Yb:KLuW channel waveguide lasers passively Q-switched by evanescent-field interaction with carbon nanotubes

Ji Eun Bae, Tae Gwan Park, Esrom Kifle, Xavier Mateos, Magdalena Aguiló, Francesc Díaz, Carolina Romero, Javier Rodríguez Vázquez de Aldana, Fabian Rotermund

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Highly efficient and compact pulsed laser sources have tremendous potential for integrated photonic devices in numerous applications including spectroscopy, metrology and microscopy. Yb3+-doped monoclinic doubletungstate crystals exhibit broad and large absorption and emission cross-sections and extremely low quantum defects. Channel waveguide structures have been actively studied for miniaturization of laser systems and efficient fundamental-mode laser operation with low lasing thresholds. One of the powerful methods to fabricate waveguide structures in a transparent material is the femtosecond direct laser writing (fs-DLW). Recently, pulsed waveguide lasers utilizing saturable absorbers (SAs) have been demonstrated with SESAM and low-dimensional carbon nanostructures. [1-3] Intrinsic characteristics such as ultrafast response, broadband nonlinear absorption and flexibility for integration make single-walled carbon nanotubes (SWCNTs) and graphene unique for various types of pulsed lasers. Placing a SA between the waveguide and the laser mirror results in additional intracavity losses and Q-switching instabilities due to thermal loads through direct-field interaction with the SA. Therefore, the damage-free coupling and the potential of a monolithic design including SAs in compact lasers are highly desired. Here we demonstrate the first Q-switched operation of the Yb-doped channel waveguides based on evanescent-field interaction with SWCNTs and compare with a direct-field interaction scheme. A surface circular cladding waveguide with a vertical width of 50 μm is inscribed in the 5 at.% Yb3+-doped KLu(WO4)2 crystal by fs-DLW (employing 120-fs / 65-nJ / 1-kHz pulses at a wavelength of 795 nm). Arc-discharged SWCNTs are spin-coated on top of the Yb:KLuW waveguide or on output couplers. A 982-nm tapered amplifier diode is used as the pump source. The polarization and power of the pump beam are controlled by a polarizer and two λ/2 wave plates. The 2.88-mm-long laser cavity consists of the Yb:KLuW channel waveguide and two mirrors directly attached to both end facets of the waveguide for two interaction schemes with SWCNTs, as shown in Fig. 1(a).

Original languageEnglish
Title of host publicationThe European Conference on Lasers and Electro-Optics, CLEO_Europe_2019
PublisherOptica Publishing Group (formerly OSA)
ISBN (Print)9781728104690
StatePublished - 2019
Externally publishedYes
EventThe European Conference on Lasers and Electro-Optics, CLEO_Europe_2019 - Munich, Germany
Duration: Jun 23 2019Jun 27 2019

Publication series

NameOptics InfoBase Conference Papers
VolumePart F140-CLEO_Europe 2019
ISSN (Electronic)2162-2701

Conference

ConferenceThe European Conference on Lasers and Electro-Optics, CLEO_Europe_2019
Country/TerritoryGermany
CityMunich
Period06/23/1906/27/19

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