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Buried heterostructure (BH) lasers are routinely fabricated for telecom applications. Development of quantum cascade lasers (QCL) for sensing applications has largely benefited from the technological achievements established for telecom lasers. However, new demands are to be met with when fabricating BH-QCLs. For example, hetero-cascade and multi-stack QCLs, with several different active regions stacked on top of each other, are used to obtain a broad composite gain or increased peak output power. Such structures have thick etch ridges which puts severe demand in carrying out regrowth of semi-insulating layer around very deeply etched (>10 mu m) ridges in short time to realize BH-QCL. For comparison, telecom laser ridges are normally only <5 mu m deep. We demonstrate here that hydride vapour phase epitaxy (HVPE) is capable of meeting this new demand adequately through the fabrication of BH-QCLs in less than 45 minutes for burying ridges etched down to 10-15 mu m deep. This has to be compared with the normally used regrowth time of several hours, e.g., in a metal organic vapour phase epitaxy (MOVPE) reactor. This includes also micro-stripe lasers resembling grating-like ridges for enhanced thermal dissipation in the lateral direction. In addition, we also demonstrate HVPE capability to realize buried heterostructure photonic crystal QCLs for the first time. These buried lasers offer flexibility in collecting light from the surface and relatively facile device characterization feasibility of QCLs in general; but the more important benefits of such lasers are enhanced light matter interaction leading to ultra-high cavity Q-factors, tight optical confinement, possibility to control the emitted mode pattern and beam shape and substantial reduction in laser threshold., QC 20150423

Together with the optimal basic design, buried heterostructure quantum cascade laser (BH-QCL) with semi-insulating regrowth offers unique possibility to achieve an effective thermal dissipation and lateral single mode. We demonstrate here for the first time realization of BH-QCLs with a single step regrowth of highly resistive (>1x10(8) ohm.cm) semi-insulating InP:Fe in less than 45 minutes in a flexible hydride vapour phase epitaxy process for burying ridges etched down to 10-15 mu m deep both with and without mask overhang. The fabricated BH-QCLs emitting at similar to 4.7 mu m and similar to 5.5 mu m were characterized. 2 mm long 5.5 mu m lasers with ridge width 17-22 mu m, regrown with mask overhang, exhibited no leakage current. Large width and high doping in the structure did not permit high current density for CW operation. 5 mm long 4.7 mu m BH-QCLs of ridge widths varying from 6-14 mu m regrown without mask overhang, besides being spatially monomode, TM00, exhibited WPE of similar to 8-9% with an output power of 1.5 - 2.5 W at room temperature and under CW operation. Thus, we demonstrate a simple, flexible, quick, stable and single-step regrowth process with extremely good planarization for realizing buried QCLs leading to monomode, high power and high WPE., QC 20141030

We report on the realization of buried single ridge and μ-stripes quantum cascade lasers using HVPE and MOVPE regrowth steps of semi-insulating InP:Fe and Si doped layers. We present here the preliminary results obtained on these devices. The reduction of the thermal resistance achieved using semi-insulating InP:Fe for regrowth planarization and μ-stripe arrays approaches are shown and performance perspectives are addressed., QC 20131112