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Published January 10, 2022 | Supplemental Material + Published
Journal Article Open

Consequences of quantum noise control for the relaxation resonance frequency and phase noise in heterogeneous Silicon/III–V lasers

Abstract

We have recently introduced a new semiconductor laser design which is based on an extreme, 99%, reduction of the laser mode absorption losses. In previous reports, we showed that this was achieved by a laser mode design which confines the great majority of the modal energy (> 99%) in a low-loss Silicon guiding layer rather than in highly-doped, thus lossy, III–V p⁺ and n⁺ layers, which is the case with traditional III–V lasers. The resulting reduced electron-field interaction was shown to lead to a commensurate reduction of the spontaneous emission rate by the excited conduction band electrons into the laser mode and thus to a reduction of the frequency noise spectral density of the laser field often characterized by the Schawlow–Townes linewidth. In this paper, we demonstrate theoretically and present experimental evidence of yet another major beneficial consequence of the new laser design: a near total elimination of the contribution of amplitude-phase coupling (the Henry αα parameter) to the frequency noise at "high" frequencies. This is due to an order of magnitude lowering of the relaxation resonance frequency of the laser. Here, we show that the practical elimination of this coupling enables yet another order of magnitude reduction of the frequency noise at high frequencies, resulting in a quantum-limited frequency noise spectral density of 130 Hz22/Hz (linewidth of 0.4 kHz) for frequencies beyond the relaxation resonance frequency 680 MHz. This development is of key importance in the development of semiconductor lasers with higher coherence, particularly in the context of integrated photonics with a small laser footprint without requiring any sort of external cavity.

Additional Information

© The Author(s) 2022. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. Received 04 July 2021; Accepted 25 November 2021; Published 10 January 2022. This work was supported by US Army Research Office (ARO) (W911NF-14-P-0020, W911NF-15-1-0584, W911NF-16-C-0026, W911NF-16-C-0105) and Defense Advanced Research Projects Agency (DARPA) (N66001-14-1-4062). The authors would like to thank the Kavli Nanoscience Institute (KNI) at Caltech for providing fabrication facilities for this work. These authors contributed equally: Dongwan Kim, Mark Harfouche and Huolei Wang. Author Contributions: A.Y. conceived the project, directed it, and acquired funding. D.K. and M.H. designed the laser. D.K and H.W. performed the device fabrication. D.K., M.H., and H.W. conducted the measurements for the laser characteristics. D.K. and M.H. wrote the manuscript with inputs from all authors. C.S., Y.V., N.S. G.R. were instrumental in conceiving the design of the lasers and experimental setup. The authors declare no competing interests.

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023