Optical frequency comb generation from a monolithic microresonator

Optical frequency combs provide equidistant frequency markers in the infrared, visible and ultra-violet and can link an unknown optical frequency to a radio or microwave frequency reference. Since their inception frequency combs have triggered major advances in optical frequency metrology and precision measurements and in applications such as broadband laser-based gas sensing8 and molecular fingerprinting. Early work generated frequency combs by intra-cavity phase modulation while to date frequency combs are generated utilizing the comb-like mode structure of mode-locked lasers, whose repetition rate and carrier envelope phase can be stabilized. Here, we report an entirely novel approach in which equally spaced frequency markers are generated from a continuous wave (CW) pump laser of a known frequency interacting with the modes of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The intrinsically broadband nature of parametric gain enables the generation of discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without relying on any external spectral broadening. Optical-heterodyne-based measurements reveal that cascaded parametric interactions give rise to an optical frequency comb, overcoming passive cavity dispersion. The uniformity of the mode spacing has been verified to within a relative experimental precision of 7.3*10(-18).Comment: Manuscript and Supplementary Informatio

Point-contact tunneling involving low-dimensional spin-triplet superconductors

We modify and extend previous microscopic calculations of tunneling in superconducting junctions based on a non-equilibrium Green function formalism to include the case of spin-triplet pairing. We show that distinctive features are present in the I-V characteristics of different kinds of junctions, in particular when the effects of magnetic fields are taken into account, that permit to identify the type of pairing. We discuss the relevance of these results in the context of quasi one-dimensional organic superconductors like (TMTSF)_2(PF_6) and layered compounds like Sr_2RuO_4.Comment: 4 pages, 1 figur

Scaling study of Si/SiGe MODFETs for RF applications

Based on the successful calibration on a 0.25 /spl mu/m strained Si/SiGe n-type MODFET, this paper presents a gate length scaling study of double-side doped Si/SiGe MODFETs. Our simulations show that gate length scaling improves device RF performance. However, the short channel effects (SCE) along with the parasitic delays limit the device performance improvements. We find that it is necessary to consider scaling (dimensions and doping) of both the lateral and vertical architecture in order to optimize the device design

Inductive algebras and homogeneous shifts

Inductive algebras for the irreducible unitary representations of the universal cover of the group of unimodular two by two matrices are classified. The classification of homogeneous shift operators is obtained as a direct consequence. This gives a new approach to the results of Bagchi and Misra

Time Spent on Higher-Order Tasks in Two Teacher-Apprentice Options

This study investigates the process of assisting a teacher prior to student teaching. Teacher candidates in two certification programs kept a log documenting the tasks they did during their on-site experiences and the time spent on eight types of tasks. A one-way analysis for repeated measures showed that, in both programs, candidates spent a majority of their time on clerical tasks, despite the value they saw in interpersonal contact. A t test for independent measures revealed no significant difference between constant and varied placements in time spent on teaching a whole class and on other highly valued tasks

Resonant X-Ray Scattering on the M-Edge Spectra from Triple-k Structure Phase in U_{0.75}Np_{0.25}O_{2} and UO_{2}

We derive an expression for the scattering amplitude of resonant x-ray scattering under the assumption that the Hamiltonian describing the intermediate state preserves spherical symmetry. On the basis of this expression, we demonstrate that the energy profile of the RXS spectra expected near U and Np M_4 edges from the triple-k antiferromagnetic ordering phase in UO_{2} and U_{0.75}Np_{0.25}O_{2} agree well with those from the experiments. We demonstrate that the spectra in the \sigma-\sigma' and \sigma-\pi' channels exhibit quadrupole and dipole natures, respectively.Comment: 3 pages, 3 figures, to be published in J. Phys. Soc. Jpn. Supp

Recent Decisions

Constitutional Law--Grandfather Clause in International Emergency Economic Powers Act Permits the President to Ban Travel to Cuba without Declaring an Emergency Regan v. Wald, 104 S. Ct. 3026 (1984) Jurisdiction--Bank may not Assert Act of State Doctrine as Defense in Action on Certificate of Deposit Garcia v. Chase Manhattan Bank, N.A., 735 F.2d 645 (2d Cir. 1984). Jurisdiction--Commercial Activity as Applied to the Foreign Sovereign Immunities Act and the Act of State Doctrine Braka v. Bancomer, S.A., 589 F. Supp. 1465 (S.D.N.Y. 1984