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The rapid advancement of information technology has driven an exponential demand for high-speed, large-capacity data transmission and processing. Traditional electronic communication systems face inherent limitations such as bandwidth constraints and electromagnetic interference, prompting a paradigm shift toward photonic technologies. Integrated optical waveguides, as core components of on-chip photonic systems, enable efficient light confinement and manipulation at microscale dimensions, offering advantages in miniaturization, low power consumption, and high compatibility with existing optical communication infrastructure. Among these, erbium-doped waveguide amplifier (EDWA) have emerged as critical active devices for signal amplification in the 1550 nm communication band, leveraging the radiative transitions of Er3+ ions to achieve optical gain. Numerous studies have shown that, the fluorescence performance of Er3+ is closely related to the factors like doping method, preparation and annealing conditions. Besides, the performance of such amplifiers heavily relies on the choice of host materials, which must exhibit low optical loss, high rare-earth ion solubility, and compatibility with complementary metal-oxide-semiconductor (CMOS) fabrication processes. Tellurium dioxide (TeO2), with its high refractive index (2.1–2.4), broad transparency range (0.33–5 μm), exceptional chemical stability, and low phonon energy, has shown significant promise as a superior alternative to conventional materials like silicon nitride (Si3N4) or aluminum oxide (Al2O3). This study focuses on the development of erbium-doped TeO2 (Er:TeO2) ridge waveguides for on-chip optical amplification. The Er:TeO2 thin films were deposited via radio frequency (RF) magnetron sputtering using high-purity Te and Er targets. Key deposition parameters, including Er2O3 target sputtering power (10-30 W), Ar/O₂ gas flow ratio (1:1 to 5:1), and post-deposition annealing conditions (200-300 ℃ under oxygen atmosphere), were systematically optimized to enhance photoluminescence properties. Scanning electron microscopy (SEM) and fluorescence spectroscopy were employed to evaluate film morphology and emission characteristics. A bilayer waveguide structure was designed to mitigate surface roughness induced by direct etching of the Er-doped layer. The lower Er:TeO2 active layer (500 nm thickness) and upper undoped TeO2 cladding layer (150 nm thickness) were patterned using ultraviolet lithography and plasma etching (O2/Ar/CHF3 gas mixture), achieving a ridge width of 2 μm. Optical confinement and mode field distribution were simulated using finite-difference eigenmode (FDE) analysis, confirming effective light-matter overlap within the Er-doped region. Experimental results revealed that the optimal Er:TeO2 film, deposited at an Er target power of 20 W, Ar/O2 flow ratio of 5:1, and annealed at 250 ℃ for 10 hours, exhibited a photoluminescence intensity of 3.5×10⁶ photon counts at 1545 nm-nearly two orders of magnitude higher than non-annealed samples. Oxygen annealing effectively activated Er3+ ions while passivating oxygen vacancies, critical for minimizing non-radiative recombination. Excessive Er doping (30 W sputtering power) led to ion clustering and fluorescence quenching, underscoring the importance of controlled dopant concentration. Surface morphology analysis via SEM and optical microscopy confirmed smooth, crack-free films with minimal particulate contamination, essential for low-loss waveguide fabrication. Waveguide performance was characterized using the cut-back method at 1310 nm, yielding a propagation loss of 0.607 dB/cm for a 0.5 cm-long device. However, coupling losses of 6.34 dB/facet were observed due to rough end-faces from mechanical dicing, highlighting the need for post-fabrication polishing or anti-reflective coatings. Amplification tests at 1545 nm under 980 nm pumping demonstrated an internal gain of 7.2 dB/cm at a pump power of 88.45 mW, with gain saturation observed beyond 90 mW. The broadband emission spectrum (80 nm full-width at half-maximum) further validated Er:TeO2’s potential for wideband amplification in the C-bands. In conclusion, this study has elucidated the advantages of erbium-doped tellurium oxide (Er:TeO2) ridge waveguides as on-chip optical amplifiers, optimized their deposition and annealing protocols, and designed a bilayer waveguide structure. The achieved low propagation loss and significant internal gain underscore the material’s compatibility with photonic integrated circuits (PICs). Future efforts will focus on refining waveguide end-face quality, enhancing pump efficiency, and scaling device lengths to realize practical net gain for telecommunications and quantum photonics applications. These advancements position Er:TeO2 as a cornerstone material for next-generation compact and high-performance photonic systems.
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Keywords:
- Optical Properties /
- Erbium-Doped Waveguide /
- Optical Amplifier /
- TeO2
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