A new temperature performance record of 199.5 K for terahertz quantum cascade lasers is achieved by optimizing the lasing transition oscillator strength resonant phonon based three-well design.The optimum 0.58 was found to be larger than that previous (0.41) Kumar et al. [Appl.Phys.Lett.94, 131105 (2009)].The choice tunneling barrier thicknesses determined with a simplified density matrix model, which converged towards higher coupling strengths previously explored and nearly perfect...

Quantum cascade lasers are unipolar semiconductor covering a wide range of the infrared and terahertz spectrum. Lasing action is achieved by using optical intersubband transitions between quantized states in specifically designed multiple-quantum-well heterostructures. A systematic improvement quantum with respect to operating temperature, efficiency, spectral requires detailed modeling underlying physical processes these structures. Moreover, laser constitutes versatile model device for...

In research and engineering, short laser pulses are fundamental for metrology communication. The generation of by passive mode-locking is especially desirable due to the compact setup dimensions, without need active modulation requiring dedicated external circuitry. However, well-established models do not cover regular self-pulsing in gain media that recover faster than cavity round trip time. For quantum cascade lasers (QCLs), this marked a significant limitation their operation, as they...

We report the observation of a coherent multimode instability in quantum cascade lasers (QCLs), which is driven by same fundamental mechanism Rabi oscillations as elusive Risken-Nummedal-Graham-Haken (RNGH) predicted 40 years ago for ring lasers. The threshold observed significantly lower than original RNGH instability, we attribute to saturable-absorption nonlinearity laser. Coherent effects, cannot be reproduced standard laser rate equations, can play therefore key role dynamics QCLs, and...

We investigate the origin of high frequency noise in Fourier Domain Mode Locked (FDML) lasers and present an extremely well dispersion compensated setup which virtually eliminates intensity dramatically improves coherence properties.We show optical tomography (OCT) imaging at 3.2 MHz A-scan rate demonstrate positive impact described improvements on image quality.Especially highly scattering samples, specular reflections for strong signals large depth images is significantly reduced.We also...

Abstract The use of fundamental modelocking to generate short terahertz (THz) pulses and THz frequency combs from semiconductor lasers has become a routine affair, using quantum cascade (QCLs) as gain medium. However, unlike classic laser diodes, no demonstrations harmonic modelocking, active or passive, have been shown in QCLs, where multiple per round trip are generated when the is modulated at harmonics cavity’s round-trip frequency. Here, time-resolved techniques, we show for first time...

Ring quantum cascade lasers have recently gained considerable attention, showing ultrastable frequency comb and soliton operation, thus opening a way to integrated spectrometers in the midinfrared terahertz fingerprint regions. Thanks self-consistent Maxwell-Bloch model, we demonstrate, excellent agreement with experimental data, that small but finite coupling between counterpropagating waves arising from distributed backscattering is essential stabilize solution.

The first theoretical model of Fourier domain mode locking operation is presented. A specially tailored dynamic equation in a moving spectral reference frame derived, enabling efficient numerical treatment, despite the broad laser spectrum and extremely long cavity. excellent agreement presented theory with experiment over wide range parameters enables quantitative assessment relevant physical effects, such as loss modulation gain saturation dynamics, amplified spontaneous emission,...

The generation of frequency combs in the mid-infrared and terahertz regimes from compact potentially cheap sources could have a strong impact on spectroscopy, as many molecules their rotovibrational bands this spectral range. Thus, quantum cascade lasers (QCLs) are perfect candidates for comb these portions electromagnetic spectrum. Here we present theoretical model based full numerical solution Maxwell-Bloch equations suitable simulation such devices. We show that our approach captures...

Due to their intuitiveness, flexibility and relative numerical efficiency, the macroscopic Maxwell-Bloch (MB) equations are a widely used semiclassical semi-phenomenological model describe optical propagation coherent light-matter interaction in media consisting of discrete-level quantum systems. This review focuses on application this advanced optoelectronic devices, such as cascade dot lasers. The Bloch here treated density matrix for driven systems with two or multiple discrete energy...

We present a quantum mechanical model for four-wave mixing Josephson traveling-wave parametric amplifier including substrate losses and associated thermal fluctuations. Under the assumption of strong undepleted classical pump tone, we derive an analytic solution bosonic annihilation operator weak signal photon field using temporal equations motion in reference timeframe, chromatic dispersion. From this result, can predict asymmetric gain spectrum due to non-zero losses. also equivalent added...

Optical frequency combs (OFCs), which establish a rigid phase-coherent link between the microwave and optical domains of electromagnetic spectrum, are emerging as key high-precision tools for development quantum technology platforms. These include potential applications communication, computation, information, sensing, metrology can extend from near-infrared with micro-resonator combs, up to technologically attractive terahertz (THz) range, powerful miniaturized cascade laser (QCL) FCs. The...

The accuracy of different transfer matrix approaches, widely used to solve the stationary effective mass Schr\"{o}dinger equation for arbitrary one-dimensional potentials, is investigated analytically and numerically. Both case a constant position dependent are considered. Comparisons with finite difference method also performed. Based on analytical model potentials as well self-consistent Schr\"{o}dinger-Poisson simulations heterostructure device, it shown that symmetrized approach yields...

Employing an ensemble Monte Carlo transport simulation, we self-consistently analyze the spectral gain for different terahertz quantum cascade laser structures, considering bound-to-continuum as well resonant phonon depopulation designs. In this context, investigate temperature dependent broadening, affecting performance of structures. Furthermore, discuss influence individual scattering mechanisms, such electron-electron, impurity and interface roughness scattering. A comparison simulation...

We present a method for self-consistently including the optical cavity field into Monte Carlo-based carrier transport simulations. This approach allows an analysis of actual lasing operation in quantum cascade lasers, considering effects such as gain saturation and longitudinal mode competition. Simulation results terahertz laser are found to be consistent with experiment.

The impact of upper state lifetime and spatial hole burning on pulse shape stability in actively mode locked QCLs is investigated by numerical simulations. It shown that an extended necessary to achieve stable isolated formation per roundtrip. Spatial helps reduce the duration supporting broadband multimode lasing, but introduces instabilities which eventually lead strongly structured shapes further degrade with increased pumping. At high pumping levels gain saturation recovery between...

We present a theoretical and experimental analysis of the instantaneous lineshape Fourier domain mode-locked (FDML) lasers, yielding good agreement. The simulations are performed employing recently introduced model for FDML operation. Linewidths around 10 GHz found, which is significantly below sweep filter bandwidth. effect detuning between drive frequency cavity roundtrip time studied revealing features that cannot be resolved in experiment, shifting power spectrum against center analyzed....