An Analytical Model of the Intracavity Optical Second Harmonic Generation in a Vertical-External-Cavity Surface-Emitting Laser (original) (raw)
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One of the promising laser constructions having much attention in the past years is thin-disc semiconductor lasers with the resonant periodic gain in a form of multiple quantum wells. The 3D numerical model is developed based on combining bi-directional beam propagation method with the round-trip operator technique. The standing wave effect in resonant gain structure and diffraction in the external laser cavity are taken into account explicitly. Characteristics of optical modes are found numerically for cylindrical vertical extended cavity surface emitting laser with above-threshold pumping. Variation of distance to the external mirror is found to result in notable changes in power and optical quality of the output beam. The decisive role of gain and index non-linearities in these changes is identified.
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We study the factors that ultimately limit the performance of an external enhancement resonator for optical second-harmonic generation (SHG). To describe the resonant SHG process we introduce a theoretical model that accounts for the intensity-dependent cavity loss that is due to harmonic generation and that also includes a realistic assumption about the shape and the frequency width of the laser mode. With the help of this model we optimized the performance of a doubling cavity based on a lithium triborate (LBO) crystal. This cavity was used for frequency doubling the output of a single-frequency titanium-doped sapphire laser at 850 nm. We were able to push the total second-harmonic conversion efficiency to 53% (a 1.54-W pump resulted in 820 mW of second-harmonic light), which to our knowledge is the best result ever reported for a LBO-based doubling cavity.
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Vertical-external-cavity surface-emitting lasers (VECSELs) yield an excellent beam quality in conjunction with a scalable output power. This paper presents a detailed numerical analysis of electrically pumped VECSEL (EP-VECSEL) structures. Electrical pumping is a key element for compact laser devices. We consider the optical loss, current confinement, and device resistance. The main focus of our investigation is on the achievement of an adequate radial carrier distribution for fundamental transverse mode operation. It will be shown that a trade off between the conflicting optical and electrical optimization has to be found and we derive an optimized design resulting in guidelines for the design of EP-VECSELs which are compatible with passive mode locking.