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Directly modulated lasers with graded-κ grating for stable single-mode operation and bandwidth enhancement
Optics Express
|May 4, 2026
Summary
A novel graded-kappa grating technique enhances directly modulated lasers for stable single-mode lasing and improved modulation bandwidth. This innovation overcomes internal reflections, enabling higher speeds for data center optical interconnects.
Area of Science:
- Photonics and Optical Engineering
- Semiconductor Device Physics
Background:
- Internal reflections at active-passive interfaces limit high-speed operation in directly modulated lasers.
- Detuned-loading and photon-photon resonance effects are degraded by these reflections.
Purpose of the Study:
- To introduce a graded-kappa grating technique for stable single-mode lasing.
- To achieve robust modulation-bandwidth enhancement in directly modulated lasers.
Main Methods:
- Implemented a graded-kappa structure to smooth photon-density and refractive-index transitions.
- Suppressed internal reflections at the active-passive region interface.
Main Results:
- Achieved a 3-dB bandwidth of 47.5 GHz.
- Supported 112-Gbps PAM4 transmission with TDECQ < 2.9 dB up to 45°C.
Conclusions:
- The graded-kappa grating technique enables stable single-mode lasing and bandwidth enhancement.
- The device is suitable for next-generation data center optical interconnects.
