2016, 4(3) Column
Photonics Research 第4卷 第3期
Intramolecular vibrations of large macromolecules reside in the terahertz range. In particular, protein vibrations are closely spaced in frequency, resulting in a nearly continuous vibrational density of states. This density of vibrations interferes with the identification of specific absorption lines and their subsequent association with specific functional motions. This challenge is compounded with the absorption being dominated by the solvent and local relaxational motions. A strategy for removing the isotropic relaxational loss and isolating specific vibrations is to use aligned samples and polarization-sensitive measurements. Here, we demonstrate a technique to rapidlyattain the anisotropic resonant absorbance using terahertz time domain spectroscopy and a spinning sample. The technique, modulated orientation-sensitive terahertz spectroscopy (MOSTS), has a nonzero signal only for anisotropic samples, as demonstrated by a comparison between a silicon wafer and a wire grid polarizer. For sucroseand oxalic acid molecular crystals, the MOSTS response is in agreement with modeled results for the intermolecular vibrations. Further, we demonstrate that, even in the presence of a large relaxational background, MOSTS isolates underlying vibrational resonances.
Instrumentation Instrumentation measurement measurement and metrology and metrology Ellipsometry and polarimetry Ellipsometry and polarimetry Spectroscopy Spectroscopy fluorescence and luminescence fluorescence and luminescence Spectroscopy Spectroscopy modulation modulation Spectroscopy Spectroscopy molecular molecular Spectroscopy Spectroscopy terahertz terahertz Study of photoexcited-carrier dynamics in GaAs photoconductive switches using dynamic terahertz emission microscopyDownload:639次
We propose dynamic terahertz (THz) emission microscopy (DTEM) to visualize temporal–spatial dynamics of photoexcited carriers in electronic materials. DTEM utilizes THz pulses emitted from a sample by probe pulses irradiated after pump pulse irradiation to perform time-resolved two-dimensional mapping of the THz pulse emission, reflecting various carrier dynamics. Using this microscopy, we investigated carrier dynamics in the gap region of low-temperature-grown GaAs and semi-insulating GaAs photoconductive switches of the identical-dipole type. The observed DTEM images are well explained by the change in the electric potential distribution between the electrodes caused by the screening effect of the photoexcited electron-hole pairs.
Terahertz imaging Terahertz imaging Ultrafast phenomena Ultrafast phenomena This publisher’s note reports corrections to three of the figures in [Photon. Res. 4, 49 (2016)].
Pulse propagation and temporal solitons Pulse propagation and temporal solitons Lasers Lasers fiber fiber Ultrafast lasers Ultrafast lasers Temperature-controlled mode selection of Er-doped random fiber laser with disordered Bragg gratingsDownload:677次
In this paper, we proposed a way to realize an Er-doped random fiber laser (RFL) with a disordered fiber Bragg grating (FBG) array, as well as to control the lasing mode of the RFL by heating specific locations of the disordered FBG array. The disordered FBG array performs as both the gain medium and random distributed reflectors, which together with a tunable point reflector form the RFL. Coherent multi-mode random lasing is obtained with a threshold of between 7.5 and 10 mW and a power efficiency between 23% and 27% when the reflectivity of the point reflector changes from 4% to 50%. To control the lasing mode of random emission, a specific point of the disordered FBG array is heated so as to shift the wavelength of the FBG(s) at this point away from the other FBGs. Thus, different resonance cavities are formed, and the lasing mode can be controlled by changing the location of the heating point.
Lasers Lasers fiber fiber Lasers Lasers erbium erbium Optimizing the design of GaAs/AlGaAs thin-film waveguides for integrated mid-infrared sensorsDownload:736次
Optical simulations of GaAs/AlGaAs thin-film waveguides were performed for investigating the dependence of the modal behavior on waveguide geometry and the resulting analytical sensitivity. Simulations were performed for two distinct mid-infrared wavelengths, thereby demonstrating the necessity of individually designed waveguide structures for each spectral regime of interest. Hence, the modal behavior, sensitivity, and intensity of the evanescent field were investigated via modeling studies at 1600 and 1000 cm?1, thereby confirming the utility of such simulations for designing mid-infrared sensors based on thin-film waveguide technology.
