Quantum well intersubband lifetimes measured by mid-IR pump-probe experiments

Conference · Sun Dec 31 04:00:00 EST 1995

OSTI ID:238889

Woods, G L; Sung, B; Proctor, M ^[1]

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1. Ginzton Lab., Stanford, CA (United States); and others

Semiconductor quantum wells exhibit quantum-confined electronic energy levels, or subbands, that are similar to one-dimensional {open_quotes}particle in a box{close_quotes} wavefunctions. The light effective mass of electrons allows large spatial extents of the wavefunctions and concomitantly large dipole overlaps between states. These large dipoles have been exploited in a variety of experiments including nonlinear frequency conversion, infrared photodetection, and lasing. A key parameter for many devices is the upper state lifetime. The decay of carriers in the upper state is believed to be dominated by optical phonon scattering and lifetimes on-the order of 1ps are expected. While Raman and saturation measurements have shown good agreement with theory, direct pump-probe measurements have reported longer lifetimes, partially due to carrier heating. In this paper, we discuss our mid-IR (5{mu}m) pump-probe measurements of intersubband lifetimes, performed at the Stanford Picosecond Free Electron Laser Center. At low excitation densities we observe lifetimes of about 1.5 ps, in good agreement with phonon theory. At high excitation densities the lifetime increases to 3.5 ps, demonstrating the transition from the low- to high-excitation agree.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• OSTI ID: 238889
• Report Number(s): BNL--61982-Absts.; CONF-9508156--Absts.; ON: DE96002729
• Country of Publication: United States
• Language: English

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