Spatial-harmonic gratings at high modulation depths in photorefractive quantum wells

Abstract

High-order spatial harmonics of photorefractive gratings are detected directly in multi wave mixing experiments in photorefractive AlGaAs/GaAs quantum wells operating in the Franz-Keldysh geometry. We have observed diffraction signals from the first-, second-, and third-harmonic refractive-index gratings. The quadratic electro-optic effect in the quantum wells second-spatial-harmonic grating.

Measurements of absorption coefficient and refractive index changes without the Kramers–Kronig relation in photorefractive quantum wells of GaAs

“…Higher-order spatial harmonics can be generated in PRMQW when the modulation index approaches 1 [9]. In our experiment we observed first-order diffraction for the first, second and third harmonics gratings.…”

Bandwidth-limited diffraction of femtosecond pulses from photorefractive quantum wells

“…In the thin grating or Raman-Nath limit, the spatially varying optical modulation diffracts the incident pulse into many orders without requiring phase-matching. The strongest diffraction is from the lowest harmonic (fundamental) grating, so is taken to be [14]. The total electric-field at the exit face of the material is (5) Using the relation (6) with the Bessel function and the previous definition for we obtain (7) which contains all diffracted orders.…”

“…To verify that the nearly transform-limited behavior of the photorefractive QW's remains the same when the photorefractive QW's are used in a pulse shaper, we placed a photorefractive MQW sample into the pulse shaper we described above. The sample used in this study had an exposure window of 14 1 mm with a dc voltage of 300 V applied vertically along the 1-mm gap. The long horizontal window ensured that all the frequency components (which were spatially separated in the Fourier plane in the pulse shaper) fall on the photorefractive grating.…”

Photoinduced Space-Charge Gratings in Semi-Insulating Multiple Quantum Wells

“…We observe a strong space-charge electric field grating in Semi-Insulating Multiple Quantum Well (SIMQW) structures [2] in photorefractive mixing experiments [3,4,5]. Space-charge fields are generated under many different conditions.…”