Terahertz Quantum Cascade lasers are very versatile sources of terahertz radiation. Frequency comb operation, surface emitting arrays, external cavity tuning have been demonstrated. For all these implementations broadband gain is strongly demanded. The intersubband gain mechanism allows to the design of different wavelength active region and their integration in the same waveguide. We have developed active regions consisting of up to four different intersubband designs. To enable a common operation not only the gain curve needs to be aligned over all sections but also the alignment electric field and subsequently the operating current. Fabry-Perot devices fabricated from the four-section active region show lasing over more than one octave. Ring resonators show also broadband laser operation and comb formation. Broadband operation is a large advantage of random lasers which we turn into useful devices by an optical machine learning approach. This allows the control of the emission wavelength beyond discrete cavity modes.
The study of high Al containing barriers in Terahertz Quantum Cascade lasers has led to the improvement of operation temperature and of the quantum efficiency. This is mainly caused by the reduction of transport channels through higher states. In consequence, the electron transport in these new devices is dominated by photon assisted tunneling. The originating non-linearity provides a huge potential for different operation modes. We try to further study this by coupling distributed QCL devices on a chip which has led to the observation of bi-stable operation and THz switching. We use the non-linear behavior for the control of the emission spectra of surface emitting random laser structures. Furthermore, ring structures can be realized which can be tuned from single mode to frequency comb operation.
We report on high performance Terahertz Quantum Cascade Lasers with InGaAs and GaAs active regions. Modified doping profiles derived from symmetric structures allowed achieving record output powers of double metal InGaAs/InAlAs THz Quantum Cascade Lasers. The increase of the Al concentration of the barriers in GaAs/AlGaAs devices helped to increase the operating temperature to above 191 K while keeping the threshold current low. This has enabled laser operation by thermoelectric cooling which is very important for application. We demonstrate laser wavelength switching by magnetic field and wavelength selection in Random THz Quantum Cascade Lasers by spatially controlled near-infrared excitation
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.