Low phonon energy gain medium and related active devices

Abstract

Using sol-gel techniques, an optical gain medium has been fabricated comprising a glass ceramic host material that includes clusters of crystalline oxide material, especially tin oxide, and that is doped with active ions concentrated at the clusters. The active ions are preferentially located at the nanoclusters so that they experience the relatively low phonon energy of the oxide and are insensitive to the phonon energy of the host. A host with a high phonon energy, such as silica, can therefore be used without the usual drawback of reduced carrier lifetimes through enhanced nonradiative decay rates.

Description

BACKGROUND OF THE INVENTION [0001] The invention relates to a low phonon energy gain medium and to active devices comprising such a gain medium. [0002] Optical gain media are well-known as forming the basis of both lasers and optical amplifiers. Many gain media are solid-state and comprise a host material doped with active dopant ions, such as rare earth ions. Silica is a particularly common host material for amplifiers, partly because the material is widely used in optical fibers. A silica amplifier is highly compatible with silica transmission fiber they can be coupled together with low losses. [0003] An integrated fiber laser may be fabricated from such a gain medium by additionally including a photosensitive dopant such as tin. The photosensitivity of tin allows optical gratings to be written directly into the fibers to provide the necessary cavity mirrors. Co-doping of silica fibers with the rare earth ions erbium or ytterbium for gain, and tin for photosensitivity, has been us...

AI Technical Summary

Benefits of technology

[0017] Gain media according to the present invention may be manaufactured by sol-gel techniques, which offer good control over the tin oxide cluster sizes. However, other techniques may be suitable for fabricating the gain medium.

Problems solved by technology

Unfortunately, silica has a high principal optical phonon energy, which arises from contributions from vibrations of the Si—O bond, in the vicinity of 1000 cm−1 [5].

Therefore, although silica is a useful host material as regards its compatibility with commonly used fibers, it is disadvantageous as far as phonon energy is concerned

However, fluoride glasses have low compatibility with silica optical fibers, and it is difficult to fabricate low loss fibers directly from fluoride glasses.

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