High power diode laser arrays

Recent progress in the development of high-power diode laser arrays for solid-state laser pumping is detailed. Advances in available wavelength, efficiency, temperature of operation, duty cycle of operation, and peak and average power levels or densities are described. A packaging architecture capable of addressing the broadest range of pump applications and designs in an economic manner is defined, and a range of such package designs is presented     

Thermal model of laser diode arrays

The analytical temperature profiles within the laser-diode-array heat sink are obtained using Green's functions. In the formulas, the temperature profiles are a function of the construction parameters, material data and supply power only. The influence of the array construction parameters on the maximal temperature increase in the heat sink is shown. The derived formulas enable thermal optimisation of the array.     

Monolithic serial InGaAs-GaAs-AlGaAs laser diode arrays

Top-contact monolithic serially-biased InGaAs-GaAs-AlGaAs (λ~0.93 μm) broad area strained-layer quantum well laser arrays have been fabricated on a semi-insulating GaAs substrate. The laser array consists of four individual laser diodes and operates up to 2.8 W at 3.6 A (supply limited) per uncoated facet under pulsed conditions (15 kHz, 2 μs). The threshold current is ~0.5 A, and the peak slope efficiency and the peak electrical-to-optical conversion efficiency of an individual laser element are ~0.53 W/A and 14%, respectively. The near-field intensity distribution is shown to be broad enough to fill the entire active region under the p-metal stripe (125 μm) of the individual laser diodes at high current levels     

Performance characteristics of high-brightness, CW, diode laser arrays

Recently developed, high-brightness diode laser arrays have been tested at 50°C at output powers of 0.5 W CW and 1.0W CW from 100?m- and 200?m-wide active regions, respectively. The extrapolated lifetimes at room temperature exceed 40000 h. The maximum CW power output prior to catastrophic degradation of the facets is 2.0 W for the 100?m device and greater than 3 W for the 200?m-aperture device.     

Analysis of injection-locked gain-guided diode laser arrays

A new model for injection-locked gain guided laser arrays is proposed. Diffraction-limited and single-lobe operation of injection-locked arrays is attributed to coherent summation of several transverse modes that are phase locked by injection. The model predicts far-field and near-field patterns, locking bandwidth, beam-steering properties, and locked output power. The effects of varying the master power, beam shape, position, and incidence angle on the slave array facet are also studied. Theoretical and experimental results are compared     

11 W quasi-CW monolithic laser diode arrays

An optical power of 11 W from one facet has been obtained from a 1 cm integrated GaAlAs laser array for 150 ?s is pulse widths (quasi-CW operation). The array consists of 20 tenstripe lasers spaced along the bar, employing about 20% of the facet length for active laser emission.     

Large laser diode arrays for high-duty-cycle operation

Large arrays stacked 3 cm high, consisting of 38 laser bars 1 cm wide, have been operated at 100 W of average power and 4.5% duty cycle (2400 W peak power) with excellent spectral characteristics. Operation consisted of a burst of 10 150 mu s pulses on a 1 ms period, with burst repetition rates of up to 30 Hz. Conventional operation with 200 and 1000 mu s pulse widths is also reported.<>     

Single-lobe `Y? coupled laser diode arrays

`Y? Coupled laser arrays have been fabricated with flared waveguides at the output facet to expand the near-field spot and increase the near-field fill factor to greater than 80%. The far-field radiation pattern is predominantly single-lobe, and power outputs of 150mW CW have been obtained with threshold currents as low as 130mA.     

High power, 60 W quasi-CW, visible laser diode arrays

Visible spectrum diode arrays have been fabricated from (Al/sub x/Ga/sub 1-x/)/sub 0.5/In/sub 0.5/P-Ga/sub 0.4/In/sub 0.6/P quantum well heterostructures operating to high output powers at wavelengths of approximately 690 nm. Bars 7.5 mm long with 110 mu m broad area emitting apertures on 125 mu m centers have reached quasi-CW output powers of 60 W.<>     

Time-resolved thermal crosstalk characterisation of laser diode arrays

Thermal crosstalk in a diode array has been investigated using a time-resolved technique. The transmission of a probe beam injected into any of the array diodes is measured while one of them is alternatively switched on and off. The dynamics of temperature evolution of each diode and the thermal crosstalk owing to lateral heat spreading are deduced from temperature-induced Fabry-Perot oscillations.     

