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Pump-probe measurements in asymmetric stepped quantum wells using FELIX

Pump-probe measurements in asymmetric stepped quantum wells using FELIX
Pump-probe measurements in asymmetric stepped quantum wells using FELIX
Three beam pump-probe measurements in asymmetric stepped quantum wells were conducted using the FELIX free electron laser. We have measured electron intersubband lifetimes of 1.8 ps and 2.5 ps in two GaAs/AlxGa1-xAs stepped quantum well samples. The two samples differ in the total number of quantum wells (80 and 50 periods), donor doping concentrations at the barrier (2 x 1017 cm-3 and 2 x 1018 cm-3) and barrier height (x=0.45 and x=0.35). Experiments were conducted on both samples at temperatures ranging from 4K to room temperature using a liquid Helium cooled cryostat. At saturation pump intensities, however, we observed an absorptive signal of sub-nanosecond lifetime following a normal positive transmissive signal of the order of picosecond lifetime. This slow decay absorptive signal is relatively stronger in intensity than the positive transmissive signal. The absorptive signal is believed to be caused by the absorption from the free electrons pumped from the ground subband to the continuum conduction band in the barrier layers associated with incoherent two-photon process. A three-level electron transition model was built to simulate the two-photon absorption process, which agrees well with the experimental data. The strong intensity dependent feature of the slow decay signal is also consistent with our model.
Tan, H.A.
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Xin, Z.J.
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Rutt, H.N.
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Wells, J.P.R.
1a5412f6-880f-4bbf-a3e0-f85db5f01675
Bradley, I.V.
96c10086-30d1-477c-b240-e5a98efe5bb9
Tan, H.A.
26280f50-8d13-4303-9cb9-e512586b8622
Xin, Z.J.
bc46917f-364a-498b-ad97-4241cabdeee4
Rutt, H.N.
e09fa327-0c01-467a-9898-4e7f0cd715fc
Wells, J.P.R.
1a5412f6-880f-4bbf-a3e0-f85db5f01675
Bradley, I.V.
96c10086-30d1-477c-b240-e5a98efe5bb9

Tan, H.A., Xin, Z.J., Rutt, H.N., Wells, J.P.R. and Bradley, I.V. (2001) Pump-probe measurements in asymmetric stepped quantum wells using FELIX. Rank Prize Symposium - Applications of Free Electron Lasers, Grasmere, UK. 16 - 19 Sep 2001.

Record type: Conference or Workshop Item (Paper)

Abstract

Three beam pump-probe measurements in asymmetric stepped quantum wells were conducted using the FELIX free electron laser. We have measured electron intersubband lifetimes of 1.8 ps and 2.5 ps in two GaAs/AlxGa1-xAs stepped quantum well samples. The two samples differ in the total number of quantum wells (80 and 50 periods), donor doping concentrations at the barrier (2 x 1017 cm-3 and 2 x 1018 cm-3) and barrier height (x=0.45 and x=0.35). Experiments were conducted on both samples at temperatures ranging from 4K to room temperature using a liquid Helium cooled cryostat. At saturation pump intensities, however, we observed an absorptive signal of sub-nanosecond lifetime following a normal positive transmissive signal of the order of picosecond lifetime. This slow decay absorptive signal is relatively stronger in intensity than the positive transmissive signal. The absorptive signal is believed to be caused by the absorption from the free electrons pumped from the ground subband to the continuum conduction band in the barrier layers associated with incoherent two-photon process. A three-level electron transition model was built to simulate the two-photon absorption process, which agrees well with the experimental data. The strong intensity dependent feature of the slow decay signal is also consistent with our model.

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e-pub ahead of print date: 2001
Venue - Dates: Rank Prize Symposium - Applications of Free Electron Lasers, Grasmere, UK, 2001-09-16 - 2001-09-19

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Local EPrints ID: 17100
URI: http://eprints.soton.ac.uk/id/eprint/17100
PURE UUID: 2009a588-d18d-4fef-ba78-eaaa51eead65

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Date deposited: 14 Sep 2005
Last modified: 22 Jul 2020 16:33

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