At the 2024 IEEE 29th International Semiconductor Laser Conference (ISLC) Orlando, FL, USA, VI Systems and partners reported on novel phenomena in electrically driven multi-aperture (MA) vertical-cavity surface-emitting lasers (VCSELs) with coupled oxide-confined apertures.

Optical injection locking (OIL) previously enabled stabilization of single mode operation in VCSELs with the optical power being transferred to one mode (University of California, Berkeley, 2005-2012). A strong increase in the modulation bandwidth with a smooth modulation response was reported (~40GHz) being limited by RC parasitic. Furthermore, it was found that VCSEL chirp was strongly suppressed under OIL allowing 90km 10Gbaud transmission over single mode fiber using a 1550nm VCSEL.

Still, OIL is not practical for standard applications in datacom transceivers.

In the present study a self-injection locking (SIL) regime, where one of the VCSEL modes acts as a master mode forcing the competing mode to disappear, is employed and the device is fully compatible with modern transceivers.

The observations demonstrate that not only is the emission spectrum narrowed by SIL but also the modulation bandwidth boosted in a broad frequency range towards 50GHz limited by RC parasitic and photoreceiver frequency response.

Single mode operation at high currents is highly advantageous for optical wireless spot-to-spot communication.

Extension of the transmission distance over multi- and single-mode fibers due to reduced chirp is to be studied in detail.

• (a) Electroluminescence spectra of the coupled aperture MA (2×1) VCSELs at currents below (7mA) and above (8mA) the onset of the SIL regime.
• (b) Change in the modulation response curve under current modulation at 7 and 8mA. The spectra are not corrected for the RF signal reflection (S11) related to the electrical impedance of the MA VCSEL mesa and the limited bandwidth of the receiver ~35GHz.

• M. Lindemann et al., “Study of Electrically Excited Photon-Photon Resonances in Self-Injection-Locked Coupled-Cavity VCSELs,” 2024 IEEE 29th International Semiconductor Laser Conference (ISLC), Orlando, FL, USA, 2024, pp. 1-2, doi: 10.1109/ISLC57752.2024.10717381. https://ieeexplore.ieee.org/document/10717381

High frequency modules based on coupled MA chips at 850nm, 880nm, 910nm, 940nm wavelengths are available at VI Systems GmbH for research purposes and module prototyping.

In modified coupled MA design (2×2) single transverse mode lasing exceeds ~30mW under continuous wave operation.

VIS research was supported by the project PERFECT (10184223) funded through the Program to Promote Research, Innovation and Technology (Programm zur Förderung von Forschung, Innovationen und Technologien – ProFIT) of the Investitionsbank Berlin (IBB). The project is cofinanced by the EU Funds for Regional Development (Europäischer Fonds für regionale Entwicklung, EFRE).

Information about VI-Systems is available at www.v-i-systems.com.