Eli Weiss

Recent advances in optically pumped semiconductor lasers

Optically pumped semiconductor lasers offer significant advantages with respect to all traditional diode-pumped solid state lasers (including fiber lasers) in regards to wavelength flexibility, broad pump tolerance, efficient spectral and spatial brightness conversion and high power scaling. In this talk we will describe our recent progress in the lab and applying this technology to commercial systems. Results include diversified wavelengths from 460 to 570nm, power scaling to >60W of CW 532nm, and the launch of a low cost 5W CW visible source for forensic applications.

Blue and green optically pumped semiconductor lasers for display

We discuss a compact RGB source with ouput power of several watts per color consisting of a red (638 nm) diode and OPS lasers with blue (460 nm) and green (530) nm output. Suitability for display applications is shown by replacing the lamp of a standard Rear Projection TV.

Power-scaling of optically pumped semiconductor lasers

Power-scaling of optically pumped semiconductor lasers (OPSLs) using a resonator with multiple OPS chips is demonstrated. With a 3-chip cavity and intra-cavity second harmonic generation, we obtain 55W of TEM00 mode output at 532 nm and 66 W in multi-transverse mode. In addition, we describe the design of a periodic dynamically stable resonator that allows scaling to more than 4 chips and demonstrate that the output power scales with the number of chips in the cavity.

New wavelengths in the yellow-orange range between 545 nm and 580 nm generated by an intracavity frequency-doubled optically pumped semiconductor laser

Diode pumped frequency doubled Optically Pumped Semiconductor lasers (OPS), has proven to be a reliable source of laser radiation in the blue and blue-green spectral range between 460 nm and 505 nm. One of the major advantages of using semiconductors as gain medium is the possibility to tailor the wavelength of the semiconductor material by means of band gap engineering. Here we report about new OPS material enabling the wavelength region between 1090 nm and 1160 nm which allows the realization of frequency doubled lasers between 545 nm and 580 nm. Laser results up to several Watts in the yellow spectral range as well as efficiency and lifetime data will be presented.

Optically pumped semiconductor lasers: a new reliable technique for realizing highly efficient visible lasers

Optically pumped semiconductor material is a complimentary gain medium for rare earth or transition metal doped crystals. The design of several compositions based on GaAs allows the realization of a wavelength range between 710nm and 1180nm. This can be diode pumped and frequency doubled to cover the near UV up to the yellow spectral range. The power is scaleable and we have realized several Watts at 488nm and 460nm. Experimental results will be presented and discussed as well as reliability data to show that this technology has ripened for industrial applications.

915 nm laser bar-based high-performance sources for fiber laser pumping

Fiber lasers have made significant progress in terms of power output, beam quality and operational robustness over the past few years. Key to this progress has been advances in two technologies - fiber technology and 9xx nm diode laser pump technology based on single emitters. We present the operational characteristics of our new high brightness 9xx nm fiber laser pump sources based on diode laser bars and diode laser bar arrays and discuss the design trade offs involved for realization of devices focused on this application. These trade offs include achieving the lowest slow axis divergence while maintaining high wall plug efficiency and minimizing facet power density to maximize reliability.

High-efficiency and high-reliability 9xx-nm bars and fiber-coupled devices at Coherent

Ongoing optimization of epitaxial design within Coherent device engineering has led to a family of high power-conversion-efficiency (PCE) products on conductively cooled packages (CCP) and fiber array packages (FAP). At a 25°C heat sink temperature, the PCE was measured at 71.5% with 75W CW output power on 30% fill-factor (FF) bars with passive cooling. At heat sink temperatures as high as 60°C the PCE of these bars is still maintained above 60%. Powered by such high efficiency 9xx nm diodes, Coherent FAP products have consistently exceeded 55% PCE up to 50W power levels, with 62% PCE demonstrated out of the fiber. High linear-power-density (LPD) operation of 100μm x 7-emitter bars at LPD = 80 mW/μm was also demonstrated. Bars with 7-emitter were measured up to 140W QCW power before catastrophic optical mirror damage (COMD) occurred, which corresponds to a COMD value of 200mW/μm or 2D facet power density of 29.4 MW/cm2. Leveraging these improvements has enabled high power FAPs with >90W CW from an 800μm-diameter fiber bundle. Extensive reliability testing has already accumulated 400,000 total real-time device hours at a variety of accelerated and non-accelerated operating conditions. A random failure rate <0.5% per kilo-hours and gradual degradation rate <0.4% per kilo-hours have been observed. For a 30% FF 50W CW 9xx nm bar, this equates to >30,000 hours of median lifetime at a 90% confidence level. More optimized 30% FF 9xx nm bars are under development for power outputs up to 80W CW with extrapolated median lifetimes greater than 20,000 hours.

Optically pumped semiconductor lasers at 505 nm in the power range above 100 mW

Lasers based on optically pumped semiconductors (OPS) offer unique capabilities in both wavelength tailoring and power scaling compared to traditional solid-state lasers. In particular, these lasers can be designed in wavelength to realize for instance 505nm, which enables excitation of two fluorescent dye chemistry sets originally established by 488 and 514 nm legacy argon lasers. Highly efficient intra cavity frequency doubling of an 1010nm OPS yields over 100 mW of output power at 505 nm. In this paper we will present a brief background on OPS technology. We will then discuss specifics of the 505 nm laser and present both performance and reliability data for this laser.

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.

Advances in optically pumped semiconductor lasers for blue emission under frequency doubling

Optically pumped semiconductor lasers (OPSL) offer the advantage of excellent beam quality, wavelength agility, and high power scaling capability. In this talk we will present our recent progress of high-power, 920nm OPSLs frequency doubled to 460nm for lightshow applications. Fundamental challenges and mitigations are revealed through electrical, optical, thermal, and mechanical modeling. Results also include beam quality enhancement in addressing the competition from diode lasers.