Unpolarized, incoherent repumping light for prevention of dark states in a trapped and laser-cooled single ion

Many ion species commonly used for laser-cooled ion trapping studies have a low-lying metastable 2D3/2 state that can become populated due to spontaneous emission from the 2P1/2 excited state. This requires a repumper laser to maintain the ion in the Doppler cooling cycle. Typically the 2D3/2 state, or some of its hyperfine components if the ion has nuclear spin, has a higher multiplicity than the upper state of the repumping transition. This can lead to dark states, which have to be destabilized by an external magnetic field or by modulating the polarization of the repumper laser. We propose using unpolarized, incoherent amplified spontaneous emission (ASE) to drive the repumping transition. An ASE source offers several advantages compared to a laser. It prevents the buildup of dark states without external polarization modulation even in zero magnetic field, it can drive multiple hyperfine transitions simultaneously, and it requires no frequency stabilization. These features make it very compact and robust, which is essential for the development of practical, transportable optical ion clocks. We construct a theoretical model for the ASE radiation, including the possibility of the source being partially polarized. Using 88Sr+ as an example, the performance of the ASE source compared to a single-mode laser is analyzed by numerically solving the eight-level density matrix equations for the involved energy levels. Finally a reduced three-level system is derived, yielding a simple formula for the excited state population and scattering rate, which can be used to optimize the experimental parameters. The required ASE power spectral density can be obtained with current technology

Dark-state suppression and optimization of laser cooling and fluorescence in a trapped alkaline-earth-metal single ion

We study the formation and destabilization of dark states in a single trapped 88Sr+ ion caused by the cooling and repumping laser fields required for Doppler cooling and fluorescence detection of the ion. By numerically solving the time-dependent density matrix equations for the eight-level system consisting of the sublevels of the 5s 2S1/2, 5p 2P1/2, and 4d 2D3/2 states, we analyze the different types of dark states and how to prevent them in order to maximize the scattering rate, which is crucial for both the cooling and the detection of the ion. The influence of the laser linewidths and ion motion on the scattering rate and the dark resonances is studied. The calculations are then compared with experimental results obtained with an endcap ion trap system located at the National Research Council of Canada and found to be in good agreement. The results are applicable also to other alkaline earth ions and isotopes without hyperfine structure

The Discursive Paradox of Environmental Conflict : Between Ecologism and Economism in Ecuador

Ecuador in times of the Rafael Correa government constitutes a prime example of the paradox of environmental conflict, in which all involved actors claim to represent the true vanguard concerning safeguarding of the environment and human conditions. The country presents the ecologically most progressive constitution in the world and also incorporates far-reaching recognition of indigenous peoples’ rights. Notwithstanding, the economy remains reliant on extractivism and the government argues that the revenues of extractive industries benefit the common good. Anchored in a distinction between environmentalism and ecologism, this article identifies and problematizes dominant narratives among the actors of the contentious discursive scenarios, and analyses how the state and its ecological-indigenous opposition aim to position themselves within the political conflict. The central questions are: How are eco-progressive politics perceived, defined and expressed in this setting of an intercultural and plurinational society economically reliant on natural resource extraction? Which values, interests and ontological assumptions are at stake and how are these expressed in the discursive struggle? The research is based on several years of ethnographic fieldwork, combined with critical reading of the previous literature and discourse analysis. The article contributes to politico-environmental debates in Ecuador and beyond and shows that environmental struggle is entangled in broader political disputes conditioned by global economic structures. It likewise communicates with debates on argumentative discourse and illustrates that the same core arguments can constitute the argumentative basis of rivalling actors in political struggles, thus emphasizing the centrality of the contextual framing amid ontological divides in contentious discursive settings. © 2018, © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Peer reviewe

Broadband, unpolarized repumping and clearout light sources for Sr+^+ single-ion clocks

Future transportable optical clocks require compact and reliable light sources. Here, broadband, unpolarized repumper and state clearout sources for Sr+ single-ion optical clocks are reported. These turn-key devices require no frequency stabilization nor external modulators. They are fiber based, inexpensive, and compact. Key characteristics for clock operation are presented, including optical spectra, induced light shifts and required extinction ratios. Tests with an operating single-ion standard show a clearout efficiency of 100%. Compared to a laser-based repumper, the achievable fluorescence rates for ion detection are a few tens of per cent lower. The resulting ion kinetic temperature is 1--1.5 mK, near the Doppler limit of the ion system. Similar repumper light sources could be made for Ca+ (866 nm) and Ba+ (650 nm) using semiconductor gain media.Comment: 4 pages, 6 figure

Large negative and positive delay of optical pulses in coherently prepared dense Rb vapor with buffer gas

We experimentally study the group time delay for a light pulse propagating through hot Rb vapor in the presence of a strong coupling field in a $\Lambda$ configuration. We demonstrate that the ultra-slow pulse propagation is transformed into superluminal propagation as the one-photon detuning of the light increases due to the change in the transmission resonance lineshape. Negative group velocity as low as -c/10^6=-80 m/s is recorded. We also find that the advance time in the regime of the superluminal propagation grows linearly with increasing laser field power.Comment: 5 pages, 6 figure

Metamorfosa Radikalisme pada Lembaga Pendidikan di Sulawesi Tenggara

Research on the metamorphosis of radicalism in educational institutions in Southeast Sulawesi has been conducted and focused on the segregation potential to be a radical individuals and groups to preach, especially in educational institutions in the Southeast Sulawesi. Data obtained through questionnaires, structured interviews, observation, document tracking and focus group discussion.The results showed that the metamorphosis of radicalism on the knot of educational institutions in Southeast Sulawesi spreading through the penetration movement in educational institutions such as on college campuses and in schools, especially in public campuses with the goal of lecturers and students and public schools targeted teachers and students. The spread on campus through student propaganda agency involving senior students and in the school and through extra-curricular involving senior students with methods of brainwashing. Lecturer plays an important role in the growth of radicalism as teachers and leaders of radical organizations with a method of indoctrination while teachers act through the hidden curriculum. The policy of the state budget subsidies to student organizations affiliated to the radical organization helped sustain the growth of radicalism on campus.The study recommends that efforts to break the chain of radicalism in educational institutions in Southeast Sulawesi can be done by educators either individually or as an educator together with governmen

NEAT-FT: the European fiber link collaboration

The development of clocks based on optical transitions during the past three decades culminates in the availability of optical clocks with unprecedented stability and uncertainty . Simultaneously, increasing requirements for accurate time and frequency signals, e.g. for tests of fundamental physics or novel applications in relativistic geodesy, put forward new challenges. Typically, such applications rely on the comparison of two remote clocks. Thus, major challenges are how to synchronize these clocks over long distances or how to get the time or frequency signal of a clock to the location where it is required. It is generally agreed that optical fiber links are an excellent alternative to established satellite based distant clock comparison and synchronization techniques. A European joint research project called Network for European Accurate Time and Frequency Transfer (NEAT-FT) has been initiated in 2011 to lay the foundations for a novel approach to disseminate high-precision timing and ultrastable frequency signals by using existing fiber infrastructure. Since Europe has a large number of modern ultra-precise clocks, special emphasis is put on the development of new techniques for time transfer and phase-coherent comparison of remotely located optical clocks and the feasibility of a European fibre network connecting optical clocks in Europe. This talk highlights recent achievements and discusses some applications and prospects