Nonlinear-optical frequency conversion in a dual-wavelength vertical-external-cavity surface-emitting laser
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ICS OF SEMICONDUCTOR DEVICES
Nonlinear-Optical Frequency Conversion in a Dual-Wavelength Vertical-External-Cavity Surface-Emitting Laser Yu. A. Morozova^, I. S. Nefedova, T. Leinonenb, and M. Yu. Morozovc aInstitute
of Radio Engineering and Electronics, Saratov Branch, Russian Academy of Sciences, Saratov, 410019 Russia ^e-mail: [email protected] bOptoelectronics Research Centre, Tampere University of Technology, P.O. Box 692, Tampere, 33101 Finland cSaratov State University, Saratov, 410026 Russia Submitted January 25, 2007; accepted for publication August 28, 2007
Abstract—A nonlinear-optical conversion process in a dual-wavelength vertical-external-cavity surface-emitting laser that leads to the generation of difference-frequency radiation in the long-wavelength part of the midinfrared range (~17.7 μm) is analyzed numerically. The nonlinear crystal of GaAs is incorporated in the outputcoupler mirror and, at the same time, is placed in a Fabry–Perot cavity tuned to the difference frequency. It is shown that the dependence of the nonlinear-conversion efficiency on the GaAs crystal thickness exhibits a pronounced resonance behavior and that the peak power of the radiation in the mid-infrared range can be as high as a few milliwatts with the parameters of the laser and the optical pump readily attainable experimentally. PACS numbers: 42.55.Px, 85.35.Be, 78.45.+h, 78.67.De DOI: 10.1134/S1063782608040167
1. INTRODUCTION Development of new semiconductor lasers for the mid-infrared (MIR) range represents an important problem of laser physics and technology. Ongoing research in this field is motivated by the fact that availability of compact sources of coherent radiation in this range of the electromagnetic spectrum is still insufficient. Meanwhile, demand for such devices exists in spectroscopy, medicine, space and military communications, etc. (see, e.g., [1–3]). Actually, only quantumcascade lasers (QCLs) [4] may be considered at present as class of devices really capable of satisfying this demand. However, the use of QCLs is impeded both by fundamental features of the continuous-wave (CW) operation of these lasers that make advancement into the wavelength range above 10 μm nearly impossible without cooling to cryogenic temperatures, and by technological difficulties caused by the sophisticated design of the active region. These circumstances necessitate studies of other possibilities for the generation of radiation in the MIR range. One of the promising alternative approaches is related to the use of coherent nonlinear three-wave mixing, which results in the generation of a difference-frequency wave in the middle or far IR range [5–7]. Designs of a stripe laser [5] and a vertical-cavity surface-emitting laser (VCSEL) [6, 7] were proposed in which dual-wavelength lasing and nonlinear frequency conversion into the mid- or far-IR range takes place in the same structure. Estimates performed indicate that the configuration with a high-Q vertical cavity used in
VCSELs provides for an intensity of the near-infrared (NI
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