Parameter optimization of hollow-core optical fiber phase modulators

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Photothermal phase modulators are crucial for optical signal processing.
• Hollow-core fibers offer unique properties for gas-based light-matter interactions.

Purpose of the Study:

• To investigate the impact of gas concentration, buffer gas, fiber length, and fiber type on the performance of acetylene-filled hollow-core fiber photothermal phase modulators.
• To optimize modulator performance for enhanced phase modulation and bandwidth.

Main Methods:

• Systematic study of varying acetylene (C2H2) concentrations and buffer gases (Argon).
• Performance evaluation using anti-resonant and photonic bandgap hollow-core fibers of different lengths.
• Measurement of phase modulation depth, frequency response, and switching times.

Main Results:

• Argon as a buffer gas yielded the highest phase modulation for a given control power.
• An optimal C2H2 concentration was identified for maximizing phase modulation at a fixed fiber length.
• A 23-cm anti-resonant hollow-core fiber modulator achieved π-rad phase modulation at 100 kHz with 200 mW control power.
• Modulation bandwidth was extended to ~1.1 MHz using a photonic bandgap hollow-core fiber, with rise/fall times under 0.6 µs.

Conclusions:

• Optimized gas mixtures and hollow-core fiber types significantly enhance photothermal phase modulator performance.
• Photonic bandgap hollow-core fibers demonstrate superior modulation bandwidth compared to anti-resonant types.
• The study provides critical insights for designing high-performance optical fiber phase modulators.