M. J. D. Esser

Estimation of thermal fracture limits in quasi–continuous–wave end–pumped lasers through a time–dependent analytical model

A time-dependent analytical thermal model of the temperature and the corresponding induced thermal stresses on the pump face of quasi- continuous wave (qcw) end-pumped laser rods is derived. We apply the model to qcw diode-end-pumped rods and show the maximum peak pump power that can be utilized without fracturing the rod. To illustrate an application of the model, it is applied to a qcw pumped Tm:YLF rod and found to be in very good agreement with published experimental results. The results indicate new criteria to avoid fracture when operating Tm:YLF rods at low qcw pump duty cycles.

330 mJ single-frequency Ho:YLF slab amplifier

We report on a double-pass Ho:YLF slab amplifier which delivered 350 ns long single-frequency pulses of up to 330 mJ at 2064 nm, with a maximum M2 of 1.5 at 50 Hz. It was end pumped with a diode-pumped Tm:YLF slab laser and seeded with up to 50 mJ of single-frequency pulses.

Ho:YLF pumped HBr laser

A Ho:YLF laser pumped HBr molecular laser was developed that produced up to 2.5 mJ of energy in the 4 micron wavelength region. The Ho:YLF laser was fiber pumped using a commercial Tm:fibre laser. The Ho:YLF laser was operated in a single longitudinal mode via injection seeding with a narrow band diode laser which in turn was locked to one of the HBr transitions. The behavior of the HBr laser was described using a rate equation mathematical model and this was solved numerically. Good agreement both qualitatively and quantitatively between the model and experimental results was obtained.

High average power 1314 nm Nd:YLF laser, passively Q-switched with V:YAG

A 1314 nm Nd:YLF laser was designed and operated both CW and passively Q-switched. Maximum CW output of 10.4 W resulted from 45.2 W of incident pump power. Passive Q-switching was obtained by inserting a V:YAG saturable absorber in the cavity. The oscillator delivered a maximum of 825 μJ energy per pulse, with a pulse duration of 135 ns at a pulse repetition frequency of 6.3 kHz, effectively delivering 5.2 W of average power.

Tm:YLF slab wavelength-selected laser

A Tm:YLF slab laser was wavelength selected to operate at 1890 nm. The oscillator consisted of a single 2.5% doped Tm:YLF slab, a volume Bragg Grating (VBG) mirror and a 90% output-coupler. The slab crystal was pumped with a 300 W diode stack using a pump reproducing configuration. The output power exceeded 80 W and the beam quality factors in the horizontal and vertical directions were 182 and 2.5 respectively.

Efficient Ho:YLF Laser Pumped by a Tm:fiber Laser

A thulium fiber laser pumped Ho:YLF laser delivering 45.1 W in a near diffraction-limited beam when pumped with 84.7 W is demonstrated. The optical-to-optical efficiency of 53 % compares favorably with similar Ho:YAG lasers.

Investigating Thermal Stresses in Quasi-CW Pumped Tm:YLF Laser Crystals

Time dependant thermally induced stresses in an end-pumped Tm:YLF laser rod are investigated numerically. The variation of the maximum incident pump power at the fracture point with respect to pulse length is investigated.

High average power Q-switched 1314 nm two-crystal Nd:YLF laser

A 1314 nm two-crystal Nd:YLF laser was designed and operated in both CW and actively Q-switched modes. Maximum CW output of 26.5 W resulted from 125 W of combined incident pump power. Active Q-switching was obtained by inserting a Brewster-cut acousto optic modulator. This setup delivered an average power of 18.6 W, with a maximum of 5.6 mJ energy per pulse with a pulse duration of 36 ns at a pulse repetition frequency of 500 Hz.

Demonstration of a wavelength selected optically pumped HBr laser

A tunable optically pumped HBr laser has been demonstrated for the first time. As pump source for the HBr oscillator, we developed a single-frequency Ho:YLF laser- amplifier system which was locked to the 2064 nm absorption line of HBr. Through the implementation of an intra-cavity diffraction grating, laser oscillation was demonstrated on nineteen molecular transition lines including both the R-branch (3870 nm to 4015 nm) and the P-branch (4070 nm to 4453 nm). The highest output energy for the given input energy was 2.4 mJ at 4133 nm.

Efficient fiber-laser-pumped Ho:YLF oscillator and amplifier utilizing the transmitted pump power of the oscillator

We present a novel scheme for a compact and robust pulsed fiber-laser-pumped Ho:YLF oscillator and amplifier system, where the pump power transmitted by the oscillator is utilized to pump the amplifier.