Dual-comb modelocked laser Sandro M. Link, * Alexander Klenner, Mario Mangold, Christian A. Zaugg, Matthias Golling, Bauke W. Tilma and Ursula Keller Department of Physics, Institute for Quantum Electronics, ETH Zürich, 8093 Zürich, Switzerland * slink@phys.ethz.ch Abstract: In this paper we present the first semiconductor disk laser (SDL) emitting simultaneously two collinearly overlapping cross-polarized gigahertz modelocked pulse trains with different pulse repetition rates. Using only a simple photo detector and a microwave spectrum analyzer directly down-converts the frequency comb difference from the optical to the microwave frequency domain. With this setup, the relative carrier- envelope-offset (CEO) frequency can be accessed directly without an f-to2f interferometer. A very compact design is obtained using the modelocked integrated external-cavity surface emitting laser (MIXSEL) which is part of the family of optically pumped SDLs and similar to a vertical external cavity surface emitting laser (VECSEL) but with both gain and saturable absorber integrated into the same semiconductor wafer (i.e. MIXSEL chip). We then simply added an additional intracavity birefringent crystal inside the linear straight cavity between the output coupler and the MIXSEL chip which splits the cavity beam into two collinear but spatially separated cross- polarized beams on the MIXSEL chip. This results in two modelocked collinear and fully overlapping cross-polarized output beams with adjustable pulse repetition frequencies with excellent noise performance. We stabilized both pulse repetition rates of the dual comb MIXSEL. ©2015 Optical Society of America OCIS codes: (140.3460) Lasers; (140.4050) Mode-locked lasers; (140.5960) Semiconductor lasers; (140.7090) Ultrafast lasers; (140.7270) Vertical emitting lasers; (300.0300) Spectroscopy; (040.2840) Heterodyne; (260.1440) Birefringence. References and links 1. F. Keilmann, C. Gohle, and R. Holzwarth, “Time-domain mid-infrared frequency-comb spectrometer,” Opt. Lett. 29(13), 1542–1544 (2004). 2. A. Schliesser, M. Brehm, F. Keilmann, and D. van der Weide, “Frequency-comb infrared spectrometer for rapid, remote chemical sensing,” Opt. Express 13(22), 9029–9038 (2005). 3. S. Schiller, “Spectrometry with frequency combs,” Opt. Lett. 27(9), 766–768 (2002). 4. I. Coddington, W. C. Swann, and N. R. Newbury, “Coherent multiheterodyne spectroscopy using stabilized optical frequency combs,” Phys. Rev. Lett. 100(1), 013902 (2008). 5. B. Bernhardt, A. Ozawa, P. Jaquet, M. Jacquey, Y. Kobayashi, T. Udem, R. Holzwarth, G. Guelachvili, T. Hänsch, and N. Piqué, “Cavity-enhanced dual-comb spectroscopy,” Nat. Photonics 4(1), 55–57 (2010). 6. A. Bartels, R. Cerna, C. Kistner, A. Thoma, F. Hudert, C. Janke, and T. Dekorsy, “Ultrafast time-domain spectroscopy based on high-speed asynchronous optical sampling,” Rev. Sci. Instrum. 78(3), 035107 (2007). 7. M. Kuznetsov, F. Hakimi, R. Sprague, and A. Mooradian, “High-power (>0.5-W CW) diode-pumped vertical- external-cavity surface-emitting semiconductor lasers with circular TEM00 beams,” IEEE Photon. Technol. Lett. 9(8), 1063–1065 (1997). 8. S. Calvez, J. E. Hastie, M. Guina, O. G. Okhotnikov, and M. D. Dawson, “Semiconductor disk lasers for the generation of visible and ultraviolet radiation,” Laser Photon. Rev. 3(5), 407–434 (2009). 9. B. Rösener, M. Rattunde, R. Moser, S. Kaspar, C. Manz, K. Köhler, and J. Wagner, “GaSb-based optically pumped semiconductor disk lasers emitting in the 2.0-2.8 μm wavelength range,” Proc. SPIE 7578, 75780X (2010). 10. D. J. M. Stothard, J.-M. Hopkins, D. Burns, and M. H. Dunn, “Stable, continuous-wave, intracavity, optical parametric oscillator pumped by a semiconductor disk laser (VECSEL),” Opt. Express 17(13), 10648–10658 (2009). #230952 - $15.00 USD Received 26 Dec 2014; revised 14 Feb 2015; accepted 14 Feb 2015; published 23 Feb 2015 (C) 2015 OSA 9 Mar 2015 | Vol. 23, No. 5 | DOI:10.1364/OE.23.005521 | OPTICS EXPRESS 5521