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A terahertz quantum cascade laser design that combines a wide gain bandwidth, large photon-driven transport and good high-temperature characteristics is presented. It relies on a diagonal transition between a bound state and doublet of states tunnel coupled to the upper state of a phonon extraction stage. The high optical efficiency of this design enables the observation of photon-driven transport over a wide current density range. The relative tolerance of the design to small variations in the barrier thicknesses made it suitable for testing different growth techniques and materials. I n particular, we compared the performances of devices grown using molecular-beam epitaxy with those achieved using organometallic chemical vapor deposition. The low-threshold current density and the high slope efficiency makes this device an attractive active region for the development of single-mode quantum cascade lasers based on third-order-distributed feedback structures. Single-mode, high power was achieved with good continuous and pulsed wave operation. [ABSTRACT FROM AUTHOR]

This paper gives an overview on the design, fabrication, and characterization of quantum cascade detectors. They are tailorable infrared photodetectors based on intersubband transitions in semiconductor quantum wells that do not require an external bias voltage due to their asymmetric conduction band profile. They thus profit from favorable noise behavior, reduced thermal load, and simpler readout circuits. This was demonstrated at wavelengths from the near infrared at 2 μm to THz radiation at 87 μm using different semiconductor material systems. [ABSTRACT FROM AUTHOR]

Strong light-matter coupling at room temperature in the terahertz (THz) range is demonstrated. The studied system consists of electronic intersubband transitions in AlxGa1-xAs parabolic quantum wells coupled to an electronic LC microcavity resonator allowing strong subwavelength confinement of the cavity mode. The measured Rabi frequency is 0.48 THz, corresponding to 14% of the center frequency, independent of the temperature of the system in the range 10-300 K. [ABSTRACT FROM AUTHOR]

We present the development of a broad gain quantum cascade active region. By appropriate cascade design and using a symmetric active region arrangement, we engineer a flat gain and increase the total modal gain in the desired spectral range. Grating-coupled external cavity quantum cascade lasers using this symmetric active region are tunable from 7.6 to 11.4 μm with a peak optical output power of 1 W and an average output power of 15 mW at room-temperature. With a tuning of over 432 cm-1, this single source covers an emission range of over 39% around the center frequency. [ABSTRACT FROM AUTHOR]

A quantum cascade laser based on a three well active module and emitting at 3 THz is demonstrated. The optical transition is vertical in real space and localized in an Al0.03Ga0.97As quantum well. Maximum operating temperature of 123 K in pulsed mode is reported, with threshold current densities as low as 110 A/cm2 at 10 K and 175 A/cm2 at 100 K. High slope efficiency values testify the good internal quantum efficiency of the structure. [ABSTRACT FROM AUTHOR]