Ultra-low mode volume on-substrate silicon nanobeam cavity

Area of Science:

• Photonics
• Materials Science
• Nanotechnology

Background:

• Photonic crystal (PhC) cavities are crucial for light manipulation.
• Existing on-substrate nanobeam cavities have limitations in mode volume and Q factor.
• Enhanced light confinement is key for improving PhC cavity performance.

Purpose of the Study:

• To design and fabricate an on-substrate bowtie PhC cavity in silicon.
• To achieve ultra-low mode volume and ultra-high quality (Q) factor.
• To investigate the impact of bowtie shape optimization on light confinement.

Main Methods:

• Designing bowtie shapes within PhC unit cells for electric field confinement.
• Fabricating the on-substrate bowtie PhC cavity in silicon.
• Simulating and experimentally measuring the Q factor and mode volume.
• Observing thermo-optic bistability to confirm light confinement.

Main Results:

• Achieved an ultra-low mode volume of approximately 0.1(λ/n_Si)³.
• Predicted an ultra-high Q factor of up to 10⁶ via simulation.
• Experimentally measured a Q factor of up to 1.4×10⁴.
• Observed pronounced thermo-optic bistability, confirming strong light confinement.

Conclusions:

• The designed bowtie PhC cavity demonstrates significantly improved light confinement compared to previous designs.
• The achieved ultra-low mode volume and high Q factor open possibilities for advanced photonic devices.
• The results validate the effectiveness of bowtie shape optimization for enhancing PhC cavity performance.