Microtraps and Atom Chips: Toolboxes for Cold Atom Physics

Magnetic microtraps and Atom Chips are safe, small-scale, reliable and flexible tools to prepare ultra-cold and degenerate atom clouds as sources for various atom-optical experiments. We present an overview of the possibilities of the devices and indicate how a microtrap can be used to prepare and launch a Bose-Einstein condensate for use in an atom clock or an interferometer.     

光子晶体光纤温度压力传感器

提出了一种在高温环境下同时测量温度和气压的光子晶体光纤温度压力传感器.在普通单模光纤和光子晶体光纤之间熔接一段空心光纤构成干涉结构.空心光纤段构成非本征法布里-珀罗干涉仪,利用光子晶体光纤的微孔与外界相通,通过气体折射率变化来测量环境中的气压变化;光子晶体光纤段构成本征法布里-珀罗干涉仪,利用热膨胀效应和热光效应来测量环境中的温度.传感器的解调通过自制的白光干涉解调仪实现,实验通过测量腔长得到被测环境的温度和气压.在不同温度和气压环境下,对腔长分别为306μm和1535μm的温度压力光纤传感器进行连续测量.实验结果表明,传感器能够在28~800℃的温度下和0~10 MPa的气压下稳定工作,测量范围内温度灵敏度可达17.4 nm/℃,压力灵敏度随温度增加而降低,在28℃时可达1460.5 nm/MPa.     

Simultaneous measurement of curvature and temperature based on PCF-based interferometer and fiber Bragg grating

A sensor head consisting of a photonic crystal fiber (PCF)-based Mach-Zehnder interferometer (MZI) and a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of curvature and temperature. The MZI fabricated by splicing a short length of PCF between two single-mode fibers with the air-hole structure that completely collapsed near the splicing points, is sensitive to fiber bending and surrounding temperature, while the FBG is only sensitive to the later. Simultaneous measurement of curvature and temperature is therefore obtained. Sensitivities of 4.06 nm/m^− 1 and 6.30 pm/°C are achieved experimentally for curvature and temperature, respectively. And the corresponding resolutions are 5.2 × 10^− 4 m^− 1 and 1.25 °C for curvature and temperature, respectively, based on the wavelength measurement resolution of 10 pm.     

Design of different bandwidth dispersive mirrors

Dispersive mirrors in the wavelength range of 960–1110 nm, 700–900 nm, 950–1150 nm, 600–900 nm, 900–1200 nm, 600–1000 nm and 550–1050 nm are designed, respectively. From the design results, we analyse the choice of material and the approach to dispersion compensation. Furthermore, along with the increase of bandwidth, interaction between group delay dispersion (GDD) oscillation and high reflectivity, and influence of bandwidth on both GDD ripple and reflectivity are discussed.     

In-process sensor for surface profile measurement applying a common-mode rejection technique

An optical non-contact profilometer is presented for super-smooth surfaces, which applies a so-called common-mode rejection technique. Environmental disturbances and laser amplitude noise, which commonly exist in similar instruments, are overcome in this system. The overall simplicity of the optics and electronics, the low cost of the components and the ease of alignment make this a convenient system to implement.     

The Use of Carousel Interferometer in Fourier-Transform Ultraviolet Spectroscopy

The carousel interferometer is a new type of an interferometer, which has been invented at the University of Turku. It consists of a beamsplitter and five plane mirrors. Four of the mirrors are mounted on a carousel, which rotates back and forth. We have modified the interferometer for use in the Fourier-transform ultraviolet (FT-UV) spectroscopy. Test measurement with plasma radiation gives favourable results. The most important property, which makes the carousel interferometer suitable for UV measurements, is its good stability in modulation.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27–29, Saitama, Japan.     

Space tests of relativistic gravity with precision clocks and atom interferometers

Precision clocks and interferometers in space can test relativistic gravity with extremely high sensitivity. Yet, only a single such test has been performed, namely the celebrated flight of a hydrogen maser in a sub-orbital trajectory in 1976 (GP-A mission). This paper suggests some of the obstacles to space flight of precision instruments, and describes how the emergence of new technology might offer a pathway for removing those obstacles. A brief review of emerging technologies is made, and new mission concepts based on them are described. Some of the technologies that can impact more tests of relativistic gravity in space at a more distant future are also described.     

Wavefront shifting photorefractive holographic interferometer and its applications in optical testing

Two simple and effective methods of interference—transverse shift technique and longitudinal shift technique—are proposed by using a photorefractive crystal as a real-time recording and reconstruction device. Their principles are analysed through the measurement of refractive index. Some experimental results are also given. These principles and techniques can be used for optical testing and have adequate accuracy.     

Wavelength-selective all-fiber filter based on a single long-period fiber grating and a misaligned splicing point

A novel wavelength-selective all-fiber filter using a single long-period fiber grating (LPG) interacting with a misaligned fusion splicing point has been demonstrated. The misaligned splicing point couples a part of the core mode power into the cladding modes, which is then recoupled into the core mode by the following LPG. As an optical path difference is introduced by the differential refractive index of the fiber, an in-fiber Mach-Zehnder interferometer is therefore formed, which may function as a cost-efficient WDM filter with good isolation and low insertion loss.     

A simple wavemeter with crossed dispersion

A simple wavemeter has been developed by crossing the dispersions of a conventional monochromator and a Fabry-Perot interferometer. The interference pattern is scanned by a linear image sensor and processed by a microcomputer to determine the wavelength of cw laser sources with a better than 0.02 Å accuracy even when the sources have more than one spectral peak.