Quantitative-phase microscopy of nanosecond laser-induced micro-modifications inside silicon

Area of Science:

• Materials Science
• Optics
• Nanotechnology

Background:

• Laser-induced permanent modifications in silicon are a recent advancement.
• These modifications are achieved using tightly focused nanosecond lasers at 1550 nm wavelength.

Purpose of the Study:

• To characterize laser-induced modifications deep within silicon.
• To quantify the associated refractive index variations.

Main Methods:

• Development of a quantitative-phase microscope operating in the near-infrared (NIR) domain.
• Systematic variation of laser pulse count and energy to induce and analyze modifications.

Main Results:

• Observation of both porous and densified regions within the silicon's focal region.
• Measured refractive index variations (|Δn|) exceeding 10^-3.

Conclusions:

• The observed refractive index changes are significant enough for practical applications.
• Enables the laser writing of optical functionalities directly inside silicon.