Thin films Thin films Waveguides Waveguides Dark solitons in WS2 erbium-doped fiber lasersDownload:981次
Tungsten disulfide (WS2) is a type of anisotropic-layered compound and has broadband saturable absorption features as saturable absorbers (SAs). With WS2-based SAs, dark solitons in erbium-doped fiber (EDF) lasers are first obtained. For the generated dark solitons, the center wavelength is measured to be 1530 nm, and the repetition rateis about 116.5 MHz. A series of optical spectra is exhibited. The electrical signal-to-noise ratio is better than 94 dB. Results in this paper demonstrate that WS2-based SAs are the promising SAs for generating dark solitons in EDF lasers.
Pulse propagation and temporal solitons Pulse propagation and temporal solitons Lasers Lasers fiber fiber Modelocked lasers Modelocked lasers Study on the key technology of spectral reflectivity reconstruction based on sparse prior by a single-pixel detectorDownload:639次
By studying the traditional spectral reflectance reconstruction method, spectral reflectance and the relative spectral power distribution of a lighting source are sparsely decomposed, and the orthogonal property of the principal component orthogonal basis is used to eliminate basis; then spectral reflectance data are obtained by solving a sparse coefficient. After theoretical analysis, the spectral reflectance reconstruction based on sparse prior knowledge of the principal component orthogonal basis by a single-pixel detector is carried out by software simulation and experiment. It can reduce the complexity and cost of the system, and has certain significance for the improvement of multispectral image acquisition technology.and the Innovation Project of Shanghai Municipal Education Commission (Grant No. 14YZ099), National Basic Research Program of China (973 Program) (Grant No. 2015CB352004).
CCD CCD charge-coupled device charge-coupled device Quantum information and processing Quantum information and processing Spectroscopy Spectroscopy surface surface We propose and demonstrate a multifunctional location-dependent metamaterial in the terahertz (THz) range in which the unit cell consists of two pairs of coupled resonators. Experimental and simulation results of our devices reveal that both pairs of the coupled resonators will keep their individual resonance modes when they join together. Thus, the overall transmission spectrum is a combination of frequency response spectra of its corresponding constituent parts. While changing the locations of the inner resonators in our structure, controllable width of transmission window and changeable number of transmission dips can be realized. Our design provides a feasiblestructure for multifunctional microelectromechanical devices.
Metamaterials Metamaterials Optoelectronics Optoelectronics Spectroscopy Spectroscopy terahertz terahertz Photonic integrated circuit components based on amorphous silicon-on-insulator technologyDownload:1650次
We present integrated-optic building blocks and functional photonic devices based on amorphous siliconon-insulator technology. Efficient deep-etched fiber-to-chip grating couplers, low-loss single-mode photonic wire waveguides, and compact power splitters are presented. Based on the sub-μmphotonic wires, 2 × 2 Mach–Zehnder interferometers and add/drop microring resonators (MRRs) with low device footprints and high finesse up to 200 were realized and studied. Compact polarization rotators and splitters with ≥10 dB polarization extinction ratio were fabricated for the polarization management on-chip. The tuning and trimming capabilities of the material platform are demonstrated with efficient microheaters and a permanent device trimming method, which enabled the realization of energy-efficient photonic circuits. Wavelength multiplexers in the form of cascaded filter banks and 4 × 4 routers based on MRR switches are presented. Fabrication imperfections were analyzed and permanently corrected by an accurate laser-trimming method, thus enabling eight-channel multiplexers with record low metrics of sub-mW static power consumption and ≤1°C temperature overhead. The high quality of the functional devices, the high tuning efficiency, and the excellent trimming capabilities demonstrate the potential to realize low-cost, densely integrated, and ultralow-power 3D-stacked photonic circuits on top of CMOS microelectronics.
