Generic foundry model for InP-based photonics

Similarities and differences between photonic and microelectronic integration technology are discussed and a vision of the development of InP-based photonic integration in the coming decade is given. 1 Photonic integration: introduction After its emergence at the end of the 60s [1], it was believed that photonic integration would take a similar development path to that followed by microelectronic integration. In his review paper in 1977, Tien [2] mentioned as one of the major goals of photonic integration or ‘integrated optics’ as it was called at the time: ‘the integration of a large number of optical devices on a small substrate, so forming an optical circuit reminiscent of the integrated circuit in microelectronics’. In the following years, a number of chips with increasing complexity were reported [3–7]. However, despite large R&D investments, photonic integrated circuits (PICs) with integration levels exceeding a few components did not succeed in entering the commercial marketplace for more than four decades. Sceptics started claiming that integrated optics was a promising technology and would ever remain so. It took until 2005 before the company Infinera introduced the first truly complex PIC in a commercial wavelength division multiplexing (WDM) system: a 10-channel WDM transmitter with more than 50 components integrated on a single InP chip, with a total capacity of 100 Gb/s [8]. Until now this is the only PIC of such a complexity that has been introduced commercially, although recent developments in the field of advanced modulation formats for telecommunications systems (like diquadrature phase-shift keying (DQPSK), pulse modulation DQPSK and quadrature amplitude modulation) indicate that other highly complex PICs will follow soon [9–12]. It is an interesting question to ask why so few of the advanced PICs reported in the literature have made it to the commercial arena up until now, despite the fact that over the last two decades there has been substantial investment and improvement in the development of integration technologies in industrial, national and international projects in Europe, in America and in the Far East. An important factor delaying the breakthrough of photonic integration to commercial applications has been the shift in technology focus from ‘technology push’ to ‘market pull’, which occurred in the early 90s of the last century. It became increasingly difficult to obtain funding without a clear and challenging system application. Viewed in isolation this seems to be a good policy for preventing the development of technology for which there is no market, as had happened frequently in the more distant past. But it had some important and undesirable side-effects which hampered the breakthrough of photonic integration. In most of the application-oriented projects, the coordination was done at the system level, and at the device level each technology partner was responsible for his own device. There was an almost complete lack of coordination in technology development, every fab developed its own processes and there was no incentive for process standardisation. As a result, we have almost as many technologies as applications, most of them very similar in their objectives, but sufficiently different to prevent both easy transfer of a design from one fab to another, and easy use of the technology for applications other than the ones for which it was developed. Owing to this huge fragmentation, the market for these application-specific technologies is in most cases too small to justify their further development into a low-cost industrial volume manufacturing process. Consequently, the chip costs remain too high to serve a large market and commercial use of PICs is limited to specific applications where they bring unique functionality that is not available in other technologies. To overcome this fragmentation, the way forward is to develop a small set of standardised technologies, in which the most frequently used basic building blocks are brought together in a single integration process, which is optimised for providing high performance for all the building blocks: a fabrication platform. Such a standardisation effort requires substantial investments in technology development, for which there was no budget available in the industrial development programs, because the market for their specific applications was too small, and IET Optoelectron., 2011, Vol. 5, Iss. 5, pp. 187–194 187 doi: 10.1049/iet-opt.2010.0068 & The Institution of Engineering and Technology 2011 www.ietdl.org