High-power Laser Diode Arrays Research Articles

Protection circuitry for high-power diode laser arrays

A comprehensive protection scheme is presented for use with high-power (∼500 W dc input) diode laser arrays. The circuitry requires no separate power, using instead the voltage from the laser’s power supply. Overcurrent and overvoltage silicon controlled rectifier crowbars are the primary protection circuits. In addition, tripping of either crowbar will turn off the main power to the laser’s power supply. This feature makes use of a main power controller that incorporates two interlock loops, for protection against overtemperature, low coolant flow, undervoltage, and other undesirable conditions.

Emitter failure and thermal facet load in high-power laser diode arrays

We report on micro-Raman facet temperature measurements carried out in asymmetrically coated high-power laser diode arrays. Facet temperatures of up to 600 °C are reproducibly found for high-power operation. The data are modeled using an approach based on the finite element method. Thus we are able to infer the power management of the device from the facet temperature data. Up to 7% of the total heat power is concentrated at the front facet. Furthermore. we determine the thermal load at the front facet versus the operation current, which is a key parameter for modeling high-power devices.

Intracavity frequency doubling of a slab Nd:YAG laser pumped by high power diode laser array

A high power diode-array-pumped slab Nd:YAG laser is described. The resonator consists of three mirrors in folded geometry. The laser is operated in acousto-optic Q-switching mode and intracavity frequency doubling is tried. We demonstrate that the laser exhibits frequency doubling efficiency of ∼60% with a type I LBO crystal.

Aging properties of high power laser diode arrays analyzed by Fourier-transform photocurrent measurements

We present the results on aging mechanisms acting in high-power laser diode arrays (LDAs) employing Fourier-transform (FT) spectroscopy. The FT spectrometer was used as an excitation source for performing photocurrent (PC) measurements in two sets of aged LDA samples. The PC spectra reveal both the evolution of a defect band located in the optically active layer as well as modifications of the interband part of the spectrum upon aging. Such changes represent sensitive quantitative measures of the aging status and provide insight into the microscopic changes of the device structure upon aging.

Solid freeform fabrication of powders using laser processing

The accurate temperature measurement of high-power laser diode arrays is a considerable challenge due to their large temperature gradient and package structure. In this study, experiments based on the forward voltage method were set up to measure the transient temperature behavior of chips after the removal of heating load. A hybrid experimental/numerical method was developed to calculate multiple unknown interface thermal resistances and improve the prediction of the temperature distribution of high-power laser diode arrays by analyzing the transient temperature behavior of chips. The largest deviation between numerical and experimental results is 1.3 K. Based on the numerical results, thermal resistances for different layers and temperature distribution inside the chip were obtained and evaluated. Some suggestions for improving the thermal design of high-power laser diode arrays were derived.

A Hybrid-Integrated Two-Dimensional ( 3×24) High-Efficiency High-Power Laser Diode Array

Using buried-heterostructure laser diodes grown by one-step metal organic chemical vapor deposition and a structure designed to dissipate heat, we have realized a hybrid-integrated two-dimensional high-power laser diode array. The array consists of 3×24 elements, which are individually addressed in a simple matrix. The laser emits at 850 nm and each element operates at 30 mW. The laser characteristics have good uniformity and an energy-conversion efficiency of 45% was achieved. Finite element analysis was used to calculate the thermal characteristics and it was shown that the laser array can be a practical device. The array was operated for more than 1100 h under constant current at room temperature without an external cooler, when the initial power of each laser element was 30 mW, the pulse width was 0.1 ms and the duty cycle was 25%.

Waveguide Effect on the Image Formation Process in Near-field Photocurrent Spectroscopy of Semiconductor Laser Diodes

Near-field photocurrent spectra of high-power laser diode arrays with different wave-guide characteristics are reported. Subwavelengtb spatial resolution is achieved by using a near-field fibre probe as the excitation source. The effect of the laser diode waveguide structure and of surface recombination processes on the near-field photocurrent image formation is discussed and analysed in terms of a beam propagation model. Experiments on laser diodes before and after accelerated ageing demonstrate the potential of the technique for analysing microscopic defect formation processes in optoelectronic devices.

Waveguide Effect on the Image Formation Process in Near‐field Photocurrent Spectroscopy of Semiconductor Laser Diodes

Near-field photocurrent spectra of high-power laser diode arrays with different wave-guide characteristics are reported. Subwavelength spatial resolution is achieved by using a near-field fibre probe as the excitation source. The effect of the laser diode waveguide structure and of surface recombination processes on the near-field photocurrent image formation is discussed and analysed in terms of a beam propagation model. Experiments on laser diodes before and after accelerated ageing demonstrate the potential of the technique for analysing microscopic defect formation processes in optoelectronic devices.© 1997 John Wiley & Sons, Ltd.

