Optical Sensitivity of Waveguides Inscribed in Nanoporous Silicate Framework

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Laser direct writing is crucial for fabricating optical waveguides in photonic devices.
• Porous glass (PG) offers unique nanoporous optical material properties for enhanced sensing capabilities.

Purpose of the Study:

• To fabricate waveguides in porous glass using femtosecond laser direct writing.
• To investigate the sensing potential of these waveguides for detecting small objects and molecules.

Main Methods:

• Femtosecond laser pulses in densification mode were used for single-scan waveguide fabrication in PG.
• Optical properties, including refractive index contrast and insertion loss, were experimentally quantified.
• Waveguide response to ethanol molecules and its response time were monitored.

Main Results:

• Three types of waveguides were fabricated with a refractive index contrast up to 1.2·10⁻² and ~1.2 dB/cm insertion loss.
• Waveguides demonstrated sensitivity to ethanol molecules, indicating penetration into the nanoporous cladding.
• A response time of 6 seconds was measured for waveguides buried 400 µm deep, with a minimum detectable refractive index change of 2 × 10⁻⁴.

Conclusions:

• Waveguides inscribed in porous glass via laser direct writing are suitable for sensor applications.
• The nanoporous structure enhances waveguide sensitivity, enabling detection of molecular infiltration.
• These results establish PG waveguides as promising primary transducers for advanced sensor development.