Two-mirror wave-front-dividing interferometer for infrared synchrotron radiation

High-power terahertz radiation from relativistic electrons

Terahertz (THz) radiation, which lies in the far-infrared region, is at the interface of electronics and photonics. Narrow-band THz radiation can be produced by free-electron lasers and fast diodes. Broadband THz radiation can be produced by thermal sources and, more recently, by table-top laser-driven sources and by short electron bunches in accelerators, but so far only with low power. Here we report calculations and measurements that confirm the production of high-power broadband THz radiation from subpicosecond electron bunches in an accelerator. The average power is nearly 20 watts, several orders of magnitude higher than any existing source, which could enable various new applications. In particular, many materials have distinct absorptive and dispersive properties in this spectral range, so that THz imaging could reveal interesting features. For example, it would be possible to image the distribution of specific proteins or water in tissue, or buried metal layers in semiconductors; the present source would allow full-field, real-time capture of such images. High peak and average power THz sources are also critical in driving new nonlinear phenomena and for pump-probe studies of dynamical properties of materials.

Wave-front-dividing circular-reflector interferometer for the far infrared

The efficiency of a wave-front-dividing interferometer with circular symmetric sets of reflectors is studied and compared with that of a lamellar grating. The circular-reflector interferometer shows more efficient modulation over larger spectral regions in the far IR than the lamellar grating does. In contrast to Michelson and Martin-Puplett interferometers no beam splitters are employed.

Wave-front-dividing array interferometers without moving parts for real-time spectroscopy from the IR to the UV

Interferometers of the Michelson or Mach-Zehnder type are designed as array interferometers. The number of array channels is equal to the number of points needed for an interferogram for Fourier transformation. Similarly one may use an array of step gratings with each grating having a different step height and producing one point of the interferogram. These interferometers, which do not have moving parts, use all the incident light, and the interferogram is instantly produced for real-time spectroscopy.