Diode
stack
Beam
shaping
Slab
Output
beam
Polarizer
Modulator
M2
Stable
Unstable
M1
Line shaped top-hat
Tailored beam profles
Rectangular top-hat
Circular Gaussian Square top-hat
22 Industrial Laser Solutions MARCH/APRIL 2017 www.industrial-lasers.com
Micromachining applications for
LASER TECHNOLOGY ALLOWS FOR FLEXIBLE BEAM
PROFILES TO SERVE MANY MICROMACHINING UTILITIES
KEMING DU, DAIJUN LI, and SHIZHOU XIAO
Compact, high-power, high- beam-quality polarized lasers are in demand for applications in industries and research such as micromachining and efficient harmonic generation. Through an optimal combination of crystal shape, cooling, and resonator design, lasers such as the
InnoSlab lasers and amplifiers possess short pulse duration,
high peak power, high pulse repetition rate, and high beam
quality at high average power. They also offer flexibility in
beam profile, from circular beam profile through line-shaped
one- and two-dimensional top hat beam profiles with rectangular cross-section to serve a variety of unique applications with added value.
Short-pulsed lasers
To get high output power at high beam
quality and at low cost, an innovative slab
laser concept (InnoSlab) was proposed
(FIGURE 1). The diodes are coupled in with
their line-shape beam profiles through the
resonator mirror. Then, a thin active crystal is partially pumped by the diodes to a
thin crystal that is conductively cooled through both large side
surfaces, leading to a one-dimensional heat flow perpendicular to the direction of the laser beam. This, in turn, leads to a
controllable thermal cylindrical lensing, with no depolarization
and no phase distortion.
In this setup, there is a polarizer and a
Pockels cell for generating Q-switched
pulses. The laser beam traverses the
resonator several times and may be
decoupled over the edge of the mir-
ror, which may remind some of the old
CO2 slab laser.
The entire resonator is shorter than 10cm, which leads to
pulse length below 10ns and high peak power. Also, the beam
profile can be easily changed from circular Gaussian to line-shaped top-hat or two-dimensional top-hat, which is the basis
for optimal industrial application solutions with tailored beam
profiles (FIGURE 2).
The parameters of commercially available Q-switched
InnoSlab lasers include:
• Pulse energy up to 50mJ;
• Beam quality of M2 < 1. 3;
• Pulse length down to 4ns;
• Peak power up to 6MW;
• Pulse repetition rate up to 100kHz;
• Average power up to 600W; and
• Availability in 1064, 532, 355, and 266nm wavelengths.
FIGURE 1.
Schematic of
an end-pumped
slab and
electro-optically
Q-switched
InnoSlab laser
with hybrid
resonator.
FIGURE 2.
Tailorable beam
profiles of an
electro-optically
Q-switched
InnoSlab laser.
