Femtosecond optical harmonic generation as a non‐linear spectroscopic probe for carbon nanotubes

Abstract

Second-and third-harmonic generation in single-wall carbon nanotube layers produced by low-velocity spraying was studied experimentally with the use of amplified 75 fs pulses of Cr : forsterite laser radiation within the range of pump pulse intensities up to the breakdown threshold. Harmonic-generation processes are shown to be ideally suited for the non-linear spectroscopy and structure analysis of carbon nanotubes, in many ways supplementary to Raman spectroscopy. The second-and third-harmonic yields scale as quadratic and cubic functions, respectively, of the pump pulse energy up to pump intensities of 10 12 W cm −2 , indicating the perturbative regime of non-linear-optical interactions and suggesting a convenient calibration for the second and third harmonics employed as spectroscopic probes. Comparison of harmonicgeneration data with absorption spectra of carbon-nanotube layers reveals an important role of quantum confinement effects in the non-linear coherent scattering of light from carbon nanotubes. Femtosecond pulses of Cr : forsterite laser radiation also generate the fifth optical harmonic at 251 nm in the glass substrate of carbon-nanotube samples, which can be employed for UV spectroscopy and subwavelength-resolution non-linear microscopy of carbon nanotubes.

Harmonic generation in laser-produced plasmas containing atoms, ions and clusters: a review

“…Third harmonic generation was observed in both samples, while second harmonic generation was observed only from the sample grown by the catalyst-free method. Evidence for second-order nonlinear optical activity in CNTs has also been demonstrated in a second harmonic generation experiment performed at femtosecond time scale [146]. These works revealed the low-order nonlinear optical properties of nanotubes.…”

Ultrafast Switching Time and Third Order Nonlinear Coefficients of Microwave Treated Single Walled Carbon Nanotube Suspensions

“…[4][5][6] Quantum confinement of -electrons 7 along the tube axis makes nanotubes one of the most promising materials with a large and ultrafast electronic third-order nonlinearity to be used in applications in terahertz optical switching for next generation ultrafast communication systems and passive mode-locking for the generation of femtosecond pulses. Thus the investigations of the nonlinearity and optical switching of SWNT using femtosecond pulses garner recent interests.…”

Finite length effects on first hyperpolarizability tensor for chiral carbon nanotubes with application to second harmonic far‐field radiation pattern

“…[1] to finite length structures. The here-presented results hold for an exciting laser beam not exceeding an intensity of 3 × 10 11 W/cm 2 , which is of the order of the experimental value used to generate SH in CNT samples [19] at femtosecond time regime. For larger intensities, the circumferential nature of the second-order induced current density should be considered, and the here-adopted Cartesian representation of the β tensor replaced by a representation in suitable curvilinear coordinates.…”