Abstract: For epitaxial-side-down bonding of quantum cascade lasers (QCLs), it is important to optimize the heat transfer between the QCL chip and the heat sink to which the chip is mounted. This is achieved by using a heatsink with high thermal conductivity and by minimizing the thermal resistance between the laser active region and said heatsink. In the epi-down configuration concerned, the active region of the QCL is located only a few micrometers away from the heatsink, which is preferable from a thermal standpoint. However, this design is challenging to implement and often results in a low fabrication yield if no special precautions are taken. Since the active region is very close to the heatsink, solder material may ooze out on the sides of the chip during the bonding process and may short-circuits the device, rendering it unusable. To avoid this happening, the invention proposes to provide a trench all around the chip with the exception of the two waveguide facets, i.e. the ends of the active region.

Abstract: For epitaxial-side-down bonding of quantum cascade lasers (QCLs), it is important to optimize the heat transfer between the QCL chip and the heat sink to which the chip is mounted. This is achieved by using a heatsink with high thermal conductivity and by minimizing the thermal resistance between the laser active region and said heatsink. In the epi-down configuration concerned, the active region of the QCL is located only a few micrometers away from the heatsink, which is preferable from a thermal standpoint. However, this design is challenging to implement and often results in a low fabrication yield if no special precautions are taken. Since the active region is very close to the heatsink, solder material may ooze out on the sides of the chip during the bonding process and may short-circuits the device, rendering it unusable. To avoid this happening, the invention proposes to provide a trench all around the chip with the exception of the two waveguide facets, i.e. the ends of the active region.

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: 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.

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: Quantum cascade laser especially comprising a gain region (14) formed from several layers (20) which each comprise:

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.

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:

Abstract: The invention concerns a quantum cascade laser, comprising a substrate (10), a stack of layers (12), having a prismatic shape with substantially trapezoidal cross-section, comprising a lower surface arranged on the substrate (10), an upper surface and lateral surfaces, said stack forming a gain region and two walls between which the gain region is interposed, two electrodes (10, 24) arranged on either side of the stack, one (24) 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 (22) interposed between the two electrodes. The invention is characterised in that the electrically insulating layer (22) 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 (12) thickness.

Abstract: A system and method for communicating a key between two stations using an interferometric system for quantum cryptography. The method includes sending at least two light pulses over a quantum channel and detecting the interference created by the light pulses. The interfering pulses traverse the same arms of an interferometer but in a different sequence such that the pulses are delayed when traversing a quantum channel. The pulses are reflected by Faraday mirrors at the ends of the quantum channel so as to cancel any polarization effects. Because the interfering pulses traverse the same arms of an interferometer, there is no need to align or balance between multiple arms of an interferometer.