Erbium-doped fiber devices have been extraordinarily successful due to their broad optical gain around 1.5–1.6 μm. Er-doped fiber amplifiers enable efficient, stable amplification of high-speed, wavelength-division-multiplexed signals, thus continue to dominate as part of the backbone of longhaul telecommunications networks. At the same time, Er-doped fiber lasers see many applications in telecommunications as well as in biomedical and sensing environments. Over the last 20 years significant efforts have been made to bring these advantages to the chip level. Device integration decreases the overall size and cost and potentially allows for the combination of many functions on a single tiny chip. Besides technological issues connected to the shorter device lengths and correspondingly higher Er concentrations required for high gain, the choice of appropriate host material as well as many design issues come into play in such devices. In this contribution the important developments in the field of Er-doped integrated waveguide amplifiers and lasers are reviewed and current and future potential applications are explored. The vision of integrating such Er-doped gain devices with other, passive materials platforms, such as silicon photonics, is discussed.

Erbium-doped integrated waveguide amplifiers and lasers

Sol-gel silica/titania-on-silicon Er/Yb-doped waveguides for optical amplification at 1.5 μm

This review presents the state of the art of the study of germanium-related colour centres in silica glass and silica-based fibres. Most attention is concentrated on the dominant colour centres such as the Ge-related oxygen-deficient centres and paramagnetic Ge(n) centres, all of them having ultraviolet absorption bands. The hypothetical models and formation mechanisms proposed so far for these colour centres are discussed in detail. The origins of the models and formation mechanisms and their weak and strong points are analysed. The origin of the less well studied Ge-related colour centres in the visible spectral range (GeH, GeX, drawing-dependent defects) is also discussed.

https://iopscience.iop.org/article/10.1088/0953-8984/6/35/003/pdf

Colour centres in germanosilicate glass and optical fibres

This paper reviews the MCVD process, with special emphasis on fiber design and material choices, understanding of mechanisms involved in the process, process improvements, and performance.

An overview of the modified chemical vapor deposition (MCVD) process and performance

This paper reviews all the interactions of hydrogen and deuterium with silica-based optical fibers. Included in the discussion are H 2 overtone absorption, OH formation, increased UV and IR absorption, radiation effects on H 2 -treated fibers, the gas-in-glass laser and applications, the reduction of OH absorption by isotope exchange OH → OD and other isotope-exchange related effects, and applications of isotope exchange and substitution for diagnostic purposes. Also included is a description of common sources of H 2 in materials used in fiber and cable manufacture, and countermeasures against hydrogen generation and intrusion into the fiber.

Interactions of hydrogen and deuterium with silica optical fibers: A review

The Er-doped silica guided-wave laser operating around 1.6 μm was realised using a low-scattering-loss planar lightwave circuit with an Er-doped silica core which was fabricated by flame hydrolysis deposition and reactive ion etching techniques on an Si substrate. CW lasing was achieved successfully with an incident threshold power of 49 mW for pumping at 0.98 μm.

Guided-wave laser based on erbium-doped silica planar lightwave circuit

An Er-doped waveguide amplifier fabricated by plasma enhanced chemical vapour deposition is described. A maximum net gain of 5 dB and a gain coefficient of 0.67 dB/cm are obtained in a 0.48 wt% Er-doped waveguide pumped at 420 mW at a wavelength of 0.98 μm. The 0 dB gain threshold is 23 mW.

Erbium-doped phosphosilicate glass waveguide amplifier fabricated by PECVD

2/spl times/2 electro-optic switching is demonstrated in an integrated Mach-Zehnder interferometer constructed with thermally poled GeO/sub 2/-doped silica-based channel waveguides on a Si substrate.

Electro-optic switch constructed with a poled silica-based waveguide on a Si substrate

The chemical change from hydrogen gas that diffuses into silica glass for optical fibres to hydroxyl function has been investigated. Hydrogen molecules that diffuse into GeO2-doped silica glass at 500°C easily change into OH ions by thermal energy, while this chemical change does not occur in pure silica glass at 500°C. Also, germanium-doped silica fibre, in which hydrogen gas is dissolved at room temperature, shows OH ion absorption loss increase with chemical change by heat treatment at above 100°C, while pure silica core fibre shows no OH ion absorption loss increase by the same treatment.

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

Spectral changes of ESR signals due to germanium associated Ge(3) centres were observed on heat-treated optical fibres and preforms. The defect centres essentially exist in as-drawn fibres, even if preforms have been oxidised prior to drawing. The 500°C heat treatment of Ge-doped fibres caused a remarkable decrease in the ESR intensity of Ge(3) centres, subsequently causing optical loss increase around the 1.39 μm wavelength.

Yasuji Ohmori

Papers

Guided-wave laser based on erbium-doped silica planar lightwave circuit

Erbium-doped phosphosilicate glass waveguide amplifier fabricated by PECVD

Electro-optic switch constructed with a poled silica-based waveguide on a Si substrate

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

ESR study on loss increase of 500°C heat-treated Ge-doped optical fibres