High-power Diode Laser Bars Research Articles

Reliability and degradation mechanisms of InGa(Al)As/GaAs DQW high-power diode lasers

Defects and degradation of InGa(Al)As/GaAs DQW diode laser bars mounted on copper micro-channel heat sinks were investigated. The analytical techniques used are optical microscopy and scanning electron microscopy. The high-power diode lasers were investigatively accompanied through the different phases of their setup process (i.e. mounting, characterization and burn-in). After the setup a long-term lifetest was performed. Changes in surface morphology in the facet area as well as changes in the threshold current, slope efficiency and emission spectrum are observed. Due to the degradation the threshold current increases and the slope efficiency decreases while the emission wavelengths are shifted to higher values showing a broadening of the spectrum. Formation of micro-cracks and alocations of crystalline areas within the facet area are observed. The influence of degradation on performance and life time of the high-power diode laser bars is discussed.

Intensification of heat transfer in high-power laser diode bars by means of porous metal heat-sink

To intensify a heat transfer in high-power emitters based on laser diode bars we propose the use of a heat sink from a porous permeable material cooled by a fluid flow [1-3]. The main advantage of this class of materials is the possibility of removing significant heat flows with compact heat sink. An analysis of the characteristic values of the thermal loads and their relations with the material and liquid parameters drawn from an one-dimensional model of stationary one-sided heat exchange shows the possibility of heat flow removal of more than 1.5 kW/cm 2 at room temperature in a liquid. Methods for improving the effectiveness of the strategy are considered.

Colorless gradient-index cylindrical lenses with high numerical apertures produced by silver-ion exchange

Colorless gradient-index cylindrical lenses with high numerical apertures in slabs 200-1000 µm thick have been fabricated by silver-sodium ion exchange in a specially developed glass. The lenses with numerical apertures of 0.6 are characterized by index profiles and by spherical and chromatic aberration. On-axis focusing properties and the application to the collimation of high-power laser diode bars are discussed.

Output beam characteristics of high-power continuous-wave diode laser bars

The output beam characteristics of individual emitting structures are investigated for high-power cw diode laser bars of two types, namely a five-zone design and a 48-widestripe design. The far-field intensity distribution, output power, and wavelength were recorded as a function of the location of the emitting structure within the diode bar and correlated to the emission of the entire diode. Significant variation of the output properties over the extent of the diode lasers was found. Several diodes of each type were examined and the results compared.

Dynamic light scattering in the vitreous: performance of the single-mode fiber technique

The output beam characteristics of individual emitting structures are investigated for high-power cw diode laser bars of two types, namely a five-zone design and a 48-widestripe design. The far-field intensity distribution, output power, and wavelength were recorded as a function of the location of the emitting structure within the diode bar and correlated to the emission of the entire diode. Significant variation of the output properties over the extent of the diode lasers was found. Several diodes of each type were examined and the results compared.

Lasing properties of diode-laser-pumped Nd:KGW

The laser performance of Nd:KGW (neodymium-doped potassium gadolinium tungstate) end pumped by cw or quasi-cw high-power diode laser bars is studied and compared to Nd:YAG. In cw operation, thermal problems in Nd:KGW are quite important, whereas in quasi-cw operation, the optical and slope efficiencies attained with Nd:KGW are clearly better than with Nd:YAG.

High-intensity rectangular fiber-coupled diode laser array for solid-state laser pumping

A high-power diode laser bar coupling scheme with rectangular optical fibers is proposed, and the concept is tested on a scale version: an individual diode laser array and a single rectangular fiber. 60% of the power from a 1-W cw, 213-µm-wide 20-stripe diode array is coupled into a 216 µm × 28 µm 0.66 numerical aperture optical fiber, which produces intensities at the fiber output face of 9.9 kW cm(-2). The elliptical, dual-lobed far-field intensity pattern of the diode laser output, with divergence of 39° × 13° FWHM is converted on passing through the fiber into a single-lobed, nearly circular pattern with a FWHM divergence of 21° × 22°. The beam quality is reduced by only a factor of 30 when this coupling method is used. Alignment tolerances in the three planes of movement are measured and found to be in excess of 10 µm.