Abstract: A quantum cascade laser or interband cascade laser for outputting a frequency comb. The laser's active waveguide comprises a combination of narrow and wide sections which are engineered in combination such that the laser is operable to produce lasing only in the fundamental mode across the operating wavelength range, the narrow section squeezing light propagating in the waveguide to output a frequency comb via four-wave mixing. The narrow and wide sections are further engineered to reduce the waveguide's net GVD, and also to reduce the GVD variation across the operating range compared to a comparable waveguide that is of constant width, thus producing a more stable frequency comb. The proportion of the laser's full dynamic range (i.e. from threshold to the rollover current where the maximum output power is achieved) over which lasing remains in the frequency comb regime is thereby increased compared with a constant width single mode waveguide.

Abstract: A waveguide heterostructure for a semiconductor laser with an active part, comprising an active region layer depending of the type of semiconductor used, which is sandwiched between an electrode layer and a substrate, usable for dispersion compensation in a semiconductor laser frequency comb setup, an optical frequency comb setup and a manufacturing method.

Abstract: An optical frequency comb setup including a semiconductor cascade laser drivable by a laser driver, emitting a laser beam through an end facet of the semiconductor cascade laser with a frequency comb with at least two given individual emission frequencies, repetition frequency, carrier envelope offset frequency shows improved comb stability and/or comb formation and/or comb bandwidth. This is achieved by an external cavity added outside of the cavity of the semiconductor cascade laser, having a reflective element with a mirror surface reflecting the at least two individual emission frequencies being arranged in a relative distance to the end facet allowing to adapt repetition frequency and/or carrier envelope offset frequency and/or the dispersion seen by the light in the optical frequency comb setup.

Abstract: A waveguide heterostructure for a semiconductor laser with an active part, comprising an active region layer depending of the type of semiconductor used, which is sandwiched between an electrode layer and a substrate, usable for dispersion compensation in a semiconductor laser frequency comb setup, an optical frequency comb setup and a manufacturing method.

Abstract: Semiconductor Quantum Cascade Lasers (QCLs), in particular mid-IR lasers emitting at wavelengths of about 3-50 ?m, are often designed as deep etched buried heterostructure QCLs. The buried heterostructure configuration is favored since the high thermal conductivity of the burying layers, usually of InP, and the low losses guarantee devices high power and high performance. However, if such QCLs are designed for and operated at short wavelengths, a severe disadvantage shows up: the high electric field necessary for such operation drives the operating current partly inside the insulating burying layer. This reduces the current injected into the active region and produces thermal losses, thus degrading performance of the QCL. The invention solves this problem by providing, within the burying layers, effectively designed current blocking or quantum barriers of, e.g. AIAs, InAIAs, InGaAs, InGaAsP, or InGaSb, sandwiched between the usual InP or other burying layers, intrinsic or Fe-doped.

Abstract: A method for optical and electrical signal processing of a multi-heterodyne signal generated by a multi-mode semi-conductor laser, for a system comprising two laser sources and an sample interaction unit. At least the beam of one of the laser passes through said sample interaction unit before being combined on a detector. The first laser is tuned (40=>42) by an amount keeping the tuning result within the available detector bandwidth (55). Then the second laser is roughly tuned by the same amount as the tuning of the first laser to bring back the signal to the vicinity (48) of the original place in the RF-domain and within the bandwidth (55) of the detector. The tuning steps are repeated with different value of mode spacing for reconstructing the sample spectrum and provide a high resolution image of the dip (41) absorption line (40).

Abstract: Semiconductor Quantum Cascade Lasers (QCLs), in particular mid-IR lasers emitting at wavelengths of about 3-50 ?m, are often designed as deep etched buried heterostructure QCLs. The buried heterostructure configuration is favored since the high thermal conductivity of the burying layers, usually of InP, and the low losses guarantee devices high power and high performance. However, if such QCLs are designed for and operated at short wavelengths, a severe disadvantage shows up: the high electric field necessary for such operation drives the operating current partly inside the insulating burying layer. This reduces the current injected into the active region and produces thermal losses, thus degrading performance of the QCL. The invention solves this problem by providing, within the burying layers, effectively designed current blocking or quantum barriers of, e.g. AIAs, InAIAs, InGaAs, InGaAsP, or InGaSb, sandwiched between the usual InP or other burying layers, intrinsic or Fe-doped.

Abstract: A method for optical and electrical signal processing of a multi-heterodyne signal generated by a multi-mode semi-conductor laser, for a system comprising two laser sources and an sample interaction unit. At least the beam of one of the laser passes through said sample interaction unit before being combined on a detector. The first laser is tuned (40=>42) by an amount keeping the tuning result within the available detector bandwidth (55). Then the second laser is roughly tuned by the same amount as the tuning of the first laser to bring back the signal to the vicinity (48) of the original place in the RF-domain and within the bandwidth (55) of the detector. The tuning steps are repeated with different value of mode spacing for reconstructing the sample spectrum and provide a high resolution image of the dip (41) absorption line (40).

Abstract: Quantum cascade laser especially comprising a gain region (14) formed from several layers (20) which each comprise: alternating strata of a first type (26) each defining a quantum barrier made of AlInAs and strata of a second type (28) each defining a quantum well made of InGaAs, and injection barriers (22), interposed between two of the layers (20). The layers of the gain region (14) each constitute an active region extending from one to the other of the injection barriers (22) which are adjacent to it. The strata (26, 28) are dimensioned such that: each of the wells comprises, in the presence of an electric field, at least a first upper subband, a second middle subband and a third lower subband and that the probability of an electron being present in the first subband is highest in the vicinity of one of the adjacent barriers, in the second subband in the middle part of the region and in the third subband in the vicinity of the other of the adjacent barriers.

Abstract: A quantum cascade laser comprising two electrodes (10, 18) for applying an electric control field and a waveguide placed between the two electrodes and which comprises: a gain region (14) consisting of several layers (20) which each comprise alternating strata (22) of a first type each defining a quantum barrier and strata (24) of a second type each defining a quantum well, and two optical confinement layers (12, 16) placed on each side of the gain region (14). According to the invention, each layer (20) of the gain region (14) is arranged so that the active region has three subbands, the potential differences between them being such that the transition of an electron between the two furthermost emits an energy (EGH, EHJ) corresponding to that needed for the emission of two optical phonons.

Abstract: The invention concerns a quantum cascade laser, comprising a substrate, a stack of layers, having a prismatic shape with substantially trapezoidal cross-section, comprising a lower surface arranged on the substrate, an upper surface and lateral surfaces, said stack forming a gain region and two walls between which the region is interposed, two electrodes arranged on either side of the stack, one of which is formed by an electrically conductive material layer covering at least partially the surface of the stack opposite the substrate, and an electrically insulating layer interposed between the two electrodes. The invention is characterised in that the electrically insulating layer completely covers the lateral surfaces of the prism, without overlapping on the upper surface, and its thickness is equal to at least a third of the stack thickness.