Possibility of femtosecond laser pulses to affect the materials properties arises the interest in ultrafast processes based research and technology. In the case of graphene surface modification and functionalization using femtosecond laser, there are several effects appear, such as ablation, covalent bonding of different chemical groups, re-crystallization in three-dimensional shapes. CVD grown graphene was transferred on Si/SiO2. Through several lithography steps, graphene-based field-effect transistors were formed with Cr/Au source-drain electrodes and Si back gate electrode. For graphene modification we used 100 fs 80 MHz laser with 780 nm wavelength with different irradiation doses. Exposure of graphene to a femtosecond laser pulse is determined by the prevalence of physical or chemical effects during exposure to a laser pulse. The range of laser exposure was narrowed down to values causing the formation of atomic defects in the carbon lattice, which makes it possible to form nanopores in graphene and these doses are below the graphene ablation. The main tool for studying the effect of femtosecond laser irradiation was Raman spectroscopy. By evaluating the intensity ratio of certain peaks, namely the G-band (~1600 cm-1) and D-band (~ 1350 cm-1), the degree of functionalization, or amorphization of graphene, was estimated. It was found that the ablation threshold starts from 18 mW at the beam speed in the range of 400-500 μm/s. Just below this range, both graphene functionalization and a change in the graphene surface roughness were observed. Despite the change in the morphology of graphene, the graphene resistance fell by only ~4 times, and the transfer current-voltage curves of the graphene transistor did not change much, showing a shift towards higher voltages. With a decrease in the slope of the transfer current-voltage characteristics, the resistance of the structure also decreases with an increase in the dose of laser exposure, since the number of defects and functional groups in graphene increases. In addition, we found the effect of the laser polarization on the modification of graphene. The difference in parameters between the samples modified with different polarization directions along the direction of the beam motion can be explained as the interference interaction of the electron density in graphene. A beam passing over the graphene region excites hot electrons, which partially cause the graphene modification. After passing by the laser, the electron density does not have time to relax, and the next beam of photons affects the already excited electrons, increasing the total dose of laser radiation.
We demonstrate the broadband visible luminescence from bulk crystalline silicon and silicon nanoparticles sized 100- 30 nm under near-infrared excitation. We show that the luminescence spectrum has two distinct peaks. The first being centered at 550 nm while the second appears close to the wavelength of the second harmonic of the excitation light. The appearance of the second peak is a signature of the highly athermal electron distribution never observed previously. The luminescence intensity and spectral shape strongly depend on the doping type and concentration. Despite being nonresonant, silicon nanoparticles enhance luminescence intensity when placed atop the silicon wafer. The observed phenomenon can be used for wafer inspection and defect detection, as well as for the creation of novel nanosources of light.
Direct printing of semiconductor nanoparticles via laser-induced transfer is a recently developed tool to obtain individual nanoparticles or their arbitrary arrays on a substrate of almost any shape and material. Semiconductor nanoparticles supporting Mie resonance are now widely explored in the pursuit for the novel all-dielectric photonic platforms. The promising direction is merging Mie-resonant nanoparticles with photonic crystals. We experimentally demonstrate excitation of a Bloch surface wave in photonic crystal mediated by an individual silicon nanoparticle. The nanoparticle being irradiated by light with the wavelength near the Mie resonance acts as a nanoantenna and allows excitation of the Bloch surface wave from the far-field. Visualization of the surface wave propagation direction is performed by the Fourier-plane imaging using the leakage radiation microscopy setup. We show that tuning the wavelength of the incident light around the Mie resonance allows for launching Bloch surface wave in both forward and backward direction.
Detection of a single nanoparticle on a bare silicon wafer has been a challenge in the semiconductor industry for decades. Currently, the most successful and widely used technique is dark-field microscopy. However, it is not capable of detecting single sub-10 nm particles owing to a low signal-to-noise ratio (SNR). As a new approach, we suggest using the second harmonic generation (SHG) to detect a single nanoparticle. The second harmonic generation in centrosymmetric materials, like silicon, is forbidden except for a thin and additionally increase local field factors, allowing for their persistent detection. Choosing the proper surface and increasing SNR. We demonstrate the feasibility of the nonlinear dark-field microscopy concept by detecting an isolated 80-nm silicon nanoparticle on the silicon wafer.
Carbon nanotubes (CNT) are being intensively studied for many applications because of their unique properties, such as high electrical and thermal conductivities, excellent mechanical and chemical stability. One of the areas of CNT application is a bolometric detection of near- and mid-infrared (IR) radiation. The record near-IR bolometric performance of CNT devices is comparable to the performance of the commercial vanadium oxide detectors . However, the low intrinsic absorption of CNT in the mid-IR range limits their applications for the detection in the crucial 3-5 µm and 8-12 µm regions. The phenomenon of surface plasmon excitation has been utilized to improve light harvesting efficiency of solar cells and to increase absorption of monolayer graphene . Plasmons were recently observed on an individual CNT , but the excitation of a surface plasmon on the macroscopic CNT films have not been reported yet.
In the study, we experimentally demonstrate the 100%-enhanced bolometric response of a single-walled carbon nanotube (SWCNT) film in the vicinity of a mid-IR surface plasmon resonance. As a basis for the sample we use a pristine SWCNT film with the thickness of 400 nm, the width of 3 mm, and the length of 6 mm, suspended between two gold contacts. The femtosecond laser is used to drill 3- µm round holes which are arranged in a 2D square lattice with a period of 10 µm. Only one half of the film (3x3 mm2) is structured, while the second half is left unstructured to perform reference measurements. Reflectance and transmittance spectra of both parts of the film are measured with the Fourier-transform infrared spectrometer in the range 2-100 µm. Surface plasmon manifests itself as a Fano-type resonance in spectra of the structured part of the film at the wavelengths around 15 µm. The absorption of the structured part is enhanced in the same spectral region by 75% as compared with the unstructured part. Spectral dependence of the bolometric voltage sensitivity is measured using the sample as a detector of the spectrometer. It is shown that the voltage response of the structured part is enhanced in the vicinity of the surface-plasmon resonance by 100%. We show that the wavelength of the resonance and its magnitude can be controlled by tailoring the geometry of the sample. Numerical calculations by scattering-matrix method show that the central wavelength of the absorption resonance can be tuned in the range 5-25 µm. The maximum available enhancement of absorption is 240% as compared with the unstructured film.
We claim that the proposed method applies to achieve enhanced spectrally selective response for any CNT-based bolometer in both near- and mid-infrared ranges of the spectrum.
 G. E. Fernandes, J. H. Kim, A. K. Sood, J. Xu, Adv. Funct. Mater. 2013, 23, 4678.
 N. K. Emani, T.-F. Chung, A. V Kildishev, et al. Nano Lett. 2013, 14, 78.
 Z. Shi, X. Hong, H. A. Bechtel, et al. Nat. Photonics 2015, 9, 515
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.