Quantum cascade laser thesis

Moreover, the mass of the adsorbed molecules is determined by measuring the resonance frequency shift of the device for the quantitative analysis.

In addition, micro-differential thermal analysis, which can be used to differentiate exothermic or endothermic reaction of heated molecules, has been performed with the same devices to provide additional orthogonal signal for trace explosive detection and sensor surface regeneration.

This mechanism is efficient and temperature insensitive, and provides protection from thermal backfilling due to the large energy separation between the lower radiative state and the injector.

The operation of terahertz QCLs at frequencies below the Reststrahlen band in the semiconductor With these techniques some record performances for terahertz QCLs are demonstrated including the highest pulsed operating temperature of K, the highest continuous-wave cw operating temperature of K, and the highest optical power output mW in pulsed and mW in cw at 5 K for any terahertz QCL.

Quantum cascade laser

The residual reflectivity on the cleaved facets from the semiconductor-to-air interface is sufficient to create a resonator. When inside a quantum well, an electron can jump from one state to the other by discrete steps, sometimes emitting photons.

The PMC design is based upon etching trenches, using the RIE lag effect, of sub-wavelength dimensions into one side of a waveguide in order to achieve an asymmetric cross-sectional profile, resulting in a waveplating effect. One print or electronic copy may be made for personal use only.

Here we describe results from a novel point scanning confocal IR microscope and demonstrate the performance imaging several important spectral bands of lung tissue. Integrated heaters can extend the tuning range at fixed operation temperature to 0.

The advantages of such capability are well understood, since it allows detection of the chemical threats without contact, eliminating possible operator and equipment contamination and the need for subsequent decontamination of both.

It was found that films deposited at room temperature have average roughness of about 5nm. This is due to an extreme sensitivity to phonons population inside the system, which hinders radiative emission at relatively high temperature.

It provides unique and important information on the history of our universe and its evolution, by getting into the insight of the physical and chemical conditions.

Theoretically, the tuning range of nm was estimated for the double ring quantum cascade laser DRQCL design employed in this thesis. However, up to now this frequency region has rarely been accessible for high-resolution spectroscopy due to the lack of suitable local oscillator technology.

Add a review and share your thoughts with other readers. THz devices are particularly promising for ultra-wide bandwidth as our group already demonstrated octave-spanning emission from heterogeneous QCL [6] Further details and introductory talks can be found in the links at the bottom of this page.

However, to date, the generation of THz pulses from QCLs has been limited to 10 - 20 ps despite several years of research effort. Massachusetts Institute of Technology.

Terahertz quantum cascade laser application in local oscillator development

This thesis reports the development of terahertz QCLs in which the lower radiative state is depopulated via resonant longitudinal-optical phonon scattering. Such a waveguide was used to obtain lasing at 3. Freona and other gases were sprayed into the beam path and the concentration-length CL product was measured as a function of time.

Photonics 9, 42—47 All these efforts should lead soon to the first realization of a terahertz quantum cascade laser for astronomical application in a telescope. Electrical stability at the operating point Population inversion and gain obtained by electron lifetime engineering Low loss optical resonator to match gain value and allow laser oscillation The following figure shows the quantum well schematic that allowed to achieve lasing emission in the first QCL demonstration in at Bell Labs by J.

Whereas in normal diode lasers the photon emission is based on electron-hole recombination across the bandgap, the QCL is based on a completely different approach.

To probe the birefringence operation, a sub-threshold electroluminescence was employed to investigate the single pass operation of the ITBW. Quantum cascade laser integration on silicon-based waveguide circuits the external cavity quantum cascade laser. High Power Quantum Cascade Laser for Terahertz Imaging In addition, the dependence of optical gain of THz and mid-IR QCLs on device parameters such as the injection and extraction coupling strengths, energy detuning and doping density are also systematically studied in details.

Direct measurements of iC4H8 were enabled by monitoring absorption in the infrared near Algorithms based on correlation methods were used to both identify the gases and determine their CL-products as a function of time.

We focus on personalized studies to better understand the role of acetone in diabetes. However, the tuning range is limited by the available gain bandwidth i.

The recently developed terahertz quantum cascade lasers become the most promising candidate as a novel solid-state terahertz source. For actual observation applications, the effective integration time is a cru- cial issue that determines the efficiency of the observation.

We have demonstrated successful detection, differentiation, and quantification of trace amounts of explosive molecules cyclotrimethylene trinitramine RDX and pentaerythritol tetranitrate PETN and their mixtures using three orthogonal sensing signals.

With the QCL operating above threshold, polarisation and wavelength tuning of the signal output was demonstrated. A dielectric material is typically deposited in the trenches to guide injected current into the ridge, then the entire ridge is typically coated with gold to provide electrical contact and to help remove heat from the ridge when it is producing light.

Dielectric material is also deposited on the overgrown material around QC ridge to guide the injected current into the QC gain medium.The Quantum Cascade Laser. Because of their small size (typically the size of a pin's head), high reliability and ease of use, conventional semiconductor diode lasers play a dominant role in telecommunications and consumer electronics in applications such as optical fiber communications and compact disk (CD) players.

Quantum cascade lasers (QCLs) are semiconductor lasers that emit in the mid- to far-infrared portion of the electromagnetic spectrum and were first demonstrated by Jerome Faist, Federico Capasso, Deborah Sivco, Carlo Sirtori, Albert Hutchinson, and Alfred Cho at Bell Laboratories in Terahertz (THz) quantum cascade lasers (QCLs) are high-quality THz sources in terms of power (>1W) and compact size, and the application of THz QCLs has been widely investigated.

Spectroscopy is one of the most widespread application for THz QCLs. The project presented in this thesis is an application of THz quantum cascade laser. The. Andreas Hugi receives ETH Medal for Outstanding Doctoral Thesis. November Andreas Hugi receives the ETH Medal for Outstanding Doctoral Thesis entitled: Single-mode and Comb Operation of Broadband Quantum Cascade Lasers.

Jérôme Faist receives an ERC Advanced Grant. In this thesis, operation of a THz quantum cascade laser (QCL) was successfully achieved using a closed cycle cryostat and nanosecond pulse generator with impedance matching circuitry.

The laser beam was imaged in real time using an uncooled microbolometer infrared camera typically used in far-infrared wavelength band ( mm). This thesis describes the theory, design, fabrication, and testing of terahertz quantum cascade laser devices.

A summary of theory relevant to design is presented, including intersubband radiative transitions and gain, intersubband scattering, and coherent resonant tunneling transport using a tight-binding density matrix model.

Quantum cascade laser thesis
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