We study the time dependence of optical power emitted by terahertz and mid-IR quantum cascade lasers in presence reinjection demonstrate unprecedented continuous wave (CW) emission stability for strong feedback. show that absence coherence collapse or other CW instabilities typical diode is inherently associated with high value photon to carrier lifetime ratio negligible linewidth enhancement factor lasers.

To monitor the density of photo-generated charge carriers on a semiconductor surface, we demonstrate detectorless imaging system based analysis optical feedback in terahertz quantum cascade lasers. Photo-excited free electron are created high resistivity n-type silicon wafers via low power (≅40 mW/cm2) continuous wave pump laser near infrared spectral range. A spatial light modulator allows to directly reconfigure and control photo-patterned intensity associated free-carrier distribution....

We have generated pulsed squeezed light using the third-order nonlinear susceptibility of semiconductor ZnS at room temperature. The photon energy was chosen to be below midgap in order minimize absorption. Efficient quadrature squeezing 2.2 dB (40%) obtained 125 fs pulses a center wavelength 780 nm. measured noise is suppressed quantum limit over entire range our detection bandwidth (30-50 MHz). scheme employed can generally applied semiconductors, and opens way for generation wide wavelengths.

We demonstrate that diode laser self-mixing interferometry can be exploited to instantaneously measure the ablation front displacement and rate during ultrafast microdrilling of metals. The proof concept was obtained using a 50-μm-thick stainless steel plate as target, 120 ps/110 kHz microchip fiber machining source, an 823 nm with integrated photodiode probe. time dependence hole penetration depth measured 0.41 µm resolution.

We report on the development of an all-interferometric optomechatronic sensor for detection multi-degrees-of-freedom displacements a remote target. The prototype system exploits self-mixing technique and consists only laser head, equipped with six sources, suitably designed reflective feasibility was validated experimentally both single or measurements, thus demonstrating simple inexpensive alternative to costly bulky existing systems.

We demonstrate a common-path interferometer to measure the independent displacement of multiple targets through nonlinear frequency mixing in quantum-cascade laser (QCL). The sensing system exploits unique stability QCLs under strong optical feedback access intrinsic nonlinearity active medium. experimental results using an external dual cavity are excellent agreement with numerical simulations based on Lang-Kobayashi equations.

In this paper, we investigate a coherent imaging system based on Terahertz and mid-infrared (MIR) quantum cascade lasers (QCLs) in terms of phase sensitivity against optical feedback. the self-mixing scheme, single QCL acting as oscillator, mixer detector infrared radiation, is used for continuous-wave reflection well profiling. We study dependence signature feedback level assess limit signal detection.

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The simultaneous measurement of the linear displacement and two rotation angles (yaw pitch) a moving object using laser sensor based on self-mixing effect is reported. head includes three commercial diode lasers equipped with monitor photodiodes. target plane mirror attached to object. angular resolutions are 0.7 <emphasis><formula formulatype="inline"><tex>$\mu$</tex></formula></emphasis>m...

We demonstrate that a single all-optical sensor based on laser diode self-mixing interferometry can monitor the independent displacement of individual portions surface. The experimental evidence was achieved using metallic sample in translatory motion while partly ablated by ps-pulsed fiber laser. A model Lang-Kobayashi approach gives an excellent explanation results.

We estimated experimentally the linewidth (0.28 MHz) of a distributed feedback quantum cascade laser emitting at 6.2 μm using optical interferometry. The method is simply based on analysis histogram self-mixing fringe periods measured directly as voltage variation across terminals. assessed optimal experimental conditions estimating influence strength interferometric phase noise and compared our results with those reported conventional methods frequency power spectral density.

We demonstrate a sensor scheme for nanoscale target displacement that relies on single quantum cascade laser (QCL) subject to optical feedback. The system combines the inherent sensitivity of QCLs reinjection and their ultrastability in strong feedback regime where nonlinear frequency mixing phenomena are enhanced. An experimental proof principle micrometer wavelength scale is provided. perform real-time measurements with λ/100 resolution by inserting fast-shifting reference etalon external...

