Femtosecond nanofocusing with full optical waveform control.

Area of Science:

• Optics and Photonics
• Nanotechnology
• Ultrafast Science

Background:

• Simultaneous nanometer spatial confinement and femtosecond temporal control of optical excitation remain a significant challenge.
• Previous methods using surface plasmon polaritons (SPPs) faced limitations like mode mismatch and laser phase dependence.

Purpose of the Study:

• To develop a method for achieving highly localized optical excitation with precise temporal control.
• To overcome the limitations of existing techniques for nanoscale optical manipulation.

Main Methods:

• Utilized a conical noble metal tip for intrinsic phase- and amplitude-independent nanofocusing.
• Employed spectral pulse shaping and feedback on second-harmonic response for waveform control.
• Leveraged weak wavelength dependence over a broad bandwidth for robust nanofocusing.

Main Results:

• Achieved 10 nm spatial and few-femtosecond temporal confinement of optical excitation.
• Demonstrated deterministic arbitrary optical waveform control.
• Showcased high-efficiency nanofocusing via continuous micro- to nanoscale mode transformation.

Conclusions:

• The nanofocusing tip offers a powerful platform for controlling light at the nanoscale.
• Enables spectroscopy of elementary optical excitations on their natural length and time scales.
• Opens avenues for ultrafast nano-opto-electronics and single-molecule quantum coherent control.