Power Laser Diode Arrays Research Articles

Optimization of a microchannel heat sink using entropy minimization and genetic aggregation algorithm

A copper heat sink with rectangular U-shaped microchannels for cooling high power laser diode arrays was numerically optimised. The control volume method based commercial software was applied for solving heat transfer and fluid flow in the considered device. The optimisation procedure included over 130 various geometrical configurations with five independent geometric parameters. The Entropy Generation Minimization criterion was applied to find the optimal geometric structure. Some relations between geometrical parameters of the microchannel heat sink were analysed through statistical studies and two most important ones, i.e., the relative height (α) and width (β) of a single microchannel, were selected. Using the genetic aggregation, the entropy generation characteristics were determined as a function of α and β as well as mass flow rate of cooling medium (Ġ). The most optimal from the second law of thermodynamics point of view configuration was the one with αopt = 0.86, βopt = 0.347 and Ġ = 0.00183 kg/s. Comparing with the initial geometry, over 35% reduction of irreversibility losses for the optimal heat sink had been achieved, i.e., heat sink thermodynamic efficiency increases from 90.05% to 91.8%, while maximum temperature of cooled semiconductor element was reduced from 333.3 K to 324.2 K.

Photodetachment of negative ion beams for the ion-neutral merged-beam experiments at RICE

SynopsisGeneration of neutral atomic beam is under development for the ion-neutral merged-beam experiment at the RIKEN Cryogenic Electrostatic ion storage ring (RICE). The beam is produced by a photodetachment of a negative ion beam using a high power laser diode array with a wavelength of 808 nm. In order to increase the detachment efficiency, we have developed an optical cavity built with a planar mirror. In this presentation we will present the current status of the neutral atom beam source.

Vascularized liquid metal cooling for thermal management of kW high power laser diode array

In this paper, the vascularized liquid metal cooling was introduced into the thermal management of high power laser diode array (HPLDA) to realize an excellent heat removal performance. A vascularized liquid metal heat sink, with channel number of 70 and characteristic dimension of 1.8 mm, was firstly designed. And experimental tests and numerical analysis were then conducted. The experimental results indicated that liquid metal cooling can achieve 2000 W heat dissipation of HPLDA, with maximum temperature of heat sink top surface lower than 54 °C. The numerical results showed that vascularized liquid metal cooling offers better cooling performance compared to vascularized water cooling when flow rate was bigger than 2.4 l/min. It was also found that the heat capacity resistance was a significant thermal resistance for vascularized liquid metal cooling, while it was rather small for vascularized water cooling. Finally, the optimization distribution of heat source was numerically conducted to reduce the maximum temperature and maximum temperature difference, and 40 mm * 72 mm HPLDA distribution was selected as the best choice. Overall, the advanced vascularized liquid metal convection cooling offers a novel and effective heat dissipation method for the thermal management of HPLDA.

Second harmonic generation of ultraviolet laser based on high power laser diode array

A 780 nm continuous-wave, which is output by extra-cavity semiconductor laser with a bulk bragg grating, is used as the fundamental input light source of the Second Harmonic Generation (SHG) system. Line width of the fundamental light is 0.13 nm. Based on the type I phase-matching and Lithium Triborate (LBO) crystal, 390 nm second harmonic is obtained. The emitted average output power is 30 W (SHG efficiency is 0.01%). We provide a new technical route for the achievement of high-power UV beams.

61.2: Cooling Design of High Power Laser Diodes Array Using Channel Flow and Vapor Chamber Method

AbstractThe maximum junction temperature (Tj,max) of high power laser diode array is cooled down by 13% using channel flow method; the junction temperature deviation is also improved by 30% using vapor chamber. With the channel flow design, Tj,max can be lower 6% by introducing air deflector, and lower additional 4% by optimizing the air separator length. With the heat sink aspect ratio optimization, Tj,max can be lower additional 3% by introducing vapor chamber. Furthermore, by the TO‐CAN packaged laser diode device model, the heat path and the distribution of the thermal resistance are thoroughly investigated.

A smile insensitive method for spectral linewidth narrowing on high power laser diode arrays

To eliminate the smile effect in spectral linewidth narrowing on high power laser diode arrays, we have introduced a plane reflective mirror into a common Littrow configuration external cavity to enhance the correlation among emitters. By this way, we obtained uniform spectral distribution among emitters of a 64-elements laser diode array with 35 GHz linewidth and 41 W output laser power.

半导体激光器阵列电光特性导数测量方法

半导体激光器阵列电光特性导数测量方法

Wavefront reconstruction of high power laser diode array

A new method for the wavefront measurement of high power laser diode array with large dynamic ranges is presented. The wavefront sensor has a large dynamic range of −π/2 to π/2 and high precision on the measured wavefront slopes (±1′). According to the measurements of the slopes and intensity of the high power laser diode array, complex amplitudes can be obtained and the wavefront can be reconstructed. The reconstructed wavefront of high power laser diode array can be used in designing a laser beam shaping system in future work.

