Room-temperature continuous wave (CW) operation of a tunable external-cavity quantum cascade laser (EC-QCL) at center wavelength around 7.2 μm is presented. The EC-QCL was implemented in a Littrow configuration. The gain chip is based on a diagonal bound-to-continuum design with a high-reflection coating on the back facet. A two-layer antireflection (AR) coating consisting of Al2O3 and ZnSe was designed and deposited on the front facet of the chip to suppress the Fabry–Pérot modes. With this AR coating, single-mode tuning range of 128 cm−1 was achieved, from 1346.7 to 1475.3 cm−1 (6.78 to 7.43 μm). High side-mode suppression ratio over 30 dB was achieved near the center gain region. A very low-threshold current density of 0.89 kA/cm2 and a high output power of 50 mW were obtained when the EC-QCL was operated in CW mode at 20°C.
Quantum cascade detectors (QCDs) are photovoltaic devices: they have a built in
asymmetric conduction band potential formed by energy band engineering design,
which allows for biasless operation. In this work, we focus on the very long wave
infrared (VLWIR) quantum cascade photodectors involving energy band engineering,
material technology, and devices physics. Targeting the common applications, we
demonstrate a series of VLWIR QCDs from 14 to 20μm. The dark current density
under 1.1×10<sup>-11</sup> Acm<sup>-2</sup> and the detectivity above 1×10<sup>11 </sup>cmHz<sup>1/2</sup>W<sup>-1 </sup>is achieved.
Many of them exhibit high performance and give a cheerful prospect for the practical
application in the near future.
Infrared detection within the atmospheric window between 3 to 5μm has gained great interest because of its wide range
of applications, such as eye-safe free-space optical communication links and high-precision time-of-flight measurements
used in 3D imaging. In this letter, we report on the characteristics of two InP-based strain-compensated InGaAs/InAlAs
quantum cascade detectors (QCDs) detecting around 4 μm and 4.5 μm, which are promising candidates for applications
in this wavelength range. Maximal responsivity values of 11.43mA/W at 180K and 10.1 mA/W at 78K and Johnson
noise limited detectivities of 2.43×10<sup>10</sup> and 2×10<sup>10</sup> Jones at 78K, for the 4.5 μm and the 4 μm device, respectively, were
obtained. In addition, both devices can work up to room temperature with responsivities of 0.81 mA/W(4.5μm) and 1.64
We designed and demonstrated a series of surface emitting quantum cascade lasers
within the range of 4.5-9.0μm with different kinds of grating structure. The 2-order
Bragg grating structure were exposed on top of the materials by means of optical
lithography or holography and realized by deeper wet chemical etching. Many of
these devices exhibit high performance in single-mode characteristics, operation
temperature, and far field characteristics. These results give a cheerful prospect for the
sensing and medical diagnosis application in the near future.
We report the design and fabrication of terahertz quantum cascade lasers at about 3 THz that use semi-insulating
surface-plasmon waveguide for optical mode confinement The single-mode operations are realized by employing
one-dimensional first-order distributed-feedback (DFB) and photonic crystal distributed-feedback (PCDFB) resonators,
respectively. The single-mode operation of up to 88 K and peak power of 9.5 mW at 10 K for the DFB devices is
obtained. The PCDFB devices also emit a single frequency at above 50 K.