Generation of optical chirality patterns with plane waves, evanescent waves and surface plasmon waves

Ultra-high sensitive dual-parameter sensor based on double-hole fiber for simultaneous detection of magnetic field and temperature

An ultra-high sensitive dual-parameter sensor based on double-hole fiber (DHF) is proposed for simultaneous detection of magnetic fields and temperatures. The sensor utilizes the DHF containing a Ge-doped core with two large air holes symmetrically arranged at its two sides. To enhance the sensitivity to both a magnetic field and temperature, Al wires with different diameters are embedded on the inner walls of the air holes in the DHF, creating a magnetic field sensing channel filled with magnetic fluid and a temperature sensing channel filled with thermo-sensitive liquid. Structural parameters and metal materials of the sensor are optimized by using the finite element method. Numerical results demonstrate that this DHF-based dual-parameter sensor can detect magnetic fields ranging from 40 Oe to 130 Oe and temperatures ranging from 24.3 °C to 49.3 °C simultaneously. The maximum magnetic field sensitivity reaches up to 64000 pm/mT, while the maximum temperature sensitivity is approximately 44.6 nm/°C, both exceeding current reports by more than one order of magnitude for simultaneous detection of magnetic field and temperature. With its high sensitivity, low fabrication difficulty, and simple structure, this DHF-based dual-parameter sensor has potential applications in the fields of material characterization analysis, geological environmental monitoring, and aeronautical engineering.

Chiral optical solitons in an electrically active multiferroic guiding structure

A stack of a dielectric planar waveguide with a Kerr-type nonlinearity, sandwiched between two oxide-based helical multiferroic layers is shown to support electrically-controlled chiral solitons. These findings follow from analytical and full numerical simulations. The analytical scheme delivers explicit material parameters for the guided mode soliton and unveils how the soliton propagation characteristics are controlled by tuning the multiferroic helicity and amplitude of the injected electromagnetic wave. Silicon and CS2 are considered as the optical media in the guiding region enclosed by the multiferroic slabs. CS2 has very similar nonlinearity characteristics to silicon but in the linear regime it exhibits a smaller refractive index in the THz frequency range. The scattering simulations are performed using our developed numerical code based on the rigorous coupled wave method and the results for the dispersion curve for the guided mode agree very well with the analytical formula that we derive in this work. The results demonstrate a case of nonlinear pulse generation with field-controlled, nontrivial topological properties.

Tunable chiral photonic cavity based on multiferroic layers

Realization of externally tunable chiral photonic sources and resonators is essential for studying and functionalizing chiral matter. Here, oxide-based stacks of helical multiferroic layers are shown to provide a suitable, electrically-controllable medium to efficiently trap and filter purely chiral photonic fields. Using analytical and rigorous coupled wave numerical methods we simulate the dispersion and scattering characteristics of electromagnetic waves in multiferroic heterostructures. The results evidence that due to scattering from the spin helix texture, only the modes with a particular transverse wavenumber form standing chiral waves in the cavity, whereas all other modes leak out from the resonator. An external static electric field enables a nonvolatile and energy-efficient control of the vector spin chirality associated with the oxide multilayers, which tunes the photonic chirality density in the resonator.

Structured illumination microscopy for simultaneous imaging of achiral and chiral domains

We propose double structured illumination microscopy (SIM) method, which enables simultaneous imaging of achiral and chiral domains at sub-wavelength resolution. In double SIM, the illumination field is spatially structured both in the intensity and optical chirality so that moiré effects can be concurrently generated on the achiral and chiral fluorescent domains of a sample. This allows for down-modulating the high spatial frequency of both domains at the same time and thus provides sub-wavelength details after image reconstruction. We introduce the working principle of double SIM and theoretically demonstrate the feasibility of this method using different kinds of synthetic samples.

Signal and noise analysis for chiral structured illumination microscopy

Recently, chiral structured illumination microscopy has been proposed to image fluorescent chiral domains at sub-wavelength resolution. Chiral structured illumination microscopy is based on the combination of structured illumination microscopy, fluorescence-detected circular dichroism, and optical chirality engineering. Since circular dichroism of natural chiral molecules is typically weak, the differential fluorescence is also weak and can be easily buried by the noise, hampering the fidelity of the reconstructed images. In this work, we systematically study the impact of the noise on the quality and resolution of chiral domain images obtained by chiral SIM. We analytically describe the signal-to-noise ratio of the reconstructed chiral SIM image in the Fourier domain and verify our theoretical calculations with numerical demonstrations. Accordingly, we discuss the feasibility of chiral SIM in different experimental scenarios and propose possible strategies to enhance the signal-to-noise ratio for samples with weak circular dichroism.

Plasmonic elliptical nanoholes for chiroptical analysis and enantioselective optical trapping

A simple yet effective achiral platform using elliptical nanoholes for chiroptical analysis is demonstrated. Under linearly polarized excitation, an elliptical nanohole in a thin gold film can generate a localized chiral optical field for chiroptical analysis and simultaneously serve as a near-field optical trap to capture dielectric and plasmonic nanospheres. In particular, the trapping potential is enantioselective for dielectric nanospheres, i.e., the hole traps or repels the dielectric nanoparticles depending on the sample chirality. For plasmonic nanospheres, the trapping potential well is much deeper than that for dielectric particles, rendering the enantioselectivity less pronounced. This platform is suitable for chiral analysis with nanoparticle-based solid-state extraction and pre-concentration. Compared to plasmonic chiroptical sensing using chiral structures or circularly polarized light, elliptical nanoholes are a simple and effective platform, which is expected to have a relatively low background because chiroptical noise from the structure or chiral species outside the nanohole is minimized. The use of linearly polarized excitation also makes the platform easily compatible with a commercial optical microscope.