C. J. Flood

Kerr lens mode locking of a diode-pumped Nd:YAG laser.

We demonstrate Kerr lens mode locking of a diode-pumped Nd:YAG laser by using the gain medium as the Kerr medium and no intracavity slit. Kerr self-focusing within the Nd:YAG rod is believed to improve matching between the cavity mode and the aperture created by thermal lens aberration and thereby discriminate against lower (cw) intensities. The laser produces 8.5-ps, 100-MHz pulses with 1 W of average output power and a 35% slope efficiency. Kerr lens mode locking is initiated by slight mechanical perturbation.

CW diode pumping and FM mode locking of a Nd: KGW laser

We have demonstrated cw diode end pumping of Nd: KGW, a novel solid-state gain medium, with up to 30% conversion efficiency into near-TEM00 (M2 < 1.05) output atλ = 1.067 µm for a pump level of 2.7 W. The slope efficiency was limited by intracavity reflections to 36%; however, direct comparison to a similar Nd:YAG laser indicates the same intrinsic slope efficiency of ≈60%. FM mode locking of this laser at 200 MHz has produced 12 ps pulses (compared to 16 ps for Nd: YAG), although an intracavity etalon was required. Considerable reduction in pulse width is possible (the line width limit is ≈0.5 ps) but different techniques may be necessary. Spatial hole burning was evident in both the ≈120 GHz free-running spectrum and the etalon-limited mode-locked spectrum.

Effect of spatial hole burning in a mode-locked diode end-pumped Nd:YAG laser

We have controlled the amount of spatial hole burning in a diode end-pumped Nd:YAG laser to quantitatively analyze its role in active mode locking. We demonstrate inhomogeneous broadening of the lasing bandwidth to >60 GHz, accompanied by a pulse-width reduction from 40 to 15 ps and an ~30% increase in the time-bandwidth product. Both homogeneous and inhomogeneous broadening have been included in a successful calculation of the steady-state pulse width.

Diode-pumped Nd:YAG laser using reflective pump optics

We have examined the performance of a diode-laser side-pumped Nd:YAG laser using elliptical mirrors to focus the output of 6 × 10 W laser-diode arrays into the Nd: YAG rod. The multimode cw output power was 14 W with an optical to optical efficiency of 29%. With a resonator designed for TEM00 mode operation 12 W of output was achieved.

Preferential operation of an end-pumped Nd:YAG laser in high-order Laguerre–Gauss modes

A small Nd:YAG laser with plano-concave resonator end pumped by a dye laser is observed to possess single Laguerre-Gauss transverse modes as the lowest-loss modes. This anomalous behavior occurs when the transverse dimension of the gain spot is much smaller than the fundamental TEM(00)-mode spot size of the resonator; the Laguerre-Gauss transverse-mode order varies with resonator length.

HIGH POWER DIODE-PUMPED ND:YAG REGENERATIVE AMPLIFIER FOR PICOSECOND PULSES

We demonstrate regenerative amplification of 25‐ps full width at half‐maximum TEM00 pulses to ≳1 mJ at a 2‐kHz repetition rate in a diode‐pumped Nd:YAG system. The single pulse energy gain is 74 dB and operation at 5 kHz has delivered ≳3.5 W of average power at λ=1.064 μm. Gain narrowing and self‐phase modulation cause significant spectral and temporal broadening, from 70 GHz and 12 ps to ∼100 GHz and 25 ps, respectively, for the shortest amplified pulses.

Efficient continuous-wave TEM 00 operation of a transversely diode-pumped Nd:YAG laser

A new, highly efficient, scalable technique for cw high-power diode-array side pumping of gain media has been eveloped. The use of simple all-reflective optics permits diode emission collection efficiencies of >95%. We have achieved a cw TEM(00) mode output (M(2) < 1.1) of 13.1 W at 1.06 microm from a Nd:YAG rod pumped with 60 W of laser-diode output (808 nm), representing 22% conversion efficiency (29% conversion of absorbed pump power). Numerical simulations and experimental results indicate that good thermal management results in thermally induced aberrations of

Kilohertz all-solid-state picosecond lithium triborate optical parametric generator

An all-solid-state picosecond optical parametric generation system that uses a single-pass noncritically phase-matched lithium triborate crystal is demonstrated. We have achieved > 20% total conversion from lambda = 532 nm (pump) to lambda = 800 nm (signal) and 1.6 microm (idler) with a pulse width of ~15 ps and average power of 200 mW at a repetition rate of 3 kHz (~50 microJ/signal pulse). Frequency tuning from <750 nm to >1.8 microm is achieved by temperature tuning of the lithium triborate.

Observation of mode locking in a synchronously pumped Nd:YAG laser

We report on the mode-locking behavior of a 1.06-microm Nd:YAG ring oscillator synchronously pumped by a 76-MHz, 20-psec dye laser at 0.59 microm with an average power of 600 mW. Gain modulation is based on relaxation from the pump band to the upper laser level with a time constant (minimum gain modulation time) of 470 psec; stable modelocked operation is achieved with a gain modulation of only 10(-4). Preliminary results give a minimum pulse width of 140 psec and suggest a novel way of mode locking rare-earth waveguide lasers.

High Effects High Power Diode-Pumped Nd:YAG Laser

Laser diode arrays are an efficient light source for optically pumping solid state laser crystals. With the availability of ever larger laser diode arrays and stacks of arrays, there is an increasing effort in using laser diodes for pumping high power lasers. In this paper we report on the results of scaling a diode pumped Nd:YAG laser. Starting out with a pump power of 60 W an output power of 12 W TEM00 mode was achieved. Applying pump powers of 90 W yielded 14.5 W in a TEM00 mode 1.1 times diffraction limited.