Optoelectronics Optoelectronics Wavelength filtering devices Wavelength filtering devices Optical interconnects Optical interconnects Nanostructure fabrication Nanostructure fabrication Integrated optics devices Integrated optics devices Resonators Resonators We investigate the nonlinear response of terahertz (THz) metamaterial perfect absorbers consisting of electric split ring resonators on GaAs integrated with a polyimide spacer and gold ground plane. These perfect absorbers on bulk semi-insulating GaAs are characterized using high-field THz time-domain spectroscopy. The resonance frequency redshifts 20 GHz and the absorbance is reduced by 30% as the incident peak field is increased from 30 to 300 kV/cm. The nonlinear response arises from THz field driven interband transitions and intervalley scattering in the GaAs. To eliminate the Fresnel losses from the GaAs substrate, we design and fabricate a flexible metamaterialsaturable perfect absorber. The ability to create nonlinear absorbers enables appealing applications such as optical limiting and self-focusing.authors would like to thank the Boston University Photonics Center for technical support.
Far infrared or terahertz Far infrared or terahertz Metamaterials Metamaterials Nonlinear optical Nonlinear optical Time-resolved terahertz spectroscopy of charge carrier dynamics in the chalcogenide glass As30Se30Te40 [Invited]Download:630次
Broadband (1.6–18 THz) terahertz time-domain spectroscopy (THz-TDS) and time-resolved terahertz spectroscopy (TRTS) were performed on a 54 μm thick chalcogenide glass (As30Se30Te40) sample with a two-color laser-induced air plasma THz system in transmission and reflection modes, respectively. Two absorption bands at 2–3 and 5–8 THz were observed. TRTS reveals an ultrafast relaxation process of the photoinduced carrier response, well described by a rate equation model with a finite concentration of mid-bandgap trap states for self-trapped excitons. The photoinduced conductivity can be well described by the Drude–Smith conductivity model with a carrier scattering time of 12–17 fs, and we observe significant carrier localization effects. A fast refractive index change was observed 100 fs before the conductivity reached its maximum, with 2 orders of magnitude larger amplitude than expected for the optically induced THz Kerr effect, indicating that free carriers are responsible for the transient index change.
Spectroscopy Spectroscopy terahertz terahertz Spectroscopy Spectroscopy ultrafast ultrafast Glass and other amorphous materials Glass and other amorphous materials Nonlinear optical materials Nonlinear optical materials Photoconductive materials Photoconductive materials Photoconductive switches were the key components that allowed the generation and detection of coherent broadband electromagnetic pulses at terahertz frequencies, opening the possibility for performing spectroscopy and, therefore, measuring complex dielectric properties of materials in this band, which was mostly unexplored. In this paper, we present a brief introduction to the operation principles of these devices. Subsequently, we present a review of the current state-of-the-art in this field and discuss the challenges to be faced in future development of these devices.
Spectroscopy Spectroscopy terahertz terahertz Far infrared or terahertz Far infrared or terahertz Photoconductive materials Photoconductive materials We give an introduction to the feature issue comprised of six articles on terahertz photonics techniques and applications.
Far infrared or terahertz Terahertz imaging Spectroscopy, terahertz 公告
动态信息
动态信息 丨 2024-04-25
PR Highlight (Vol. 12, Iss. 2): 封面|超紧凑片上偏振控制器动态信息 丨 2024-04-11
PR Highlight (Vol. 11, Iss. 12): 亮点 | 十亿像素级、高通量的无透镜偏振编码叠层成像技术动态信息 丨 2024-03-29
PR 封面故事 (Vol. 12, Iss. 3): 封面 | 基于时空编码神经网络的像差感知超分辨成像动态信息 丨 2024-03-25
PR 封面故事 (Vol. 12, Iss. 1) 光涡旋与手性器件微纳3D打印动态信息 丨 2024-03-14
PR Highlight (Vol. 12, Iss. 1): 同步双脉冲激光烧蚀中的气泡相互作用效应激光评论微信公众号
点击菜单“联系编辑”即可添加期刊编辑为好友啦