Femtosecond Optical Kerr Shutter Research Articles

Ultrafast lasing due to electron–hole plasma in ZnO nano-multipods

Dynamics of stimulated emission and ultrafast lasing in ZnO nano-multipods has beeninvestigated with a femtosecond optical Kerr shutter technique. Under band-to-bandexcitation with high density, stimulated emission is observed around 395–400 nm witha mode-like structure. The stimulated emission emerges with an onset time of∼2 ps and then the intensity gradually decreases with time having a blue-shift and a spectralnarrowing. The characteristics of the blue-shift and spectral narrowing suggest that notonly recovery of bandgap renormalization but also conversion from an electron–hole plasma(EHP) state to high density excitonic state takes place as the carrier density decreases dueto recombination of electrons with holes. The mode-like structure observed stronglyindicates that a high quality resonant cavity is formed between the two facets toward theleg length direction of individual nano-multipod. These results show that the ultrafastlasing observed around 395–400 nm in ZnO nano-multipods comes from populationinversion in the EHP regime. We also found that the initial carrier distribution ofthe EHP regime in nano-multipods is much wider than that in ZnO thin films,implying that the carrier diffusion might be suppressed by their nano-size structure.

Polarization dependence of optical Kerr effect in metallophthalocyanine-doped inorganic–organic hybrid materials

Ultrafast optical Kerr effect of metallophthalocyanine-doped inorganic–organic materials was investigated using a femtosecond optical Kerr shutter at wavelength of 800 nm. Experimental results showed that the dependence of the Kerr signals on the polarization angle between the pump beam and the probe beam could be controlled by changing the pump-probe intensity ratio. The pump-intensity dependence of the polarization characters of the Kerr signals probably arose from the contribution of light induced transient grating (LITG) to the Kerr signals.

Femtosecond laser-induced birefringence and transient grating in lead(II) phthalocyanine-doped hybrid silica gel glasses

Ultrafast nonlinear optical properties of lead(II) phthalocyanine (PbPc)-doped silica gel glasses were investigated using a femtosecond optical Kerr shutter (OKS) setup at wavelength of 800 nm. The nonlinear response time of the PbPc-doped silica gel glasses was measured to be less than 90 fs. Measurements for the dependence of Kerr signals on the polarization angle between pump and probe beams showed that the Kerr signals induced by 30-fs pulses arose mainly from photoinduced birefringence effect and not from a laser-induced transient grating as observed when using a 200-fs pulse laser.

Ultrafast nonlinear optical properties of Bi 2O 3–B 2O 3–SiO 2 oxide glass

The ultrafast nonlinear optical properties of Bi 2O 3–B 2O 3–SiO 2 oxide glass were investigated using a femtosecond optical Kerr shutter (OKS) at wavelength of 800 nm. The nonlinear response time of this Bi 2O 3-doped glass was measured to be <90 fs. The nonlinear refractive-index n 2 was estimated to be 1.6 × 10 −14 cm 2/W. Measurements for the dependence of Kerr signals on the polarization angle between the pump and probe beams showed that the Kerr signals induced by 30-fs pulse laser arose mainly from the photoinduced birefringence effect.

Mechanism of a Terahertz Optical Kerr Shutter with a Gold Nanoparticle System

We observed an ultrafast response as fast as 240 fs in a gold nanoparticle system, in a femtosecond optical Kerr shutter experiment. We successfully demonstrate 2.5 THz optical switching. The ultrafast response of the Kerr signal is explained by a simple model taking into account the self-diffraction of the pump pulse by the generated transient grating.

Efficient femtosecond optical Kerr shutter

Conjugated molecules, with large optical nonlinearities, are tested as materials usable for femtosecond optical Kerr shutter technique. With β-carotene, in acetone solution, we have achieved responses limited by the 100-fs width of the optical pulses and characterized by a resolution better than 1 ps with a dynamic range of 100.