Analysis and optimization of rubidium spectrum lamp to eliminate frequency fluctuations of rubidium atomic frequency standard

Rubidium atomic frequency standard (RAFS) is the most widely used frequency standard in space. The light used to pump the atoms and detect the resonance signal is emitted by rubidium spectrum lamp, so the light intensity of rubidium spectrum lamp directly determines the performance of RAFS. This paper discussed on-board RAFS’ output frequency fluctuations caused by rubidium spectrum lamp. The reason of frequency fluctuations from rubidium lamps was described. To obtain stable lamp light intensity, analysis and optimization of the lamp was developed. Relevant experiments were carried out to verify the optimization. The study content of this paper is beneficial to improve the performance of a single temperature controlled space RAFS physics package

Broadband absorption tailoring of SiO2/Cu/ITO arrays based on hybrid coupled resonance mode

Sub-wavelength artificial photonic structures can be introduced to tailor and modulate the spectrum of materials, thus expanding the optical applications of these materials. On the basis of SiO2/Cu/ITO arrays, a hybrid coupled resonance (HCR) mechanism, including the epsilon-near-zero (ENZ) mode of ITO, local surface plasmon resonance (LSPR) mode and the microstructural gap resonance (GR) mode, was proposed and researched by systematically regulating the array period and layer thickness. The optical absorptions of the arrays were simulated under different conditions by the finite-difference time-domain (FDTD) method. ITO films were prepared and characterized to verify the existence of ENZ mode and Mie theory was used to describe the LSPR mode. The cross-sectional electric field distribution was analyzed while SiO2/Cu/ITO multilayers were also fabricated, of which absorption was measured and calculated by Macleod simulation to prove the existence of GR and LSPR mode. Finally, the broad-band tailoring of optical absorption peaks from 673 nm to 1873 nm with the intensities from 1.8 to 0.41 was realized, which expands the applications of ITO-based plasmonic metamaterials in the near infrared (NIR) region.Published versio

Analysis and optimization of rubidium spectrum lamp to eliminate frequency fluctuations of rubidium atomic frequency standard

Rubidium atomic frequency standard (RAFS) is the most widely used frequency standard in space. The light used to pump the atoms and detect the resonance signal is emitted by rubidium spectrum lamp, so the light intensity of rubidium spectrum lamp directly determines the performance of RAFS. This paper discussed on-board RAFS’ output frequency fluctuations caused by rubidium spectrum lamp. The reason of frequency fluctuations from rubidium lamps was described. To obtain stable lamp light intensity, analysis and optimization of the lamp was developed. Relevant experiments were carried out to verify the optimization. The study content of this paper is beneficial to improve the performance of a single temperature controlled space RAFS physics package

Defect-Induced Tunable Permittivity of Epsilon-Near-Zero in Indium Tin Oxide Thin Films

Defect-induced tunable permittivity of Epsilon-Near-Zero (ENZ) in indium tin oxide (ITO) thin films via annealing at different temperatures with mixed gases (98% Ar, 2% O2) was reported. Red-shift of λENZ (Epsilon-Near-Zero wavelength) from 1422 nm to 1995 nm in wavelength was observed. The modulation of permittivity is dominated by the transformation of plasma oscillation frequency and carrier concentration depending on Drude model, which was produced by the formation of structural defects and the reduction of oxygen vacancy defects during annealing. The evolution of defects can be inferred by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and Raman spectroscopy. The optical bandgaps (Eg) were investigated to explain the existence of defect states. And the formation of structure defects and the electric field enhancement were further verified by finite-difference time domain (FDTD) simulation

Ultrathin Terahertz Dual-Band Perfect Metamaterial Absorber Using Asymmetric Double-Split Rings Resonator

In this article, an ultrathin terahertz dual band metamaterial absorber made up of patterned asymmetrical double-split rings and a continuous metal layer separated by a thin FR-4 layer is designed. Simulation results show that two almost identical strong absorption peaks appear in the terahertz band. When the incident electric field is perpendicular to the ring gaps located at 11 μm asymmetrically, the absorptivity of 98.6% at 4.48 THz and 98.5% at 4.76 THz can be obtained. The absorption frequency and the absorptivity of the absorber can be modulated by the asymmetric distribution of the gaps. The perfect metamaterial absorber is expected to provide important reference for the design of terahertz modulator, filters, absorbers, and polarizers

Polarization Controllable Device for Simultaneous Generation of Surface Plasmon Polariton Bessel-Like Beams and Bottle Beams

Realizing multiple beam shaping functionalities in a single plasmonic device is crucial for photonic integration. Both plasmonic Bessel-like beams and bottle beams have potential applications in nanophotonics, particularly in plasmonic based circuits, near field optical trapping, and micro manipulation. Thus, it is very interesting to find new approaches for simultaneous generation of surface plasmon polariton Bessel-like beams and bottle beams in a single photonic device. Two types of polarization-dependent devices, which consist of arrays of spatially distributed sub-wavelength rectangular slits, are designed. The array of slits are specially arranged to construct an X-shaped or an IXI-shaped array, namely X-shaped device and IXI-shaped devices, respectively. Under illumination of circularly polarized light, plasmonic zero-order and first-order Bessel-like beams can be simultaneously generated on both sides of X-shaped devices. Plasmonic Bessel-like beam and bottle beam can be simultaneously generated on both sides of IXI-shaped devices. By changing the handedness of circularly polarized light, for both X-shaped and IXI-shaped devices, the positions of the generated plasmonic beams on either side of device can be dynamically interchanged

Dual-Band Perfect Metamaterial Absorber Based on an Asymmetric H-Shaped Structure for Terahertz Waves

We designed an ultra-thin dual-band metamaterial absorber by adjusting the side strips’ length of an H-shaped unit cell in the opposite direction to break the structural symmetry. The dual absorption peaks approximately 99.95% and 99.91% near the central resonance frequency of 4.72 THz and 5.0 THz were obtained, respectively. Meanwhile, a plasmon-induced transmission (PIT) like reflection window appears between the two absorption frequencies. In addition to theoretical explanations qualitatively, a multi-reflection interference theory is also investigated to prove the simulation results quantitatively. This work provides a way to obtain perfect dual-band absorption through an asymmetric metamaterial structure, and it may achieve potential applications in a variety of fields including filters, sensors, and some other functional metamaterial devices