High-brightness Semiconductor Lasers Research Articles

High-power and high-beam-quality photonic-crystal surface-emitting lasers: a tutorial

Realization of single-mode, high-power and high-beam-quality (namely, high-brightness) semiconductor lasers, which can rival or even replace bulky lasers such as gas, solid, and fiber lasers, is one of the ultimate goals of laser physics and photonics. The demand for such ultimate single-mode high-brightness semiconductor lasers is increasing for a wide variety of emerging applications including next-generation remote sensing for smart mobility and high-precision laser processing for smart manufacturing. Photonic-crystal surface-emitting lasers (PCSELs) show promise to meet these demands, based on their broad-area coherent two-dimensional (2D) resonance at a singularity (Γ) point of their 2D photonic band structure. In this tutorial paper, the lasing principle, theoretical analysis, and experimental demonstration of PCSELs are described. Recent progress in PCSEL development, including the formulation of a design guideline for realizing 100-W-to-kW-class single-mode operation, the experimental demonstration of a brightness of 1 GW cm–2 sr–1, and an extension of the lasing wavelengths to telecommunication and mid-infrared wavelengths are also covered.

Design of Fiber Coupling System for High Brightness Semiconductor Laser Pump Source

Design of Fiber Coupling System for High Brightness Semiconductor Laser Pump Source

High-brightness 808 nm semiconductor laser diode packaged by SiC heat sink

In order to further improve the reliability of high-power output of high-brightness semiconductor lasers, 808 nm semiconductor laser chips with a stripe width of 100 µm were packaged by SiC and AlN heat sinks, and the thermal performance of the composed SiC and AlN devices were investigated. First, the finite element method (FEM) is adopted to simulation and calculation, and then the thermal resistance of the device is measured by wavelength drift method experimentally. Both results show that the thermal resistance of the laser packaged by SiC heat sink is lower and the experimentally measured value is 2.95 K·W−1. In addition, the test results also indicate that the laser packaged by SiC heat sink has higher output power and higher wall-plug efficiency. The output power attains 10.3 W at the injection current of 10 A. and the maximum wall-plug efficiency can reach 53.5% at 25°C.

Lasers that shine brighter.

A photonic crystal design, consisting of two separated lattices arranged in a specific way, forms the base of high-brightness semiconductor lasers, with a very narrow beam divergence angle.

Double-lattice photonic-crystal resonators enabling high-brightness semiconductor lasers with symmetric narrow-divergence beams.

Achieving high brightness (where brightness is defined as optical power per unit area per unit solid angle) in semiconductor lasers is important for various applications, including direct-laser processing and light detection and ranging for next-generation smart production and mobility. Although the brightness of semiconductor lasers has been increased by the use of edge-emitting-type resonators, their brightness is still one order of magnitude smaller than that of gas and solid-state/fibre lasers, and they often suffer from large beam divergence with strong asymmetry and astigmatism. Here, we develop a so-called 'double-lattice photonic crystal', where we superimpose two photonic lattice groups separated by one-quarter wavelength in the x and y directions. Using this resonator, an output power of 10 W with a very narrow-divergence-angle (<0.3°) symmetric surface-emitted beam is achieved from a circular emission area of 500 μm diameter under pulsed conditions, which corresponds to a brightness of over 300 MW cm-2 sr-1. In addition, an output power up to ~7 W is obtained under continuous-wave conditions. Detailed analyses on the double-lattice structure indicate that the resonators have the potential to realize a brightness of up to 10 GW cm-2 sr-1, suggesting that compact, affordable semiconductor lasers will be able to rival existing gas and fibre/disk lasers.

高亮度大功率半导体激光器光纤耦合模块

高亮度大功率半导体激光器光纤耦合模块

Researching the 915 nm high-power and high-brightness semiconductor laser single chip coupling module

Based on the high-speed development of the fiber laser in recent years, the development of researching 915 nm semiconductor laser as main pumping sources of the fiber laser is at a high speed. Because the beam quality of the laser diode is very poor, the 915 nm laser diode is generally based on optical fiber coupling module to output the laser. Using the beam-shaping and fiber-coupling technology to improve the quality of output beam light, we present a kind of high-power and high-brightness semiconductor laser module, which can output 13.22 W through the optical fiber. Based on 915 nm GaAs semiconductor laser diode which has output power of 13.91 W, we describe a thoroughly detailed procedure for reshaping the beam output from the semiconductor laser diode and coupling the beam into the optical fiber of which the core diameter is 105 μm and the numerical aperture is 0.18. We get 13.22 W from the output fiber of the module at 14.5 A, the coupling efficiency of the whole module is 95.03% and the brightness is 1.5 MW/cm2 -str. The output power of the single chip semiconductor laser module achieves the advanced level in the domestic use.

Novel types of photonic band crystal high power and high brightness semiconductor lasers

A novel type of high power edge-emitting semiconductor laser (SL) with extended vertical photonic band crystal (PBC) waveguide was reviewed. Simulations predict narrow beam divergence, resulting from the thick PBC waveguide, to be independent of realistic variations of the growth parameters. Narrow ridge lasers fabricated along the simulations indeed demonstrate superior output power, narrow beam divergence, circular beam profile, excellent beam quality and very low astigmatism. Efficient fiber coupling decisive for most applications was thus eased. Stability of the laser under a wide range of operating temperature was demonstrated. Ultrashort pulses with few ps of duration at GHz repetition rates were generated by passively mode locking the lasers.

