The performance of space-borne infrared detectors is required higher sensitivity, higher resolution, or larger format in
comparison with that of ground-based infrared detectors. In order to realize higher mission requirements, JAXA decided
to position the infrared detector technology as one of the strategic technologies of JAXA and to promote the
development of the infrared detectors.
InAs/GaSb Type II superlattice (T2SL) is the only known infrared material that has a theoretically predicted higher
performance than HgCdTe. If the T2SL detector is realized, it can be applied for high sensitivity infrared sensors, which
are required for many advanced instruments such as an imaging Fourier Transform Spectrometer. The final goal of the
T2SL detector development is to realize an array detector having a cutoff wavelength of λc=15μm.
We have started a basic research on the T2SL detector. In this paper, we report on the first results of the development of
T2SL detectors of mid-wave infrared regime. The detector structure is a pin photodiode with SL of 9 InAs monolayers
(MLs) and 7 GaSb MLs. We present results of optical evaluation of the detector. The cutoff wavelength is 5.5μm at 30K.
The responsivity is 0.33±0.05A/W at 4.5 μm.
GaAs/AlAs coupled multilayer cavity structures on high-index substrates have been proposed as novel terahertz emission
devices. Two cavity modes with an optical frequency difference in the terahertz region are realized when two cavity
layers are coupled by an intermediate distributed Bragg reflector multilayer. Optical responses to ultrashort laser pulses
have been simulated using the transfer matrix method. Interference between the enhanced light fields of the cavity modes
was demonstrated when they were simultaneously excited by 100 fs Gaussian pulses. Extremely strong sum-frequency
generation was experimentally observed in the (113)B coupled multilayer cavity. We also found that the polarization
control by wafer-bonding might be one of the best ways to generate terahertz difference-frequency signal of two modes.