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In present literature on integrated modulation and filtering, limitations in the extinction ratio are dominantly attributed to a combination of imbalance in interfering wave amplitude, instability of control signals, stray light (e.g., in the cladding), or amplified spontaneous emission from optical amplifiers. Here we show that the existence of optical frequency noise in single longitudinal mode lasers presents an additional limit to the extinction ratio of optical modulators. A simple frequency-domain model is used to describe a linear optical system's response in the presence of frequency noise, and an intuitive picture is given for systems with arbitrary sampling time. Understanding the influence of frequency noise will help guide the design choices of device and system engineers and offer a path toward even higher-extinction optical modulators.Surface enhanced infrared absorption (SEIRA) spectroscopy and surface plasmon resonance (SPR) make possible, thanks to plasmonics nanoantennas, the detection of low quantities of biological and chemical materials. Here, we investigate the infrared response of 2,4-dinitrotoluene deposited on various arrays of closely arranged metal-insulator-metal (MIM) resonators and experimentally show how the natural dispersion of the complex refractive index leads to an intertwined combination of SEIRA and SPR effect that can be leveraged to identify molecules. They are shown to be efficient for SEIRA spectroscopy and allows detecting of the dispersive explosive material, 2,4-dinitrotoluene. By changing the in-plane parameters, a whole spectral range of absorptions of 2,4-DNT is scanned. selleck compound These results open the way to the design of sensors based on SEIRA and SPR combined effects, without including a spectrometer.The microfiber-based optical structures have been attracting increasing research interests in communications and sensing fields. However, the fabrication of forming structures on fragile microfibers requires delicate operations, which limits the developments of their practical applications. In this work, a one-step-tapering technique is proposed to manufacture structures on microfibers. As a demonstration, the fiber preform, consisting of sawtooth shaped solid-air interfaces with designed dimensions, is obtained using a femtosecond laser milling technique. By one-step tapering the preform, periodic bumps are formed, resulting in a bamboo-like microfiber device. The fabricated structure shows spectral characteristics of a long-period grating, of which extinction ratio is up to 18.2 dB around 1553.3 nm. The response to refractive index is measured to be ∼875.02 nm/RIU and the temperature coefficient is ∼5.78 pm/°C. The theoretical analysis shows good agreement with the experimental results. The microfiber-based structure fabricated using the one-step-tapering-preform technique is featured with flexibility of design, reproducibility, and structural stability.We propose a method to create selective interactions with Dicke-Stark model by means of a time-dependent perturbation theory. By choosing the proper rotating framework, we find that the time oscillating terms depend on the number of atomic excitations and the number of photonic excitations. Consequently, the Rabi oscillation between selective states can be realized by properly choosing the frequency of the two-level system. The second order selective interactions can also be studied with this method. Then various states, such as Dicke states, superposition of Dicke states and GHZ states, can be created by means of such selective interactions. The numerical results show that high fidelity Dicke states and Greenberger-Horne-Zeilinger states can be created by choosing the proper frequency of the two-level system and controlling the evolution time.It is a great challenge in two-photon microscopy (2PM) to have a high volumetric imaging speed without sacrificing the spatial and temporal resolution in three dimensions (3D). The structure in 2PM images could be reconstructed with better spatial and temporal resolution by the proper choice of the data processing algorithm. Here, we propose a method to reconstruct 3D volume from 2D projections imaged by mirrored Airy beams. We verified that our approach can achieve high accuracy in 3D localization over a large axial range and is applicable to continuous and dense sample. The effective field of view after reconstruction is expanded. It is a promising technique for rapid volumetric 2PM with axial localization at high resolution.A light-driven diffraction grating incorporating two grating patterns with different pitches atop a photothermal actuator (PTA) has been proposed. It is based on graphene oxide/reduced graphene oxide (GO/rGO) induced via femtosecond laser direct writing (FsLDW). The rGO, its controllable linewidth, and transmission support the formation of grating patterns; its noticeably small coefficient of thermal expansion (CTE), good flexibility, and thermal conductivity enable the fabrication of a PTA consisting of a polydimethylsiloxane layer with a relatively large CTE. Under different intensities of light stimuli, diffraction patterns can be efficiently tailored according to different gratings, which are selectively addressed by incident light beam hinging on the bending of the PTA. This is the first demonstration of combining gratings and PTA, wherein the GO plays the role of a bridge. The light-driven mechanism enables the contactless operation of the proposed device, which can be efficiently induced via FsLDW. The diffraction angle could be changed between 2° and 6° horizontally, and the deviation of side lobes from the main lobe could be altered vertically in a continuous range. The proposed device may provide powerful support for activating dynamic diffraction devices in photothermally contactless schemes.We demonstrate a novel scheme to increase the accuracy of time-delay measurement of an insufficient stimulated Brillouin scattering (ISBS) based pulse compression system. It is realized by relating the time delay with the pulse compression gain, which is accumulated by a lock-in amplifier (LIA). We theoretically demonstrate that the time delay is proportional to the accumulated gain via the LIA. In the experiment, the pulse compression gain is accumulated through lock-in detection. It narrows down the detection bandwidth and reduces the influence from the broadband noise. The time-delay measurement is completed in a real-time manner and thus provides a possible solution to realizing a high-speed process in the future. The accuracy of measurement of a linear frequency modulated (LFM) signal with a bandwidth of 1 GHz is 1 ns.
Homepage: https://www.selleckchem.com/products/b-ap15.html
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