Terahertz amplifier based on gain switching in a quantum cascade laser

The spectral gain of a multi-stack terahertz quantum cascade laser, composed of three active regions with emission frequencies centered at 2.3, 2.7, and 3.0 THz, is studied as a function of driving current and temperature using terahertz time-domain spectroscopy. The optical gain associated with the particular quantum cascade stacks clamps at different driving currents and saturates to different values. We attribute these observations to varying pumping efficiencies of the respective upper laser states and to frequency dependent optical losses. The multi-stack active region exhibits a spectral gain full width at half-maximum of 1.1 THz. Bandwidth and spectral position of the measured gain match with the broadband laser emission. As the laser action ceases with increasing operating temperature, the gain at the dominant lasing frequency of 2.65 THz degrades sharply.

mentioning

confidence: 99%

Spectral gain profile of a multi-stack terahertz quantum cascade laser

Bachmann

Rösch

Deutsch

et al. 2014

“…5 There has also been significant interest in understanding emission from QCLs in the time-domain, and the generation of pulses on ultrafast timescales. The integration of THzQCLs with time-domain spectroscopy (TDS) [6][7][8] techniques has allowed the measurement of the electric field of the laser emission with an extremely high time resolution. This has revealed a complex time-domain pulse structure, even when the QCL is operated at a fixed current.…”

mentioning

confidence: 99%

Gain recovery time in a terahertz quantum cascade laser

Bacon

Freeman

Mohandas

et al. 2016

Self Cite

The gain recovery time of a bound-to-continuum terahertz frequency quantum cascade laser, operating at 1.98 THz, has been measured using broadband terahertz-pump-terahertz-probe spectroscopy. The recovery time is found to reduce as a function of current density, attaining a value of 18 ps as the laser is brought close to threshold. We attribute this reduction to improved coupling efficiency between the injector state and the upper lasing level as the active region aligns.

“…5,6 Although considerable progress has been recently achieved in the buildout of sub-THz/THz sources, 7-10 the development of amplifiers of sub-THz/THz signals still remains a significant challenge. 5,11 In this paper, we explore the feasibility of using semiconductor superlattices (SLs) 12,13 for the amplification of electromagnetic waves in the sub-THz range when moving charge domains are present in the device. [14][15][16][17][18][19] SLs comprise multiple alternating layers of different semiconductor materials, 12,13 which form a periodic modulation of the conduction band.…”

mentioning

confidence: 99%

Sub-terahertz amplification in a semiconductor superlattice with moving charge domains

Макаров

Hramov

Короновский

et al. 2015

We theoretically study the high-frequency response of charge domains traveling through a strongly coupled semiconductor superlattice with an applied harmonic electromagnetic signal. Our calculations show that the superlattice alone can amplify signals with a frequency close to the domain transient frequency. Moreover, we show that if the superlattice is connected to a resonator, amplification becomes possible for much higher frequencies of the external signal (several hundred GHz). These promising results open the way to using semiconductor superlattices as efficient sub-THz amplifiers.