High power compact UV lasers with diffraction limited beam are required for industrial applications such as laser direct
imaging, wafer inspection or photo voltaic. By use of a Nd:YVO4 oscillator with a Saturable Bragg Reflector and a
single pass amplifier, 73 W output power in mode-locked operation at 80 MHz have been generated with high peak
power. By use of two LBO crystals a third harmonic output power of 35 W at 355 nm was demonstrated with an M2
value of <1.2. This corresponds to 48% nonlinear conversion efficiency.
Pulsed lasers with high average output power in the green spectral range are of interest for laser annealing applications.
In this paper an efficient pulsed diode-pumped Yb:YAG thin disk laser with intracavity frequency doubling is
presented. The Yb:YAG laser crystal disk has a thickness of 180 &mgr;m and a diameter of 10 mm and is pumped by a laser
diode stack at a wavelength of 938 nm. The disk is soldered to a water-cooled Cu-W heat sink and exhibits a nearly
perfect spherical surface. The folded resonator is dynamically stable with a beam factor of M2 = 5 and which is matched
to the requirements of the application. Acousto-optical and electro-optical switches are investigated to operate the laser
in the cavity-dumping mode. An average output power of 150 W at 515 nm is achieved. The diode-to-green efficiency
is about 28%. A critically phase matched LBO crystal is used for intracavity second harmonic generation. We show that
stable pulsing is obtained from 10 kHz to 150 kHz. The pulse-width can be varied from 200 ns to 700 ns by control of
the low-loss period of the switching element. The experimental results are compared with theoretical modeling of the
system and first application results are discussed.
A novel Nd:YAG micro slab laser amplifier is presented and experimental results for Q-switched operation are discussed. The laser crystals are directly pumped by conduction cooled laser diodes with an ISO/FDIS 17526 extrapolated standard lifetime above 30,000 h. The diffraction limited cw output power of the amplifier is 50 W. In pulsed operation, the laser shows a pulse energy of 4.65 mJ and a pulse length of 12 ns FWHM at a pulse repetition rate of 6 kHz. Beam quality has been measured to be M2 = 1.1. The beam pointing stability was 10 μrad and the pulse-to-pulse stability was 1.5% rms in a linear-polarised beam.
In this paper recent research on high-power laser displays for large display applications is reported. We discuss our compact high-power red-green-blue laser system for use as a light source based on a passively mode-locked solid-state laser with an optical parametric oscillator and sum- frequency mixing with very high efficiency and 19 W of white light. Concepts for power scaling to 35 W of white laser light are presented. A direct laser beam scanning technology is described which results in high resolution displays. Multi channel concepts as required in flight simulator applications are discussed. The laser light is modulated at 32 MHz using acousto-optic modulators with 75% diffraction efficiency. A high contrast ratio of 1:150,000 is achieved and has been successfully tested in novel planetarium applications. We also present performance and lifetime data of initial commercial laser display systems in the field.
JENOPTIK Laser, Optik, Systeme GmbH has developed for the first industrial all-solid-state Red-Green-Blue laser system for large image projection systems. Compact in design (0.75 m3, 180 kg, 3 kW power consumption), the system consists of a modelocked oscillator amplifier subsystem with 7 ps pulse duration and 85 MHz pulse repetition frequency, an optical parametric oscillator, and several non-linear stages to generate radiation at 628 nm, 532 nm and 446 nm with an average output power above 18 W. Each of the three colors is modulated with the video signal in a contrast ratio of 1000:1 and coupled into a common low order multi mode fiber. The system architecture relies on efficiently manufacturable components. With the help of FEM analysis, new engineering design principles and subsequent climatic and mechanical tests, a length stability below 50 micrometers and an angle stability below 10 (mu) rad have been achieved. The design includes efficient laser diodes with integrated thermo- electric cooler and a lifetime above 10000 hours. The stability of the output power is better than +/- 2% in a temperature range from 5 degree(s)C to 40 degree(s)C. The system operates reliably for more than 10000 hours under field conditions. The design is based (among others) on work by Laser-Display-Technologie KG and the University of Kaiserslautern.
Room temperature operation of a Nd:YVO4 thin disk laser with excellent beam quality is reported. Pumping by a fiber coupled diode laser with 10 W at the fiber end yields a continuous wave output power of 4.4 W at 1064 nm. The corresponding total optical efficiency is 44% and the average slope efficiency is 46%. For higher pump powers, a maximum output power of 13.7 W was achieved in a near diffraction limited beam.
The use of a cw diode-pumped Nd:YAG rod laser for industrial applications is investigated. The laser is pumped by water cooled high-power laser diode bars in a star-shaped transverse pumping configuration. An output power of 75 W is achieved with 240 W of pumping power, corresponding to 40% slope efficiency. Thermal lensing and birefringence of a laser rod with a diameter of 4 mm is investigated. High fundamental transverse mode and second harmonic efficiency is reported. A simple scalable concept for lasers with 10 W to 100 W output power is presented.
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