We present a time-multiplexed interferometer based on Faraday mirrors, and apply it to quantum key distribution. The interfering pulses follow exactly the same spatial path, ensuring very high stability self balancing. use of mirrors compensates automatically any birefringence effects polarization dependent losses in transmitting fiber. First experimental results show fringe visibility 0.9984 for 23-km-long interferometer, installed telecom fibers.

A quantum cryptography set-up is described. It uses polarized photons to code the key. The remain guided from semiconductor laser diode until photon counter module. feasibility of establishing a key over more than 1 km by this method has been experimentally demonstrated.

Generalized quantum measurements can be used to separate deterministically two nonorthogonal states. However, such also lead inconclusive results, where the initial state remains unknown. We introduce a particular type of generalized measurement, which we term loss induced (LIGe) and present an experimental realization. This LIGe measurement achieves optimal deterministic separation nonorthogonally polarized single photons. \textcopyright{} 1996 The American Physical Society.

We report on a gas sensor based quartz-enhanced photoacoustic spectroscopy (QEPAS) able to detect multiple species for environmental monitoring applications, by exploiting Vernier effect-based quantum cascade laser as the excitation source. The device emission spectrum consists of ten separated clusters covering range from 2100 up 2250 cm

A quantum cryptographic channel using a 23 km long installed standard telecom optical cable is reported. The key encoded in the polarization of very weak laser pulses average photon number 0.12. measured error rate lower than 3.4%. ability system to establish at wavelength (1300 nm) cables thus assessed.

We demonstrate room-temperature, single-mode, continuous-wave operation of a λ≃5.4μm quantum-cascade laser up to the temperature 30°C⁠. Processing is done using standard lithography in ridge waveguide mounted junction-up. The active region based on bound-to-continuum transition. high performances were achieved with low doping and thick electroplated gold deposition, resulting characteristic T0=155K threshold current density jth=2.05kA∕cm2 at 300K⁠.

Quantum cryptography over 23 km of installed telecommunications fibre using a novel interferometer with Faraday mirrors is presented. The needs no alignment nor polarisation control and features 99.8% fringe visibility. A secret key 20 kbit length an error rate 1.35% for 0.1 photon per pulse was produced.

Intermittent scanning for continuous-wave quantum cascade lasers is proposed along with a custom-built laser driver optimized such operation.This approach lowers the overall heat dissipation of by dropping its drive current to zero between individual scans and holding longer pause scans.This allows packaging cw-QCLs in TO-3 housings built-in collimating optics, thus reducing cost footprint device.The fully integrated, largely analog, yet flexible eliminates need any external electronics...

We report here on a quartz-enhanced photoacoustic (QEPAS) sensor employing quantum cascade laser (QCL) structure capable of operating in pure amplitude or wavelength modulation configuration.The QCL is composed three electrically independent sections: Gain, Phase (PS) and Master Oscillator (MO).Selective current pumping these sections allows obtaining tuning without changes the optical power, power emission shifts.A QEPAS condition obtained by modulating PS current, while achieved...

A method of calculating the characteristics noncollinear phase matching in both uniaxial and biaxial crystals is presented. Al- though significant work has been done to characterize collinear present many its applications, also unique characteristics, leading several useful ap- plications. The presented enables calculations collin- ear cases, a far larger set nonlinear configurations be studied. © 2000 Society Photo-Optical In- strumentation Engineers. (S0091-3286(00)02304-7)

In this work, we present the development of low consumption quantum cascade lasers across mid-IR range. particular, short cavity single-mode with optimised facet reflectivities have been fabricated from 4.5 to 9.2 μm. Threshold dissipated powers as 0.5 W were obtained in continuous wave operation at room temperature. addition, beneficial impact reducing chip length on laser mounting yield is discussed. High power same processed wafers are also presented.

We demonstrate dispersion compensation in mid-infrared quantum cascade laser frequency combs (FCs) emitting at 7.8 μm using the coupling of a dielectric waveguide to plasmonic resonance top cladding layer latter. Devices with group velocity lower than 110 fs2/mm were fabricated, and narrow beatnotes FWHM linewidths below 1 kHz measured on entire operation range. At −20°C, optical output power reaches 275 mW, spectrum spans 60 cm−1. The multi-heterodyne beating two devices was 46 cm−1,...

GaAs-based quantum-cascade lasers based on a bound-to-continuum transition have been realized and characterized. This band structure design combines the advantages of well known three-well superlattice active regions. We observed lasing Fabry–Pérot in pulsed mode up to temperature 100 °C. Multimode emission with peak power 340 mW is at room 42 80 Further, from aging tests we expect lifetime over 60 years for these devices.

An investigation is made of a recently introduced quantum interferometric method capable measuring polarization mode dispersion (PMD) on sub-femtosecond scales, without the usual stability problems associated with such small time scales.The technique makes use extreme temporal correlation orthogonally polarized pairs photons produced via type-II phase-matched spontaneous parametric down-conversion.When sent into simple interferometer these photon produce sharp interference feature seen in...

We report on power, spectral linewidth, and mode purity for a cw 5.3 microm quantum cascade laser operated thermo-electric cooler. A totally noncryogenic nitric oxide monitor was constructed by integrating this with an astigmatic multipass cell thermo-electrically cooled infrared detector. The resulting instrument is capable of continuous unattended monitoring ambient, atmospheric several weeks no operator intervention. detection method rapid sweep, direct absorption spectroscopy....

A Fabry-Perot quantum cascade laser (QCL) was used as a powerful light source for mid infrared (MIR) detection in flow injection analysis. The QCL lased at several wavelengths close to each other within few wavenumbers (990-1010 cm-1), hence fitting well the broad absorption bands of molecules liquid phase. As compared with that state-of-the-art Fourier transform spectrometer, signal-to-noise ratio could be improved by factor 50. Additionally, using source, optical path lengths more than 100...

We present measurement results on high-power low threshold quantum cascade distributed feedback lasers emitting infrared radiation at 10.16 μm. A lateral current injection scheme allowed the use of a strongly coupled surface grating without metal coverage and epitaxial regrowth. Although this design resulted in simplified processing, fabrication high performance devices was demonstrated. The laser emitted 230 mW pulsed power 85 K, 80 room temperature. Threshold densities 1.85 kA/cm2 K 5.4...

In this work, we demonstrate broad electrical tuning of quantum cascade lasers at 9.25 μm, 8.5 and 4.4 μm in continuous wave operation using Vernier-effect distributed Bragg reflectors based on superstructure gratings. Integrated micro-heaters allow to switch from one Vernier channel the other, while predictable mode-hop free can be obtained each modulating laser current with a side mode suppression ratio as high 30 dB. The resulting device behaves effectively switchable multicolour tunable...

We present single mode quantum cascade lasers including a microscopic heater for spectral emission tuning. Through the use of buried element, active region temperature can be modified without changing submount one. Emission frequency tuning in continuous-wave as large 9 cm(-1) at 1270 and 14 2040 are observed, corresponding to an increase temperatures ∼ 90 K. Due proximity heaters region, modulated several kHz range absence moving parts guarantees mechanical stability system. This method...