Three- And Four-Photon Absorption In Inas

In a series of experiments using 125 ps CO2 laser pulses, the authors identified conditions for three- and four-photon absorption in 1-mm samples of bulk InAs (N approx. 5 × 1016 cm-3). Three-photon absorption (3PA) is studied at a fixed laser wavelength of 9.54 μm. At room temperature, 3ℏω \u3e Eg = 0.36 eV. At 15 K, however, 3 ℏω \u3c Eg = 0.42 eV and 3PA cannot occur. A sequence of open aperture Z scans were performed, varying only sample temperature