Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals

Abstract

An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 microm.

Two-Dimensional Materials with Giant Optical Nonlinearities near the Theoretical Upper Limit

“…In addition, nonlinear optical (NLO) spectroscopy is extensively employed to obtain insights into materials properties that are not accessible by, for example, linear optical spectroscopy. For instance, polarization-resolved second-harmonic generation (SHG) is used to identify crystal orientations and symmetries. , SHG has also been used for direct visualization of the electric field inside integrated circuits or examining fabricated nanostructures with high spatial and temporal resolutions . Recently, two-dimensional (2D) materials and their van der Waals heterostructures , have become attractive for realizing compact NLO devices due to their extreme thinness and strong NLO response. − In particular, highly nonlinear 2D materials have already been integrated into photonic devices. , Moreover, their atomic thickness and relaxed phase-matching restrictions in the out-of-plane direction make 2D materials suited for emerging applications such as nonlinear quantum cavity optics .…”

“…For instance, polarization-resolved second-harmonic generation (SHG) is used to identify crystal orientations and symmetries. 9,10 SHG has also been used for direct visualization of the electric field inside integrated circuits 11 or examining fabricated nanostructures with high spatial and temporal resolutions. 12 Recently, two-dimensional (2D) materials and their van der Waals heterostructures 13,14 have become attractive for realizing compact NLO devices due to their extreme thinness and strong NLO response.…”

Material characterisation with methods of nonlinear optics

“…The SHGM provides several advantages due to the unique properties of the SHG process itself, such as: better resolution-the intensity of the SHG radiation depends quadratically on the incident intensity having a Gaussian distribution in the cross-section of the beam that leads to the decrease of the focal excitation volume ∆z SHG by a factor of √ 2 [43] as schematically depicted in the inset of figure 3; selectivity-a significant SHG signal is generated only within media with a broken centrosymmetry; deep penetration-there is less scattering, since the wavelength of the pump radiation is typically in the NIR spectral range; polarisation sensitivity-SHG is highly sensitive to the orientation, birefringence and local symmetry properties of a medium. Due to the above facts, SHGM is actively used for the investigation of various materials and structures, as particularly demonstrated for: monitoring the corrosion products found below a painted metal surface [44], probing the interplay of nanoscale structures [45], noninvasive detection of strain fields around through-silicon-vias conducting rods in Si(0 0 1) [46], direct 3D visualization of the electric field in integrated circuits [47], etc.…”

Two-dimensional Materials with Giant Optical Nonlinearities Near the Theoretical Upper Limit

“…For instance, polarization-resolved second-harmonic generation (SHG) is used to identify crystal orientations and symmetries [9,10]. SHG has also been used for direct visualization of the electric field inside integrated circuits [11] or examining fabricated nanostructures with high spatial and temporal resolutions [12]. Recently, two-dimensional (2D) materials and their van der Waals heterostructures [13,14] have become attractive for realizing compact NLO devices due to their extreme thinness and strong NLO response [15][16][17][18].…”