Absolute optical frequency measurement of saturated absorption lines in Rb near 422 nm

We present absolute optical frequency measurements of the 5s² S _1/2–6p² P _1/2 hyperfine resolved transitions in both ⁸⁵Rb and ⁸⁷Rb near 422 nm. The frequency of each transition was measured by stabilizing a narrow-linewidth extended cavity diode laser to the transition under study and by measuring that frequency with a femtosecond laser frequency comb. A frequency-doubled 844 nm laser was used as a frequency link to connect the 422 nm probe laser to the near infrared part of the comb. The resulting uncertainties of <70 kHz in the Rb transition frequencies represent a four-order of magnitude improvement over previously published results. The frequencies reported in this paper are one of the most accurate series of measurements made in the violet region of the spectrum. PACS 06.30.Ft; 33.20.Kf; 43.62.Fi     

Extension of measurement range in Brillouin optical correlation domain analysis by pump-probe switching

We propose and experimentally demonstrate a novel method for the extension of the measurement range in Brillouin optical correlation domain analysis by switching the pump and probe waves for selectively inducing the stimulated Brillouin scattering (SBS) in the sensing fiber. In this scheme, two correlation peaks are located in the sensing fiber and SBS is alternatively induced at each position by pump/probe selective switching and optical attenuation. In the experiment, twice enlargement of measurement range is successfully achieved with 146-m fiber with a 10-cm spatial resolution.     

Performance of a polarizer using synthetic mica crystal in the 12-25 nm wavelength range

To develop polarizer functioning in the extreme ultraviolet (EUV) and soft X-ray region, the polar- ization performance of synthetic mica has been investigated theoretically with a simulation code using Fresnel equations and optical constants from the Henke database. The reflectance of synthetic mica crystal for s and p polarization was measured to investigate its polarization performance in a home-made synchrotron radiation soft X-ray polarimeter at beamline 3W1B, Beijing Synchrotron Radiation Facility (BSRF). The reflectivity of the synthetic mica crystal at an angle of grazing incidence of 48° was obtained from the experimental data, which is about 4.8x10<'-3> at 25 nm and 6.0×10<'-4> at 12 nm, and the linear polarizance of the X-ray reflected by the synthetic mica crystal that we measured using an analyzer-rotating method increases from 80% to 96.6% in this EUV region, while higher than 98.2% in the simulation. The result indicates that this synthetic mica crystal works as a practical polarizer in this EUV region of 12-25 nm, and also in an extensive wavelength region higher than 25 nm.     

Absorption measurement of a 50-mm-Long periodically poled lithium niobate optical parametric oscillator pumped at 1064 nm by a Nd: YAG laser

We measured the absorption of different periodically poled lithium niobate crystals when different wavelength beams come through them. The choice of a periodically poled lithium niobate crystal is utilized by a singly resonant oscillator to efficiently generate 3800-nm light when it is pumped by a 1064-nm laser and to generate the 2600-nm signal, and, then, injection seeded at 1550 nm. The temperature-tuning curve and idler output power of the chosen crystal are measured.     

281-332nmSO+2的光碎片激发谱研究

在超声分子束条件下,利用380.85nm的电离激光使SO2分子经由[3+1]共振增强多光子电离(REMPI)制备纯净的分子离子SO+2((X)2A1(000)),用另一束解离激光在281-332nm扫描获得了光解碎片激发(PHOFEX)谱.获得的光碎片SO+激发谱基本可以归属为SO+2((E),(D))←SO+2((X)2A1)序列跃迁.尝试性地标识了(X)2A1(000)到(D)电子态弯曲振动能级的跃迁,给出(D)电子态新的弯曲振动频率ν2=241.78±0.92cm-1和非谐常数X22=-1.71±0.01cm-1.结合可见光波长区(562-664nm)的PHOFEX连续谱讨论了SO+2的(E),(D),(C)电子态的对称性和它们的预解离动力学.结果表明:SO+2的(E),(D),(C)电子态附近可能存在着两个和解离限SO+(X2П)+O(3Pg)相关、对称性分别为2A2,2B2的排斥态α2A2和β2B2,由此得到SO+2的(E),(D),(C)电子态的对称性分别为(E)2B2,(D)2B1,(C)2A1,(D)2B1和α2A2排斥态的电子-振动耦合、(E)2B2和β2B2排斥态的电子-电子、电子-振动耦合导致了到SO+(X2П)+O(3Pg)的解离.     

Sub-milliwatt sub-millisecond recording of population gratings in ytterbium-doped optical fibers at 976 nm

We report effective formation of population gratings in ytterbium-doped fibers by coherent light at 976 nm, i.e. at the wavelength that is typically utilized for optical pumping of these fibers. The dynamic gratings need sub-mW cw laser power to be recorded and have comparable amplitude (absorption) and phase (refractive index) components. Given the spontaneous relaxation time of a Yb³⁺ meta-stable level of ~ 0.8 ms, the grating formation time proved also to be in the sub-ms region with the phase grating component significantly slower than the amplitude one.     

