In this Letter, ceramic Nd:YAG is charactrizeby electron spin resonance(ESR) measurements. The ESR results indicate that the polycrystalline ceramic Nd:YAG has barely native defects and impurity ions localization defects, compared to an Nd:YAG crystal with the same Nd doping concentration, due to its density structure by sintering in a vacuum pure raw material and additives during the fabrication. It may conclude that the high quality ceramic Nd:YAG may have greater ability on optical characteristic, mechanical performance,and laser damage than that of the crystals, which is a promising candidate to use on laser diode-pumped solid-state lasers.
In order to realize single emissive white phosphorescent organic light-emitting devices(PHOLEDs) with three color phosphorescent dopants(red, green, and blue), the energy transfer between the host material and the three dopants, as well as the among the three dopants themselves, should be considered and optimized. To explore the effect of red phosphorescent dopant on the color rendering index(CRI), the authors investigate the wavelength position of the maximum emission peak from three phosphorescent dopants. The CRI and luminous efficiency of white PHOLED in which Ir(pq)_2(αcαc) acts as the red phosphorescent dopant are found to be greater than those of devices prepared using Ir(pig)_3 and Ir(pq)_2(αcαc) as the emission spectrum has a relatively high intensity near the human perception of blue, red, and green wavelengths. Furthermore, we demonstrate that the performance of the three dopants is related to the absorption characteristics of the red phosphorescent dopant.With a maximum emission peak at 600 nm, Ir(pq)_2(αcαc) has a higher intensity in the concave section between 550 and 600 nm seen for red and blue dopants. In addition, the long metal-to-ligand charge transfer(MLCT)absorption tail of Ir(pq)_2(αcαc) overlaps with the emission spectra of the green dopant, enhancing emission. Such energy transfer mechanisms are confirmed to optimize white emission in the single emissive white PHOLEDs.
The plasmonic mode in graphene metamaterial provides a new approach to manipulate terahertz(THz) waves.Graphene-based split ring resonator(SRR) metamaterial is proposed with the capacity for modulating transmitted THz waves under normal and oblique incidence. Here, we theoretically demonstrate that the resonant strength of the dipolar mode can be significantly enhanced by enlarging the arm-width of the SRR and by stacking graphene layers. The principal mechanism of light–matter interaction in graphene metamaterial provides a dynamical modulation based on the controllable graphene Fermi level. This graphene-based design paves the way for a myriad of important THz applications, such as optical modulators, absorbers, polarizers, etc.
In this work, we investigate a new type of fluoride glasses modified by Al(PO_3)_3 with various Tm~(3+)∕Ho~(3+) doping concentrations. The introduced PO_-~3 plays an effective role in improving the glass-forming ability and thermal stability. Besides, 1.47, 1.8, and 2.0 μm emissions originating from Tm~(3+)and Ho~(3+), respectively, are observed.The spectroscopic properties and energy transfer mechanisms between Tm~(3+)and Ho~(3+)are analyzed as well. It is noted that the higher predicted spontaneous transition probability(118.74 s-1) along with the larger product of measured decay lifetime and the emission cross section(σemi×τ) give evidence of intense 2.0 μm fluorescence.
An endoscopic imaging system using a plenoptic technique to reconstruct 3-D information is demonstrated and analyzed in this Letter. The proposed setup integrates a clinical surgical endoscope with a plenoptic camera to achieve a depth accuracy error of about 1 mm and a precision error of about 2 mm, within a 25 mm × 25 mm field of view, operating at 11 frames per second.
Five conical harmonic beams are generated from the interaction of femtosecond mid-infrared(mid-IR) pulses at a nominal input wavelength of 1997 nm with a 2D LiNbO_3 nonlinear photonic crystal with Sierpinski fractal superlattices. The main diffraction orders and the corresponding reciprocal vectors involved in the interaction are ascertained. Second and third harmonics emerging at external angles of 23.82° and 36.75° result from nonlinearerenkov and Bragg diffractions, respectively. Three pathways of fourth-harmonic generation are observed at external angles of 14.21°, 36.5°, and 53.48°, with the first one resulting from nonlinearerenkov diffraction, and the other two harmonics are generated via different cascaded processes.
We show how to optimally protect quantum states and freeze coherence under incoherent channels using a quantum weak measurement and quantum measurement reversal. In particular, we present explicit formulas for the conditions for freezing quantum coherence in a given quantum state.
The cavity ring-down(CRD) technique is adopted for simultaneously measuring s-and p-polarization reflectivity of highly reflective coatings without employing any polarization optics. As the s-and p-polarized light trapped in the ring-down cavity decay independently, with a randomly polarized light source the ring-down signal recorded by a photodetector presents a double-exponential waveform consisting of ring-down signals of both s-and p-polarized light. The s-and p-polarization reflectivity values of a test mirror are therefore simultaneously determined by fitting the recorded ring-down signal with a double-exponential function. The determined s-and p-polarization reflectivity of 30° and 45° angle of incidence mirrors are in good agreement with the reflectivity values measured with the conventional CRD technique employing a polarizer for polarization control.
We review over a decade of technology evolution and advancement of intra-datacenter optical interconnect,mainly driven by the explosive bandwidth growth of web and cloud-based services. Emerging trends and technology options to scale interface bandwidth beyond 400 Gb/s will also be discussed.