Analysis of germanium waveguide laser performance under external phonon injection

Area of Science:

• Photonics
• Materials Science
• Quantum Optics

Background:

• Integrated photonics requires efficient light sources.
• Germanium (Ge) waveguide lasers offer potential but face challenges with high thresholds.
• Photon-phonon interactions are a promising avenue for laser performance enhancement.

Purpose of the Study:

• To design and analyze a germanium waveguide laser utilizing external phonon injection.
• To investigate the role of phononic crystal waveguides in enhancing acousto-optic interaction.
• To determine optimal parameters for reducing laser threshold and improving slope efficiency.

Main Methods:

• Development of photon-phonon laser action theory considering external phonon injection and acousto-optic overlap.
• Introduction of a phononic crystal waveguide to intensify acousto-optic interaction.
• Analysis of photon-phonon laser action characteristics in germanium waveguides.

Main Results:

• External phonon injection facilitates two-quantum transitions, enabling photon-phonon laser action.
• Optimal waveguide parameters were identified to maximize optical and acoustic field overlap.
• A 200 μm Ge waveguide with 2.5 × 10^21 cm^-3 phonon injection achieved a threshold current of 0.2 μA and slope efficiency of 0.7 W/A.

Conclusions:

• External phonon injection is an effective method to reduce the threshold of germanium waveguide lasers.
• Phononic crystal waveguides enhance acousto-optic interaction, crucial for photon-phonon laser action.
• The proposed scheme provides a viable pathway for achieving efficient laser oscillation in integrated germanium waveguides.