Near-field photocurrent spectroscopy: A novel technique for studying defects and aging in high-power semiconductor lasers

We present the first comparative study of spatially resolved near-field photocurrent spectra for high power laser diode arrays with different wave guide characteristics before and after accelerated aging of the laser device. Sub-wavelength spatial resolution is demonstrated by using a near-field fiber probe as the excitation source. The potential of the technique for analyzing microscopic aging processes in optoelectronic devices is demonstrated. The experiments provide insight into mechanisms of defect formation within the p-i-n junction of InA1GaAs/GaAs laser diodes upon aging. The effect of the wave guide structure and of surface recombination processes on the near-field photocurrent images is discussed and analyzed in terms of a beam propagation model. The non-destructiveness makes this technique a particularly attractive method for in-situ analysis in high power laser diodes.

Improved heat sinking for laser-diode arrays using microchannels in CVD diamond

This work proposes a novel cooling system for high-power laser-diode arrays, for which the maximum optical output power density per unit surface area is limited by the temperature rise due to self-heating. The proposed system uses a microchannel heat sink made of chemical-vapor-deposited (CVD) diamond, whose high thermal conductivity increases the efficiency of the channel-wall fins and reduces the array-to-coolant thermal resistance using a simple model for the combined conduction and convection problem. The resistance is calculated to be 75% less than that for a conventional configuration using a silicon microchannel heat sink. The present analysis strongly motivates a future experimental study.

High Power Laser Diode Arrays for pumping Solid State Laser

High Power Laser Diode Arrays for pumping Solid State Laser

Laser-Diode Pumped High Power Solid-State Lasers. High Power Laser Diode Arrays.

Recent progress in high power laser diodes and 2-dimensional high power laser LD arrays is reviewed. We have developed 0.8-0.9 μm band high power LD arrays for pumping solid state lasers and evaluated their characteristics. With 10-stack LD arrays, 750W peak power was obtained under the quasi-CW conditions.

High Power Laser Diode Arrays for Pumping Solid State Laser and Pumping Characteristics

High Power Laser Diode Arrays for Pumping Solid State Laser and Pumping Characteristics

Optical pumping of Rb vapor using high-power Ga1-xAlxAs diode laser arrays.

The use of high-power ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As diode laser arrays for optical pumping of Rb vapor has been examined both theoretically and experimentally. Our studies show that large atomic polarizations can be obtained using the broad spectral output of a diode laser array if the Rb resonance line is collisionally broadened by several atmospheres of a buffer gas. The objective was to study the effectiveness of diode laser arrays as light sources for optically pumped spin-exchange polarized $^{3}\mathrm{He}$ targets. The average Rb polarization was deduced at three different Rb vapor pressures using the polarization induced in the $^{3}\mathrm{He}$ buffer gas. The largest $^{3}\mathrm{He}$ polarization observed was 53% using a 20-W diode array with 1.9-nm full width at half maximum spectral width in 10.5 amagat of $^{3}\mathrm{He}$. This result compares favorably with other light sources for this target. The measured average Rb polarizations are compared to theoretical calculations.

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.

High Power Laser Diode Arrays for Pumping Solid State Laser (Development of 2-D High Power LD Arrays).

High Power Laser Diode Arrays for Pumping Solid State Laser (Development of 2-D High Power LD Arrays).

Tunable, narrow-linewidth output from an injection-locked high-power AlGaAs laser diode array

An injection-locking technique has been employed to produce single-frequency tunable output from a high-power AlGaAs laser diode array. A narrow-linewidth external cavity laser is used as a master oscillator. With an injected power of 15 mW, a total output power of 1.0 W was obtained from the laser diode array with a spectral linewidth of less than 38 kHz, a wavelength tuning range of 13 nm, and a 0.67 degrees -wide single-lobed far-field beam.

Injection locking a laser-diode array with a phase-conjugate beam

We use a mutually pumped phase conjugator to guide the output beam of a single-mode laser diode into the active region of a high-power laser-diode array. This injected beam locks the frequency of the array, causing it to emit a single, 1.45 times diffraction-limited, continuous-wave output beam containing 85% of the array’s total output power. Phase-conjugate injection dramatically improves the coupling into the laser array, so that less than a milliwatt of injected power is sufficient to lock all the array’s 450-mW output to the frequency of the master laser.

High-duty cycle, high-power two-dimensional laser diode arrays

Two-dimensional (2-D) laser diode arrays, stacked in a one square centimetre (1 × 1 cm2) format with five bars and five thick heat spreaders, achieve electrical-to-optical conversion efficiencies up to 44%. They have been operated at duty cycles up to 50% with up to 150 W of average power (300 W peak power).

Beam Shaping of High-power Laser Diode Arrays by Continuous Surface-relief Elements

Abstract A breadboard for beam shaping of high-power laser diode arrays (LDAs) has been realized. The coherent beams are added with the aid of a continuous surface-relief fan-in element. It results in a nearly symmetric single lobed beam of collimated light with maximum conversion efficiency. The theoretical efficiency is determined to be 96·7%. Experimentally, one third of the total power is now in the central peak.