Optoelectronic Thz Impulse Ranging
Abstract
We have used our THz impulse range to measure the late time response of targets following excitation by a short THz impulse: (1) Our measurements on dielectric cylinders showed unprecedented agreement with theory in both the time and frequency domains and enabled the first direct experimental comparison for the predicted surface wave with exact numerical calculations as well a simple geometrical optics model. (2) Our measurements on dielectric spheres had sufficiently high temporal resolution to permit the surface wave contribution to the total impulse response to be isolated. These results enabled the first direct experimental comparison for the predicted surface wave with numerical calculations using the Mie theory as well as the surface wave approximation of van de Hulst. (3) We have performed a direct observation of the Gouy effect through THz impulse scattering from cylindrical and spherical targets; the Gouy phase shift through a one-axis (cylindrical) focus of (lamba)/2 in comparison with a two-axis (spherical) focus of it is required to interpret our results. (4) Using similar THz optoelectronic techniques, we have characterized the response from an impulsively-excited, micron-sized dipole antenna on a dielectric surface. These THz experimental results scale and compare well with a previous GHz geo-radar theoretical calculation of a horizontal dipole on a dielectric. (5) For the first time we have used quasi-optical methods to efficiently couple freely propagating, subpsec pulses of THz radiation into sub-mm circular metal tubes (waveguides), single crystal fibers and plastic ribbon waveguides and to consequently measure the transmitted pulses from these waveguides.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 06, 2000
- Accession Number
- ADA384379
Entities
People
- Daniel R. Grischkowsky
Organizations
- Oklahoma State University–Stillwater