We present results from studying dynamic aspects of the pair-induced quenching (PIQ) process in holmium-doped optical fibers. The PIQ process is detrimental for the efficiency of Ho-doped fiber lasers operating in the eye-safe 2.1 μm wavelength regime, and has been suggested to be the dominating cause of efficiency degradation in such lasers. Time-resolved fluorescence experiments were used to determine the rate of the PIQ-related upconversion process occurring within pairs of Ho-ions, i.e. the lifetime of doubly-excited Ho-pairs. Measurements were performed on twelve different Ho-doped fibers varying by an order of magnitude in Ho-doping concentration. The lifetime of doubly-excited Ho-pairs was measured to be 460 ns on average, varying only slightly for the different fibers.
We present a pulsed all-fiber Er/Yb-doped master oscillator power amplifier at 1.55 μm wavelength. In a simple two-stage amplifier design, the source delivers 140 μJ pulses at 25 kHz and 50 kHz pulse repetition frequency, and 100 μJ at 100 kHz, with pulse durations of ∼10 ns and beam quality of M2 = 1.3. The MOPA is suitable as a robust field source for ladar applications, and has been tested in an in-house developed scanning ladar system.
Several types of infrared sensors are based on sensitive focal plane arrays. In such sensors, the intensity will typically increase by a factor ~107 at the focal plane, compared to the intensity of the incoming radiation. Such arrays are thus vulnerable when illuminated with high-intensity laser pulses. One solution for protecting the array against such pulses is to use an optical limiter. We here present results where carbon disulfide (CS2) has been tested as an optical limiting material against high-energy laser pulses at 2.05 μm wavelength.
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