Investigation of germanium Raman lasers for the mid-infrared

Abstract

In this paper we present a detailed theoretical investigation of integrated racetrack Raman lasers based on the germanium material system operating in the mid-infrared beyond the germanium two-photon absorption cut-off wavelength of 3.17 μm. The effective Raman gain has been estimated in waveguides based on germanium-on-silicon, germanium-on-SOI and germanium-on-Si3N4 technology platforms as a function of their crystallographic orientations. Furthermore, general design guidelines have been determined by means of a comparative analysis of Raman laser performance, i.e. the threshold power, polarization and directionality of the excited Stokes signals as a function of racetrack cavity length and directional-coupler dimensions. Finally, the emitted Raman laser power has been evaluated as a function of overall propagation losses and operative wavelengths up to 3.8 μm, while the time dynamics of Raman lasers has been simulated assuming continuous and pulse waves as input pump signals.

Stimulated Brillouin Scattering in an AlGaN Photonics Platform Operating in the Visible Spectral Range

“…In particular, we consider the architecture sketched in 18 where the input pump signal, S p ( ), is injected into the racetrack resonator by means of the evanescent coupling between the resonant microcavity and the input external bus. According to the mathematical model proposed in our previous work 18 , the calculations at λ p = 450 nm give a nonlinear Kerr effective modal area (defined as in 36 ) A kerr = 5.4 × 10 −2 μm 2 and the group effective index, n g , p = n g , s = 2.7130. The conventional approach for designing a Brillouin laser based on optical resonators consists in satisfying the condition Δ f FSR = Δ f B , whereΔ f FSR is the free spectral range (FSR) of the racetrack resonator.…”

Modelling of Supercontinuum Generation in the Germanium-on-Silicon Waveguided Platform

“…In our very recent work, the stimulated Raman scattering (SRS) features in Ge-based platforms have been investigated [20]. Actually, the results indicate that, in the case of fixed polarizations, the effective Raman gain can induce Raman emission only if both the [011] waveguide orientation (θ =45°) and the quasi-TE polarization are assumed.…”

“…In particular, 0° and 45° correspond to [001] and [011] orientations, respectively. In (1), the terms , , and represent the peak gain, the phonon angular frequency and the FWHM of the germanium Raman-gain spectrum [20]. In addition, the time function ℎ( ) indicates the nonlinear Raman response that takes into account the intrapulse Raman scattering effect [3].…”

Stimulated Raman scattering induced dark pulse and microcomb generation in the mid-infrared

“…Recently, optical frequency comb generation in Si and Ge has attracted lots of interest [34,[38][39][40]. Group IV photonics materials also have large Raman gain coefficient [41,42], constituting an opportunity to dark pulses excitation without additional techniques.…”