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By introducing side-absorbers to metal-metal waveguides of broadband terahertz quantum cascade lasers, we are able to control and completely suppress higher-order lateral waveguide modes. This change leads to an octave spanning laser spectrum with a 600 GHz wide flat top. In addition, the absence of higher order lateral modes has a strong effect on the pulse generation of injection seeded QCLs. We...
We report on a monolithic extracting structure for terahertz quantum cascade laser based frequency combs. For a spectral bandwidth of more than 600 GHz at a center frequency of 2.5 THz a frequency comb with well-defined farfield pattern could be achieved. In addition the dynamic range of the frequency comb has been significantly improved.
Laser-based frequency combs play an important role in applications as spectroscopy. In the visible and infrared regime devices are already commercially available. Since a lot of rotation and vibration frequencies of gases lie in the THz domain, it is desirable to realize a powerful and broad frequency comb at such frequencies. THz Quantum cascade lasers (QCLs) are able to operate in this frequency...
The 3–4 μm spectral region is relevant since the fundamental C-H, N-H and O-H stretching modes have strong resonances in this region (e.g. Methane, Formaldehyde). This is important for applications like pollution control, breath analysis or detection of water contaminants. The unique possibility offered by quantum cascade lasers (QCLs) to tailor the emission frequency, makes them ideal sources for...
The quantum cascade laser, operates over an extremely wide wavelength range in the mid-infrared with high output power and low power consumption (<1W). A new generation of devices show enhanced wavelength multiplexing and tuning agility capabilities as well a frequency comb generation over more than 100cm−1.
Broadband-Quantum-Cascade-Lasers in the 3.3 μm and the 8 μm regions were tuned over 277 cm−1 and 445 cm−1 respectively using a grating-tuned external cavity set-up. The junction-up mounted devices were HR and AR coated and operated in pulsed mode. Another device of the 8 μm design was operated in cw and yielded a tuning range of 247 cm−1 without AR coating.
EC-QCLs operated in pulsed mode have a broader linewidth compared to EC-QCL operated in continuous-wave (CW), but offer wider tuning ranges using the same chip media. EC- QCLs using a heterogeneous active region have already shown broad tuning ranges in pulsed mode, covering the region from 8.2 mum to 10.4 mum using one single chip. This corresponds to 201 cm-1 tuning in wavenumbers, which is 18%...
An ultra-broadband distributed-feedback quantum cascade laser array was fabricated, using a heterogeneous cascade based on two bound-to-continuum designs centered at 8.4 and 9.6 mum. This array emitted in a range over 220 cm-1 near a 9-mu m wavelength, operated in pulsed mode at room temperature. The output power of the array varied between 100- and 1100-mW peak intensity.
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