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The transient terahertz radiation emitted by a spin coherence optically generated in CdMnTe two-dimensional electron gases is directly measured in the time domain using electro-optic sampling. The spin radiation decays in a few ps at high magnetic fields. We also provide a full theoretical description within first principle calculations of both the generation of spin waves, precession and emission...
Laser action normally is initiated by the amplification of spontaneous emission. As spontaneous emission is a random process, the carrier phase of a laser is different each time a laser is turned on. As a consequence, it is not possible to measure the time-resolved field of a free-running laser using coherent detection techniques [1, 2]. Here we show [3] that it is possible to fix the carrier phase...
The QCL carrier phase is set by coherent injection seeding with a THz pulse. This enables the phase-resolved laser emission to be measured in the time-domain and the QCL to be used directly for time-domain-spectroscopy.
The transient terahertz radiation emitted by a spin coherence optically generated in CdMnTe two-dimensional electron gases is directly measured in the time domain using electro-optic sampling. The spin radiation decays in a few ps at high magnetic fields.
Integrated THz pulse generation and amplification in THz QCLs is demonstrated. Intracavity narrowband THz pulses are generated at 2.1THz by exciting the facet of a THz quantum cascade laser with a resonant interband-intersubband transition and detected using electro-optic sampling.
Gain and losses in a LO-phonon THz QCL are studied using TDS. At threshold the gain clamps at 25cm-1 and the gain FWHM is 0.6THz. At low biases, absorption features are observed below and above the laser frequency. They are shown to originate from the population of a parasitic electronic channel.
The population inversion of a terahertz quantum cascade laser is placed out of equilibrium using an integrated Auston switch. As a result, the dynamic gain of the laser is no longer clamped at threshold by the mirror losses, and large amplification of input terahertz probe pulses is observed.
Terahertz pulse generation is demonstrated by a resonant femtosecond interband excitation of the miniband of a quantum-cascade-laser. The laser gain is subsequently used to amplify the terahertz pulse generated as it propagates through the cavity.
A 3.1THz phonon depopulation-based quantum-cascade-laser is investigated using terahertz time domain spectroscopy. A gain of 25cm−1 and absorption features due to the lower laser level being populated from a parasitic electronic channel are highlighted.
A terahertz quantum cascade laser and an integrated Auston-switch are coupled to perform ultrafast gain switching. The resulting non-equilibrium gain is not clamped above laser threshold and large amplification of input terahertz pulses is demonstrated.
Frequency tunable terahertz (THz) interdigitated photoconductive antennas (PCAs) are realised by adjusting electrode spacing. An interdigitated geometry allows fabrication of PCAs with small gaps and large surface area for optical excitation. The pulsed electric field and emission spectra are measured using THz-time domain spectroscopy (TDS). It is observed that the peak frequency of the emitted spectra...
Terahertz time-domain spectroscopy is used to determine gain related parameters of terahertz quantum-cascade lasers. Due to the techniquespsila insensitivity to the QCL emission, spectral gain narrowing is observed above laser threshold. By correlating these measurements with bandstructure simulations, insight into the subband alignment as a function of the applied field is acquired.
Terahertz time-domain spectroscopy is used to determine the gain of terahertz quantum-cascade lasers. Gain clamping and spectral gain narrowing are observed above threshold, giving insight into subband alignment as a function of the applied voltage.
Terahertz time-domain spectroscopy is used to determine the gain of terahertz quantum-cascade lasers. Gain clamping and spectral gain narrowing are observed above threshold, giving insight into subband alignment as a function of the applied voltage.
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