Second-harmonic generation using gratings optically written by mode interference in poled optical fibers.

Area of Science:

• Nonlinear optics
• Materials science
• Optical engineering

Background:

• Second-order nonlinear optical effects are crucial for frequency conversion in photonics.
• Inducing stable and efficient nonlinear gratings in optical fibers remains a challenge.
• Mode interference offers a potential mechanism for grating inscription.

Purpose of the Study:

• To investigate the induction of second-order nonlinear susceptibility gratings in optical fibers.
• To achieve efficient second-harmonic generation (SHG) across a broad range of infrared wavelengths.
• To explore the role of mode interference and electric poling in grating formation.

Main Methods:

• Utilizing mode interference of high-intensity blue light within optical fibers.
• Applying an external DC electric poling field during the inscription process.
• Characterizing the induced gratings and their second-harmonic generation efficiency.

Main Results:

• Successfully induced second-order nonlinear susceptibility gratings in optical fibers.
• Demonstrated efficient second-harmonic generation for arbitrary infrared design wavelengths.
• Established a correlation between blue light mode interference, electric poling, and grating properties.

Conclusions:

• Mode interference of blue light, combined with electric poling, is an effective method for creating nonlinear gratings in optical fibers.
• The developed technique enables versatile and efficient frequency conversion for infrared light.
• This work advances the fabrication of nonlinear optical components for integrated photonics.