강명수 교수

We report the observation of a novel nonlinear optoacoustic phenomenon, that we name forward stimulated interpolarization scattering. When two frequency-offset laser signals are colaunched into orthogonally polarized guided modes of a birefringent small-core (1.8 μm diameter) photonic crystal fiber, a pattern of axially moving polarization fringes is produced, with a velocity and spacing that depends on the frequency offset. At values of frequency offset in the few-GHz range, the pattern of movi

We report the experimental demonstration of a passively mode-locked Er-doped fiber ring laser operating at the 337th harmonic (1.80 GHz) of the cavity. The laser makes use of highly efficient Raman-like optoacoustic interactions between the guided light and gigahertz acoustic resonances trapped in the micron-sized solid glass core of a photonic crystal fiber. At sufficient pump power levels the laser output locks to a repetition rate corresponding to the acoustic frequency. A stable optical puls

Transverse acoustic resonances at gigahertz frequencies are excited by electrostriction in the few-micrometer-thick waists of low-loss optical fiber tapers of up to 40 cm long. A pump-probe technique is used in which the resonances are excited by a train of optical pulses and probed in a Sagnac interferometer. Strong radially symmetric acoustic resonances are observed and the dependence of their frequencies on taper thickness is investigated. Such easily reconfigurable acousto-optic interactions

This paper demonstrates and characterizes a novel wavelength-tunable single-frequency erbium-doped fiber ring laser incorporating an all-fiber acoustooptic tunable bandpass filter and a self-constructed saturable absorption grating (SAG). Stable single-longitudinal-mode operation was achieved over the wavelength range of 48 nm with a sidemode suppression ratio higher than 50 dB. The wavelength tuning characteristics, and the laser dynamics in wavelength switching and sweeping are analyzed in det

Abstract Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. While previously demonstrated applications relied exclusively on the low-loss transmission of only the fundamental mode, the implementation of multimode tapers that adiabatically transmit several modes has remained very challenging, hindering their use in various emerging applications in multimode nonlinear optics and quantu

We propose and experimentally demonstrate a novel configuration for an acoustooptic tunable bandpass filter based on intermodal coupling in a two-mode fiber. The double-pass scheme provides zero frequency-shift, bandwidth narrowing, and enhanced extinction ratio. A 3-dB bandwidth of 2.0 nm, insertion loss of 5.6 dB, and sidelobe suppression ratio of 14 dB were achieved. The wavelength tuning range was greater than 90 nm for the transmission dynamic range larger than 20 dB. Multiwavelength operat

We propose and demonstrate methods for suppressing the polarization dependence in the interrogation of birefringent fiber Bragg gratings. A wavelength-swept fiber laser with a polarized output was used as the light source. Two polarization-averaging methods, a depolarization scheme and a polarization scrambling scheme, were investigated and compared. The proposed techniques successfully stabilized the reflection spectrum of a birefringent grating regardless of the polarization state of the sourc

Vector beams, structured optical beams with nonuniform polarization distributions over the cross-section, have been recently found to be more beneficial than the scalar beams to many applications ranging from super-resolution imaging and creation of strongly localized spins or magnetic resonances to multimode classical and quantum communications. The distribution of vector beams over a strand of low-cost optical fiber would alleviate the space constraint in their use and radically broaden their

Received 10 December 2010DOI:https://doi.org/10.1103/PhysRevLett.105.269908© 2010 The American Physical Society

We describe two methods for evaluating the dead time of a time-to-amplitude converter (TAC). The dead time is obtained by measuring either the corresponding time interval in an oscilloscope trace or the relation between the single count rate and the coincidence count rate. Values for the TAC dead time are obtained in the range from 3.4 µs to 14.3 µs for the two methods with respective standard uncertainties of 2.9 × 10−8 s and 3.3 × 10−9 s. The TAC dead time is applied to the calibration of coin

Leaky orbital angular momentum (OAM) resonances cause a series of sharp dips in the transmission spectrum of a twisted PCF. Analysis shows that these OAM resonances are precisely quantized, despite the complexity of the structure.

A continuously twisted PCF can be viewed as a one-dimensional metamaterial in which both ε and μ tensors develop off-diagonal elements. Finite-element calculations confirm the appearance of unique loss peaks in the experimental transmission spectrum.

We successfully fabricate silica nanofibers that permit adiabatic transmission of the higher-order spatial modes by tapering wet-etched optical fibers. Phase-matched intermodal third-harmonic generation in a 760-nm-thick nanofiber is demonstrated with an efficiency higher than 1.05*10 -4 .