Triggering GaAs lock-on switches with laser diode arrays

Progress toward the triggering of high-power photoconductive semiconductor switches (PCSSs) with laser diode arrays, is reported. An 850-W optical pulse from a laser diode array was used to trigger a 1.5-cm-long switch that delivered 8.5 MW to a 38.3-Ω load. Using 166-W arrays, it was possible to trigger a 2.5-mm-long switch delivering 1.2 MW with 600-ps rise-times at pulse repetition frequencies of 1 kHz. These 2.5-mm-long switches survived 10⁵ pulses at 1.0 MW levels. In single-pulse operation, up to 600 A was switched with laser diode arrays. The goal is to switch up to 5 kA in a single-shot mode and up to 100 MW repetitively at up to 10 kHz. At electric fields below 3 kV/cm GaAs switches are activated by creation of one electron-hole pair per photon. This linear mode demands high laser power and, after the light pulse, the carriers recombine in nanoseconds. At higher electric fields GaAs acts as a light-activated Zener diode. The laser light generates carriers as before, but the field induces gain such that the amount of light required to trigger the switch is reduced by a factor of up to 500. The gain continues until the field across the sample drops to a material-dependent lock-on field. The gain in the switch allows for the use of laser diodes     

Highly stable strained layer leaky-mode diode laser arrays

A simple fabrication process for InGaAs strained quantum well leaky-mode laser arrays is demonstrated. The arrays are ten-element devices grown by two-step metal-organic chemical vapor deposition. The structure consists of a strained quantum well InGaAs graded index-separate confinement active region and a thin (0.12 μm), transparent GaAs waveguide region. The near-field pattern typical of leaky-mode phase-locked arrays was measured. Fundamental mode oscillation was observed up to 2 A (threshold was as low as 175 mA). The authors observed a 1 μs pulsed optical output power of 172 mW per facet and a far-field angle (full width at half maximum) of 1.6 times the diffraction limit at 1 A. This is the first reported operation of a strained quantum well leaky-mode laser utilizing a built-in index step     

Direct supermode analysis of phase-locked diode laser arrays

Supermode structures of phase-locked diode laser arrays are predicted using the finite-element technique. In this approach, modal information such as effective refractive index, modal gain and near-field pattern can be obtained straightforwardly by solving a standard matrix eigenvalue problem. Application to an eight-element array successfully demonstrates the power of the method.     

15 W CW monolithic AlGaAs laser diode arrays

Good continuous-wave lifetimes have been demonstrated for 1 cm wide monolithic AlGaAs laser diode arrays with a 3500 mu m total aperture width at a power level of 15 W. This represents the highest CW power level at which long lifetimes have been obtained.<>     

10 watt CW, 5000 h lifetime monolithic AlGaAs laser diode arrays

1 cm-wide monolithic laser diode arrays emitting at about 810 nm with a 3 mm total active aperture width have been life-tested at 10 W constant power at 20 degrees C heat-sink temperature. One array has been operated for over 3000 h and has a projected lifetime in excess of 5000 h.<>     

0.3 W CW single-spatial-mode operation from large-core ARROW-type diode lasers

Large-core-width (6 mu m) antiresonant reflecting optical waveguide (ARROW)-type diode lasers are demonstrated for the first time. The structures have strong intermodal discrimination with low loss for the fundamental mode. As a result, stable, single-spatial-mode operation under CW conditions is obtained up to 300 mW output power at an emission wavelength of 0.98 mu m from strained-layer InGaAs-AlGaAs devices.<>     

High speed performance of 2-D vertical-cavity laser diode arrays

We have fabricated and tested 10×10 independently addressable vertical-cavity surface-emitting laser diode arrays. Arrays with 55 μm active diameter devices show an average threshold current density of 590 A/cm² and an excellent homogeneity of the output characteristics over the full array size with maximum CW output powers of 12 mW. Broad area laser diodes with active diameters of 75 μm reach output powers of 18 mW for CW operation and 180 mW under pulsed conditions. Small-signal modulation bandwidths are beyond 10 and 8 GHz for the 55 and 75 μm devices, respectively