Diode Bars Research Articles

Efficient high-power Tm:YAG laser at 2 μm, end-pumped by a diode bar

Efficient, room-temperature operation of a Tm:YAG laser, end-pumped by the re-shaped output beam from a 20 W diode bar, is reported. At a rod mount temperature of 20°C and with 13.5 W of diode pump power incident on the Tm:YAG rod we obtained 4.1 W of output at 2.013 μm in a near-diffraction-limited beam with corresponding M 2 values in orthogonal planes of 1.4 and 1.2. The prospects for further power-scaling are discussed.

Diode-bar end-pumped high-power Nd:Y_3Al_5O_12 planar waveguide laser

A compact high-power planar waveguide laser end pumped by a diode-bar is reported. The waveguide was fabricated by liquid-phase epitaxy and had an 80-microm-thick, 1.5-at. % Nd:Y(3)Al(5)O(12) core on a Y(3)Al(5)O(12) substrate. A maximum output power of 6.2 W was obtained at 1.064 microm when the device was pumped with a 20-W diode bar operating near 807 nm, giving an overall optical-to-optical conversion efficiency of 31%. The total device length was 5 cm.

Beam-Shaping Techniques and Focusing Performance for a Diode Bar Used as a Pumping Source.

The end-pumping scheme in diode-pumped solid-state lasers has promised the achivement of high opticalconversion efficiency. However, in the case of using high-power diode bars as a pumping sourse, it is difficultto focuse the small-diamater beams required for an end-pumping laser due to the poor beam quality of thediode bar. This paper reviews beam-shaping techniques to improve the quality of the diode-bar and to achievea suitably focused spot size for end pumping.

Systematic Approach to the Synthesis of Organic-Inorganic Nanocomposites Based on Dmta Measurements and Ir Spectroscopy

AbstractSol-gel derived organic-inorganic hybrid materials with potential fields of application as refractive optical components for example laser diode bars and ophthalmic lenses are presented. The main components of the hybrid materials under investigation are precondensed methacryloxypropyltrimethoxysilane (MPTS, denoted: M) with an organically polymerisable methacrylic functionality and tetraethyleneglycoldimethacrylate (TEGDMA, denoted: T) as crosslinking organic monomer with two polymerisable double bonds. The molar ratios of the components ranged from M/T 10/90 up to M/T 70/30. The polymer derived from pure TEGDMA (M/T 0/100) served as a reference material. In addition to this nanoscaled TiO2 particles (5 wt.% and 10 wt.%) were incorporated in the organic-inorganic M/T 30/70 matrix to increase the refractive index of the resulting nanocomposites. For the preparation of the different systems, precondensed MPTS was mixed with TEGDMA, the nanoparticulate titania sol (when used), an appropriate photoinitiator and a thermoinitiator. The reaction mixtures were polymerised photochemically and/or thermally. The propagation of the free radical polymerisation reaction after photopolymerisation and subsequent thermal curing was followed by IR-spectroscopy, showing that the degree of double bond conversion is strongly increased by the thermal curing step. Incorporation of increasing amounts of TiO2 nanoparticles resulted in reduction of the double bond conversion compared to the corresponding unfilled system. The homogeneous dispersion of the titania particles in the completely cured M/T 30/70 matrix could be manifested by high resolution transmission electron microscopy (HTEM). The thermomechanical properties of the completely cured nanocomposites were monitored by dynamic mechanical thermal analysis (DMTA) showing a strong dependence on composition.

High energy erbium laser end-pumped by a laser diode bar array coupled to a Nonimaging Optic Concentrator

A high energy Er 3+, Yb 3+:glass laser end pumped by a laser diode array emitting at 980 nm coupled to a Nonimaging Optic Concentrator (NOC) is demonstrated. Energy up to 100 mJ and a 16% slope efficiency are achieved in a plano-plano laser cavity. The energy transfer coefficient from Yb 3+ to Er 3+ is estimated by a new method.

