Monolithic Array Of 980 nm Lasers Heralds Breakthrough For Optical Network System Builders

- first commercial product to use company s unique optical integration process, QWI

- integration concept is expected to slash costs for optical networking OEMs

High Blantyre, Scotland. The first product to be announced by Intense Photonics is a monolithic array of 980 nm EDFA pump lasers providing a breakthrough in cost and space savings for system builders targeting the emerging market for metropolitan optical networking.

The device - the first to be manufactured at the company s brand new III-V semiconductor fabrication facility - is purpose-designed for simple systems integration, and may be specified with a range of application-specific parameters to suit individual customers applications. These include output power levels, number of laser sources up to 10, physical dimensions and fibre coupling interfaces.

Designated the IP0980, the device has been fabricated using Intense Photonics unique quantum well intermixing (QWI) process. QWI simplifies the production of monolithic photonic ICs by eliminating the requirement for standard regrowth techniques, with their associated optical loss and yield drawbacks. In this application, QWI is exploited to allow each InGaAs laser source to be integrated with non-absorbing mirrors (NAMs) structures on device facets, for exceptional performance, combined with reliability and yield.

NAMs combat hot spots - tackling a common laser failure mode: catastrophical optical damage caused by energy absorption at the laser facet, which can be aggravated by micro-positioning inaccuracies of the active chip onto the sub-mount. Combined with the use of P-side-down mounting - which further optimises heat transfer - the design breaks new ground in manufacturing yield and in-service reliability for laser pumps.

Users may specify the IP0980 device in arrays with up to 10 laser elements, with physical spacings and interface angles to simplify connection to an arrayed waveguide (AWG), and with output power selections of up to 250mW and beyond to suit different EDFA pump applications.

This advance is expected to yield enormous savings for system builders. The savings will come from interconnection designs which make it possible to attach fibre optic cable assemblies easily; from reduced packaging - as only one device must now be temperature controlled instead of up to 10; from higher reliability - because of the dramatic reduction in component count; and from size reductions.

Such integration provides the kind of progress that is essential if broadband optical communications services are to move out from the telecommunications network backbone, into metropolitan areas, and finally to the desktop.

What is a quantum well intermixing? QWI is a technique that allows the properties of a semiconductor material to be modified, typically allowing its energy bandgap to be controlled - making it opaque or transparent to light - such that multiple optical communications functions can be integrated on a monolithic chip. Quantum wells are active elements in opto-electronic (III-V compound) semiconductor devices. Electrons tend to gravitate to the lowest possible energy position and the term wells refers to an area which is [processed] grown especially to have a lower energy, so that it acts as a trap for electrons. They are referred to as quantum wells because these areas are extremely small - of the order of a few atomic layers thick - which makes their operation governed by quantum mechanics, allowing only specific energies and bandgaps.

Because quantum well structures are extremely thin they can be affected easily. This is achieved by depositing [or regrowing] additional layers and then applying heat - exciting the atoms and thereby causing intermixing with surrounding materials. By careful choice of capping layers it is possible to selectively intermix the quantum wells across a wafer, thus allowing a single chip to perform various optical functions. For example, Intense Photonics 980 nm pump laser uses quantum well structures to provide more efficient and higher power light output. Quantum well structures improve its performance by forcing electrons from the N material and holes from the P material to be at the same energy levels, thereby optimising the strength of the combination process (which results in photon emission). By closely controlling the thickness of the quantum layer, quantum wells are also used to optimise the wavelength of the emitted light. And, by eliminating the quantum well structures at the device s edges, these regions become passive and transparent to the emitted light, thus preventing a common laser failure mode caused by heating damage. In other devices, QWI principles might be used to achieve absorption - facilitating data modulation for example - or filtering, for selecting and switching particular data transmission wavelengths.

Contact: Intense Photonics Ltd Tel: +44 (0)1698 827000 Fax: +44 (0)1698 827262 enquiries@intensephotonics.com www.intensephotonics.com