Localised laser joining of glass to silicon with BCB intermediate layer

The use of a laser to provide localised heating is an ideal solution to the problem of packaging micro-electro-mechanical-systems (MEMS) whilst maintaining a low device temperature to avoid changes in temperature-sensitive materials in the device. In this paper we present localised laser bonding of glass to silicon (normally used as the MEMS substrate) by using a fibre-delivered high power laser diode array to cure an intermediate layer of the thermosetting polymer Benzocyclobutene (BCB). In our experiments, we use two techniques to realise localised heating: one is to use an axicon together with a conventional positive lens to generate a ring focus; the other is to use a scanning focused laser beam. In both cases localised cooling is required to confine the elevated temperatures to the bonding area. Finite Element (FE) simulation indicates that both techniques should keep the temperature in the centre of the package to approximately that of the ambient environment (300 K) during the process. However, experiments show that the temperature in the centre of the package rises to a value of around 500 K, likely due to poor contact between silicon and cooling sink. Experimentally, we confirmed that either technique can be used to obtain excellent bonding of glass to silicon with leak rate at a level of 10−10 mbar l s−1, whilst keeping the centre of device at a lower temperature.

半导体激光器阵列偏振特性及其与应力关系的实验研究

半导体激光器阵列偏振特性及其与应力关系的实验研究

Coherent addition of high power laser diode array with a V-shape external Talbot cavity

We designed a V-shape external Talbot cavity for a broad-area laser diode array and demonstrated coherent laser beam combining at high power with narrow spectral linewidth. The V-shape external Talbot cavity provides good mode-discrimination and does not require a spatial filter. A multi-lobe far-field profile generated by a low filling-factor phase-locked array is confirmed by our numerical simulation.

Present Status and Future Prospects of High Power Laser Diode Arrays

Present Status and Future Prospects of High Power Laser Diode Arrays

60%电光效率高功率激光二极管阵列

60%电光效率高功率激光二极管阵列

A novel technique for improving beam quality of high power laser diode arrays

According to optical waveguide theory, the far-field profile of laser diode arrays is derived. Basing on the distribution, an off-axis external cavity is designed. By employing the external cavity, at the operating current of 17A, the BPP of output laser is reduced from 1100mm·mrad to 128mm·mrad and the beam quality has about 8.5-fold improvement. The output power is 75% of the radiated power in free-running state without external cavity.

Investigation of reliability issues in high power laser diode bar packages

As applications continue to demand increasingly higher optical output power and longer lifetime, thermo-mechanical stresses on dissimilar materials interfaced for packaging pose an ever-growing challenge for the realization of a durable system. Particularly important for an epitaxy-down configuration is the die-attachment interface, which is desired to be defect free and stress managed for reliable optical alignment. A knowledge of the changes in the physical defect density and magnitude of the thermo-mechanical stress present in the active region as a function of the fabrication process and aging is crucial to an understanding of the influence of the process parameters and operating conditions on device performance and reliability. In this study, we investigated high power laser diode array packages aged under various conditions. Microscopic defect analyses of the die attachment interface and device stress were carried out using primarily metallography, scanning electron microscopy, scanning acoustic microscopy, microhardness, and micro-Raman spectroscopy. It was noted that the intermetallic compounds and microscopic physical defects at the die attach interface are detrimental to transient heat transfer, and thus, overall package reliability. Using micro-Raman spectroscopy, we found that tensile stress near the bar-package interface increases with aging for the first few hundred hours and then decreases with further aging.

Packaging-induced stress distribution in high power AlGaAs laser diodes by photoluminescence mapping

The microphotoluminescence (μ-PL) technique is proposed for mapping local stress distribution in GaAs/AlGaAs high power laser diode arrays (LDAs). This technique will be used to monitor the stresses that can be induced on the bars during the packaging process. We show herein that also a detailed study of the stress profiles that could exist in the bars before mounting and after aging can be achieved with this technique.

2D high power laser diode arrays for solid-state laser driver inertial fusion energy project

2D arrays of laser diodes were developed and investigated under QCW operating conditions. Output power and energy density up to 1 kW/cm2 and 0.45 J/cm2 (at pulse duration 0.5 ms) were measured at the wavelength 810 nm. The spectral composition of radiation, shape of the output pulses, and far-field and near-field radiation zones were examined under various pumping parameters. The kinetics of the temperature profiles in monolithic QCW AlGaAs/GaAs linear bars and 2D arrays, emitting at the wavelength 810 nm was modeled numerically. Quasi-CW and CW operation under various pump parameters were considered as a function of a heat sink design. A calculation model was used to interpret the experimental dependences of the output parameters of the arrays on the pump conditions for application in the solid-state laser driver project. The limit of total power conversion efficiency of diode lasers was analyzed in respect of the threshold current density, series resistance and external differential quantum efficiency. The estimated maximum value of 75% was obtained for the present technological level of the diode lasers production. The corresponding limit of the output optical power density of 2D laser array was defined around 10 kW/cm2.

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.

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.

High Power Laser Diode Arrays for pumping Solid State Laser

High Power Laser Diode Arrays for pumping Solid State Laser