High-power operation of InGaAsP-InP laser diode array at 1.73 /spl mu/m

InGaAsP-InP laser bars with an emission wavelength of 1.73 μm have been fabricated using compressively strained multiple-quantum-well (MQW) separate-confinement heterostructures (SCH). One-cm-wide, 0.7-fill-factor, diode bars are bonded onto Si microchannel heatsinks and stacked into a two-dimensional (2-D) laser array, 16 W of continuous-wave (CW) power was produced from a 1-cm bar and 200 W of peak power was generated from a 10-bar array with an emitting aperture of 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Yb^3+-ring-doped fiber for high-energy pulse amplification

We report what is to our knowledge the first demonstration of pulse amplification in a cw-pumped fiber in which the doped gain medium has a ring shape surrounding a single-mode core. For a given pump power, ring doping reduces the gain and hence the power lost to amplified spontaneous emission. Thereby, a significantly larger amount of energy can be stored in the amplifier. Using an Yb(3+)-doped fiber pumped by 540 mW of power at 1000 nm, we measured 69 microJ of extracted pulse energy at 1047 nm, the highest value reported to date from a single-mode Yb(3+)-doped fiber. We predict that a fiber cladding pumped by a diode bar can produce pulse energies in excess of 1 mJ.

High-power single-frequency operation, at 1064 nm and 1061.4 nm of a Nd:YAG ring laser end-pumped by a beam-shaped diode bar

A Nd:YAG laser having a ring configuration, with a Faraday rotator to provide unidirectional operation has been end-pumped by a single 20 W diode bar equipped with a beam-shaper. A single-frequency TEM 00 output of 5.4 W is achieved at 1064 nm. Using a thin intracavity etalon for wavelength selection, a single-frequency output of 4.2 W is obtained on the 1061.4 nm transition.

Laser microsoldering of tape‐automated bonding leads using an Nd:YAG laser end‐pumped by a laser diode bar with gradient index lens array coupling

A laser soldering of tape-automated bonding (TAB) leads is tried with a diode-pumped Nd:YAG laser. A 15-W laser diode bar, a multistripe monolithic laser diode array, is used to end-pump Nd:YAG. Twelve beams emitted from 12 stripes, center-to-center spaced 800 mm, of a 1-cm linear diode array were collimated by a lens array of width 1 cm, consisting of 12 gradient-index (GRIN) lenses with 800-mm width, to pump the Nd:YAG facet. The maximum Nd:YAG output power at 1064 nm of 6.3 W is obtained in cw operation. The Nd:YAG laser beam is focused to a spot with a FWHM diameter of 112337 mm. A TAB device with 215-mm-width leads, center-to-center spaced 430 mm, is success- fully soldered by 98-ms irradiation of the laser power of 5.8 W/lead. Soldering is tried with a fiber-coupled Nd:YAG output as well. © 1996 Society of Photo-Optical Instrumentation Engineers.

3 W of single-frequency output at 532 nm by intracavity frequency doubling of a diode-bar-pumped Nd:YAG ring laser

A beam-shaped 20-W diode bar has longitudinally pumped a Nd:YAG laser in a ring configuration. Unidirectional single-frequency operation is enforced by a Faraday rotator. Intracavity frequency doubling with a KTP crystal has produced 3 W of stable single-frequency TEM00 output at 532 nm.

Room-temperature diode-bar-pumped Nd:YAG laser at 946 nm

Efficient, high-power operation of a diode-bar-pumped Nd:YAG laser on the quasi-three-level transition at 946 nm is reported. Longitudinal pumping of a simple folded cavity by a 20-W diode bar, with a two-mirror beam shaper used to reformat the bar's output, yields a continuous-wave output power at room temperature of ~3 W in a 1.5-times diffraction-limited beam for 13.6 W of incident pump power. The corresponding optical slope efficiency was approximately 33%.

