Operational Characteristics of Intracavity Singly- Resonant Optical Parametric Oscillator Pumped by Vertical External Cavity Surface-Emitting Laser

The operational characteristics of a novel continuous-wave compact intracavity singly-resonant optical parametric oscillator pumped by a vertical external cavity surfaceemitting laser are numerically analyzed. Keywords—nonlinear frequency conversion; semiconductor laser; intracavity optical parametric oscillator Continuous-wave optical parametric oscillators (OPOs) take up a distinguished niche among the variety of optical sources which may be exploited for high-resolution spectroscopy of gaseous substances in the midand far-infrared ranges [1]. These coherent sources are especially attractive because of ability to produce a wide wavelength tuning combined with a narrow spectrum line under room temperature operation. Its mechanism is based on energy transfer from an optical field at the highest frequency (pump) to radiation at the intermediate frequency (signal) and at the lowest frequency (idler), the energy and momentum conservation hold. Depending on how many optical fields suffer a resonance enhancement in an appropriate cavity, the OPOs will fall into singly-, doublyand triply-resonant devices. Now, the singly-resonant OPOs (SROs) are only widespread design because of hop-free wavelength tuning combined with a simple scheme and usability. However, SROs need tens-of-watt pumping lasers to overcome the threshold of parametric generation. This threshold could be reduced if an SRO is placed within a high-finesse cavity of a pumping laser. In particular, such the intracavity SRO (ICSRO) was demonstrated with a neodymium laser [2]. Unfortunately, an ICSRO pumped by a neodymium laser appears to show pronounced relaxation oscillations of output intensity because laser active medium exhibits a long lifetime of excited state. D. Stothard et al. [3] have proposed pumping of an ICSRO by a semiconductor vertical external cavity surface-emitting laser (VECSEL) in order to prevent the relaxation oscillations. Recently, we have proposed a novel type of the continuous-wave ICSRO pumped by a VECSEL [4]. One of the primary goals of the proposal was to build a fairly compact device. Unlike to the ICSRO presented in [3], we have use of the same plano-concave cavity both for the pumping laser and the signal down-converted wave. The total length of the cavity with a nonlinear crystal of quasi-phase-matched GaAs used as the SRO’s gain medium is less than 20 mm. Here we report on the numerical analysis of operational characteristics of the ICSRO. The VECSEL with a quantum-well (QW) active medium based on GaSb material system is supposed to generate pump radiation (p≈1.98 m) for the ICSRO. These active media are known to be homogeneously broadened and free of spatial hole-burning. Both these features in combination with a large intermode beating frequency determined by the short length cavity encourage the single-mode operation of ICSRO without frequency selective elements [5]. Our analysis shows that about 35 mW of one-direction idler power (i≈16.5 m) could be generated for 15 W of primary pump power. This study was supported by RFBR grant No.13-0212070-OFI_M. [1] F. Tittel, D. Richter, A. Fried, “Mid-infrared laser applications in spectroscopy”, in Solid-state mid-infrared laser sources, T. Sorokina, K. L. Vodopyanov, Eds. Springer-Verlag Berlin Heidelberg, 2003. [2] D. Stothard, M. Ebrahimzadeh, M. Dunn, “Low pump threshold, continuous-wave, singly resonant, optical parametric oscillator”, Opt. Lett., vol.23, pp. 1895-1897, 1998. [3] D. Stothard, J. Hopkins, D. Burns, M. Dunn, “Stable, continuous-wave, intracavity, opical parametric oscillator pumped by a semiconductor disk laser (VECSEL)”, Opt. Express, vol.17, pp. 10648-10658, 2009. [4] Yu. A. Morozov, M. Yu. Morozov, “ Intracavity singly-resonant optical parametric oscillator pumped by a semiconductor disk laser”, Proc. of 6th Intern. Conf. on Adv. Optoel. and Lasers (CAOL’2013), Crimea, Ukraine, pp.100-101, 2013. [5] A. Garnache, A. Ouvrard, D. Romanini, “Single-frequency operation of external-cavity VCSELs: non-linear multimode temporal dynamics and quantum limit”, Opt. Express, vol.15, pp. 9403-9417, 2007.