Optical links on silicon photonic chips using ultralow-power consumption photonic-crystal lasers

Abstract

Ultrashort-distance optical interconnects are becoming increasingly important due to continuous improvements in servers and high-performance computers. As light sources in such interconnects, directly modulated semiconductor lasers with an ultrasmall active region are promising. In addition, using Si waveguides is important to provide low loss optical links with functions such as wavelength filtering and switching. In this paper, we demonstrate a wafer-scale heterogeneous integration of lambda-scale embedded active-region photonic-crystal (LEAP) lasers and Si waveguides, achieved through precise alignment. We numerically and experimentally demonstrated the coupling design between the LEAP lasers and Si waveguides; it is important to match propagation constants of Si waveguides and wavenumber of the optical cavity modes. The LEAP lasers exhibit an ultralow threshold current of 13.2-μA and 10-Gbit/s direct modulation. We also achieved the first data transmission using an optical link consisting of a LEAP laser, Si waveguide, and photodetector and obtained an averaged eye diagram at a bit rate of 10 Gbit/s with a bias current of 150 μA.

Modal Properties of Photonic Crystal Cavities and Applications to Lasers

“…A very important application of PhC cavities is the realization of a new generation of microcavity lasers, e.g., for on-chip optical interconnects [62,63]. In this section we summarize key laser properties, which are determined by the characteristics of the cavity.…”

“…Overall, PhC lasers have a small threshold current [54,59,60] because they allow one to scale down the active volume, while keeping high the Q-factor and optical confinement factor. It should be noted that heterogeneous [60,63] and epitaxial [6] integration of PhC lasers on silicon have also been demonstrated. The energy cost, EC, is a common figure of merit encompassing the static and dynamic characteristics of semiconductor lasers in terms of energy efficiency.…”

“…Secondly, via the enhanced modulation bandwidth at a given current in excess to threshold (i.e., a larger σ). The low threshold current and small active volume equip PhC lasers with reduced energy cost, around 1-10 fJ/bit [54,63]. This makes PhC lasers promising light sources for chip-scale optical interconnects [69].…”

Electrically‐Driven Photonic Crystal Lasers with Ultra‐low Threshold

“…Photonic crystal (PhC) nanolasers have been developed by various groups and have showcased great potential and rich physics [4][5][6][7], however, most these studies were limited to optical pumping, while electrical operation was achieved under pulsed pumping [8], or cryogenic temperatures [9]. Recently, this steep technological barrier has been overcome and monolithic, [10][11][12] and heterogeneously-integrated [13][14][15] electrically-pumped PhC lasers achieved continuous-wave room-temperature operation. However, there is significant room for improvement in terms of power consumption and energy efficiency and thus further research is essential.…”

“…The combination of lateral injection and a buried-heterostructure active region has been shown numerically to be more efficient, [20] however, recent demonstrations show that the efficiency of vertical doped nanolasers [14] outperforms the ones that are based on lateral carrier injection. [13,15] Thus, understanding the properties and limitations of the lateral p-i-n junction is of utmost importance for the development of ultra-low power consumption nano-lasers and nano-LEDs.…”