GaAs quantum well devices for detection and nonlinear optics in the mid-infrared

Citation

Grave, Ilan (1993) GaAs quantum well devices for detection and nonlinear optics in the mid-infrared. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/mjwc-4k88. https://resolver.caltech.edu/CaltechETD:etd-08272007-111424

Abstract

The basic physical limits for infrared detection based on intersubband processes in semiconductor quantum wells are presented. An evaluation of the potential of GaAs intersubband detectors and a comparison with other systems is attempted. It is shown that the performances of the single GaAs detector falls short with respect to the single HgCdTe detector. Still, the performances of GaAs intersubband detectors answer the needs of many conceivable applications; this fact, together with the maturity, integrability and uniformity of the cheaper GaAs technology might make these detectors the choice for many future applications and systems.

Optimization of parameters in the design and epitaxial growth of these structures yield standard intersubband detectors with very respectable performances at reasonable cooling costs.

The narrow bandwidth and the lack of post-growth tunability limit the capability and versatility of intersubband detection. A new kind of intersubband detector, the multistack integrated detector, is conceived in an attempt to address these issues. This detector can operate in a number of modes; it can have a narrow or wide bandwidth of detection, and even a voltage-controlled expandable bandwidth. Among its features a multi-color option and a switching-peak option for combined or alternate color detection. The underlying physics involves the formation, expansion and readjustment of electric field high and low domains along the multi-quantum well region.

Additional topics in the physics and applications of intersubband processes for detection of infrared light are explored: a band-gap design involving a variably-spaced superlattice barrier, is investigated by photocurrent spectroscopy. The experiments reveal the subtle breaking of the parity selection rules, and also the possibility of detecting infrared light at shorter wavelengths than previously thought possible in the GaAs/AlGaAs system.

The second part of this thesis deals with the study and observation of enhanced nonlinear optical effects at the mid infrared, close to intersubband resonances. Second harmonic generation is obtained around 5 µm. Third-order effects are then investigated in different experimental configurations, including the first observation of phase conjugation based on these nonlinearities. Very large third-order susceptibilities and intensity-dependent refractive indices are deduced from the experimental results.

Thesis Files