Frequency stabilization of quantum-cascade lasers by use of optical cavities.

We report a heterodyne beat with a linewidth of 5.6+/-0.6 Hz between two cavity-stabilized quantum-cascade lasers operating at 8.

Kolmogorov-Arnold-Moser transition and laser action on scar modes in semiconductor diode lasers with deformed resonators.

Measurements of the optical spectra of semiconductor injection lasers with deformed cylinder resonators show strong indications of the classical Kolmogorov-Arnold-Moser transition from integrability to chaos for devices with small deformation. At larger deformation, evidence for laser action on scar modes is obtained. The diode lasers operate with TE polarization, resulting in laser action on (partially) chaotic whispering-gallery modes for all deformations.

Generation of tunable far-infrared radiation with a quantum cascade laser.

We demonstrate the generation of cw tunable far-infrared radiation by mixing a quantum cascade laser and a CO>(2) laser in a W-Ni metal-insulator-metal diode. The first known spectroscopic application to the recording of an H(79)Br transition near 4.47 THz is reported.

A frequency-modulated quantum-cascade laser for spectroscopy of CH4 and N2O isotopomers.

We report the development of a novel laser spectrometer for high-sensitivity detection of methane and nitrous oxide. The system relies on a quantum-cascade laser source emitting wavelength of around 8.06 microm, where strong fundamental absorption bands occur for the considered species and their isotopomers.

Raman injection laser.

Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material. This effect is the basis for a broad class of tunable sources known as Raman lasers. In general, these sources have only small gain (approximately 10(-9) cm W(-1)) and therefore require external pumping with powerful lasers, which limits their applications.

Third harmonic generation in a Quantum Cascade laser with monolithically integrated resonant optical nonlinearity.

We present third harmonic generation from an InGaAs/AlInAs Quantum Cascade laser based on a three-well diagonal transition active region with an integrated third-order nonlinear oscillator. The device displays pump radiation at lambda ~ 11.1 mum and third order nonlinear light generation at lambda ~ 3.

Quantum cascade surface-emitting photonic crystal laser.

We combine photonic and electronic band structure engineering to create a surface-emitting quantum cascade microcavity laser. A high-index contrast two-dimensional photonic crystal is used to form a micro-resonator that simultaneously provides feedback for laser action and diffracts light vertically from the surface of the semiconductor surface. A top metallic contact allows electrical current injection and provides vertical optical confinement through a bound surface plasmon wave.

Resonant second-order nonlinear optical processes in quantum cascade lasers.

We demonstrate an efficient intracavity nonlinear interaction of laser modes in a specially adapted quantum cascade laser. A two-wavelength quantum cascade laser structure emitting at wavelengths of 7.1 and 9.

Transportable automated ammonia sensor based on a pulsed thermoelectrically cooled quantum-cascade distributed feedback laser.

A compact ammonia sensor based on a 10-microm single-frequency, thermoelectrically cooled, pulsed quantum-cascade laser with an embedded distributed feedback structure has been developed. To measure NH3 concentrations, we scanned the laser over two absorption lines of its fundamental v2 band. A sensitivity of better than 0.

Thermoelectrically cooled quantum-cascade-laser-based sensor for the continuous monitoring of ambient atmospheric carbon monoxide.

We report the first application of a thermoelectrically cooled, distributed-feedback quantum-cascade laser for continuous spectroscopic monitoring of CO in ambient air at a wavelength of 4.6 microm. A noise-equivalent detection limit of 12 parts per billion was demonstrated experimentally with a 102-cm optical pathlength and a 2.

Ultra-broadband semiconductor laser.

The fundamental mechanism behind laser action leads in general only to narrowband, single-wavelength emission. Several approaches for achieving spectrally broadband laser action have been put forward, such as enhancing the optical feedback in the wings of the gain spectrum, multi-peaked gain spectra, and the most favoured technique at present, ultrashort pulse excitation. Each of these approaches has drawbacks, such as a complex external laser cavity configuration, a non-flat optical gain envelope function, or an inability to operate in continuous mode, respectively.