Atiyeh Zarifi

Compact Brillouin devices through hybrid integration on silicon

A range of unique capabilities in optical and microwave signal processing and generation have been demonstrated using stimulated Brillouin scattering (SBS). The need to harness SBS in mass-manufacturable integrated circuits has led to a focus on silicon-based material platforms. Remarkable progress in silicon-based Brillouin waveguides has been made, but results have been hindered by nonlinear losses present at telecommunications wavelengths. Here, we report on a new approach to surpass this issue through the integration of a high Brillouin gain material, As2S3, onto a silicon-based chip. We fabricated a compact spiral device within a silicon circuit, achieving an order-of-magnitude improvement in Brillouin amplification. To establish the flexibility of this approach, we fabricated a ring resonator with free spectral range precisely matched to the Brillouin shift, enabling the first demonstration, to our knowledge, of Brillouin lasing in a planar integrated circuit. Combining active photonic components with the SBS devices shown here will enable the creation of compact, mass-manufacturable optical circuits with enhanced functionalities.

Highly localized distributed Brillouin scattering response in a photonic integrated circuit

The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit. This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift and linewidth, essential information for the further development of high quality photonic-phononic waveguides for SBS applications.The interaction of optical and acoustic waves via stimulated Brillouin scattering (SBS) has recently reached on-chip platforms, which has opened new fields of applications ranging from integrated microwave photonics and on-chip narrow-linewidth lasers, to phonon-based optical delay and signal processing schemes. Since SBS is an effect that scales exponentially with interaction length, on-chip implementation on a short length scale is challenging, requiring carefully designed waveguides with optimized opto-acoustic overlap. In this work, we use the principle of Brillouin optical correlation domain analysis to locally measure the SBS spectrum with high spatial resolution of 800 μm and perform a distributed measurement of the Brillouin spectrum along a spiral waveguide in a photonic integrated circuit. This approach gives access to local opto-acoustic properties of the waveguides, including the Brillouin frequency shift and linewidth, essential information for the further development of high quality photonic...

Localized high resolution Brillouin spectrum measurement of a photonic integrated circuit

Stimulated Brillouin scattering (SBS) is a phonon-photon interaction in which the energy of an optical pump transfers to a Stokes wave through an acoustic wave. Chalcogenide glass (As2S3) photonic integrated circuits (PIC) are among the most efficient platforms for SBS and have been extensively developed for several applications, including microwave photonic filters, lasers and optical memory. In these applications, the acoustic properties of the waveguide are paramount to achieve high performance. A distributed SBS measurement with high spatial resolution reveals information about the local phonon-photon interactions along the waveguide in contrast to traditional techniques, which only capture an integrated SBS response. Among different SBS-based distributed measurement techniques, Brillouin optical correlation domain analysis (BOCDA) has achieved the highest spatial resolution, which is essential for scanning cm-scale PICs. Different implementations of BOCDA use frequency and phase modulation [1] [2] or are based on amplified spontaneous emission (ASE) [3]. The latter requires only a simple ASE source, however the drawback is that this technique typically leads to a low signal-to-noise ratio (SNR). In this work, we use an ASE-based BOCDA system with a lock-in amplifier to achieve higher SNR by rejecting the excess noise from the ASE spectrum. We scan the local SBS response of a chalcogenide PIC with 2.5 mm spatial resolution. This approach provides critical information about acoustic properties of the waveguide.

Brillouin lasing in a hybrid silicon chip

Low phase noise lasers are used throughout many applications including precision metrology [1], and pure microwave synthesis [2], among others. Stimulated Brillouin scattering (SBS), a coherent interaction between photons and phonons, is capable of spectrally purifying optical sources to sub-Hz levels [3]. Previous demonstrations of Brillouin lasers have been limited to fiber based systems or micro-resonators which use tapered fibers or prisms to couple to external setups, preventing wafer scale integration and mass production.

Nonlinear Loss Engineering in a Silicon-Chalcogenide Hybrid Optical Waveguide

We fabricated a nonlinear loss engineered silicon-chalcogenide hybrid waveguide and experimentally demonstrated TPA reduction.Additionally, we showed a five-fold improvement in the figure of merit compared to standard silicon nanowire.