arXiv subjects

Daichi Okada

Publications and source records attributed to Daichi Okada.

5 recordsLinked to original sources

arXiv2026

Telecom-band Chiral Light Detection through Hidden Giant Third-Order Nonlinear Circular Dichroism in Two-dimensional Halide Perovskite

Chiral nonlinear optical (NLO) responses enable efficient discrimination of circularly polarized light (CPL) and are attracting increasing interest for optical and optoelectronic technologies. However, studies on NLO properties in chiral materials have largely focused on second-order NLO processes, while the role of chirality in third-order NLO processes remains poorly explored. Here, we demonstrate telecom-band CPL detection by third harmonic generation circular dichroism (THG-CD) in the chiral two-dimensional perovskite (R/S-MBACl)2PbI4 and uncover a giant hidden THG-CD anisotropy that is accessible via polarization-resolved detection. Polarization-resolved THG measurements reveal that opposite chiral NLO responses emerge in orthogonal THG polarization channels. Therefore, these chiral anisotropic contributions largely cancel each other in the total-THG signal detection, leading to underestimation of the THG-CD dissymmetry in conventional evaluations based on total-THG intensity. By separating these hidden chiral contributions, we observe exceptionally large dissymmetry factors exceeding 1.9 and achieve selective extraction of chiral NLO responses with opposite handedness, without any structural chiral inversion. These findings highlight the importance of polarization-resolved analysis for evaluating more accurate chiral NLO responses inherent to the material and provide a promising platform for optical information processing, encryption, and anti-counterfeiting technologies at technologically relevant telecommunication wavelengths.

cond-mat.mtrl-sci↗

arXiv2024

Tunable Intracavity Coherent Up-conversion with Giant Nonlinearity in a Polar Fluidic Medium

We demonstrate a novel microcavity-based photon up-conversion using second harmonic generation (SHG) from a polar nematic fluid media doped with a laser dye. The present idea is based on coherent light generation via simultaneous frequency doubling and stimulated emission (lasing) inside a microcavity. The polar nematic fluid equips very high even-order optical nonlinearity due to the polar symmetry and large dipole moment along the molecular long axis. At the same time, its inherent fluidic nature allows us to easily functionalize the media just by doping, in the present case, with an emissive laser dye. Our demonstrated system exhibits a giant nonlinear optical response to input light, while enabling spectral narrowing and multiple-signal output of up-converted light, that is not attainable though the simple SH-conversion of input light. Furthermore, susceptibility of the liquid crystal offers dynamic modulation capabilities under external stimulus, such as signal switching with electric field application or wavelength tuning through temperature variation. Such a brand-new type of simple coherent flexible up-conversion system must be promising as a new principle for easy-accessible and down-scalable wavelength conversion devices.

physics.optics↗

arXiv2024

Emergent Ferroelectric Nematic and Heliconical Ferroelectric Nematic States in an Achiral "Straight" Polar Rod Mesogen

Ferroelectric nematic liquid crystals (NFLCs) are distinguished by their remarkable polarization characteristics and diverse physical phenomena, sparking significant interest and excitement within the scientific community. To date, over 150 NFLC molecules have been developed; however, there are no reports regarding straight linear polar molecules with a parallel alignment of the permanent dipole moment and the molecular axis. The straight polar mesogen nBOE exhibited an enantiotropic NF phase with a wide temperature window (up to 100 K) despite having a longer alkyl chain (up to n = 6) than the critical alkyl chain length of conventional models. Interestingly, nBOE with a medium length alkyl chain displayed an exotic phase sequence of NF-HCNF-SmCF during the elimination of positional displacement among adjacent molecules. Furthermore, we demonstrate the reflective color modulation of the HCNFLC over the entire VIS-NIR spectral regime by ultralow E-field (up to 0.14 V um^-1).

cond-mat.mtrl-sci↗

arXiv2024

Significant impact of light-matter strong coupling on chiral nonlinear optical effect

Light-matter strong coupling (LMSC) is intriguing state in which light and matter are coherently hybridized inside cavity. It has been gaining widespread recognition as an excellent way for controlling material properties without any chemical modification. Here we show the LMSC is a powerful state to manipulate and improve a chiral nonlinear optical (NLO) effect through the investigation of second harmonic generation circular dichroism. At the upper polaritonic band in LMSC, in addition to an enhancement of SHG intensity by more than one order of magnitude, the responsivity to the handedness of circular polarized light is largely modified, where sign inversion and increase of dissymmetric factor is achieved. Quarter wave plate rotation analysis reveals that the LMSC clearly influence the coefficients associated with chirality in NLO process and it also contributes to the enhancement of nonlinear magnetic dipole interactions. This study demonstrates that LMSC serves as a novel platform for control of chiral optoelectronics and magneto-optics.

physics.optics↗

arXiv2024

Magneto-chiral nonlinear optical effect with large anisotropic response in two-dimensional halide perovskite

The chiral organic-inorganic halide perovskites (OIHPs) are vital candidates for superior nonlinear optical (NLO) effects associated with circularly polarized (CP) light. NLO in chiral materials often couples with magnetic dipole (MD) transition, as well as the conventional electric dipole (ED) transition. However, the importance of MD in NLO process of chiral OIHPs has not yet been well recognized. Here, the analysis of second harmonic generation circular dichroism (SHG-CD) provides the direct evidence that the MD contribution leads to a large anisotropic response to CP lights in chiral OIHPs, (R-/S-MBACl)2PbI4. The thin films exhibit great sensitivity to CP lights over a wide wavelength range, and the g-value reaches up to 1.57 at the wavelength where the contribution of MD is maximized. Furthermore, it is also effective as CP light generator, outputting CP-SHG with maximum g-factor of 1.76 upon the stimulation of linearly polarized light. This study deepens the understanding of the magneto-optical NLO processes in chiral systems.

physics.optics↗