Heng Xie

Mode conversion based on forward stimulated Brillouin scattering in a hybrid phononic-photonic waveguide

We propose a scheme for on-chip all optical mode conversion based on forward stimulated Brillouin scattering in a hybrid phononic-photonic waveguide. To describe the mode conversion the theoretical model of the FSBS is established by taking into account the radiation pressure and the electrostriction force simultaneously. The numerical simulation is carried out for the mode conversion from the fundamental mode E11x to the higher-order mode E21x. The results indicate that the mode conversion efficiency is affected by the waveguide length and the input pump light power, and the highest efficiency can reach upto 88% by considering the influence of optical and acoustic absorption losses in the hybrid waveguide. Additionally, the conversion bandwidth with approximate 12.5 THz can be achieved in 1550nm communication band. This mode converter on-chip is a promising device in the integrated optical systems, which can effectively increase the capacity of silicon data busses for on-chip optical interconnections.

Simultaneous measurement of strain and temperature based on hybrid EDF/Brillouin laser.

Simultaneous temperature and strain sensing is experimentally demonstrated based on erbium-doped fiber laser (EDFL) and Brillouin erbium fiber laser (BEFL) incorporated in a single ring laser cavity. The EDFL can be switched to BEFL by injecting the Brillouin pump into the laser cavity. Longitudinal modes beat frequency and Brillouin frequency shift are monitored to discriminate strain and temperature. The longitudinal modes beat frequency is measured by observing the self-beating signals of the EDFL, while the Brillouin frequency shift is measured by monitoring the heterodyning signal of the BEFL. The simultaneous measurement errors of strain and temperature are within ± 25.8με and ± 0.8°C. The sensor is of simple structure and compact size.

Photonic approach for microwave frequency measurement with adjustable measurement range and resolution using birefringence effect in highly non-linear fiber

We experimentally demonstrate a novel approach for microwave frequency measurement utilizing birefringence effect in the highly non-linear fiber (HNLF). A detailed theoretical analysis is presented to implement the adjustable measurement range and resolution. By stimulating a complementary polarization-domain interferometer pair in the HNLF, a mathematical expression that relates the microwave frequency and amplitude comparison function is developed. We carry out a proof-to-concept experiment. A frequency measurement range of 2.5-30 GHz with a measurement error within 0.5 GHz is achieved except 16-17.5 GHz. This method is all-optical and requires no high-speed electronic components.

Simultaneous generation of a frequency-multiplied and phase-shifted microwave signal with large tunability

We demonstrate a photonic approach to simultaneously realize a frequency-multiplied and phase-shifted microwave signal based on the birefringence effects in the high nonlinear fiber. The phase shift caused by asymmetric variations in refractive indexes of fiber between two orthogonal polarization states is introduced into two coherent harmonic of the modulated signals. By beating the phase-modulated sidebands, a frequency-multiplied microwave signal is generated and its phase can be adjusted by simply controlling the pump power. A microwave signal at doubled- or quadrupled-frequency with a full 2π phase shift is obtained over a frequency range from 10 GHz to 30 GHz. The proposed approach has the potential applications in the system with larger-broadband, higher-frequency and -data-rate system, even to handle a multi-wavelength operation.

Compact Multiwavelength Brillouin Fiber Laser by Utilizing EDF as Hybrid Gain Media

We have experimentally demonstrated a compact multiwavelength Brillouin fiber laser by introducing an optical feedback mechanism in the laser configuration. A piece of erbium-doped fiber (EDF) is utilized as both linear gain media and Brillouin gain media. The influence of Brillouin pump power and wavelength, EDF length, and pump power on the laser performance are analyzed and discussed. Up to six Stokes lasing lines are generated, and the Stokes lasing lines show high temporal stability with the maximum power ripple less than 0.45 dB. By shortening the EDF length to 7 m, a dual-wavelength single-longitudinal-mode Brillouin fiber laser is achieved. Microwave signals at 11.02 and 22.04 GHz without disturbing side modes are obtained. This laser has potential applications in microwave generation, Brillouin fiber sensors, and high-speed optical communication.

Hybrid EDF/Brillouin laser for discriminative measurement of strain and temperature

Discriminative measurement of temperature and strain sensing is proposed and experimentally demonstrated based on erbium-doped fiber laser (EDFL) and Brillouin erbium fiber laser (BEFL). The EDFL and the BEFL share the same laser cavity. The EDFL can be easily switched to BEFL when the Brillouin pump is injected into the cavity. Longitudinal modes beat frequency generated from EDFL and Brillouin frequency shift originated from BEFL are monitored to discriminate strain and temperature. The simultaneous measurement errors of strain and temperature are within ± 25.8µε and ± 0.8°C.

Simultaneous Realization of Frequency Multiplication and Single Sideband Modulation by Exploiting Nonlinear Birefringent Effect

We theoretically analyze and experimentally demonstrate a photonic scheme to realize light-controlled microwave frequency multiplication and single sideband (SSB) modulation simultaneously. By properly choosing operational parameters of the orthogonal polarized pump light to stimulate the nonlinear birefringent effect in highly nonlinear fiber, the proposed scheme can realize different functions. One is to generate a high-frequency microwave signal with a tunable multiplication factor among 1, 2, 4, and 8. The other is to obtain an SSB signal with tunable optical carrier to sideband ratio (OCSR) or simultaneous suppression of the - first- and + second-order sidebands. We demonstrate the frequency multiplication function theoretically. A frequency-octupled signal at 144 GHz is obtained. The SSB modulation from 10 to 40 GHz with OCSR ranging from -8.7 to 26.7 dB is demonstrated by experiment. The SSB modulation with simultaneous suppression of the - first- and + second-order sidebands is also observed. The proposed approach operates easily and no wavelength-depended device is required. Results show that it has potential applications in improving the transmission of photonic microwave signal processing systems.

Mode conversion based on the acousto-optical interaction in photonic-phononic waveguide

We present a scheme for on-chip optical mode conversion in a hybrid photonic-phononic waveguide. Both propagating optical and acoustic wave can be tightly confined in the hybrid waveguide, and the acoustooptical interaction can be enhanced to realize optical mode conversion within a chip-scale size. The theoretical model of the acousto-optic interaction is established to explain the mode conversion. The numerical simulation results indicate that the high efficient mode conversion can be achieved by adjusting the intensity of the acoustic wave. We also show that the mode conversion bandwidth can be dramatically broadened to 13 THz by adjusting the frequency of the acoustic wave to match phase condition of the acousto-optic interaction. This mode converter on-chip is promising in order to increase the capacity of silicon data busses for on-chip optical interconnections.