Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation

Area of Science:

• Nonlinear optics
• Photonics
• Ultrafast spectroscopy

Background:

• Cherenkov radiation is a known phenomenon in nonlinear optics.
• Nonlinear photonic crystal fibers (NPCFs) are used for generating supercontinuum and other optical effects.
• Ultrafast laser sources are crucial for various scientific applications.

Purpose of the Study:

• To demonstrate spectrally-isolated narrowband Cherenkov radiation as an ultrafast optical source.
• To extend the tuning range of ultrafast optical sources into the visible spectrum.
• To achieve efficient pump-to-signal conversion and suppress supercontinuum generation.

Main Methods:

• Utilizing commercial nonlinear photonic crystal fibers.
• Pumping with a femtosecond Ti:sapphire laser.
• Carefully selecting fiber parameters and pumping conditions.

Main Results:

• Achieved spectrally-isolated narrowband Cherenkov radiation with a visible tuning range of 485-690 nm.
• Extended the near-infrared tuning range (690-1020 nm) of the Ti:sapphire pump laser.
• Demonstrated pump-to-signal conversion efficiency routinely surpassing 10%.
• Enabled multimilliwatt visible output across the entire tuning range.
• Successfully suppressed supercontinuum generation.

Conclusions:

• Spectrally-isolated narrowband Cherenkov radiation from NPCFs is a viable ultrafast optical source.
• This technique complements existing ultrafast sources by providing tunable visible light.
• High conversion efficiency and suppressed supercontinuum generation make this method practical for applications.