High Gain Indirectly LED-Pumped Nd:Glass Lasers

Flashlamp Nd:glass is used in many high-energy laser facilities as power amplifiers for nanosecond and CPA-based sub-picosecond pulses [1]. Despite all the problems associated with flashlamps (high voltage handling, high thermal effects, short lifetime), this pumping architecture is still in use in today's facilities and is still considered for the next generation. LED pumping could be an interesting alternative, since the lighting market offers a mass production of LEDs at a cost per watt much lower than laser diodes. Direct LED pumping of Nd:glass has been recently demonstrated [2] but with a limited small signal gain (typically 1.05) and with pump power scaling limited by the LED density and by the surface of the Nd:glass rod. In this paper, we propose an alternative approach to indirectly pumping Nd:glass using LEDs via a luminescent concentrator. In fact, this architecture has already proven its efficiency for low gain transition metal lasers [3]. It consists of a Ce-doped luminescent concentrator pumped by blue LEDs. At the output of the concentrator, the pump power density can reach 10 kW/cm2, matching the power density typically achievable with laser diodes. The emission spectrum is in the yellow-orange range and it can be used to pump Nd-doped materials [4].