Dual resonance phonon–photon–phonon terahertz quantum-cascade laser: physics of the electron transport and temperature performance optimization

The state of the art terahertz-frequency quantum cascade lasers have opened a plethora of applications over the past two decades by testing several designs up to the very limit of operating temperature, optical power and lasing frequency performance. The temperature degradation mechanisms have long been under the debate for limiting the operation up to 210 K in pulsed operation in the GaAs/AlGaAs material system. In this work, we review the existing designs and exploit two main temperature degradation mechanisms by presenting a design in which they both prove beneficial to the lasing operation by dual pumping and dual extracting lasing levels. We have applied the density matrix transport model to select potential candidate structures by simulating over two million active region designs. We present several designs which offer better performance than the current record structure

High-Speed Modulation of a Terahertz Quantum Cascade Laser by Coherent Acoustic Phonon Pulses

The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conventional electronic modulation is limited fundamentally by parasitic device impedance, and so alternative physical processes must be exploited to modulate the QCL gain on ultrafast timescales. Here, we demonstrate an alternative mechanism to modulate the emission from a QCL device, whereby optically-generated acoustic phonon pulses are used to perturb the QCL bandstructure, enabling fast amplitude modulation that can be controlled using the QCL drive current or strain pulse amplitude, to a maximum modulation depth of 6% in our experiment. We show that this modulation can be explained using perturbation theory analysis. While the modulation rise-time was limited to ~800 ps by our measurement system, theoretical considerations suggest considerably faster modulation could be possible

High-speed modulation of a terahertz-frequency quantum-cascade laser using coherent acoustic phonon pulses

We demonstrate a new method for high-speed modulation of the electron transport and photon generation within a terahertz-frequency quantum-cascade laser (THz QCL). An amplified femtosecond laser is used to generate coherent acoustic-phonon pulses, which are injected into the device, resulting in an electronic bandstructure perturbation, with ~1-ns rise-time. The corresponding change in optical gain allows up to ~6% amplitude modulation, with results explained accurately using a perturbation-theory model

Acoustic band engineering in terahertz quantum-cascade lasers and arbitrary superlattices

Data associated with publication: "Acoustic band engineering in terahertz quantum-cascade lasers and arbitrary superlattices", the repository contains raw data presented in the paper

Modulation of the THz Emission by a Quantum Cascade Laser using Coherent Acoustic Phonon Pulses

We use laser-generated coherent acoustic phonon (strain) pulses to modulate the electronic transport and THz emission of a 2.6 THz Ga(Al)As quantum cascade laser. The modulation amplitude is of the order of a few % and the rise time, limited by the measurement system response, is less than 1 nanosecond

High-Speed Modulation of a Terahertz Quantum Cascade Laser Using Coherent Acoustic Phonon Pulses

We demonstrate a new method for high-speed modulation of terahertz emission and electronic transport of a Ga(Al)As quantum cascade laser using coherent acoustic phonon pulses. The modulation, which is on the order of 6%, can be partially explained by a perturbation-theory analysis. The 100 GHz are possible

Optical feedback effects on terahertz quantum cascade lasers: modelling and applications

Terahertz (THz) quantum cascade lasers (QCLs) are compact sources of radiation in the 1–5 THz range with significant potential for applications in sensing and imaging. Laser feedback interferometry (LFI) with THz QCLs is a technique utilizing the sensitivity of the QCL to the radiation reflected back into the laser cavity from an external target. We will discuss modelling techniques and explore the applications of LFI in biological tissue imaging and will show that the confocal nature of the QCL in LFI systems, with their innate capacity for depth sectioning, makes them suitable for skin diagnostics with the well-known advantages of more conventional confocal microscopes. A demonstration of discrimination of neoplasia from healthy tissue using a THz, LFI-based system in the context of melanoma is presented using a transgenic mouse model. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

A Novel High-Contrast Ratio Electrochromic Material from Spiro[cyclododecane-1,9 '-fluorene]bicarbazole

WOS: 000287258500002A novel electroactive spirocyclododecylfluorene monomer named 2,7-bis(carbazol-9-yl)-9,9'-spiro[cyclododecane- 1,9'-fluorene] (SFC) was synthesized and electrochemically polymerized to give a very stable multi-electrochromic polymer (poly-SFC). Two separate oxidation processes were observed for both SFC monomer and poly-SFC that carries two carbazole units. The polymeric film of poly-SFC was coated onto ITO/glass surface, and it shows different colors (transparent, yellowish green, green, and dark green) upon stepwise oxidations. An electrochromic device based on poly-SFC was assembled in the sandwich cell configuration of ITO/poly-SFC// gel electrolyte//PEDOT/ITO. Poly-SFC exhibits 90% of transparency at neutral state and a high contrast ratio (Delta T = 58% at 800 nm). This device constructed from it represents a response time of about 1 s, high coloration efficiency (1377 cm(2) C-1) and retained its performance by 96.4% even after 1000 cycles. Exhibiting high transparency at neutral state, reversible redox behavior, resistance to overoxidation, and especially high contrast ratio at near IR region can make poly-SFC be useful and promising candidate for electrochromic applications despite having a relatively slow response time. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 333-341, 2011State Planning Organization of Turkey (DPT); Ege University Research Funds OfficeEge University; Scientific and Technical Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [104T191]We acknowledge the supports from the State Planning Organization of Turkey (DPT) and Ege University Research Funds Office. S. Demic is also grateful to Scientific and Technical Research Council of Turkey (TUBITAK, project #: 104T191) for financial support. The authors acknowledge the efforts of Dr. B. F. M. de Waal and R. A. A. Bovee (Eindhoven University of Technology) for MALDI-TOF