A high-gain cladded waveguide amplifier on erbium doped thin-film lithium niobate fabricated using photolithography assisted chemo-mechanical etching

TL;DR

This paper demonstrates a high-gain erbium-doped lithium niobate waveguide amplifier with a Ta2O5 cladding fabricated via photolithography assisted chemo-mechanical etching, achieving over 20 dB gain at 1532 nm.

Contribution

It introduces a novel Ta2O5 cladding approach on LNOI waveguides, enhancing gain and power scaling in integrated micro-scale amplifiers using PLACE fabrication.

Findings

Achieved over 20 dB small signal gain at 1532 nm.

Ta2O5 cladding improves optical gain compared to air cladding.

Theoretical modeling supports experimental gain enhancement.

Abstract

Erbium doped integrated waveguide amplifier and laser prevail in power consumption, footprint, stability and scalability over the counterparts in bulk materials, underpinning the lightwave communication and large-scale sensing. Subject to the highly confined mode and moderate propagation loss, gain and power scaling in such integrated micro-to-nanoscale devices prove to be more challenging compared to their bulk counterparts. In this work, stimulated by the prevalent success of double-cladding optical fiber in high-gain/power operation, a Ta2O5 cladding is employed in the erbium doped lithium niobate (LN) waveguide amplifier fabricated on the thin film lithium niobate on insulator (LNOI) wafer by the photolithography assisted chemomechanical etching (PLACE) technique. Above 20 dB small signal internal net gain is achieved at the signal wavelength around 1532 nm in the 10 cm long LNOI amplifier pumped by the diode laser at ~980 nm. Experimental characterizations reveal the advantage of Ta2O5 cladding in higher optical gain compared with the air-clad amplifier, which is further explained by the theoretical modeling of the LNOI amplifier including the guided mode structures and the steady-state response of erbium ions.