Femtosecond filamentation and supercontinuum generation in bulk silicon

Area of Science:

• Nonlinear Optics
• Condensed Matter Physics
• Laser Physics

Background:

• Mid-infrared (mid-IR) femtosecond lasers are crucial for nonlinear optics.
• Silicon's nonlinear optical properties are being explored for novel light generation.
• Filamentation and supercontinuum generation are key nonlinear optical phenomena.

Purpose of the Study:

• To experimentally investigate filamentation and supercontinuum generation in bulk silicon.
• To study the impact of multi-photon absorption on these processes using mid-IR pulses.
• To characterize the spectral and spatiotemporal properties of the generated supercontinuum.

Main Methods:

• Utilized femtosecond mid-IR pulses with wavelengths from 3.25 to 4.7 μm.
• Employed bulk silicon crystals as the nonlinear medium.
• Performed spectral measurements and recorded spatiotemporal intensity distributions of filaments.

Main Results:

• Observed stable filamentation and supercontinuum generation.
• Demonstrated octave-spanning supercontinuum from 2.5 to 5.8 μm with 4.7 μm input pulses.
• Identified pulse splitting after the nonlinear focus, consistent with theoretical models.

Conclusions:

• Bulk silicon supports efficient supercontinuum generation via filamentation with mid-IR pulses.
• Multi-photon absorption plays a significant role in the observed nonlinear processes.
• The results highlight silicon's potential for broadband light generation in the mid-IR.