Dana Turčinková

Ultra-broadband heterogeneous quantum cascade laser emitting from 2.2 to 3.2 THz

We present a heterogeneous terahertz quantum cascade laser that emits continuously between 2.2 and 3.2 THz, covering an emission range of over 40% around the central frequency. Devices were realized by stacking different active region designs into a double-metal waveguide. They operate up to 125 K with 15 mW peak power at 10 K in pulsed mode. Smaller devices show broadband emission also in continuous wave. Time-resolved measurements of the emission spectra were realized, confirming the broadband emission within a 5 ns time window.

Continuous tuning of terahertz distributed feedback quantum cascade laser by gas condensation and dielectric deposition

We present the continuous tuning of a terahertz quantum cascade laser based on 3rd order distributed feedback. This source provides a single mode emission with low dissipation power (∼400 mW) and milliwatt-level output power. The laser is tuned by nitrogen-gas condensation or by dielectric deposition. The former method offers a reversible, reproducible, and continuous mode-hop free tuning over 25 GHz at a frequency of ∼3.3 THz (Δf/f ∼ 0.75%). The latter is convenient for precise post-process targeting of a desired frequency.

Electrically tunable terahertz quantum cascade lasers based on a two-sections interdigitated distributed feedback cavity

The continuous electrical tuning of a single-mode terahertz quantum cascade laser operating at a frequency of 3 THz is demonstrated. The devices are based on a two-section interdigitated third-order distributed feedback cavity. The lasers can be tuned of about 4 GHz at a constant optical output power of 0.7 mW with a good far-field pattern.

Magnetically assisted quantum cascade laser emitting from 740 GHz to 1.4 THz

In this paper we show that by applying a perpendicular magnetic field to a quantum cascade structure it is possible to enhance the gain of different optical transitions. The combination of magnetic confinement with a broadband, cutoff-free optical resonator allows the demonstration of laser action over a large bandwidth, from 733 GHz to 1.38 THz together with the emission at 3.2 THz. A different lasing scheme is revealed that does not rely on resonant tunneling as the main injection mechanism. In combination with the magnetically enhanced gain laser emission at 1 THz is observed up to a temperature of 115 K, which corresponds to a ratio kBT/hν=2.3 between the lattice thermal energy and the laser photon energy.

High performance 4.7 THz GaAs quantum cascade lasers based on four quantum wells

GaAs/AlGaAs quantum cascade lasers based on four quantum well structures operating at 4.7 THz are reported. A large current density dynamic range is observed, leading to a maximum operation temperature of 150 K for the double metal waveguide device and a high peak output power more than 200 mW for the single surface plasmon waveguide device. A continuous wave, single mode, third order distributed feedback laser with a low electrical power dissipation and a narrow far-field beam pattern, which is required for a local oscillator in astronomy heterodyne spectrometers, is also demonstrated.

Waveguide Embedding of a Double-Metal 1.9-THz Quantum Cascade Laser: Design, Manufacturing, and Results

We present the details of a coupling structure to embed a 1.9-THz double-metal quantum cascade lasers (QCLs) into a 120-

Portable real-time THz imaging setup based on QC lasers

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Ultra-broadband THz semiconductor laser based on heterogeneous quantum cascade gain medium

m-wide full-height rectangular waveguide. We describe the split-block manufacturing of the waveguide coupler together with a diagonal feed horn and present power and beam shape measurements of two different devices. The two devices differ in coupling factor, which can be chosen in a wide range by the mounting position of the QCL. Our waveguide embedding allows coupling of a large fraction of the laser power into the waveguide and the subsequent horn antenna emitting with a large Gaussian mode content, enabling efficient integration into a diffraction limited optics setup. This is illustrated by a self-mixing experiment and by using the embedded QCL as a local oscillator in a heterodyne receiver.

Broadband semiconductor terahertz laser based on heterogeneous cascades

A portable, stand-alone, real-time THz imaging system for high resolution is presented. The total weight of the apparatus is less than 15 kg and its physical dimension is of approximately (65 cm)3. A quantum cascade laser emitting at 3.4 THz based on a third-order distributed feedback cavity is used as radiation source for transmission and reflection imaging modes. We report real-time THz imaging with a bolometric camera operating at 15 Hz producing movies with a resolution of 120 x 160 pixels. With the help of a Stirling motor cryocooler the laser operates in continuous-wave at 40 K with more than 1 mW output power and less than 300 mW of power consumption. We were able to image small objects employing refractive elements that we manufactured in high density polyethylene achieving a resolution of twice the wavelength.

High power terahertz quantum cascade laser at 63 µm

We report broadband laser emission from a quantum cascade laser based on heterogeneous gain medium. Gapless emission exceeding 1 THz bandwidth is reported around 2.66 THz (40% of the central frequency) from devices operating in double metal waveguides. Pulsed operating temperatures of 125 K with peak powers of 14 mW at 10 K are observed. CW operation is demonstrated and 1 THz bandwidth is observed above 80 K in pulsed mode. Time-resolved spectral analysis with 5 ns resolution revealing strong mode competition is also discussed.