Figure 4 shows both a scanning electron
micrograph (SEM) of a fiber tip and the infrared transmittance of this tip at
relevant infrared wavelengths. The SEM shows the tip to be 200 nm in
diameter. The IR spectrum shows the transmissivity to be about
Figure 7 shows a transient four-wave mixing
signal from a multiple quantum well as a function of both the laser photon
energy and the time delay between the two incident pulses. At zero time delay,
a well-resolved spectrum is seen. As the time delay increases to 0.8 ps,
the intensity of the peaks decreases. At 1.6 ps no peaks are evident.