Spanning the Microwave Infrared Gap

The basic problems encountered in both classical and quantum electronics when attempting to produce coherent radiation in the microwave-infrared gap region extending from roughly 100- to 1000-microns wavelength are reviewed. Brief historical accounts are given of past work leading up to the submillimeter wave frontier. Some selected examples of current work are described to indicate the direction research in this area is taking. While it is the conclusion that a real breakthrough in the microwave infrared problem is not imminent, it is felt that the new background knowledge and the increased applied physics experience now acquired by the ultramicrowave engineer will hasten the day when a solution to the problem will be obtained.