Abstract
We report on the first demonstration of laser-diode-pumped master-oscillator power-amplifier (MOPA) system based on Er-doped bulk material working at 2920 nm. The relaxation oscillation at the beginning of the laser pulse from the Er:YAlO3 (YAP) oscillator was suppressed effectively when the pump frequency was increased to 140 Hz, as a result of the establishment of a three-level system. In the amplifier, the small signal gain of the Er:YAP strongly depends on pump duration and repetition frequency, and can reach the upper limit of parasitic oscillation. Further, 25.5 mJ of output pulse energy has been achieved from the amplifier at 150 Hz frequency (2.2 ms pump duration), with over 32% of optical-to-optical efficiency. Further improvement of the amplification ability of the MOPA system was discussed.
Highlights
Er3+ -doped lasers emitting in the mid-infrared spectral region (∼3 μm) have increasingly become the forefront research topic for environmental monitoring, remote sensing [1], and some surgical applications [2] because they can effectively cover the absorption lines of many molecules [3].It is expected that the 3 μm Er3+ -doped lasers may be applied in the industry specially for the processing of some hard and brittle glasses and flexible resin materials, benefitting from the strong stretching absorption of OH and C–H bonds [4,5]
We found that at a low frequency, i.e., 60 Hz, a giant pulse appeared at the beginning of the laser pulse, and only a slight part of other signals existed within the pump duration
The laser will gradually transform into a three-level system when the pumping period approaches the radiative lifetime (∼9.59 ms [20]) of 4 I13/2, and remain in a three-level system when the repetition frequency is beyond 140 Hz, since the pumping period was too short for the system to exhaust the excited ions on 4 I13/2 level
Summary
Er3+ -doped lasers emitting in the mid-infrared spectral region (∼3 μm) have increasingly become the forefront research topic for environmental monitoring, remote sensing [1], and some surgical applications [2] because they can effectively cover the absorption lines of many molecules [3].It is expected that the 3 μm Er3+ -doped lasers may be applied in the industry specially for the processing of some hard and brittle glasses and flexible resin materials, benefitting from the strong stretching absorption of OH and C–H bonds [4,5]. Er3+ -doped lasers emitting in the mid-infrared spectral region (∼3 μm) have increasingly become the forefront research topic for environmental monitoring, remote sensing [1], and some surgical applications [2] because they can effectively cover the absorption lines of many molecules [3]. The demand for power enhancement of 3 μm laser is continuing to increase considering these potential applications [6], and scaling mid-infrared lasers to high-average power or high-energy levels have become one of the goals of current laser research [6,7,8,9,10]. The 3 μm Er laser that pumped by commercially available 976 nm LD features a higher quantum efficiency via the energy-transfer up-conversion effect (ETU) between Er3+ ions [11,12]. The gain medium often has a high doping concentration
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