Optical coherence microscopy is a promising method for visualization of the material refractive index, that is actively used for medical application. The implementation of the pump-probe scheme into optical coherence microscopy makes it possible to measure not only stationary quantities, but also to study the temporal dynamics of the optical properties changes of a sample under the optical pumping. In this work we demonstrate the possibility of the visualization of the refractive index modulation in semiconductor structures and estimation of the Q-factor of the excited resonances for lasing perovskite structure.
Neural networks are powerful tools for solving many modern problems. One of the options for the optical implementation of a neural network is a diffraction neural network, which consists of one or several layers of different-sized pixels on which radiation diffracts. The pixel parameters are tightly bound with the desired radiation wavelength. In this work, we printed masks for diffraction neural networks for the optical range using two-photon laser lithography. Applying coordinate stabilization approach and preserving temperature and humidity allowed to print pixels with up to 10 nm height difference and 2.3 nm average surface roughness.
Methylammonium lead iodide (CH3NH3PbI3 or MAPI) is an organohalide lead perovskite, a promising material for optoelectronic application, e.g. in solar cells and photodetectors. It has a number of advantages over more traditional photovoltaics materials such as CIGS, GaAs, and even silicon due to facile solution processing, direct bandgap, high optical absorption, sufficiently high, balanced carrier mobilities, shallow trap defects and low-cost synthesis. At present moment there are number of article which reported measurement of second-harmonic generation in MAPI single crystals and presented contradictory results demonstrating the presence or absence of second-harmonic signal from MAPI. In this work, the second-harmonic generation (SHG) is observed in MAPI thin film that can be used as a base of high efficient solar sell.
The SHG intensity from MAPI is measured to be at least three orders of magnitude more than one from substrate and encapsulation glasses. The MAPI nonlinear second-order susceptibility is estimated as compared to reference sample of y-cut quartz. In case of bulk contribution, the MAPI second-order susceptibility of 10-15 m/V is achieved.
The polarization of SHG signal is experimentally studied in MAPI samples. The fraction of linearly polarized SHG signal is different for p- and s-polarization of fundamental wave and increases in case of p-polarized pump. The large non-polarized background of SHG signal is partly corresponded to SHG hyper-Rayleigh scattering. The hyper-Rayleigh scattering angle is experimentally estimated using the diaphragm behind the collimating objective lens and found to be less then 11 degrees.
Tamm plasmon-polariton (TPP) is an optical analogue of Tamm state and appears as spatial localization of the
electromagnetic field near the boundary of one-dimensional photonic crystal (PC) (distributed Bragg reflector) and a
metal film. TPP can be detected experimentally as a narrow resonance in the reflectance or transmittance spectrum
of a PC/metal structure. Contrary to surface plasmon-polariton TPP occurs at any angles of incident light for both TE and TM polarizations, and it excitation does not require sophisticated optical schemes (such as Kretchmann scheme). The peculiarities of TPP optical properties led to considerable interest to the design, fabrication and study of TPP-supported structures in the past several years.
In present work, the ultrafast relaxation dynamics of TPP excited in the PC/metal structures is measured using intensity cross-correlation scheme. The TPP lifetime is obtained for different polarizations and incident angles of light, and compared with one obtained from numerical calculations. A femtosecond pulse reflected from such a structure is found to be significantly distorted if its spectrum overlaps with the TPP resonance. The TPP lifetime possesses strong polarization and angular dependence and is shown to vary from 20 fs for p-polarized light to 40 fs for s-polarized light at a 45◦ angle of incidence. The reported lifetime of TPP is several times smaller than the previously reported lifetime of surface plasmons. Short lifetime and sharpness of resonance make TPP a good candidate for use in all-optical switches and modulators.
Tamm plasmon-polaritons (TPPs) have attracted many interest due to the peculiarities of their optical properties. TPPs are optical surface states, which can be excited at the boundary of distributed Bragg reflector and metal film. Like in case of surface plasmon-polaritons or surface electromagnetic waves excitation, the emergence of the TPP leads to the localization of the electromagnetic field near the DBR/metal interface. Experimentally, TPP can be detected by a narrow resonance in reflectance or transmittance spectrum of the DBR/metal structure. Tamm plasmon-polaritons were proposed to be used in several types of novel optical elements, such as sensors and lasers. It was also shown that TPPs can be effectively coupled with other localized states like surface plasmons and microcavity modes. In this contribution the direct measurements of the Tamm plasmon-polariton relaxation dynamics are presented. The lifetime of the TPP in one-dimensional photonic crystal is estimated experimentally and compared to the results of numerical calculations. The dependence of the lifetime on the angle of incidence and duration of the incident pulse is supported by numerical studies performed with the finite difference time-domain technique.
We have studied an influence of Tamm plasmon-polaritons (TPPs) excitation on the nonlinear-optical response of one-dimensional photonic crystal/metal structures. It was shown that in case when the fundamental radiation is in resonance with the TPP, second-harmonic generation in the sample is enhanced over two times of magnitude in comparison with a bare metal film. Using methods of nonlinear transfer matrices it was demonstrated that the third-order nonlinear response of a metal/dielectric heterostructure, when both fundamental and third-harmonic radiation are in resonance with the first- and third-order TPPs respectively, can be enhanced via two mechanisms: fundamental field localization and optical harmonic resonant tunneling. The overall enhancement of the third harmonic generation in that case can exceed three orders of magnitude in comparison with the non-resonant case.
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