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Poster De Conférence Année : 2014

LED pumped QCW Nd3+ :YVO4 laser

Amandine Paul
  • Fonction : Auteur
Jean-Philippe Blanchot
  • Fonction : Auteur
Anne-Lise Viotti
  • Fonction : Auteur
François Balembois
  • Fonction : Auteur
  • PersonId : 915455
Frédéric Druon
Patrick Georges

Résumé

The lighting market has lately made LED performance improved by orders of magnitudes (with efficiency reaching now more than 200 lm/W at room temperature [1]). In parallel, massive production decreases dramatically LED price. A new interest has been triggered by those improvements and since the 2000’s, several research teams start to revisit the concept of LED pumped lasers, in standby since the early 80s [2]. Polymer laser [3,4], fiber laser [5,6] and semiconductors [7] have recently demonstrated laser effect under visible LED pumping. The pumping of bulk crystals by white and blue LEDs was studied theoretically by Lee et al. [8]. However, no experimental results were presented. We carried out a systematic study of the potential of LED pumping for bulk crystals and found that the Nd:YVO4 crystal could be an interesting candidate since its high emission and absorption cross sections. By rough calculations of gain we anticipated that the pump power density of actual LED (typically 100 W/cm2) is just enough to obtain laser threshold. In order to increase the laser performance, we decided to operate the LED in pulsed operation, allowing higher peak power. As LED emission is nearly lambertian, optical systems can not increase significantly the power density in the gain medium. Therefore, we decided to operate our laser in a transverse pumping configuration. We used an a-cut 20 mm long Nd:YVO4 crystal with a doping concentration of 1 at.% and a 2x2 mm2 square section. Laser faces were AR coated and two transverse faces were optically polished for pumping. As pump source, we used 2 LED arrays consisting of 18 1x1 mm2 dices and emitting a 50 nm spectrum centered at 850 nm. In pulsed regime, each chip emitted 100 μs pulses at 250 Hz with a power density of 200 W/cm². The cavity consists in a plane and a 100 mm radius of curvature concave mirrors. Different plane output mirrors have been tested with transmissions between 1% and 6% at 1064 nm. We investigated the laser threshold for different output couplers and deduced the small signal gain versus the pump power (Fig. 1(a)). A significant gain of 6% has been obtained at maximum pump power. Best output energy was obtained with the 1% output coupler (Fig. 1(b)). The laser emitted 65 μs pulses with an energy of 40 μJ for a pump energy of 7.5 mJ. We measured a M2 factor of 19, explained by transverse pumping and non optimised fundamental mode. This represents, to our best knowledge, the first demonstration of a Nd:YVO4 laser pumped by LED.

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Dates et versions

hal-01097170 , version 1 (19-12-2014)

Identifiants

  • HAL Id : hal-01097170 , version 1

Citer

Adrien Barbet, Amandine Paul, Jean-Philippe Blanchot, Anne-Lise Viotti, François Balembois, et al.. LED pumped QCW Nd3+ :YVO4 laser. 6th EPS-QEOD EUROPHOTON CONFERENCE, Aug 2014, Neuchatel, Switzerland. pp.163306 - 81116, 2014. ⟨hal-01097170⟩
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