We report on the instantaneous detection of ablation rate as a function depth during ultrafast microdrilling metal targets. The displacement front has been measured with sub-wavelength resolution using an all-optical sensor based laser diode self-mixing interferometry. time dependence process within aluminum and stainless steel targets investigated to study evolution material removal in high aspect-ratio micromachined holes.

Laser-self-mixing has been successfully applied to measuring both mechanical and thermal deformations in single-mode optical fibers attached a solid bar. Strain resolution of achieved continuous range spanning three orders magnitude. Temperature compensation is not necessary if deformations/vibrations occurred on time scale faster than environmental changes. A calibrated fiber thermometer implemented correct for the temperature induced phase drift case deformations.

We present a contactless optical sensor based on the laser-self-mixing effect for real-time measurement of linear and transverse displacements moving stage. The is able to measure up 400 mm along main axis while simultaneously estimating straightness flatness deviations 1 mm. exploits two identical coplanar nonparallel self-mixing interferometers requires only one reference plane. reduction in number elements allowed by configuration intrinsic stiffness adopted geometry result compact,...

We analyze the laser-self-mixing process in Gaussian beam approximation and reformulate expression of feedback coefficient C terms effective power coupled back into laser diode. Our model predicts a twenty-fold increase ratio between maximum minimum measurable displacements judged against current plane-wave model. By comparing interaction collimated or diverging beams with plane mirror target, we demonstrate that tolerate larger wobbling during target displacement allow for measurement...

The linear and nonlinear optical properties of a series ternary alloy AlxGa1−xAs/AlAs multiple-quantum-well structures have been investigated related to the multilayer configuration. direct energy gap was found scale with AlAs mole fraction as predicted by Lee Yuravel [Phys. Rev. B 21, 659 (1980)] band offset ratio depend on composition. Exciton absorption bleaching observed at room temperature cross sections were estimated for first two confined excitonic states. Finally, possibility...

We report an optical investigation of the excitons in ZnSe/ZnSeS superlattices well widths ranging between 2 and 15 nm. An almost constant exciton binding energy is found. The confinement found to be dominated by hole quantization, consistent with expectation negligible conduction-band discontinuity these heterostructures. effect strain has been included properly reproduce width dependence light-hole energies. Finally strong evidence hot photogeneration obtained from oscillatory behavior...

A general model is proposed for a Vertical Cavity Surface Emitting Laser (VCSEL) with medium aspect ratio whose field profile can be described by limited set of Gauss-Laguerre modes. The adapted to self-mixing schemes supposing that the output beam reinjected into laser cavity an external target mirror. We show interferometric signal exhibits features peculiar spatial distribution emitted and target-reflected we suggest applicative scheme could exploited experimental displacement...

Numerous biological surfaces exhibit intricate micro- and nano-structures, which fulfill various functions such as anti-reflective properties, structural coloration, anti-fouling capabilities, pro- or anti-adhesive characteristics. These features have inspired a plethora of industrial applications. In recent years, there has been significant surge in research this domain, largely attributable to the growing interdisciplinary nature approaches applied investigation structured biosurfaces. The...

We studied the laser ablation dynamics of steel in thermal regime both experimentally and theoretically. The real-time monitoring process shows that rate depends on energy density ambient pressure during exposure time. demonstrated efficiency can be enhanced when is reduced with respect to atmospheric for a given fluence, reaching an upper limit despite high-vacuum conditions. An analytical model based Hertz-Knudsen law reproduces all experimental results.

We have measured the real ${\mathit{n}}_{2}$ and imaginary \ensuremath{\beta} parts of ${\mathrm{\ensuremath{\chi}}}^{(3)}$ nonlinear susceptibility in polycrystalline ZnS ZnSe its anisotropy \ensuremath{\sigma} cubic near half-band-gap using femtosecond spectroscopy. obtain values good agreement with recent studies. The dispersion is compared two- four-band model calculations. strongly affects pulse transmission through thick samples, has been included a that describes spectrum after...