Face pumping of thin, solid-state slab lasers with laser diodes

A new technique for face pumping of slab lasers uses transfer of light from 10 quasi-cw laser diode bars through a slotted mirror into a rectangular, highly ref lective pump chamber, giving efficient multipass pumping of a thin Nd:glass slab laser. A slope efficiency of 28% and a maximum pulse energy of 65 mJ have been obtained, and gain and loss measurements with thickness t = 0.45-1.04 mm have confirmed the 1/t scaling of gain in thin slabs and the high efficiency of pump light transfer.

Two-mirror beam-shaping technique for high-power diode bars

A simple beam-shaping technique is described whereby the output from a highly asymmetric non-diffractionlimited laser source, such as a high-power diode bar, can be reconfigured with nearly equal beam-quality factors in orthogonal planes and without a significant reduction in brightness. Using this technique, in conjunction with conventional lenses, we have focused the output from a 20-W cw diode bar to a very intense, nearly circular spot with a 1/e(2) beam diameter of ~100 microm and a far-field beam divergence (half-angle) of ~0.2 rad.

Diode pumped CW Nd:YAG laser operating at 938.5nm

Efficient operation of a Nd:YAG laser on the quasi-three-level transition at 938.5 nm, end-pumped by a 20 W diode bar is reported. For the maximum available incident power of 13.6 W we have obtained a CW laser output at room temperature of 2.0 W in a near diffraction-limited TEM00 beam.

Lasers for materials processing: specifications and trends

An overview is given of the types of lasers dominating the field of laser materials processing. The most prominent lasers in this field are the CO2 and the Nd: YAG laser. The domain of CO2 lasers is applications which demand high laser powers (up to 30 kW are available at present), whereas the domain of Nd:YAG lasers is micro-machining applications. In the kilowatt range of laser output power, the two types of lasers are in competition. New diffusion-cooled CO2 laser systems are capable of output laser powers of several kilowatts, with good beam qualities, while still being quite compact. The output power and beam quality of Nd:YAG lasers has been improved in recent years, so that Nd:YAG lasers are now an alternative to CO2 lasers even in the kilowatt range. This is especially true for applications that demand optical fibre transmission of the laser beam, which is possible with Nd:YAG laser light but not with the longerwavelength light emitted by CO2 lasers. The main problem in solid-state lasers such as Nd:YAG is the thermal lensing effect and damage due to thermal stresses. In order to reduce thermal loading, cooling has to be enhanced. Several alternative geometries have been proposed to reduce thermal loading and, by this, thermal lensing effects. There are now slab and tube geometries which allow much higher output powers than the conventionally used laser rods. A very new scheme proposes a thin slab whose cooled side is also used as one of the laser mirrors, so that thermal gradients occur mainly in the direction of the beam propagation and not perpendicular to it, as is the case in the other geometries. As well as CO2 and Nd:YAG lasers, semiconductor laser diodes are very promising for direct use of the emitted light or as pump sources for Nd:YAG and other solid-state lasers. When packaging together thousands of single laser diodes, output powers of several kilowatts can be realized. Major problems are collimation of the highly divergent laser beams and cooling of the laser diode bars.

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.

Semimonolithic Nd:YAG ring resonator for generating cw single-frequency output at 106 μm

We report 2.1 W of unidirectional single-frequency laser output from a novel Nd:YAG ring laser longitudinally pumped by a laser diode bar. The resonator requires only a single discrete optic and magnet, in addition to the laser medium, for stable multiwatt single-frequency operation. Undoped YAG is diffusion bonded to the Nd:YAG laser crystal at the pump face to eliminate residual spatial hole burning and improve thermal conductivity. This new laser design can be scaled to higher powers through more facile diode access and is useful for cw intracavity doubling.

High-power continuous wave 690 nm AlGaInP laser-diode arrays

High-power diode laser arrays emitting at 690 nm have been developed for solid-state laser pumping. The laser diode bars (fill factor ≊0.7) have been fabricated from single quantum well AlGaInP-based heterostructures. Using silicon microchannel heatsinks, a record high 360 W/cm2 per emitting aperture is achieved under continuous wave operation.