Unidirectional hybrid silicon ring laser with an intracavity S-bend

Unidirectional hybrid diode laser through the integration of a hook-shaped traveling-wave semiconductor optical amplifier and Taiji ring resonator

We demonstrate a unidirectional ring diode laser based on hybrid integration of a hook-shaped traveling-wave semiconductor optical amplifier (SOA) and a Taiji ring resonator. The additional crossover bending waveguide inside the silicon nitride Taiji ring introduces a non-reciprocal loss in the laser cavity while the gain is provided by a multiple depth etched hook-shaped SOA. We present the detailed design flow for both active and passive components of the unidirectional hybrid diode laser. This work paves the way to use a hook-shaped SOA-based hybrid platform for various applications including optical sensing, all-optical switching, photonic memories, and topological optics.

Unidirectional light emission in PT-symmetric microring lasers

The synergetic use of gain and loss in parity-time symmetric coupled resonators has been shown to lead to single-mode lasing operation. However, at the corresponding resonance frequency, an ideal ring resonator tends to support two degenerate eigenmodes, traveling along the cavity in opposite directions. Here, we show a unidirectional single-moded parity-time symmetric laser by incorporating active S-bend structures with opposite chirality in the respective ring resonators. Such chiral elements break the rotation symmetry of the ring cavities by providing an asymmetric coupling between the clockwise (CW) and the counterclockwise (CCW) traveling modes, hence creating a new type of exceptional point. This property, consequently, leads to the suppression of one of the counter-propagating modes. In this paper, we first measure the extinction ratio between the CW and CCW modes in a single ring resonator in the presence of an S-bend waveguide. We then experimentally investigate the unidirectional emission in PT-symmetric systems below and above the exceptional point. Finally, unidirectional emission will be shown in systems of two S-bend ring resonators coupled through a link structure.

Topological insulator laser: Experiments

Physical systems exhibiting topological invariants are naturally endowed with robustness against perturbations, as manifested in topological insulators-materials exhibiting robust electron transport, immune from scattering by defects and disorder. Recent years have witnessed intense efforts toward exploiting these phenomena in photonics. Here we demonstrate a nonmagnetic topological insulator laser system exhibiting topologically protected transport in the cavity. Its topological properties give rise to single-mode lasing, robustness against defects, and considerably higher slope efficiencies compared to the topologically trivial counterparts. We further exploit the properties of active topological platforms by assembling the system from S-chiral microresonators, enforcing predetermined unidirectional lasing without magnetic fields. This work paves the way toward active topological devices with exciting properties and functionalities.

Unidirectional, widely-tunable and narrow-linewidth heterogeneously integrated III-V-on-silicon laser

A heterogeneously integrated widely tunable III-V-on-silicon ring laser with unidirectional operation is demonstrated. 40 nm tuning range (from 1560 nm to 1600 nm) is obtained using the Vernier effect between two ring resonators incorporated in the ring laser cavity. Unidirectional operation is obtained by integrating a DBR reflector coupling the clockwise and counterclockwise mode of the ring laser cavity. Unidirectional operation is obtained over the entire tuning range with about 10 dB suppression of the clockwise mode. The laser linewidth is lower than 1 MHz over the entire tuning range, down to 550 kHz in the optimum operation point. The waveguide-coupled output power is above 0 dBm over the entire tuning range.