高亮度大功率宽条形半导体激光器腔面氮氢钝化研究

高亮度大功率宽条形半导体激光器腔面氮氢钝化研究

2D substrate imaging of a tapered laser cavity based on InGaAs quantum dots

Tapered cavities are an excellent solution to obtaining high brightness semiconductor laser sources for use in applications from frequency doubling to material processing. The high power density levels reached in such lasers can lead to nonlinear mechanisms related to the refractive index variations that de-stabilise the optical field distribution inside the laser cavity. These mechanisms are detrimental to the beam quality of the laser limiting its focussing ability. In this work we map the spatial distribution and evolution of the carrier density in tapered lasers as a function of injection current. A device with a taper length of 2.75 mm, taper angle of 6° and ridge length of 1.25 mm is used to demonstrate the principle. The active region consists of three layers of InGaAs quantum dots emitting around 950 nm. A window for imaging the spontaneous emission profile through the transparent GaAs substrate was formed by patterning the n-contact metal layer. The imaging was performed in the continuous wave regime to include the thermal-induced refractive index perturbation. The results show a non-uniform carrier and thermal distribution inside the cavity even at low current levels.

High-brightness diode lasers

The basic concepts and some modelling aspects of high-brightness semiconductor lasers are reviewed. The technology of lasers with a tapered gain-region is described. They provide the highest brightness of a semiconductor source with continuous wave emission in the visible and near infrared spectral range. Experimental results are presented for tapered lasers emitting at 735 nm and 808 nm. Output powers of 3 W were achieved in nearly diffraction limited beams. To cite this article: H. Wenzel et al., C. R. Physique 4 (2003).

High-Brightness Unstable-Resonator Lasers Fabricated with Improved Dry-Etching Technology for Ultra-Smooth Laser Facets

In this article, we present the fabrication and investigation of high-brightness semiconductor lasers. Details about the epitaxial growth together with results of broad-area lasers are shown. For the fabrication of the dry-etched laser mirrors, a multilayer etch mask together with an optimized chemically-assisted ion-beam etching (CAIBE) process have been developed leading to ultra-smooth laser facets. With this technique, unstable-resonator lasers with curved mirrors have been fabricated. The devices were tested in pulsed and continuous wave operation, exhibiting high optical output powers. Corrected far fields were measured and the corresponding virtual source size was calculated to be in the range of 2 µm leading to a brightness of 60 MW/(cm2 sr). This was achieved in cw operation using only the main lobe intensity of the uncoated single-facet output power.

High-brightness semiconductor laser sources for materials processing: stacking, beam shaping, and bars

A compact, reliable semiconductor laser source for materials processing, medical, and pumping applications is described. This industrial laser source relies on a combination of technologies that have matured in recent years. In particular, effective means of stacking and imaging monolithic semiconductor laser arrays (a.k.a., bars), together with advances in the design and manufacture of the bars, have enabled the production of robust sources at market-competitive costs. Semiconductor lasers are presently the only lasers known that combine an efficiency of about 50% with compact size and high reliability. Currently the maximum demonstrated output power of a 10-mm-wide semiconductor laser bar exceeds the 260 W level when assembled on an actively cooled heat sink. (The rated power is in the range of 50-100 W). Power levels in the kilowatt range can be reached by stacking such devices. The requirements on the stacking technique and the optic assembly to achieve high brightness are discussed. Optics for beam collimation in fast and slow axis are compared. An example for an optical setup to use in materials processing will be shown. Spot sizes as low as 0.4 mm/spl times/1.2 mm at a numerical aperture of 0.3 and output power of 1 kW are demonstrated. This results in a power density of more than 200 kW/cm/sup 2/. A setup for further increase in brightness by wavelength and polarization coupling will be outlined. For incoherent coupling of multiple beams into a single core optical fiber, a sophisticated beam shaping device is needed to homogenize the beam quality of stacked semiconductor lasers. Applications economics dictate that reliable operation is achievable at numerous wavelengths (both for wavelength-specific applications and for brightness scaling through geometric wavelength multiplexing) and at ever higher per bar power levels. New material systems and epitaxial structures continue to be evaluated in this pursuit. Here we include details of designs and performance for devices operating at 808, 830, and 915 nm. These include characteristics of both single-emitter devices and bars.

Enhanced diffiraction limited output powerof tapered gain semiconductor lasers

The spatiotemporal dynamics of linearly and trumpet flared high brightness semiconductor lasers are compared and contrasted using a comprehensive model built up from the microscopic physics. While both devices display complex multi longitudinal mode dynamics, the trumpet flared device is less susceptible to transverse filamentation instabilities and, hence, displays superior time-averaged far-field imaging properties.

Full space-time simulation for high-brightness semiconductor lasers

A semiconductor laser model is presented, which resolves the full time, longitudinal and lateral space dependences. The model is applied to an investigation of the dynamical stability of an integrated master-oscillator power-amplifier (MOPA) device. The model captures the full gain and refractive index bandwidth as a function of total carrier density. Our simulation confirms, for the first time, some recent experimental observations of high frequency whole beam oscillations and experimental reports that complex transverse filamentation occurs at high power amplifier currents.