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Enhanced electroluminescence in arrays of double metal patch microcavities is demonstrated. The enhancement originates from high Purcell factors and efficient photon out-coupling as the period of the array is increased.
We measure the opto-electronic properties of femtosecond-laser-ablated GaAs and demonstrate its utility towards THz devices. In particular, we show that laser-ablated THz antennas are 65% more efficient than non-ablated antennas at high powers. Our results demonstrate the possibility of using femtosecond-laser-ablation as a cost-effective technique to engineer material properties for THz devices.
Optical sidebands are generated by difference frequency mixing between a resonant bandgap near-infrared beam and a terahertz (THz) wave. This is realized within the cavity of a THz quantum cascade laser using resonantly enhanced non-linearities. Multiple order optical sidebands and conversion efficiencies up to 0.1% are shown.
We study the generation of broadband THz radiation (∼18 THz) with high peak electric field (∼0.5 kV/cm) using a low temperature GaAs interdigitated photoconductive antenna and a high-power, high repetition rate, 15 femtosecond Ti:Sapphire oscillator.
Difference frequency mixing between a resonant bandgap near-infrared beam and a THz wave is demonstrated within the cavity of a quantum cascade laser using a resonantly enhanced second order non-linearity. Conversion efficiencies up to 0.13% are shown that are comparable to those shown by Free Electron Laser measurements.
The emission of a quantum cascade laser can be synchronized to the repetition rate of a femtosecond laser through the use of coherent injection seeding. This synchronization defines a sampling coherence between the terahertz laser emission and the femtosecond laser which enables coherent field detection. In this contribution the sampling coherence is measured in the time-domain through the use of...
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...
Phase-matched difference frequency mixing between a resonant bandgap near-infrared beam and a THz wave is demonstrated within a quantum cascade laser using second order non-linearities. Conversion efficiencies up to 0.16% are shown.
We measure the sampling coherence between a quantum cascade laser and a reference femtosecond laser. In addition to complete and incomplete sampling coherence, quantum cascade lasers can exhibit partial sampling coherence that varies with time.
A quantum-cascade-laser (QCL) is used as an integrated injection seeded source and amplifier for terahertz (THz) pulses. A coupled-cavity scheme is implemented to generate THz pulses on the QCL and to saturate the amplified pulse.
Ultrafast gain switching of THz quantum cascade lasers is demonstrated and applied to amplify sub-ps THz pulses as well as to initiate THz laser emission with a controlled phase. Impact on THz time domain spectroscopy and on future development for mode-locking will be discussed.
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.
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