Chester Shu

Polarization-insensitive widely tunable wavelength converter based on four-wave mixing in a dispersion-flattened nonlinear photonic Crystal fiber

Polarization-insensitive widely tunable wavelength conversion has been demonstrated using four-wave mixing in a 64-m-long dispersion-flattened nonlinear photonic crystal fiber. A 3-dB conversion range over 40 nm (1535-1575 nm) is obtained with a flat conversion efficiency of -16 dB and a polarization sensitivity of less than 0.3 dB. The measured power penalty is less than 1 dB for a 10-Gb/s converted nonreturn-to-zero signal at 10/sup -9/ bit-error rate.

Rational harmonic mode locking of an optically triggered fiber laser incorporating a nonlinear optical loop modulator

Rational harmonic mode locking is first demonstrated in an erbium-doped fiber laser using an all-optical approach. Both bright and dark pulse trains up to 4.58 GHz are obtained at 1.55 /spl mu/m by adjusting the initial reflection state of the intracavity loop mirror. The nonlinear loop modulator serves as a mode locker and an adjustable end reflector in the laser. The setup is useful for optional bit-rate multiplication while providing a means for the conversion of wavelength, as well as the conversion between bright and dark pulses. The output wavelength is also tunable upon the adjustment of a cavity fiber Fabry-Perot filter.

Depolarization technique for wavelength conversion using four-wave mixing in a dispersion-flattened photonic crystal fiber.

We have developed a depolarization technique to achieve polarization-insensitive wavelength conversion using four-wave mixing in an optical fiber. A maximum conversion efficiency of -11.79 dB was achieved over a 3 dB bandwidth of 26 nm in a 100-m-long dispersion-flattened photonic crystal fiber. The polarization-dependent conversion efficiency was less than 0.38 dB and the measured power penalty for a 10 Gbit/s NRZ signal was 1.9 dB. The relation between the conversion efficiency and the degree of polarization of the pump was also formulated.

Multiple fiber Bragg grating interrogation based on a spectrum-limited Fourier domain mode-locking fiber laser

A novel fiber Bragg grating (FBG) sensing system based on a spectrum-limited Fourier domain mode-locking (SL-FDML) fiber laser is proposed. Multiple FBGs cascaded in a long fiber are utilized as both the sensors in the system and the wavelength-selected components in the SL-FDML fiber laser. Both wavelength-division multiplexing and spatial-division multiplexing techniques are demonstrated for interrogation of multiple FBGs by mapping the wavelength measurement to the time measurement and by adjusting the driving frequency of the SL-FDML fiber laser. The proposed FBG sensing system, employing techniques of the wavelength- and spatial-domain interrogation of multiple FBGs, can be used in remote and quasi-distributed multipoint sensing.

Waveband-switchable SOA ring laser constructed with a phase modulator loop mirror filter

An electrically tunable multiwavelength source has been developed using a birefringence-based optical comb filter in a semiconductor optical amplifier ring laser. The filter is constructed with an electrooptic phase modulator placed inside a fiber loop mirror. By controlling the birefringence of the modulator through the applied bias, the radio-frequency power, or the modulation frequency, we achieve a continuous shift of the spectral comb to access different interleaved wavebands. Electrical waveband switching has been successfully demonstrated for 21 wavelengths at 100-GHz grid spacing with an optical signal-to-noise ratio over 40 dB.

Synergistic Effects of Plasmonics and Electron Trapping in Graphene Short-Wave Infrared Photodetectors with Ultrahigh Responsivity

Graphenes unique electronic and optical properties have made it an attractive material for developing ultrafast short-wave infrared (SWIR) photodetectors. However, the performance of graphene SWIR photodetectors has been limited by the low optical absorption of graphene as well as the ultrashort lifetime of photoinduced carriers. Here, we present two mechanisms to overcome these two shortages and demonstrate a graphene-based SWIR photodetector with high responsivity and fast photoresponse. In particular, a vertical built-in field is employed in the graphene channel for trapping the photoinduced electrons and leaving holes in graphene, which results in prolonged photoinduced carrier lifetime. On the other hand, plasmonic effects were employed to realize photon trapping and enhance the light absorption of graphene. Thanks to the above two mechanisms, the responsivity of this proposed SWIR photodetector is up to a record of 83 A/W at a wavelength of 1.55 μm with a fast rising time of less than 600 ns. This device design concept addresses key challenges for high-performance graphene SWIR photodetectors and is promising for the development of mid/far-infrared optoelectronic applications.

4 /spl times/ 2.5 GHz repetitive photonic sampler for high-speed analog to digital signal conversion

This letter presents a 10-gigasample/s (GS/s) photonic analog-to-digital converter (ADC) system constructed using a four-wavelength picosecond pulsed source. The lasing-to-nonlasing modes suppression ratio of the optical source is over 24 dB. By using the 10-GHz optical source, a 10-GS/s photonic ADC has been demonstrated and was used to sample an arbitrary radio-frequency signal. The system was further investigated by sampling a 2.4-GHz sinusoidal signal. Important parameters including the signal-to-noise and distortion ratio and the spurious-free dynamic range have been determined.

Multipump Four-Wave Mixing in a Photonic Crystal Fiber for 6

We demonstrate differential phase-shift keying wavelength multicasting using four-wave mixing in a 64-m dispersion-flattened highly nonlinear photonic crystal fiber. The power penalty is less than 2.9 dB for all the 10-Gb/s multicast channels spaced at 200 GHz.

\times

We propose a new type of dynamically tunable birefringence comb filter based on a semiconductor optical amplifier Sagnac loop interferometer. By optically modulating the birefringence of the amplifier, we demonstrate a tuning of the output wavelengths. The shift of wavelength increases monotonically with the power of the control light until saturation occurs. The tuning relation is independent of the comb spacing governed by the length and birefringence of the polarization maintaining fiber inside the loop. A tuning range up to 59% of the comb spacing has been achieved at 18.5 dBm input power.

10 Gb/s Wavelength Multicasting of DPSK Signals

We demonstrate room-temperature operation of a spacing-adjustable multi-wavelength erbium-doped fiber laser using stimulated Brillouin scattering. With the use of an intra-cavity birefringent loop mirror filter, the laser output wavelengths can be well defined without applying an external Brillouin pump. By adjusting the comb spacing of the filter, a wide range of mode spacings can be obtained to support the oscillations of up to 49 output wavelengths.