Inhibition of Linear Absorption in Opaque Materials Using Phase-Locked Harmonic Generation

Dipartimento di Energetica, University of Rome La Sapienza, Via Scarpa 16, Rome, Italy.
Physical Review Letters (Impact Factor: 7.51). 10/2008; 101(11):113905. DOI: 10.1103/PhysRevLett.101.113905
Source: PubMed

ABSTRACT We theoretically predict and experimentally demonstrate inhibition of linear absorption for phase and group velocity mismatched second- and third-harmonic generation in strongly absorbing materials, GaAs, in particular, at frequencies above the absorption edge. A 100-fs pump pulse tuned to 1300 nm generates 650 and 435 nm second- and third-harmonic pulses that propagate across a 450-microm-thick GaAs substrate without being absorbed. We attribute this to a phase-locking mechanism that causes the pump to trap the harmonics and to impress on them its dispersive properties.

Download full-text


Available from: Joseph W Haus, Sep 28, 2015
21 Reads
  • Source
    • "The formation of filaments in the interaction of femtosecond laser pulses with homogeneous transparent media such as gases and liquids, is a common phenomenon and is well understood [1] [2] [3] [4] [5] [6]. One of the specific features of this interaction is the absence of a second harmonic of the laser frequency due to the lack of second order nonlinear optical interactions in centro-symmetric media [7]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We show that a spectral resonance between the π→π<sup>*</sup> absorption band in liquid benzene and the third harmonic (TH) of a propagating 800 nm femtosecond laser beam causes large positive changes in the real refractive index at the TH wavelength. This produces an increase in the third-order optical susceptibility and leads to the enhancement of nonlinear optical effects including TH generation and self-focusing. Enhanced filamentation is observed in liquid benzene, but this effect is not seen in perdeuterated liquid benzene under similar irradiation conditions. Filamentation is associated with the decomposition of benzene molecules, plasma emission from the focal region, and the appearance of carbon nanoparticles. This indicates that a complex chemistry accompanies the onset of filamentation. Chemical products formed under these conditions have been characterized using combined gas chromatography mass spectroscopy techniques. We also find that the presence of a TH filament is indicated by the appearance of a photocurrent and increased electrical conductivity in the solution. This photocurrent is found to be 50-60 times smaller in C<sub>6</sub>D<sub>6</sub> where the π→π<sup>*</sup> resonance with the TH is much weaker. The intensity dependence of this photocurrent confirms the role played by TH generation in the overall interaction.
    Applied Optics 11/2013; 52(33):8169-75. DOI:10.1364/AO.52.008169 · 1.78 Impact Factor
  • Source
    • "In fact, the PL component displays the same propagation properties (absorption and phase) as the fundamental wavelength [5]. Thus, the PL component survives even if the material at the SH wavelength is characterized by huge absorption, in either bulk or cavity environments [6], provided the pump is tuned to a region of relative transparency. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a study on nonlinear optical processes in GaAs gratings, made by perforating a single layer of GaAs with very narrow slits. Large enhancement of conversion efficiency, for both second and third harmonic generation, is predicted when a TE-polarized pump field excites the guided mode resonances of the grating. At the onset of these modes the spectrum near the pump wavelength shows abrupt changes of linear transmission and reflection that follow a typical Fano-like shape. Under these circumstances, the grating provides dramatic enhancement of local fields and fosters favorable conditions for harmonic generation processes, even in regimes of strong linear absorption at the harmonic wavelengths. In a GaAs grating pumped at 1064nm, we predict second (532nm) and third (354nm) harmonic conversion efficiencies several orders of magnitude larger than conversion rates achievable in either bulk or etalon structures made of the same material. These efficiencies are not influenced by linear absorption, and they are unrelated to grating thickness. We discuss the influence of self-phase modulation on the harmonic generation conversion efficiencies. Finally, we also analyze self phase modulation effects on resonant gratings tuning the input signal at guided mode resonances, demonstrating the possibility of triggering optical bistability at relatively low switching intensities.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2011; DOI:10.1117/12.893696 · 0.20 Impact Factor
  • Source
    • "Beyond this, the INH-SH behavior is completely general and possible devices could be designed by choosing more appropriate materials, such as polymers, to outperform GaAs given the potential for much higher nonlinear coefficients [18]. Finally, these results are easily extended to third harmonic generation, as shown in references [15] [16] [17]. In this particular case the cavity was not optimized for third harmonic generation, which happened to be tuned inside the band gap of the stack. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this letter we experimentally demonstrate second harmonic conversion in the opaque region of a GaAs cavity with efficiencies of the order of 0.1% at 612nm, using 3ps pump pulses having peak intensities of order of 10MW/cm2. We show that the conversion efficiency of the inhomogeneous, phase-locked second harmonic component is a quadratic function of the cavity factor Q.
Show more