Backward phase-matching for nonlinear optical generation in negative-index materials

Abstract

Metamaterials have enabled the realization of unconventional electromagnetic properties not found in nature, which provokes us to rethink the established rules of optics in both the linear and nonlinear regimes. One of the most intriguing phenomena in nonlinear metamaterials is 'backward phase-matching', which describes counter-propagating fundamental and harmonic waves in a negative-index medium. Predicted nearly a decade ago, this process is still awaiting a definitive experimental confirmation at optical frequencies. Here, we report optical measurements showing backward phase-matching by exploiting two distinct modes in a nonlinear plasmonic waveguide, where the real parts of the mode refractive indices are 3.4 and -3.4 for the fundamental and the harmonic waves respectively. The observed peak conversion efficiency at the excitation wavelength of ∼780 nm indicates the fulfilment of the phase-matching condition of k(2ω) = 2k(ω) and n(2ω) = -n(ω), where the coherent harmonic wave emerges along a direction opposite to that of the incoming fundamental light.

Metawaveguide for Asymmetric Interferometric Light-Light Switching

“…Here, a relatively small value of δ ¼ 2 was chosen to obtain a reasonable transmission efficiency and ensure that fabrication imperfections do not make the system deviate strongly from the designed CPA condition. We find that the intensity ratio ξ is given by ðδ þ 1Þ=ðδ − 1Þ, leading to ξ of 3∶1 between the strong signal beam and the weak control beam [33], which is in contrast to the previous approaches of controlling light with light using both linear and nonlinear strategies [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”

“…DOI: 10.1103/PhysRevLett.117.193901 Effective light-light switching promises optical information processing, which has been a long-standing driving force for high-speed and energy-efficient optical networks. Strong optical modulations are initiated in nonlinear optical media by intense laser fields to enable switching of a weak signal, for example, intensity modulation of light by light has been demonstrated based on the all-optical Kerr effect [1][2][3][4][5][6]. Nevertheless, the high power requirement for the intense control or pump light becomes a significant barrier for practical applications.…”

Coupling Surface Plasmon Polariton Modes to Complementary THz Metasurfaces Tuned by Inter Meta‐Atom Distance

“…These insights are crucial for the correct design of efficient complementary metasurfaces for research [11][12][13] and applications for example as narrow band filters [24] or sensing. The exchange of the role of metal and vacuum for the complementary metaatoms and a very high dielectric constant of gold in the THz, lead to the observation of surface plasmon polaritons modes due to the meta-atom spacing.…”

Shaping Light in Backward-Wave Nonlinear Hyperbolic Metamaterials

“…Among the prospective materials are refractory materials that can work at very high temperatures [42], transparent conducting ceramics [43], and plasmonic materials, where properties can be dynamically tuned [44]. Phase matching of contra-propagating fundamental and backward second harmonic wave in a plasmonic metamaterial is reported in [45]. The described approach can be applied to layered metal-dielectric metamaterials, which include layers of highly nonlinear dielectric as was proposed in [46] for the case of co-propagating waves.…”