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A fast and continuous tuning of a 3.1-THz GaAs-based quantum-cascade laser is demonstrated. This is achieved by illuminating its rear facet with a high-power, near-infrared diode laser. The spectral position of the THz laser modes can be adjusted by the illumination power. The maximum tuning range achieved in pulsed mode at a temperature of 35 K is 9.1 GHz.
We demonstrated the gapless THz comb by combination of dual THz comb spectroscopy and spectrally interleaving technique. This method enhanced the spectral resolution to the comb-mode linewidth rather than its interval.
We have developed a stable two-mode laser by using a quantum dot optical gain chip in an external cavity. In this study, we demonstrate continuous change of frequency separation of a two-mode laser by using a birefringent etalon filter. Since the polarization of the quantum dot optical gain chip is TE-dominant, the frequency separation of the two-mode laser is controlled by rotating the birefringent...
We demonstrate coherent THz emission based on the stable operation of a dual-frequency vertical-external-cavity surface-emitting laser. The laser operates on two Laguerre-Gauss transverse modes in a single-axis cavity, thanks to sub-wavelength thick metallic transverse mask deposit on the surface emitting semiconductor structure. A beat note at frequencies from 50 GHz to 3 THz has been demonstrated...
We present a compact, room-temperature, high-power and broadly tunable terahertz source based on a two-section digital distributed feedback laser diode and a plasmonic photomixer. It offers a 3 THz radiation frequency tuning range with a radiation power of 0.45 mW at 1.62 THz.
We devise arrays of surface emitting THz QCLs exploiting two novel lithographic configurations: a) a dual periodicity slit architecture and b) corrugated sinusoidal wire laser cavities. Extremely low divergent optical beams, with up to 85 mW of emitted optical powers and 245 mV/A slope efficiencies have been reached.
Mode-selective phonon excitation induced by MIR-FEL laser irradiation on a bulk 6H-SiC has been investigated by anti-Stokes (AS) Raman scattering spectroscopy using pico-second laser. We observed a clear peak at 965 cm−1 which corresponds to the absorption energy of the lattice vibration of 6H-SiC when the pump laser wavelength was 10.4 μm (962 cm−1). However, two peaks were observed by slightly detuned...
We report high-performance continuous-wave (C-W) THz quantum cascade lasers with semi-insulating surface-plasmon waveguide. Epitaxial-side down mounting process was developed to enhance heat extraction from the active region. C-W power above 100 mW and C-W wall-plug efficiency above 1.5% was obtained. The highest C-W operation temperature was 70 K.
We have demonstrated THz quantum-cascade metasurface vertical external cavity surface emitting lasers (VECSELs) using a variety of metasurfaces. The dependence of the laser spectrum on the metasurface design parameters is analyzed via simulation and experiment.
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...
A laser system emitting within the IR wavelength range from 12 to 16.6 micron is discussed. The hybrid laser system consists of molecular gas lasers with a frequency conversion in a nonlinear crystal. One gas laser is a carbon monoxide laser operating in multi-line or single-line mode. Another one is a carbon dioxide laser operating in multi-line mode. These lasers operate in a Q-switched mode. Spectrum...
Compact repetitively pulsed cryogenically cooled slab RF discharge CO laser with double path V-type laser resonator equipped with external Q-switch system based on rotating mirror was developed and studied. The laser produced IR (λ∼5–6 μm) radiation pulses of −1+2 μs duration (FWHM), peak power up to ∼3 kW and pulse repetition rate up to 130 Hz. Averaged output laser power reached 0.4 W, the laser...
A THz laser source based on stimulated polariton scattering (SPS) in an intracavity RbTiOPO4 (RTP) crystal is reported, with frequency-tunable output from 3.10 to 3.16 THz and from 3.50 to 4.15 THz. The gap exhibited from 3.17 to 3.49 THz is located in the vicinity of the 104 cm−1 absorbing mode in RTP. A maximum average output power of 16.2 μW was measured at 3.80 THz.
Radially polarized intense terahertz (THz) radiation is measured experimentally behind a thin foil irradiated by ultrashort relativistic intense laser pulse of ultrahigh contrast. As the target thickness is reduced from 30 to 2 μm, the energy of the THz emission increases dramatically, which even reaches up to 10.5 mJ per pulse, corresponding to energy conversion efficiency of 1.7%. This efficient...
The time-dependent optical properties of molecular systems are investigated by step-scan Fourier-transform spectroscopy to explore the dynamics at phase transitions in the milli-and microsecond range. The electrical switching of liquid crystals traced by vibrational spectroscopy reveals a rotation of the molecules with a relaxation time of 2 ms. The photo-induced neutral-ionic transition in TTF-CA...
A distributed-feedback (DFB) dual-gate graphene-channel field-effect transistor was fabricated as a current-injection terahertz laser. A single mode emission at 5.2 THz was observed at 100K beyond the threshold carrier injection level. Spectral narrowing with increasing the carrier injection around the threshold was also observed. The result is still preliminary level but the linewidth fairly agrees...
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