Photon-counting Raman spectroscopy of silicon nanowires

Raman scattering can be exploited for amplification in optical fiber telecommunications or, chemical identification in spectroscopy, but represents a source of detrimental noise photons for quantum communications. The spectral distribution of spontaneous Raman scattering (SpRS) can be measured in bulk samples with the free-space 90° scattering method [1]. In long fibers the SpRS spectra can be measured using a pulsed laser to achieve measurable signals [2], incompatible with the damage threshold of many on-chip devices. Measurements of stimulated Raman scattering have been performed using nonlinear pump-probe techniques [3], requiring the addition of either a highly tunable or ultra-broad bandwidth probe. Recently photon-counting techniques have been demonstrated to measure weak SpRS signals in fibers [4-6], however no direct measurements of the SpRS spectra of nanophotonic chip-devices over a broad bandwidth have been performed.