Brian O. Faircloth

Requirements for long-life microchannel coolers for direct diode laser systems

High power direct diode lasers have made significant impact in the industry as an alternative heat source for material processing. In order, to be readily adopted by the industry they have to show >99% uptimes. One of the much-discussed issues associated with copper based micro channel coolers has been the lifetime of the micro channel cooler in High Power Direct Diode Laser (HPDDL) systems. HPDDLs with micro channel coolers have shown long life in some installations, but have shown to work only a few thousands of hours in others. These have been attributed to the erosion, corrosion, or clogging of the micro channel coolers. This paper will describe the proper design of the water system for use with a micro channel cooled laser system. This paper focuses on the water chemistry and its impact on erosion and corrosion of the copper based micro channel coolers. Using previously reported data; we will give erosion rates for different water chemistries.

900-mW high brightness buried ridge lasers by selective area epitaxy

A study has been made of high power single lateral mode buried ridge lasers fabricated by selective area epitaxy. Several ridge thicknesses have been evaluated simultaneously in a single fabrication run. These lasers operate purely in the fundamental mode to output powers in excess of 450 mW, after which they are subject to beam steering or higher order mode operation. For weakly guided lasers, the output remains in a narrow lobe [full-width at half-maximum (FWHM)] = 4/spl deg/-6/spl deg/, stable at a given current value, up to output powers of 900 mW in CW tests.

Development of high power high brightness fiber coupled diode laser systems

The improved wall-plug efficiency and minimal maintenance of diode laser systems over Nd:YAG and CO2 lasers has been admired by many manufacturers. Until recently, most diode laser systems could not compete at high-power levels or with the same beam quality. Nuvonyx reports the design and initial development of a diode laser system that delivers 2000 W from a 600 μm core fiber with a 0.22 NA. This system is suitable as a stand-alone industrial direct diode laser system or as a multi-kilowatt fiber laser pump source. The development of a high brightness bar technology by Nuvonyx and its collaborators along with the use of polarization beam combining is the core of this laser system. Each emitter operates with a single lateral mode resulting in a high brightness bar that outputs up to 50 W. The wavelength of the laser is centered at 975 nm with a width of less than ± 3 nm. The demonstration of this laser system defines a clear path to scale this technology to 4000 W.

Novel design for high-power single-lateral-mode lasers

A new laser design for single-mode high-power applications is reported. The waveguide is a laterally flaring and transversely tapering GaAs buried ridge fabricated by selective area epitaxy. Single-lateral-mode powers of 200 mW were achieved.

650-mW single lateral mode power from tapered and flared buried ridge laser

Very high single lateral mode output powers of 650 mW are obtained from a diode laser with a unique waveguide design. The waveguide flares in the lateral dimension to create a larger spot size on the facet and simultaneously tapers in the transverse dimension to inhibit propagation of higher order lateral modes. These GaAs buried ridge devices are fabricated by selective area epitaxy.

Development of high-brightness high-power fiber laser pump sources

High power fiber lasers have strong potential for use in both commercial and military applications. Improved wall plug efficiency over Nd:YAG and CO2 lasers combined with up to a 10-fold improvement in beam quality, make fiber lasers extremely attractive for industrial applications such as welding and cutting. In military applications, fiber lasers offer a simplified logistic train, a deep magazine limited only by electric power, and a compact footprint, allowing theater defense and self-protection of combat platforms with speed of light engagement and flexible response. Commercial viability of these systems, however, is limited by the availability of compact, cost effective, and reliable diode laser pump sources in the multi-kilowatt regime. The relatively low brightness of diode laser sources has complicated the task of building high power pumps at a reasonable cost. In response to this need, Nuvonyx, Inc. in conjunction with the University of Illinois at Urbana-Champaign, has been developing a new technology for producing high power, single lateral mode devices which do not suffer form the instabilities mentioned above. The waveguide consists of a narrow section, approximately 2 μm wide, which flares to approximately 12 μm wide at the output facet. The flaring of the waveguide increases the gain volume and reduces the optical power density at the facet allowing for higher output power capability. The index guide is defined using an epitaxial process which allows the confinement of the mode to be reduced as the width of the guide expands. Thus, the mode is confined in a single mode waveguide throughout the cavity maintaining stability of the mode to the emitting facet. In November 2002, Nuvonyx, Inc. was awarded a contract with the Air Force Research Lab, Kirtland AFB, Albuquerque, NM, to transition these devices to production quality for use in high-power fiber laser pumps. Partnered with Alfalight, Inc. and the University of Illinois, we have begun initial device fabrication and testing of these devices with the goal of achieving production quality, long lifetime, 50W bars exhibiting stable single lateral mode operation. The goal of this program is to ultimately deliver multi-kilowatt fiber laser pumps and direct diode laser systems for both military and industrial applications. Currently, we are in the process of developing the necessary device growth, processing, and packaging technologies. Several devices have been made and tested yielding promising results. In this paper, we present some of these results along with an examination of the system implications and capabilities of these devices.

A novel separate lateral confinement quantum-well heterostructure laser

Utilizing separate structures for the lateral confinement of the optical mode and injected carriers, we optimize the overlap of the optical mode with the gain to demonstrate lasers with lower threshold currents than standard ridge waveguide lasers.

DIRECT DIODE LASER SYSTEM REQUIREMENTS FOR LONG LIFE MICRO CHANNEL COOLERS

High power direct diode lasers have made significant impact in the industry as an alternative heat source for material processing. In order, to be readily adopted by the industry they have to show >99% uptimes. One of the much-discussed issues associated with copper based micro channel coolers has been the lifetime of the micro channel cooler in High Power Direct Diode Laser (HPDDL) systems. HPDDLs with micro channel coolers have shown long life in some installations, but have shown to work only a few thousands of hours in others. These have been attributed to the erosion, corrosion, or clogging of the micro channel coolers. This paper will describe the proper design of the water system for use with a micro channel cooled laser system. This paper focuses on the water chemistry and its impact on erosion and corrosion of the copper based micro channel coolers. Using previously reported data; we will give erosion rates for different water chemistries.High power direct diode lasers have made significant impact in the industry as an alternative heat source for material processing. In order, to be readily adopted by the industry they have to show >99% uptimes. One of the much-discussed issues associated with copper based micro channel coolers has been the lifetime of the micro channel cooler in High Power Direct Diode Laser (HPDDL) systems. HPDDLs with micro channel coolers have shown long life in some installations, but have shown to work only a few thousands of hours in others. These have been attributed to the erosion, corrosion, or clogging of the micro channel coolers. This paper will describe the proper design of the water system for use with a micro channel cooled laser system. This paper focuses on the water chemistry and its impact on erosion and corrosion of the copper based micro channel coolers. Using previously reported data; we will give erosion rates for different water chemistries.