A novel type of multiple-wavelength focusing plasmonic coupler based on a nonperiodic nanoslit array is designed and experimentally demonstrated. An array of nanoslits patterned on a thin metal film is used to couple free-space light into surface plasmon polaritons (SPPs) and simultaneously focus different-wavelength SPPs into arbitrary predefined locations in the two-dimensional plane. We design and fabricate a compact triplexer on a glass substrate with an integrated silicon photodetector. The photocurrent spectra demonstrate that the incident light is effectively coupled to SPPs and routed into three different focal spots depending on the wavelength. The proposed scheme provides a simple method of building wavelength-division multiplexing and spectral filtering elements, integrated with other plasmonic and optoelectronic devices.

A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated. In this scheme, binary-phase-shift-keying modulation is applied to the pump wave to broaden and shape the Brillouin gain spectrum. By choosing an appropriate modulation data pattern, we realized a flat-top steep-cutoff optical bandpass filter with a 3-dB bandwidth of 1.5 GHz and a 10-dB bandwidth of 2 GHz is realized. In addition, a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.

We introduce a new figure of merit (FOM) including the input pump power limit associated with stimulated Brillouin scattering (SBS) for evaluation of the Kerr nonlinearity efficiency of optical fibers. The new FOM is expressed as gammaL(eff)P(SBS) (gamma is a nonlinearity parameter, L(eff) is effective length, and P(SBS) is the SBS threshold), while the conventional FOM is given by gammaL(eff). Using the new FOM, we perform an efficiency comparison among four types of state-of-the-art nonlinear optical fiber: a Bi2O3-based nonlinear fiber, a silica-based holey fiber, a highly nonlinear dispersion-shifted fiber, and a conventional dispersion-shifted fiber. The Bi2O3-based nonlinear fiber is found to have the best Kerr nonlinearity efficiency owing to the superior nonlinear property of the Bi2O3 glass compared with that of the silica.

We show that modulational instability may arise even in the normal group-velocity dispersion regime of an optical fiber when the fiber loss (gain) varies depending on the wavelength. A simple analytical expression for the instability gain is obtained, which reveals that the odd-order terms of the loss dispersion are responsible for this phenomenon. The instability gain is measured experimentally in an optical-parametric-amplification configuration. Large parametric gain is induced in a non-phase-matched regime as we apply narrow band loss at the idler wavelength.

No abstract

Semiconductor devices capable of generating a vortex beam with a specific orbital angular momentum (OAM) order are highly attractive for applications ranging from nanoparticle manipulation, imaging and microscopy to fiber and quantum communications. In this work, an electrically pumped integrated OAM emitter operating at telecom wavelengths is fabricated by monolithically integrating an optical vortex emitter with a distributed feedback laser on the same InGaAsP/InP epitaxial wafer. A single-step dry-etching process is adopted to complete the OAM emitter, equipped with specially designed top gratings. The vortex beam emitted by the integrated device is captured and its OAM mode purity characterized. The integrated OAM emitter eliminates the external laser required by silicon- or silicon-on-insulator-based OAM emitters, thus demonstrating great potential for applications in communication systems and the quantum domain.

No abstract

No abstract