Andreas Diening

Semiconductor-laser-pumped high-power upconversion laser

A high-power optically pumped semiconductor laser operating around 970 nm has been used as a pumping source for an upconversion laser based on an Er3+ doped LiLuF4 crystal. Nearly 0.5 W of continuous wave (cw) output power and 0.8 W peak power at a 50% pump duty cycle could be achieved at a wavelength of 552 nm. This represents the highest output power from a room temperature upconversion laser ever reported. Laser threshold and slope efficiency were measured to be below 100 mW of absorbed pump power and 30%, respectively. This experiment could be an important step along the route to realizing a compact and efficient upconversion laser emitting in the Watt level power regime.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF(4) and Pr:BaY(2)F(8) was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB(3)O(5) as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF(4) and Pr:BaY(2)F(8), respectively.

Highly Stable UV-Mode-Locked Lasers with an Output Power of 35 W at 355 nm

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.

High average power 258nm generation in a nanosecond fiber MOPA system

Quasi-cw UV light sources are of interest for replacing frequency-doubled Ar-Ion lasers in several applications. Our target application in semiconductor inspection requires a narrow bandwidth cw or quasi-cw source at 258nm, which cannot be achieved by frequency converting the output of a (modelocked) Neodymium-based laser. We developed a fiber MOPA system which operates at a high repetition rate of 5MHz and generates 1ns long pulses. The system consists of a low power oscillator and four consecutive amplifier stages. which boost the average power to 40W at 1031nm. The IR output of the fiber system is frequency doubled and quadrupled using LBO and CLBO crystals for SHG and FHG, respectively. We achieved SHG conversion efficiencies of up to 82% and a UV power of up to 14W.

Frequency-tripled and quadrupled air-cooled modelocked Nd:YVO 4 laser with greater 6W average power

Compact DPSS UV sources are of interest for replacing Ar-Ion lasers in applications that require cw or quasi-cw laser radiation. One way to generate UV light at 355nm and 266nm is by modelocking an IR Nd:YVO4 laser and converting the ps pulses into the second, third, and fourth harmonic. The mechanism of choice is passive modelocking using a Saturable Bragg Reflector (SBR). We have developed an air-cooled system capable of UV output powers in excess of 6W. Laser performance as well as lifetime data will be presented for wavelengths at 355nm and 266nm.

AlGaAs-based optically pumped semiconductor lasers

The most technologically mature optically pumped semiconductor lasers (OPSL) are based on InGaAs quantum wells (QW) for emission in the 900-1200 nm range. The low wavelength boundary is set by both the bandgap of InGaAs and the most common pump wavelength of 808 nm. To extend the wavelength coverage into 700 – 900 nm, a different QW system and a different pump wavelength are needed. In this work, we present the progress and result in the development of AlGaAs-based OPSL.

Gain modeling and thermal management of optically pumped semiconductor lasers

Optically pumped semiconductor lasers (OPSL) have been replacing legacy gas lasers and solid state lasers for over a decade, due to their superior properties such as compactness, high efficiency, low noise, wavelength scalability, and power scalability. It has wide applications in life sciences, medical therapeutics, light show, and other scientific researches. In this work, we present a gain model and couple it to the thermal management of high power OPSL.

High power upconversion laser under OPS pumping

Using an optically pumped semiconductor laser as pumping source nearly 0.5 W cw and 0.8 W maximum output at 50% pump duty cycle are achieved from a room temperature Er3+:LiLuF4 upconversion laser at 552 nm.

Semiconductor laser pumping of a continuous-wave Pr/sup 3+/:LiYF/sub 4/ laser emitting at several wavelengths

We report continuous-wave laser operation of Pr/sup 3+/:LiYF/sub 4/ at 639.7 nm, 607.3 nm, and 522.6 nm using a frequency-doubled optically pumped semiconductor laser as pump source. Furthermore, a red continuous-wave Pr/sup 3+/:LiYF/sub 4/ laser was realized under GaN laser diode pumping.

Investigation of the power limiting factors for a Q-switched 2.0 /spl mu/m Tm:YAG laser

Laser applications used for atmospheric measurements demand eye-safe wavelengths of high atmospheric transmission. These requests can be fulfilled by a Tm:YAG laser using the ground state laser transition at 2.0 /spl mu/m. In many cases, e.g. LIDAR systems, Q-switched lasers are employed in order to obtain high intensities and runtime information for long distance measurements.