Ho:LuAG single crystal fiber: growth, spectroscopy and laser characteristics

Abstract

Lutetium aluminum garnet single-crystal fiber (SCF, ∼ Φ 0.9 mm – 165 mm) doped with 0.5 at.% Ho3+ has been grown by the micro-pulling-down (µ-PD) technique. The room-temperature absorption and emission spectra exhibit similar features to the bulk crystal. Laser performances of the SCFs with two different pump configurations, i.e., pump guiding and free-space propagation, are studied by employing a 1.9-µm laser diode and a high-brightness fiber laser, respectively. Laser slope efficiencies obtained with both pump configurations can be higher than 50%, and a maximum output power of 6.01 W is achieved at ∼ 2.09 µm with the former pump. The comparable efficiency to the high-brightness pump is an indication of that high laser performance can also be expected through pump-guiding in the SCF even with a low pump beam quality.

Highly efficient Ho: YAP laser with 202 W of linearly polarized output power at 2118 nm

“…Moreover, the good beam quality of Tm fiber and bulk pump sources makes it possible that relatively low Ho 3+ concentrations can be used with reduced ETU rates and hence improved energy storage capability in pulsed mode of operation. So far, high power and efficient laser operation of Ho 3+ doped diverse gain media, such as YAG, Y 2 O 3 , YLF, LuAG and LuLiF 4 etc., have been demonstrated [12][13][14][15][16][17][18][19]. Up to 142 W and 450 W of continuous-wave (CW) output power at ~2.1 μm have been generated from Ho: YAG oscillator and amplifier with slope efficiencies of 56.7% and 62.5% [12,13].…”

High-efficiency Ho:YAG single-crystal fiber laser in-band pumped by a 1.9 μm laser diode

“…Fortunately, the single-crystal fiber, a long and thin crystalline rod with a length of a few centimeters and a diameter less than 1 mm, is an ideal gain medium to solve this problem [20][21][22]. Such a unique structure can offer multiple total internal reflections bounces for the pump light [23] and give a relatively higher gain than free-space propagation in the SCF laser [24]. In addition, the single crystal fiber (SCF) offers efficient heat dissipation due to its small diameter and large surface-to-volume ratio [25].…”