VCSELs are semiconductor micro-lasers, a Key Enabling Technology for many ICT applications, from datacom to sensors. Nowadays they are the main semiconductor optical source on the market and their production volume is exponentially increasing. Soon they will be part of every smart-phone and used for intra- and inter-chip communications in future microprocessors. VCSELs are complex dielectric resonator, composed of hundreds of layers and with plenty of possible transverse geometries, which can provide very different features, depending on its specific application. Those are micro-lasers, driven by a few milliamps currents and delivering some milliwatts of optical power. Nowadays these devices represent more than 90% of semiconductor laser market, with applications ranging from datacom to sensors. Their production volumes exponentially grows and soon will be indispensable part of smartphones and in micro-processors for intra- and inter-chip data exchanges. This is due to their superior features: smaller production costs, circular beam emission for best fiber coupling, small consumption (green electronics), high wall-plug efficiency, easy to have in linear of bidimensional arrays for higher powers.
In 2002 IEIIT presented a model, base on coupled mode theory, that allows to compute the verctorial VCSEL modes very efficiently (a few minutes on a normal PC). This fully in-house developed code has been validated by numerous comparisons with experimental results from very different devices. It allowed to design, realize and patent a technique to stabilize the emitted polarization, via a monolithically etched grating. Such technique has now become the standard for polarization control, an issue which is relevant in many applications. The most successful one so far is the laser-mouse, which consumed 8 millions VCSEL so far; this device is equipped by the VCSELs designed by IEIIT.
In the European STREP project SUBTUNE (www.subtune.org) IEIIT lead the desing and modeling of the tunable VCSELs, which ended up in 2011 with the record of 102nm continuous tuning (Fig. 1), still unbeaten.
Recently, in collaboration with TUB (Berlin, D), a new class of VCSELs is under investigation, aiming at superior single mode devices. Those will find an application in datacenters; in fact, by using the so-called vortex-modes and particular modulation schemes, one can predict multi-Terabit transmission in the future Ethernet infrastructure.
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