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We report studies on bidirectional emission of ring cavity surface emitting quantum cascade lasers. Special attention is put on substrate emission and methods for favoring one single emission direction.
Detectivity enhancement up to 20 times is achieved by fabricating a quantum well infrared photodetector as a photonic crystal slab. This enhancement is the combined effect of increased responsivity and noise current reduction. We report a peak detectivity of 2.6E10 cmHz1/2/W at 80 K and were able to operate the device up to 200 K.
Reduced threshold currents and high temperature operation in surface emitting quantum cascade lasers are demonstrated by using ring-based cavities. The devices exhibit robust and tunable single-mode operation as well as low divergence symmetric beams.
A monolithic coupling scheme for mid-infrared InP-based quantum cascade laser arrays is presented. The tree-shaped resonator exhibits phase-locking, which leads to in-phase emission from the coupled branches and a high level of modal control.
The demonstration of an aluminium-free quantum cascade laser is reported. The presented quantum cascade laser has been realised in an InGaAs/GaAsSb material system lattice-matched to InP. Laser emission is observed at a wavelength around 11.3 mum. The threshold current density is 1.7 kA/cm2 at 78 K, and a maximum optical output power of 20 mW at the same temperature is reported.
Mid-infrared beam shaping is demonstrated by using grating coupled surface emitting quantum cascade ring lasers. The devices allow for far-field tuning, ranging from highly symmetric spot-to ring-shaped beam patterns, depending on the grating period.
We present a novel method for the thermal tuning of a grating-free mid-IR QCLs utilizing the absorbance changes of a thermochromic cladding. Both higher tuning coefficients as well as thermostable emission are achievable.
The development of planar chalcogenide glass waveguides leads the way toward integrated mid-infrared optics. As2S3 waveguides fabricated by solution casting have a transmission loss of 9.47 dB/cm at 4.8 mum.
A monolithic coupling scheme with two active waveguides merging into a single waveguide is presented for a mid-infrared GaAs/AlGaAs quantum cascade laser. The rapid development of unipolar quantum cascade lasers (QCLs) creates a basis for a broad variety of technological applications. Farfield patterns of the identical laser with a truncated mixing region result in a different superposition of the...
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