Analysis and Design of Vertical Cavity Surface Emitting Lasers

Citation

Andrew, A.M. (2004), "Analysis and Design of Vertical Cavity Surface Emitting Lasers", Kybernetes, Vol. 33 No. 9/10, pp. 1546-1547. https://doi.org/10.1108/03684920410556133

Wiley Series in Lasers and Applications

This is an extremely thorough treatment of its somewhat specialised but important topic. VCSELs are generators of light that can be modulated as required in fibre‐optic communication and opto‐electronic devices generally. A variety of applications is mentioned including barcode scanners and digital displays. Special mention is made of “smart pixel” devices in which each VCSEL is combined with a phototransistor to produce a component that is useful in optical information processing, and of circular or pie‐like arrays of VCSELs each producing light of a different wavelength, hence allowing multiplexed use of a single optical fibre.

A number of advantages are claimed for VCSELs compared to the earlier possibility of facet‐emitting lasers. VCSELs can be produced at lower cost and are smaller, and also have narrow beam divergence, low power consumption, high modulation bandwidth, and easy polarisation control. The amount of wafer space required for one unit is typically a square of side 400 μm. The use of these devices is also compared to that of light‐emitting diodes (LEDs) as sources for fibre optic communications and it is shown that VCSELs, of similar cost to LEDs, can achieve higher transmission speeds with better noise immunity, to such a degree that systems can be upgraded by replacing LEDs with VCSELs. For a newcomer to the topic it is rather startling to realise that the robust‐looking discs in the unscaled exploded view on the front cover of the book probably have a diameter similar to that of a human hair.

VCSELs, most of them operating at wavelengths in the region of 850 nm, are produced commercially by a number of companies. The book's author sees the future as lying with longer‐wavelength devices still to be developed. As he puts it (p. 21):

It is believed that the future industrial standard of VCSELs is an even higher modulation rate (>10 Gbits/s), longer link lengths (>60 km), and lower power consumption (<10 mW) and the further development of 1300/1550‐nm VCSEL technology in mass production is the key to the success of a billion‐dollar business.

A great deal of relevant mathematical theory is given, not only of the basic laser operation but of associated such aspects as the occurrence of spontaneous emission and the distribution of heat throughout the laser and its effect on performance. The author has chosen the method of treatment of each topic, from the choice offered in the current literature, which he believes to be most valuable. Some of the results can be applied only using finite‐element computing methods, and recommendations are made for suitable software packages. The book will certainly be a standard reference where development work on VCSELs and related devices is going on. It is highly mathematical and the details must be of only specialist interest, though the author's assessment of the opportunities gives a strong incentive to develop interest.