Third-harmonic generation in an elliptical-core ZBLAN fluoride fiber

Area of Science:

• Nonlinear Optics
• Materials Science
• Photonics

Background:

• Fluoride fibers, particularly ZBLAN, are promising for nonlinear optical applications due to their unique transmission properties.
• Third-harmonic generation (THG) is a key nonlinear optical process for frequency conversion, enabling the generation of shorter wavelengths from longer ones.

Purpose of the Study:

• To demonstrate third-harmonic generation (THG) in an elliptical-core ZBLAN fluoride fiber for the first time.
• To investigate the effect of fiber length on THG performance, specifically extinction ratios.
• To explore the tunability of THG by varying the pump wavelength.

Main Methods:

• Utilizing an elliptical-core ZBLAN fluoride fiber.
• Pumping the fiber with a pulsed laser at 1560 nm to achieve THG around 523 nm.
• Measuring average and peak power extinction ratios for different fiber lengths (10 m and 35 cm).
• Employing an optical parametric oscillator (OPO) to achieve tunable THG (605–740 nm) by varying pump wavelengths (1800–2200 nm).

Main Results:

• Successful demonstration of linearly polarized THG around 523 nm in elliptical ZBLAN fiber.
• Observed improved extinction ratios (average power ~11.1 dB, peak power ~12.6 dB) with a shorter fiber length (35 cm) compared to a 10 m fiber.
• Achieved tunable THG spanning 605–740 nm using a tunable OPO as the pump source.

Conclusions:

• Elliptical-core ZBLAN fiber is a viable platform for efficient third-harmonic generation.
• Fiber length plays a critical role in optimizing THG extinction ratios, with shorter lengths yielding better results.
• The demonstrated tunable THG capability opens possibilities for various photonic applications requiring wavelength flexibility.