Hexagonal Transverse Coupled Cavity VCSEL Redefining the High-Speed Lasers

TL;DR

This paper introduces a novel hexagonal transverse coupled cavity VCSEL that achieves a 45 GHz modulation bandwidth, significantly surpassing conventional VCSELs, with improved single-mode operation, higher power, and potential for high-speed optical interconnects.

Contribution

The paper presents a new hexagonal coupled cavity design for VCSELs that dramatically increases modulation bandwidth and power while maintaining single-mode operation, using a gain-induced symmetry breaking approach.

Findings

Achieved 45 GHz modulation bandwidth, five times higher than conventional VCSELs.

Demonstrated >30 dB side-mode suppression ratio and >45 dB SNR.

Produced three times higher throughput power compared to traditional VCSELs.

Abstract

The vertical-cavity surface-emitting lasers (VCSELs) have emerged as a vital approach for realizing energy efficient, high speed optical interconnects in the data center and supercomputers. As of today, VCSEL is the most suitable for mass production in terms of cost-effectiveness and reliability. However, there are still key challenges for higher speed modulation above 40 GHz. Here, a hexagonal transverse coupled cavity VCSEL adiabatically coupled through the center cavity is proposed. A 3-dB roll-off modulation bandwidth of 45 GHz is demonstrated, which is five times greater than a conventional VCSEL fabricated on the same epi-wafer structure. While a parity time (PT) symmetry approaches add loss to engineer the topological state of the laser system, here, a radical paradigm shift with gain introduces symmetry breaking. This idea, then enables a single mode operation with a side-mode suppression-ratio (SMSR) of > 30 decibels and signal-to-noise ratio (SNR) of > 45 decibels. The energy distribution inside the coupled cavity system is also redistributed to provide a coherent gain in a spatially separated system. Consequently, throughput power is three times higher than that of the conventional VCSEL.