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

Analisis Hukum Islam terhadap penerapan tarif Surge Pricing pada sewa taksi online Uber di wilayah Surabaya

Skripsi ini adalah hasil penelitian lapangan (field research). Rumusan masalahnya: Pertama, bagaimana praktek penerapan tarif surge pricing pada sewa taksi online Uber di wilayah Surabaya. Kedua, bagaimana analisis hukum Islam terhadap penerapan tarif surge pricing pada sewa taksi online Uber di wilayah Surabaya .Data penelitian ini dihimpun melalui observasi, wawancara kemudian dianalisis dengan menggunakan metode deskripsi kualitatif. Penelitian ini menggunakan pola pikir deduktif, yang diawali dengan mengemukakan pengertian-pengertian, teori-teori, atau fakta-fakta yang bersifat umum, yaitu ketentuan-ketentuan hukum Islam mengenai Ija>rah dan Upah dalam hukum Islam yang selanjutnya dipaparkan dari kenyataan yang ada di lapangan mengenai praktik penerapan tarif surge pricing pada sewa taksi online Uber di wilayah Surabaya, kemudian diteliti dan dianalisis.Hasil penelitian menyimpulkan bahwa penerapan tarif surge pricing yang diberlakukan oleh Uber pada saat terjadinya jam jam sibuk yang menggunakan prinsip ekonomi persediaan dan permintaan, dimana jika permintaan sedang tinggi sedangkan persediaan tidak mencukupi maka biaya perjalanan otomatis meningkat. Dalam penerapannya biaya perjalanan akan meingkat antara 1.1x – 5.5x lipat. Hal ini terjadi secara tiba tiba dan menjadikan penumpang membayar biaya yang lebih mahal dibandingkan dengan perjalanan biasa, dan juga hal ini hanya terjadi di wilayah tertentu dan hanya terjadi beberapa menit atau jam saja. Dalam hukum Islam sebernarnya penerapan ini diperbolehkan, akan tetapi harus diberlakukan secara adil, jelas, transparan dan melihat kerelaan antara penumpang dengan driver. Dan dalam hal ini uber juga memberlakukan perjanjian baku yang terdapat pada buku panduan uber yang sedikit menerangkan tentang adanya tarif surge pricing ini, jadi dengan adanya perjanjian baku ini Uber sudah benar dalam penerapan adanya tarif surge pricing ini.Sejalan dengan kesimpulan di atas, maka disarankan kepada Uber supaya memberi fasilitas kepada pelanggan untuk juga mengetahui di mana atau akan terjadinya penerapan tarif surge pricing dan kepada pengguna layanan Uber agar jika terkena penerapan tarif surge pricing untuk bersabar menunggu hingga harga kembali normal atau tetap memesan taksi online uber dengan cepat agar tarif tidak semakin naik, dan juga kepada driver agar tidak memanfaatkan keadaan saat terjadinya penerapan tarif surge pricing

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Observation of Brillouin optomechanical strong coupling with an 11 GHz mechanical mode

Achieving cavity-optomechanical strong coupling with high-frequency phonons provides a rich avenue for quantum technology development, including quantum state transfer, memory, and transduction, as well as enabling several fundamental studies of macroscopic phononic degrees of freedom. Reaching such coupling with GHz mechanical modes, however, has proved challenging, with a prominent hindrance being material- and surface-induced optical absorption in many materials. Here, we circumvent these challenges and report the observation of optomechanical strong coupling to a high-frequency (11 GHz) mechanical mode of a fused-silica whispering-gallery microresonator via the electrostrictive Brillouin interaction. Using an optical heterodyne detection scheme, the anti-Stokes light backscattered from the resonator is measured, and normal-mode splitting and an avoided crossing are observed in the recorded spectra, providing unambiguous signatures of strong coupling. The optomechanical coupling rate reaches values as high as /2=39  MHz through the use of an auxiliary pump resonance, where the coupling dominates both optical (/2=3  MHz) and mechanical (m/2=21  MHz) amplitude decay rates. Our findings provide a promising new approach for optical quantum control using light and sound

Impact of nitrogen seeding on confinement and power load control of a high-triangularity JET ELMy H-mode plasma with a metal wall

This paper reports the impact on confinement and power load of the high-shape 2.5MA ELMy H-mode scenario at JET of a change from an all carbon plasma facing components to an all metal wall. In preparation to this change, systematic studies of power load reduction and impact on confinement as a result of fuelling in combination with nitrogen seeding were carried out in JET-C and are compared to their counterpart in JET with a metallic wall. An unexpected and significant change is reported on the decrease of the pedestal confinement but is partially recovered with the injection of nitrogen.Comment: 30 pages, 16 figure