Ultrastable low-cost colloidal quantum dot microlasers of operative temperature up to 450 K

Quantum dot microlasers, as multifunctional optical source components, are of great importance for full-color high-pixel display, miniaturized coherent lighting...     

全保偏掺铒光纤光梳

搭建了基于非线性放大环形镜的全保偏掺铒光纤激光器,它可为光梳系统在室外环境中的应用提供稳定运行的光学振荡源。在实验上,通过两级光学预放大及高非线性光纤获得了1000~2300 nm的超连续谱,采用共线型f-2f干涉仪检测到的载波包络偏移频率f0的信噪比高达35 dB。研究了腔内净色散和f0线宽的关系,并将自由运转状态下的f0线宽窄化至5 kHz。将光梳系统的主要参数(重复频率fr和载波包络偏移频率f0)溯源至同一台铷原子钟,锁定后所测标准偏差分别为780μHz和308 mHz。该光纤光梳系统具有集成度高、体积小的特点。     

Focusing and defocusing dynamics of weak-light beam in a resonant three-level atomic system

Focusing and defocusing dynamics of weak-light ring-shaped beams in a Λ-type atomic system are investigated. It is found that focusing of weak light is possible due to the quantum interference effect. The focusing or defocusing regime with vanishing absorption can be manipulated by adjusting detunings from the resonant transition. When the fields are tuned appropriately larger than resonant frequencies, the beam propagates in the defocusing regime and diffraction of the beam takes place. Conversely, the beam focuses in the medium when the laser frequencies are tuned smaller than the resonant frequencies.     

Graphene and its derivatives for laser protection

The development of functional materials for laser protection is an extremely important research field for the safety and security of users. To achieve simultaneous protection against both pulsed and continuous wave (cw) or quasi-cw lasers, significant research effort has been invested into state-of-the-art broadband optical limiting (OL) materials and processes in an attempt to achieve some measure of protection from such laser beams in the past decades. As the first truly two-dimensional material, graphene is being considered as an ideal material for modern photonic, optoelectronic and electronic devices because of its fantastic physical properties. Graphene shows ultrafast carrier relaxation dynamics and ultra-broadband resonate nonlinear optical (NLO) response due to their extended π-conjugate system and the linear dispersion relation holding for their electronic band structure. Almost all types of graphene-based materials described in this review exhibit strong broadband OL response. The dominant limiting mechanism of graphene is nonlinear scattering, which is very effective in liquid suspensions rather than in solid state hosts. In contrast to the pure graphene, the solubilized graphene and its derivatives optically limits through nonlinear absorption mechanism, nonlinear scattering as well as the photoinduced electron transfer and/or energy transfer between graphene and organic/polymeric species. This review describes systematically the OL mechanisms and the recent achievements on the graphene-based functional materials (i.e., graphene nanostructures, graphene composites, and covalently modified graphene) for OL applications. The future major ongoing areas of effort have also been suggested.     

钛宝石晶体的制备、光学和激光性能研究

阐述了温梯法生长大口径、高质量的掺钛蓝宝石晶体。生长的钛宝石在300~900nm波段具有较好的光学吸收特性,通过测定晶体横截面不同位置处的吸收系数来表征掺杂浓度的均匀性。测定钛宝石在200~1100nm波段的透射率,计算品质因素(FOM)值在240以上。钛宝石晶体的静态和单发放大的光斑质量较高、无畸变,其抽运激光的放大输出能量达到国际相同规格钛宝石的同等水平。     

Standing Ultrashort Relativistic Solitons in Overdense Plasmas

By using a one-dimensional self-consistent relativistic fluid model, an investigation is made numerically on relativistic electromagnetic solitons with a high intensity in cold overdense plasmas with an electrons＇ initial velocity opposite to the laser propagating direction. Two types of standing solitons with zero group velocity are found at the given electrons＇ initial velocities. One is single-humped with a weakly relativistic intensity; the another is multi-humped with a strong relativistic amplitude. The properties of these two types of solitons are presented in detail.     

Spatial anisotropy of photoelastic and acoustooptic properties in β-BaB2O4 crystals

The paper deals with the spatial anisotropy of photoelastic and acoustooptical properties in β-BaB₂O₄ (BBO) crystals. Our method is based on the construction and analysis of the indicative surfaces describing the spatial anisotropy of the longitudinal and transverse photoelastic effects. By means of the stereographic projections we have determined the maximum values of photoelastic interaction and the anisotropy power. Having the complete photoelastic tensor we calculated the effective photoelastic constant p_ef and the efficiency of isotropic and anisotropic acoustooptical diffractions (the figure of merit M) for different geometries of acoustooptical interactions. The most optimal sample geometries suitable for acoustooptical applications were determined within the computer simulations based on the optimization procedure, namely we have found the sample geometries characterizing by the maximal efficiency for the isotropic (M = 6.3 × 10⁻¹⁵ s³/kg) and anisotropic (M = 40 × 10⁻¹⁵ s³/kg) diffractions. Taking into account that BBO is known as a rather strong radiation-steady crystal it may be considered as new efficient acoustooptical material for applications in optical systems with superpower laser irradiation.     

Investigation on the luminescence of RE3+ (RE = Ce,Tb, Eu and Tm) in KMGd(PO4)2 (M = Ca,Sr) phosphates

The VUV excited luminescent properties of Ce³⁺, Tb³⁺, Eu³⁺ and Tm³⁺ in the matrices of KMGd(PO₄)₂ (M = Ca, Sr) were investigated. The bands at about 165 nm and 155 nm in the VUV excitation spectra are attributed to host lattice absorptions of the two matrices. For Ce³⁺-doped samples, the Ce³⁺ 5d levels can be identified. As for Tb³⁺-doped samples, typical 4f–5d absorption bands in the region of 175–250 nm were observed. For Eu³⁺ and Tm³⁺-doped samples, the O²⁻–Eu³⁺ and O²–Tm³⁺ CTBs are observed to be at about 229 nm and 177 nm, respectively. From the standpoints of color purity and luminescent efficiency, KCaGd(PO₄)₂:Tb³⁺ is an attractive candidate of green light PDP phosphor.     

Fabrication of high quality factor lithium niobate double-disk using a femtosecond laser

We demonstrate fabrication of a high-quality factor lithium niobate double-disk whispering-gallery microcavity using femtosecond laser assisted ion beam milling. Using this method, two vertically stacked 30-µm diameter disks with a 200-nm gap are fabricated. With our device, an optical quality factor as high as 1.35?×?10⁵ is demonstrated. Our approach is scalable to fabricate multiple disks on a single chip.     

Two-colour two-photon confocal microscopy with isotropic three-dimensional resolution and parallel excitation

We demonstrate a novel design of two-colour two-photon fluorescence microscope in which isotropic three-dimensional imaging resolution and high scanning speed can be achieved simultaneously. In our scheme, a three-dimensional optical lattice constructed by multi-beam interference is used for two-colour two-photon fluorescence excitation. Our simulation results show that a resolution of 113.5 nm can be achieved in both transverse and axial directions with two pump pulses at the wavelengths of 400 and 800 nm, respectively; meanwhile, imaging speed can be greatly improved compared with that of traditional two-photon scanning fluorescence microscopes.