Electro-Optics - Applied Optics Fundamentals and Device Applications - page 31

2.2.9 Future Needs and Trends
The future requirements of electronic systems warranting the use of opti-
cally controlled devices are many. Optical control promises to solve many
of the current limitations of electronic systems. One of these is the need for
faster switching devices. Switching speed improvements are required for on/
off, frequency, and power level switching. Wider bandwidth systems are also
needed to improve the locking range of injection locked systems. Improving
the locking system will allow even more modulation of the carrier frequen-
cies. With this comes wider bandwidth capability and the requirement for
higher modulation rates.
Another requirement will be to control electronics with less optical signal
power. Currently, the coupling efficiency between the light source and the
microwave device is very poor. Higher reliability and producibility require-
ments will follow the successful laboratory demonstrations of new concepts.
Size and weight reduction will be stressed.
One key trend is the fabrication of optical and microwave components on
a single monolithic device. As discussed in Section 5.11, much of the MMIC
technology can be directly applied to the development of optics modules.
Optomicrowave monolithic integrated circuits will assist in obtaining better
control of the microwave devices with less optical power because the cou-
pling efficiency will increase. Size, weight, reliability, and manufacturability
will ultimately improve with the OMMIC systems as well. Laser technology
will also continue to improve on the current limitations of optical control.
Higher modulation rates and noise reduction improvement will parallel the
improvements in laser technology.
2.3 LithiumNiobateDevices
A large number of important devices that are fabricated in LiNbO 3 have
been discussed in the literature. Some of the most interesting of these are
described in this section [37].
2.3.1 Optical Switches
One of the most important LiNbO 3 devices is the optical switching device.
Response times as fast as 1 ps are possible [38] due to the electro-optic effect
inherent in lithium niobate, so that high-speed switching is limited merely
by the circuit delays that result from the finite length of these devices. The
fundamental building block of any optical switching network is the simple
changeover point or 2 × 2 optical cross point shown in Figure 2.17 [39]. In
the through state ports, 1 and 3 and 2 and 4 are connected. In the crossed