Field renormalization in Photonic Crystal waveguides

A novel strategy is introduced in order to include variations of the nonlinearity into the nonlinear schrodinger Equation. This technique, which relies on renormalization, is in particular well adapted to nanostructured optical systems where the nonlinearity exhibits large variations up to two orders of magnitude larger than in bulk material. We show that it takes into account in a simple and efficient way the specificity of the nonlinearity in nanostructures that is determined by geometrical parameters like the effective mode area and the group index. The renormalization of the nonlinear schrodinger Equation is the occasion for physics oriented considerations and unveils the potential of Photonic Crystal waveguides for the study of new nonlinear propagation phenomena.Comment: to be published, Phys. Rev. A (2015

‘The “Bowl of Jelly”: The Department of State in the Kennedy and Johnson Years, 1961-68’,

The article explores efforts to reform the State Department under presidents Kennedy and Johnson, with the intention of making the Department better able to lead and coordinate the sprawling foreign policy apparatus. However, Kennedy soon gave up on what he described as the 'bowl of jelly', so the reform effort was left to Johnson. Under him there were attempts to boost the State Department's internal efficiency and its ability to support counterinsurgency efforts. Yet there was a justified perception by the end of 1968 that the State Department was unredeemed managerially and in terms of its standing in the foreign policy nexus. Reasons for the lack of progress include sporadic presidential engagement, and Secretary of State Dean Rusk's limited aptitude for managerial affairs

The London Ambassadorship of David K.E. Bruce during the Wilson-Johnson years, 1964-68

Using recently released sources, this article offers a fresh perspective on the London ambassadorship of David K. E. Bruce in the years of Harold Wilson and Lyndon Johnson, 1964–68. Bruce's running of the US Embassy is examined, as are his views of the Anglo-American relationship. Further attention is given to his diplomatic management of the Anglo-American relationship in the context of the difficult personal relations between Wilson and Johnson and with regard to policy differences over the Vietnam War and Britain's position as a world power. It is argued that while Bruce did help to ease some of the personal strains between Wilson and Johnson, he was generally less significant to the White House than has previously been asserted. It is also contended that his vision of Britain joining the EEC, yet retaining extensive military commitments beyond Europe was not viable

Communication: 'What now for Britain?' The state department's intelligence assessment of the 'Special Relationship' 7 February 1968

The period 1967-1968 was a difficult one for the Anglo-American relationship, as a result of developments such as British defense cuts “East of Suez.” In the run-up to a visit to Washington by Prime Minister Harold Wilson in February 1968, the State Department's Intelligence and Research Bureau provided a lively and detailed evaluation of American bonds with Britain. The analysis maintained that the relationship was based on deeply established cooperation in defense, diplomacy and intelligence, and that despite recent problems Britain would remain of unparalleled importance as an American ally. The immediate impact of the memorandum in the White House of Lyndon B. Johnson was quite limited, but among other things the document helps to explain the ready blossoming of close high-level Anglo-American bonds during, for example, the Falklands War of 1982. The most important sections of the memorandum are reproduced, and a brief analysis is provided to put the issues in context

Giant anomalous self-steepening in photonic crystal waveguides

Self-steepening of optical pulses arises due the dispersive contribution of the $\chi^{(3)}(\omega)$ Kerr nonlinearity. In typical structures this response is on the order of a few femtoseconds with a fixed frequency response. In contrast, the effective $\chi^{(3)}$ Kerr nonlinearity in photonic crystal waveguides (PhCWGs) is largely determined by the geometrical parameters of the structure and is consequently tunable over a wide range. Here we show self-steepening based on group-velocity (group-index) modulation for the first time, giving rise to a new physical mechanism for generating this effect. Further, we demonstrate that periodic media such as PhCWGS can exhibit self-steepening coefficients two orders of magnitude larger than typical systems. At these magnitudes the self-steepening strongly affects the nonlinear pulse dynamics even for picosecond pulses. Due to interaction with additional higher-order nonlinearities in the semiconductor materials under consideration, we employ a generalized nonlinear Schr\"{o}dinger equation numerical model to describe the impact of self-steepening on the temporal and spectral properties of the optical pulses in practical systems, including new figures of merit. These results provide a theoretical description for recent experimental results presented in [Scientific Reports 3, 1100 (2013) and Phys. Rev. A 87, 041802 (2013)]. More generally, these observations apply to all periodic media due to the rapid group-velocity variation characteristic of these structures.Comment: 7 pages, 4 figure