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Directly modulated membrane lasers with 108 GHz bandwidth on a high-thermal-conductivity silicon carbide substrate


Increasing the modulation speed of semiconductor lasers has attracted much attention from the viewpoint of both physics and the applications of lasers. Here we propose a membrane distributed reflector laser on a low-refractive-index and high-thermal-conductivity silicon carbide substrate that overcomes the modulation bandwidth limit. The laser features a high modulation efficiency because of its large optical confinement in the active region and small differential gain reduction at a high injection current density. We achieve a 42 GHz relaxation oscillation frequency by using a laser with a 50-μm-long active region. The cavity, designed to have a short photon lifetime, suppresses the damping effect while keeping the threshold carrier density low, resulting in a 60 GHz intrinsic 3 dB bandwidth (f3dB). By employing the photon–photon resonance at 95 GHz due to optical feedback from an integrated output waveguide, we achieve an f3dB of 108 GHz and demonstrate 256 Gbit s−1 four-level pulse-amplitude modulations with a 475 fJ bit−1 energy cost of the direct-current electrical input.

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Fig. 1: Fundamentals of conventional DMLs and membrane DR lasers.
Fig. 2: Calculated laser characteristics of membrane lasers on SiC.
Fig. 3: Static lasing characteristics without using PPR.
Fig. 4: Small-signal modulation characteristics without using PPR.
Fig. 5: Device characteristics with using PPR.
Fig. 6: BER performance.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.


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We thank Y. Shouji, Y. Yokoyama, M. Hosoya, K. Ishibashi, J. Asaoka, and Y. Kawaguchi for assistance with device fabrication. We also thank Y. Maeda, T. Aihara and H. Fukuda for technical support with the measurements and K. Nozaki, H. Yamazaki and M. Nagatani for lending us the measurement equipment.

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Authors and Affiliations



S.Y. calculated, designed, fabricated and measured the devices and prepared the manuscript. N.-P.D. performed the digital signal processing for the BER evaluation and assisted in the large-signal characteristic measurements. H.N. assisted in the small-signal and large-signal characteristic measurements. R.N. helped to calculate the thermal properties and discussed the design and fabrication processes. T.F. performed the epitaxial growth of the group III–V semiconductor layer. K.T. assisted in the fabrication processes and analysis of the small-signal responses. T.H. assisted in the calculation of the optical confinement factor. T. Tsurugaya assisted in the calculation of the thermal properties. H.T and S.K. assisted in the large-signal characteristic measurements. T.K. assisted in the calculations of the thermal properties and grating design. T. Tsuchizawa contributed to the fabrication of the bonding layer. F.K. discussed the experimental results related to PPR. S.M. designed and discussed the fabrication processes and measurement results, supervised the project and assisted with revising the manuscript.

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Correspondence to Suguru Yamaoka.

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Supplementary Information

Supplementary Table 1 and Fig. 1, and description of the experimental set-up.

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Yamaoka, S., Diamantopoulos, NP., Nishi, H. et al. Directly modulated membrane lasers with 108 GHz bandwidth on a high-thermal-conductivity silicon carbide substrate. Nat. Photonics 15, 28–35 (2021).

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