers and plasmonic nanolasers

Area of Science:

• Plasmonics
• Nanolasers
• Quantum Optics

Background:

• Spasers (surface plasmon amplification by stimulated emission of radiation) function as coherent near-field generators and nanolasers.
• Experimental demonstrations confirm the viability of nanoscale plasmonic resonators for spaser applications.

Purpose of the Study:

• To establish a theoretical framework for describing the linewidth of active plasmonic structures, specifically addressing linewidth enhancement.
• To quantify the linewidth enhancement factor in semiconductor gain media for spasers.

Main Methods:

• Introduced time dependence into the quasistatic description of localized surface plasmon resonances.
• Incorporated the dispersion of the spectral parameter defining resonant frequency.
• Estimated the linewidth enhancement factor for a semiconductor gain medium.

Main Results:

• Developed a theoretical framework for spaser linewidth, including resonator noise effects.
• Quantified the linewidth enhancement factor for semiconductor gain media, finding values of 3 to 6.
• Observed linewidth broadening exceeding an order of magnitude compared to Schawlow-Townes predictions.

Conclusions:

• Linewidth enhancement due to resonator noise significantly impacts spaser performance.
• The developed theoretical framework provides crucial insights into the fundamental linewidth limitations of nanolasers.
• Findings highlight the importance of carrier density in active layers for controlling linewidth broadening in spasers.