Eur. Phys. J. Appl. Phys. 42, 121–124 (2008) DOI: 10.1051/epjap:2008030 T HE EUROPEAN P HYSICAL JOURNAL APPLIED PHYSICS Single-frequency operation of an orange avalanche upconversion laser for high-resolution laser spectroscopy T.H. My 1 , Ph. Goldner 2 , O. Guillot-No¨ el 2 , M. Tonelli 3 , and F. Bretenaker 1, a 1 Laboratoire Aim´ e Cotton, CNRS-Universit´ e Paris Sud 11, Bˆat. 505, 91405 Orsay Cedex, France 2 Laboratoire de Chimie de la Mati` ere Condens´ ee de Paris, CNRS-UMR 7574, ´ Ecole Nationale Sup´ erieure de Chimie de Paris, 11 rue Pierre et Marie Curie, 75005 Paris, France 3 NEST-INFM, Dipartimeto di Fisica, Universit`a di Pisa, Via Buonarroti, 2, I-56127 Pisa, Italy Received: 26 November 2007 / Accepted: 21 January 2008 Published online: 28 March 2008 – c  EDP Sciences Abstract. We report single transverse and longitudinal mode operation of an all solid-state orange laser pumped at 821 nm. Oscillation at 607 nm by avalanche upconversion in Pr, Yb:BaY2F8 pumped by a Ti-Sapphire laser at 821 nm is obtained with a threshold as low as 570 mW. A maximum output power of 12 mW is obtained for a pump power of 2.5 W. PACS. 42.55.-f Lasers – 42.70.Hj Laser materials – 42.55.Rz Doped-insulator lasers and other solid state lasers 1 Introduction High-resolution spectroscopy [1] or quantum information processing techniques [2,3] using rare-earth ions embed- ded in solid-state matrices [4] make use of the coher- ent optical excitation of transitions that lie in the visi- ble or infrared range. Among the possible active centers, praseodymium ions embedded in a Y 2 SiO 5 matrix repre- sent at the present time the most promising system for these applications, because of their relatively large opti- cal transition oscillator strengths and long coherence life- times [5]. The optical transition used in these experiments is the 3 H 4 (0) → 1 D 2 (0) transition at 605.977 nm vacuum wavelength. To coherently drive such a system, it is nec- essary to use a laser source with a coherence time longer than the optical coherence lifetime of the considered tran- sition, i. e., in the 100 μs range [6]. Dye lasers are currently available sources at this wavelength but they are cumber- some and difficult to stabilize below the kHz range. This is mainly due to the large bandwidth of the frequency noise created by the dye jet. In fact, only a few teams around the world have built such ultra-stable dye lasers [7–9]. Conse- quently, the development of all solid-state ultrastable laser sources in the red-orange part of the visible spectrum, i.e., where diode lasers are not available, is an important step towards the real development of quantum information pro- cessing systems using such rare-earth ions. One possible track consists in exploring the possibilities offered by op- tical parametric oscillators. Some promising results have recently been obtained with a singly resonant optical para- a e-mail: fabien.bretenaker@lac.u-psud.fr metric oscillator using a PPSLT crystal [10]. However, one disadvantage of such sources is the fact that they cannot be pumped by diode lasers. Another interesting possibility would be to build a laser based on another transition of Pr 3+ ions, namely the 3 P 0 → 3 H 6 transition, which is also located in the red-orange part of the visible spectrum. Indeed, visible laser emission of this transition in praseodymium doped fluoride crystals at room temperature has been demon- strated in cw regime by direct pumping with a blue laser diode [11,12]. However, blue laser diodes with sufficient power are not yet readily available. This, and the fact that a minimum power of 100 mW in the orange would be necessary for our application, explains why the orange laser recently obtained using Pr, Yb:BaY 2 F 8 pumped by a Ti-Sapphire laser in the 820–840 nm wavelength range is particularly attractive [13]. In this system, the upper level of the laser transition in praseodymium is populated under infrared excitation thanks to a process called avalanche upconversion [14,15] and based on the interaction between Yb 3+ and Pr 3+ ions in the matrix in this material. This result opens the perspective of an orange solid-state laser pumped by cheap and easily available 800 nm diode lasers. However, Pr, Yb: BaY 2 F 8 emission peaks at 607.5 nm with a 1 nm linewidth and is therefore non resonant with Pr 3+ :Y 2 SiO 5 . But recent work [16] has shown a strong orange emission at 606 nm for Pr 3+ , Yb 3+ :PbF 2 . So we are now actively engaged in the optimization of this mate- rial to obtain laser emission at 606 nm. In the meantime, one important question that remains consists in wondering whether such avalanche up-conversion lasers are able to Article published by EDP Sciences