Optically injected semiconductor lasers operating several orders of magnitude below the Schawlow-Townes linewidth limit

Amith Karuvath; Thidsanu Apiphatnaphakul; Sabarinath Sunil; Pascal Besnard

doi:10.1117/12.3022327

6 June 2024 Optically injected semiconductor lasers operating several orders of magnitude below the Schawlow-Townes linewidth limit

Amith Karuvath, Thidsanu Apiphatnaphakul, Sabarinath Sunil, Pascal Besnard

Author Affiliations +

Proceedings Volume PC13002, Semiconductor Lasers and Laser Dynamics XI; PC130020H (2024) https://doi.org/10.1117/12.3022327
Event: SPIE Photonics Europe, 2024, Strasbourg, France

Conference Poster

Abstract

The width of a laser line may be reduced by increasing the length of a laser cavity with the help of an extended cavity (optical feedback), or also by transferring the purity from another laser (master laser) through the process of frequency-locking brought by optical injection. In this presentation, using a Hz-linewidth master laser, we reduce the linewidth a DFB laser by around 70 dB of magnitude (depending on the operating pump rate). The result is obtained for a null detuning (or a null frequency difference between the master and the slave). We show that the optically-injected laser is indeed operating as a laser and not an optical amplifier by studying the frequency-locking threshold with respect to the injected optical power. This result is not in contradiction with the Schawlow-Townes limit, which is obtained for an internal source, the spontaneous emission, which is coupled to the stimulated emission, while in this case, the seeding photons for the laser process are coming from the external master source. However, these results clearly show that a laser can operate well below its Schawlow-Townes limit.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Amith Karuvath, Thidsanu Apiphatnaphakul, Sabarinath Sunil, and Pascal Besnard "Optically injected semiconductor lasers operating several orders of magnitude below the Schawlow-Townes linewidth limit", Proc. SPIE PC13002, Semiconductor Lasers and Laser Dynamics XI, PC130020H (6 June 2024); https://doi.org/10.1117/12.3022327

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