IOP PUBLISHING LASER PHYSICS Laser Phys. 23 (2013) 075801 (7pp) doi:10.1088/1054-660X/23/7/075801 Laser emission in Nd 3+ doped barium–titanium–silicate microspheres under continuous and chopped wave pumping in a non-coupled pumping scheme L L Mart´ ın 1 , D Navarro-Urrios 2 , F Ferrarese-Lupi 3 , C P´ erez-Rodr´ ıguez 1 , I R Mart´ ın 1,4 , J Montserrat 5 , C Dominguez 5 , B Garrido 3 and N Capuj 6 1 Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Av Astrofisico Francisco Sanchez, Universidad de la Laguna, E-38206, S/C de Tenerife, Spain 2 Catalan Institute of Nanotechnology (ICN), Campus UAB, Edifici CM3, E-08193 Bellaterra, Spain 3 Departament d’Electr` onica, Universitat de Barcelona, Carrer Mart` ı i Franqu` es 1, Barcelona E-08028, Spain 4 MALTA Consolider Team, Av Astrofisico Francisco Sanchez, Universidad de la Laguna, E-38206, Spain 5 Instituto de Microelectr ` onica de Barcelona-CNM-CSIC, Bellaterra, E-08193, Barcelona, Spain 6 Departamento de Fisica Basica, Av Astrofisico Francisco Sanchez, Universidad de la Laguna, E-38206, Spain E-mail: lmartin@ull.es Received 22 February 2013 Accepted for publication 2 April 2013 Published 13 May 2013 Online at stacks.iop.org/LP/23/075801 Abstract Laser action using non-coupled excitation and detection of microspheres made of Nd 3+ doped barium–titanium–silicate glass has been demonstrated and measured. The microspheres have also been successfully deposited over Si 3 N 4 strip waveguides with a SiO 2 separation layer, thus enabling the laser emission extraction onto a CMOS compatible photonic circuit. The dynamics of the lasing wavelength and intensity has been studied as a function of the pump power and interpreted in terms of thermal effects generated through non-radiative recombination of the excited ions. (Some figures may appear in colour only in the online journal) 1. Introduction Optical microcavities are structures where the light is confined into a small volume by means of resonant phenomena. In particular, microdisks, microrings, microtoroids and microspheres use a total internal reflection mechanism that produces the so called whispering gallery mode (WGM) resonances. On fluorescent optical microcavities, the luminescent spectrum of the active material is modulated by the WGM spectrum, which may even enhance the spontaneous emission rate. One of the most direct applications of these structures is in chemical or bio-sensing [1], refractive index sensing and temperature sensing [2, 3], but relevant findings have also been achieved towards using them as all-optical switches [4] and micro-mechanical oscillators [5]. Among all microresonators, the microspheres have some key features: they can be made from many compositions including polymers, crystalline or glassy phases, and they can have ultra-high quality factors (Q) up to 8 × 10 9 [6], which means a very high storage time of the light in the resonant cavity. 1 1054-660X/13/075801+07$33.00 c  2013 Astro Ltd Printed in the UK & the USA