Blue-shifting of coherent plasmon radiation due to Landau damping
Restricting the wave vector of coherent plasmons excited by ultrashort laser pulses results in a frequency blue-shift of the emitted THz radiation, consistent with the onset of Landau damping.
Coherent plasmons in n-doped GaAs
Femtosecond laser excitation of bulk $n$-doped GaAs leads to coherent plasmon excitations that emit intense submillimeter wave radiation. We investigated the underlying plasmon dynamics in time-resolved experiments on the emitted THz radiation. The results show that THz pulses are emitted due to the coherent oscillation of the extrinsic electron plasma in the bulk. The plasmon excitations are started by single-sided screening of the surface depletion field after photoexcitation. Temperature-dependent measurements indicate that the plasmon damping is due to phonon scattering.
GUNN EFFECT IN n‐TYPE InSb
In this letter we report the observation of the Gunn effect in n‐type InSb at 77°K and atmospheric pressure. This result is surprising, since it was previously thought that the large amount of carrier multiplication at fields below the Gunn threshold would preclude observation of the Gunn effect in InSb and similar materials. Several explanations for the negative differential conductivity underlying the Gunn effect in this case are possible, but the intervalley transfer mechanism is most consistent with the observed negative pressure coefficient of the threshold field.