Full C- and L-band tunable erbium-doped integrated lasers via scalable manufacturing

TL;DR

This paper presents a scalable, wafer-scale fabrication of tunable erbium-doped integrated lasers covering the C- and L-bands, with high power, narrow linewidth, and temperature stability, suitable for various photonic applications.

Contribution

It introduces a low-energy ion implantation process for Er doping in Si3N4 waveguides, enabling scalable manufacturing of integrated lasers with wide tuning range and stable operation.

Findings

Wavelength tuning range of 91 nm covering C- and L-bands.

Fiber-coupled output power of 36 mW with linewidth of 95 Hz.

Stable operation up to 125°C with less than 15 MHz drift over 6 hours.

Abstract

Erbium (Er) ions are the gain medium of choice for fiber-based amplifiers and lasers, offering a long excited-state lifetime, slow gain relaxation, low amplification nonlinearity and noise, and temperature stability compared to semiconductor-based platforms. Recent advances in ultra-low-loss silicon nitride (Si$_3$N$_4$) photonic integrated circuits, combined with ion implantation, have enabled the realization of high-power on-chip Er amplifiers and lasers with performance comparable to fiber-based counterparts, supporting compact photonic systems. Yet, these results are limited by the high (2 MeV) implantation beam energy required for tightly confined Si$_3$N$_4$ waveguides (700 nm height), preventing volume manufacturing of Er-doped photonic integrated circuits. Here, we overcome these limitations and demonstrate the first fully wafer-scale, foundry-compatible Er-doped photonic integrated circuit-based tunable lasers. Using 200 nm-thick Si$_3$N$_4$ waveguides, we reduce the ion beam energy requirement to below 500 keV, enabling efficient wafer-scale implantation with an industrial 300 mm ion implanter. We demonstrate a laser wavelength tuning range of 91 nm, covering nearly the entire optical C- and L-bands, with fiber-coupled output power reaching 36 mW and an intrinsic linewidth of 95 Hz. The temperature-insensitive properties of erbium ions allowed stable laser operation up to 125$^{\circ}$C and lasing with less than 15 MHz drift for over 6 hours at room temperature using a remote fiber pump. The fully scalable, low-cost fabrication of Er-doped waveguide lasers opens the door for widespread adoption in coherent communications, LiDAR, microwave photonics, optical frequency synthesis, and free-space communications.