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A unique feature of Quantum Cascade lasers is the possibility to stack active regions. Using a three stack heterogeneous Quantum Cascade laser ultra broadband amplification and short pulse generation is demonstrated. High power output is achieved by two stacked symmetric active regions.
Terahertz (THz) quantum-cascade lasers (QCLs) constitute a very promising candidate for compact, wide bandwidth, integrated frequency combs [1, 4-7]. QCLs based on heterogeneous cores display the widest spectral coverage reaching more than one octave [2]. The possibility to engineer the gain profile turns out to be fundamental also with respect to dispersion compensation in order to extended the comb...
We report on a detector-free on-chip dual frequency comb setup based on terahertz quantum cascade lasers. The presented dual-comb covers a bandwidth of 630 GHz with a centre frequency of 2.5 THz. Instead of a fast detector one of the lasers has been used as a fast detector itself. The frequency comb spacing was analysed using frequency counting techniques revealing an accuracy down to δfrep/fcarrier...
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.
Time-domain terahertz spectroscopy (THs-TDS) has demonstrated its power in last two decades. With technological development of ultra-fast lasers and THz photonics, the sensitivity, signal dynamic range and the speed of acquisition of spectral information have been continuously improved. Here we present a proof of the principle of a confluence of THz-TDS and quantum cascade laser that holds promise...
We present an array of single-mode quantum cascade lasers operating in the range 8–$9.5~\mu \text{m}$ . The resonator features a pair of distributed Bragg reflectors for the mode selection, together with a second-order extraction grating. The radiation of these substrate emitting devices was combined in a single collector ridge. A proof of principle featured seven laser devices with a coverage of...
We report on design, fabrication and investigation of a buried heterostructure photonic crystal quantum cascade laser operating in the mid-IR (8.5μm) at room temperature, leading to single mode emission on a 600μm by 600μm mesa.
We demonstrate an amplification of broadband terahertz pulses in the bandwidth of 500 GHz centered at 2.5 THz. The amplification is based on gain switched quantum cascade structure width the heterogeneous active region.
By combining first and second order DFB gratings, a new solution for surface emission QCL is presented. A QWS mode and a buried hetero-structure process allow single mode emission and low dissipation devices.
We present a terahertz quantum cascade laser providing 875 mW two-facet output power in pulsed mode, at a frequency around 4.7 THz and at a heatsink temperature of 10 K. The laser has a single plasmon waveguide. The active region is based on four quantum wells with longitudinal optical phonon extraction.
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...
Leak detection of aerosol can propellants by means of optical spectroscopy allows for faster and safer operation, at much lower energy consumption than standard technologies. In this paper we present a Mid-infrared (IR) optical analyzer that has been developed for ultra-fast leak detection of most common aerosol propellants such as propane and butane.
Quantum Cascade Lasers (QCL) [1] are readily used sources in the mid-infrared serving mostly spectroscopic purposes, but also countermeasures and medical applications. For many of these purposes a single mode emission at a previously determined wavelength is required. This can be achieved for instance by adding Distributed-Feedback (DFB) [2] into the emitter. One approach to generate a DFB QCL is...
Quantum cascade lasers (QCLs)[1] are widely used sources of coherent radiation based on intersubband (ISB) transitions in quantum wells (QWs) with particularly good performance in the mid-IR spectral region. Due to their operation mechanism, QCLs would benefit from improved confinement in the upper lasing state by the introduction of 3D-confined quantum dots (QDs)[2] or quantum dashes (QDashes), which...
InGaAs/AlInAs/InP is a successful semiconductor material for operation of high performance mid-infrared quantum cascade lasers (QCLs) [1, 2]. However, in the THz region, a thin AlInAs barrier is required due to its high conduction band offset energy (530 meV) and is believed to limit a laser performance since subband position would be very sensitive to the layer thickness. In this work, we use a different...
Quantum Cascade Lasers (QCLs) are considered as one of the most versatile sources of light in the mid-IR spectral range. The need for mid-IR lasers not only emitting at precisely selected wavelengths but showing also a high spectral purity is now growing, driven by numerous possible applications such as high-resolution spectroscopy in the molecular fingerprint region, e.g. in combination with optical...
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...
Since the first demonstration of distributed feedback quantum (DFB) quantum cascade (QC) lasers in 1997 [1] tremendous progress has been made in the development of single-mode emitting QC lasers [2-4]. Such kind of devices are of particular interest because a lot of different molecules, like CO2, N2O or CH4, have their fundamental modes in the mid-infrared spectral region (3–12 μm).
Frequency noise and linewidth properties of different mid-infrared DFB-QCLs using buried-heterostructures and ridge waveguides are compared. The physical origin of frequency noise and the impact of the different lasers parameters are discussed.
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