Terahertz Ring Oscillators based on Electrically Biased
Super-superlattice.
Recent
experiments [[1]]
have demonstrated potential crossover from terahertz loss to terahertz gain in
an electrically biased super-superlattice.
The crossover occurs at a voltage that causes the spacing between rungs
of the Stark ladder to exceed the measurement frequency. In essence the experiments demonstrate
that the system may support sufficient gain below the Stark ladder splitting to
overcome losses and make a coherent terahertz oscillator.
We propose to exploit these
results by fabricating ring shaped ridge waveguides sandwiched between metallic
floor and ceiling. These confine
the radiation in the ring to a planar waveguide and provide electrical contact
to the top and bottom of the superlattice for electrical excitation. The ring geometry requires no end
reflectors; radiation leaks out through the evanescent wave whose strength is
determined by the radius of curvature.
(See Fig. 1)
|
a b c Fig. 1 a). 10 mm high ring resonator confined by an in-plane terahertz photonic band gap structure. Waveguide ceiling removed. b) Schematic of metalized ridge. c) Estimated gain versus frequency compared to ridge waveguide loss. |
Statement of
work.
- Fabricate ring resonator
structures like that shown in Fig. 1.
- Electrically excite and
measure incoherent and potential coherent emission.
- Model and document
electrical I-V characteristics, and terahertz emission.
- Assess potential for a
solid-state coherent terahertz oscillator.