Mid-infrared supercontinuum generation in As2S3-silica "nano-spike" step-index waveguide

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Generating broad-band mid-infrared supercontinuum spectra is crucial for various spectroscopic and metrology applications.
• Chalcogenide waveguides offer unique nonlinear optical properties suitable for supercontinuum generation.

Purpose of the Study:

• To demonstrate efficient generation of a broad-band mid-infrared supercontinuum spectrum.
• To utilize a novel nano-spike structure for efficient light coupling into sub-wavelength waveguides.

Main Methods:

• Fabrication of an arsenic trisulphide waveguide embedded in silica with a specialized nano-spike for light injection.
• Launching ultrashort pulses (65 fs, 2 µm wavelength) from a Tm-doped fiber laser into the sub-wavelength waveguide.
• Characterization of the generated supercontinuum spectrum using nonlinear optical processes like soliton fission and dispersive wave generation.

Main Results:

• Achieved high launch efficiency (~12%) into a 1 µm diameter chalcogenide waveguide using the nano-spike.
• Generated a broad supercontinuum spectrum spanning from 2 µm to almost 4 µm.
• Observed efficient spectral broadening with low launched energies (18 pJ).

Conclusions:

• The developed nano-spike approach enables efficient light coupling into sub-wavelength chalcogenide waveguides.
• The generated broad-band mid-infrared supercontinuum spectrum is promising for applications in metrology and infrared spectroscopy.