Prospects for Silicon Mid-IR Raman Lasers

This paper presents the case for the silicon Raman laser as a potential source for the technologically important midwave infrared (MWIR) region of the optical spectrum. The mid-IR application space is summarized, and the current practice based on the optical parametric oscillators and solid state Raman lasers is discussed. Relevant properties of silicon are compared with popular Raman crystals, and linear and nonlinear transmission measurements of silicon in the mid-IR are presented. It is shown that the absence of the nonlinear losses, which severely limit the performance of the recently demonstrated silicon lasers in the near IR, combined with unsurpassed crystal quality, high thermal conductivity and excellent optical damage threshold render silicon a very attractive Raman medium, even when compared to the very best Raman crystals. In addition, silicon photonic technology, offering integrated low-loss waveguides and microcavities, offers additional advantages over today´s bulk crystal Raman laser technology. Using photonic crystal structures or microring resonators, the integrated cascaded microcavities can be employed to realize higher order Stokes emission, and hence to extend the wavelength coverage of the existing pump lasers. Exploiting these facts, the proposed technology can extend the utility of silicon photonics beyond data communication and into equally important applications in biochemical sensing and laser medicine