Analyses of transmission characteristics of Rb, Rb and Rb Faraday optical filters at 532 nm

In this paper, the transmission characteristics for Rb, ⁸⁵Rb and ⁸⁷Rb Faraday optical filters at 532 nm that can be used to detect the practical and important frequency-doubled Nd:YAG laser are analyzed and discussed. The theoretical model of an excited-state Faraday optical filter based on the hyperfine structures of atomic system in the intermediate field, what is to our knowledge, is firstly reported. This model predicts that the peak transmission is approximately 50% with an equivalent bandwidth of less than 3 GHz for filters operating on the 5P_1/2 → 10S_1/2 transition in Rb, ⁸⁵Rb and ⁸⁷Rb vapors, respectively. Moreover, the transmission property of ⁸⁷Rb atomic vapor is superior to that of Rb, ⁸⁵Rb atomic vapors, which makes it more suitable for the operation material of Faraday optical filters by comparison with natural Rb vapor.     

Luminescence of the semimagnetic semiconductor CdMnTe in the wavelength range 370–400 nm at high excitation levels

Luminescence of the semimagnetic semiconductor CdMnTe was studied. It was revealed that, in the near-UV range, the luminescence spectrum of CdMnTe contains a band whose position does not depend on the Mn concentration in the solid solution. The temperature and lux-watt characteristics of the band were investigated, and time-resolved measurements were performed. The totality of the data obtained permits the conclusion that the revealed band can be attributed to the luminescence of clusters of a metastable cubic modification of manganese telluride.     

Impact of polarized illumination on high NA imaging in ArF immersion lithography at 45 nm node

Immersion lithography has been considered as the mainstream technology to extend the feasibility of optical lithography to further technology nodes. Using proper polarized illumination in an immersion lithographic tool is a powerful means to enhance the image quality and process capability for high numerical aperture (NA) imaging. In this paper, the impact of polarized illumination on high NA imaging in ArF immersion lithography for 45 nm dense lines and semi-dense lines is studied by PROLITH simulation. The normalized image log slope (NILS) and exposure defocus (ED) window are simulated under various polarized illumination modes, and the impact of polarized illumination on image quality and process latitude is analyzed.     

Optical measurement of the speed of sound in air over the temperature range 300-650 K

Using laser-induced thermal acoustics (LITA), the speed of sound in room air (1 atm) is measured over the temperature range 300-650 K. Since the LITA apparatus maintains a fixed sound wavelength as temperature is varied, this temperature range simultaneously corresponds to a sound frequency range of 10-15 MHz. The data are compared to a published model and typically agree within 0.1%-0.4% at each of 21 temperatures.     

Visible light scattering study at 470, 550, and 660 nm of components of mineral dust aerosol: Hematite and goethite

Iron oxides, usually in the form of hematite or goethite, comprise an important component of atmospheric mineral dust aerosol. Because these minerals are strong visible absorbers they play a critical role in determining the overall impact of dust aerosol on climate forcing. In this work, results from light scattering measurements from hematite and goethite dust aerosol are presented for three visible wavelengths, λ=470, 550, and 660 nm. We observe important systematic differences in the scattering between these different iron oxide samples, as well as significant wavelength dependence across the visible region of the spectrum. Aerosol size distributions are measured simultaneously with the light scattering, enabling a rigorous comparison between theoretical light scattering models and experimental data. Theoretical simulations of the scattering are carried out using both Mie and T-Matrix theories. Simulations are in reasonably good agreement with experimental data for hematite; thus, our data offer a useful check on tabulated optical constants for hematite. However, simulations show very poor agreement for goethite. The poor agreement in the goethite case is likely the result of particle shape effects related to the rod-like morphology of the goethite particles. This study demonstrates how particle mineralogy and morphology play an important role in dictating the optical properties of mineral dust aerosol, a major component of tropospheric dust.     

Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz

The work within this paper focuses on the application and validation of numerical methods for predicting the acoustic and structural NVH behaviour of trimmed body components in an automotive context. In particular, the level of modelling refinement and accuracy necessary to establish a reliable finite element analysis model for comparative purposes in the development of alternative designs is investigated.Specifically, the roof structure of a passenger car was investigated from various performance aspects, using both structural and acoustic excitation. The roof was initially tested in situ, with and without interior lining, to provide a reference for subsequent component tests. It was then detached from the car, mounted in a stiff frame and tested in a transmission window using both acoustic and structural excitation.A finite element model of the detached component was developed using shell and solid elements for the structure and solid elements for the interior lining. Predictions were carried out to evaluate the STL as well as the vibrational frequency response due to a force applied to the structure. Special attention was given to the modelling of the headliner as well as the air gap separating the headliner from the outer sheet metal. A sensitivity study of various headliner properties was performed in addition to a comparison between solutions calculated using standard Nastran elements and augmented poro-elastic elements via the software package CDH/EXEL.The main objective of the current work has been to establish a datum reference for alternative designs. From this aspect, the validation of the numerical modelling methodology, in particular the level of detail and accuracy used, was a crucial step. It was found that the predictions agreed very well with the measured data. As an additional, very interesting result, it was also found that the in situ testing correlated well with the transmission suite testing.     

Improved short-term stability of optical frequency standards: approaching 1 Hz in 1 s with the Ca standard at 657 nm

For a neutral (40)Ca-based optical frequency standard we report a fractional frequency instability of 4 x 10(-15) in 1 s, which represents a fivefold improvement over existing atomic frequency standards. Using the technique of optical Bordé-Ramsey spectroscopy with a sample of 10(7) trapped atoms, we have resolved linewidths as narrow as 200 Hz (FWHM). With colder atoms this system could potentially achieve an instability as low as 2 x 10(-16) in 1 s. Such low instabilities are important for frequency standards and precision tests of fundamental physics.