Silicon-based stimulated Brillouin scattering (SBS) promotes the on-chip all-optical signal processing network by interfacing silicon photonic and phononic technologies. Controllable and strong Brillouin coupling in silicon is a key requirement for this purpose. Here, we demonstrate traveling-wave forward SBS and Brillouin gain through a class of hybrid photonic-phononic silicon waveguides on the silicon-on-insulator (SOI) platform. This design combines the advantages of a silicon ridge waveguide and phononic crystal slab, allowing the independent control on the confined optical and acoustic modes. The strong and tailorable Brillouin nonlinearity is demonstrated via the heterodyne four-wave mixing spectroscopy. Three-tone gain experiment reveals a small-signal Stokes gain of 0.9 dB in a 1.085 cm length straight waveguide device at moderate pump power. The limiting factors and further improvements of net Brillouin amplification in our system are also discussed. This design can also be applied to the intermodal SBS as well as other silicon-based material platforms, and thus it offers the pathway toward on-chip microwave photonic filters, Brillouin amplifiers, and nonreciprocal devices.
The strain technology is accelerating the progress on the CMOS compatible Ge-on-Si laser source. Here, we report a monolithically integrated microbridge-based emitting-detecting configuration, equipped with lateral p–i–n junctions, waveguide and gratings. The operating wavelength range of the emitting bridge and the detecting bridge are matched through the designed same dimensions of the two microbridges, as well as the strain. Strain-enhanced spontaneous emission and the effect of spectra red-shifting on low-loss transmission of on-chip light are discussed. Temperature dependence experiments reveal that in devices with highly strain-enhanced structure, the strain variation can offset the effect of electron thermalization, so that the performance of the device remains stable when temperature changes around room temperature.
We design and demonstrate an asymmetric Ge/SiGe coupled quantum well (CQW) waveguide modulator for both intensity and phase modulation with a low bias voltage in silicon photonic integration. The asymmetric CQWs consisting of two quantum wells with different widths are employed as the active region to enhance the electro-optical characteristics of the device by controlling the coupling of the wave functions. The fabricated device can realize 5 dB extinction ratio at 1446 nm and 1.4 × 10−3 electrorefractive index variation at 1530 nm with the associated modulation efficiency V π L π of 0.055 V cm under 1 V reverse bias. The 3 dB bandwidth for high frequency response is 27 GHz under 1 V bias and the energy consumption per bit is less than 100 fJ/bit. The proposed device offers a pathway towards a low voltage, low energy consumption, high speed and compact modulator for silicon photonic integrated devices, as well as opens possibilities for achieving advanced modulation format in a more compact and simple frame.
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