We describe the design of photonic crystal circular defect (CirD) lasers to construct a compact optical module with a wavelength division multiplexing function for the application of inter-chip or intra-chip optical interconnects. Subsequently, we investigated the characteristics of CirD lasers including the quality factor of the cavity, the lasing threshold, and the modulation speed with a three-dimensional finite-difference time-domain method and two-dimensional rate equations. Finally, we demonstrated the single mode lasing and wavelength tuning behaviors of the CirD lasers using optical pumping technology under room-temperature continuous-wave conditions.

We describe a device for inter-chip or intra-chip optical communications that contains the Circular Defect in photonic crystal (CirD) lasers array driven by vertical current injection. In order to improve the conductivity of the structure while also preventing current leakage, we introduce the oblique deposition of electrodes on a photonic crystal pattern by using an electron beam evaporation apparatus. The performance of an electrode is investigated by a transmission line method, and the CirD structure is fabricated with the electrode. We analyze the voltage-current relationship and confirm the CirD structure’s low resistance of under 1 kΩ.

Herein a circular defect in a 2D photonic crystal (CirD) laser for wavelength division multiplexing (WDM) optical communications is theoretically analyzed. By coupling CirD lasers to a waveguide, a huge communication capacity can be expected. For example, if high‐speed, 50 Gbps laser operations are successfully achieved, WDM devices with 20 CirD lasers could achieve a communication capacity of 1 Tbps. Based on finite‐difference time‐domain (FDTD) simulation results, in this study, both current‐output and high‐frequency characteristics are investigated by solving 2D rate equations, revealing that an excessively high‐quality factor in laser cavities reduces the relaxation‐oscillation frequency. When the photon lifetime is 2 ps, which corresponds to a quality factor of ≈3000, a small threshold current of 5 μA and a high relaxation‐oscillation frequency of 40 GHz can be simultaneously obtained. These results suggest the potential of developing a WDM device using CirD lasers.

To achieve wavelength division multiplexing of optical communications for short distances, we have theoretically investigated a photonic crystal waveguide we call an orthogonal lattice waveguide (OLW), which may have a communication wavelength bandwidth of about 20 nm. In this paper, we fabricate CirD laser structures with air cladding layers and OLWs of different cavity radii. We confirm that the light emitted from the OLW is the light generated in the cavity. OLW has a wavelength bandwidth of about 20 nm, which agrees with the results of our previous theoretical study. The wavelength shift is about 4 nm when the radius of the circular defect cavity increases by 0.01 a, where a is the lattice constant.

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