M. Punke, F. Hoos, C. Karnutsch, U. Lemmer, N. Linder, K. Streubel (pdf)
Optics Letters 31 (8), p. 1157-1159 (2006)
We have realized a 76 MHz white-light differential transmission spectroscopy system. The technique employs a Ti:sapphire laser oscillator TIF-50, Del Mar Ventures, San Diego (current model name Trestles 50) and a tapered fiber (NT&C, Marnheim, Germany) to generate a white-light continuum spanning almost the full visible to near-infrared spectral range. Using acousto-optical modulation and subsequent lock-in detection, transient relative transmission changes as small as 10−5 are detected. The method is applied to study the ultrafast gain dynamics of the active layer of a vertical-external-cavity surface-emitting laser based on a multiple-quantum-well structure.
Fig.1 Schematic diagram of the experimental setup.
AOM, acousto-optic modulator; DC, dichroic mirror; DL, delay line; IF, variable interference filter; SHG, second harmonic generation.
Fig 2. Tapered fiber output spectra.
(Photograph of the beam after diffraction on a grating.)
Fig. 3 Differential transmission measurements of the investigated AlGaInP MQW structure.
Pump wavelength, 400 nm; pump pulse energy, 150 pJ.
