Abstract
We present the direct measurement of the refractive index distribution (spectral dispersion) arising from an intersubband transition in GaN/AlN multi quantum wells structure. The measurement is carried out through a novel interferometric technique. The measured interferogram yields a change in the refractive index varying from -5 × 10(-3) to 6 × 10(-3) as a function of the wavelength, introduced by the intersubband resonance at 1.5 µm. These results compare well with those derived using Kramers-Kronig transform of the measured absorption spectrum.
Highlights
Intersubband transitions (ISBTs) in III-nitride (GaN, InN, AlN and their alloys) quantum wells (QWs) have attracted considerable interest over the past few years due to their possible applications as ultrafast optoelectronic devices, such as all-optical switches for optical communication networks, near-infrared (NIR) photodetectors, and quantum cascade lasers [1–10]
In contrast to other III-V semiconductors, ISBTs in GaN/AlGaN QWs can be tuned to the optical fibers transmission windows at 1.3 and 1.55-μm due to the large conduction band offset [11, 12]
Additional key feature of nitride-based ISBTs is the ultra-fast intersubband (ISB) relaxation lifetimes due to the highly polar nature of the III-nitride material system [1, 4]. These properties are well suited for the development of fast all-optical switches and modulators operating at fiber-optic communication wavelengths
Summary
Intersubband transitions (ISBTs) in III-nitride (GaN, InN, AlN and their alloys) quantum wells (QWs) have attracted considerable interest over the past few years due to their possible applications as ultrafast optoelectronic devices, such as all-optical switches for optical communication networks, near-infrared (NIR) photodetectors, and quantum cascade lasers [1–10]. Additional key feature of nitride-based ISBTs is the ultra-fast intersubband (ISB) relaxation lifetimes (few hundreds femtoseconds) due to the highly polar nature of the III-nitride material system [1, 4] These properties are well suited for the development of fast all-optical switches and modulators operating at fiber-optic communication wavelengths. A number of GaN ISBT based devices, operating in the NIR spectral region, have been demonstrated These include photodetectors [7], Tera bit/s all-optical switches [5, 6] and electro-optical modulators relying either on biascontrolled QW depletion [8, 11], or on charge transfer between coupled QWs [9, 10]. The direct spectral dispersion measurement agrees very well with the spectral dispersion calculated from the K-K relations
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