Diode Laser Bars Research Articles

适用于金属薄板焊接的柔性光纤耦合半导体激光加工光源

A high power fiber-coupled flexible source is fabracated in which 20 conduction cooled diode laser bars were intergrated in manner of linear array coupling.Under the macrochannel cooling with industrial water,a CW output power of 907 W,a beam parameter product of 47 mm.mrad,an optical power density of 3.21 ×10 5 W/cm2 and a maximum wall-plug efficiency of 39% on the work piece are demonstrated from a 600 μm,NA 0.2 fiber.This source has a great potential to be directly adapted in materials processing,especially in metal sheet welding.

基于组合模理论设计的激光二极管阵列外腔

基于组合模理论设计的激光二极管阵列外腔

Viscoelastic Response of Red Blood Cells in Linear Optical Traps

The mechanical properties of biological cells can be used as a marker for individual cell's health, information not accessible by bulk measurements. For example malaria parasites are known to significantly stiffen the red blood cell (RBC) membrane, allowing identification of single infected cells based on their deformability. We have developed a non-contact method employing non-invasive optical forces, efficiently elongating RBCs within microfluidic channels to determine cell elastic properties. In this, the anisotropic beam of a single laser diode bar is used to create a line-shaped optical trap, capturing and elongating specimens along the laser axis. We perform static measurements on single RBCs to demonstrate the utility of this method. Simulations employing ray-tracing methods illustrate how the refraction of the asymmetric laser profile inherently creates antipodal stretching forces. Applying the membrane theory of thin shells enables us to determine the expected deformation based on our simulations and compare results to measured data.As the behavior of a viscoelastic material, such as the RBC's membrane, strongly depends on the timescales of applied forces, we perform frequency-dependent measurements with modulated external stimulus to determine the RBC's complex elastic moduli, properties not accessible by comparable techniques. Laser intensity, and therefore the forces responsible for cell deformation, is modulated at frequencies varying over three orders of magnitude. Cell response is recorded using a high-speed camera system, allowing us to correlate the applied external load to the phase-shifted viscoelastic behavior of the RBC and to obtain the frequency-dependent dissipation of energy during one cycle of oscillation.Employing this new technique, cells can be deformed while streaming along the line-shaped trap in flowing environment, allowing application in high-throughput systems. Use of comparably simple optics and inexpensive laser sources facilitates potential implementation in small platforms and hand-held devices.

Record High-Temperature Long-Pulse Operation of 8xx-nm Diode Laser Bar with Aluminum-Free Active Region

We report on the first demonstration of long-pulse (milliseconds) operation of aluminum-free active-region 8xx-nm diode laser bar at heat-sink temperature of 180 °C. This is, to the best of our knowledge, the highest published operating temperature for a long-pulse 8xx-nm laser bar with Al-free active region. The laser bars have very robust performance at 130 °C without any active cooling. At this high temperature, the laser bars provide both high peak power (60 W at 100 A) and good pulse shape for tens of milliseconds pulse width, maintaining high energy per pulse. The dependence of laser output pulse shape on the pulse width and pump current is experimentally investigated at 130 °C. We find that the transient output power of the laser bar follows P(t) = A exp(-t /t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) + Bt + C, where A, B, C, and t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> are fitting parameters that are pulse width and current dependent. We have also investigated the transient thermal behavior of the laser bar at high temperature and high pump current.

Nd:GdVO4 slab laser with line-shaped end-pumping profile operating at 912 nm

A continuous-wave laser with line-shaped end-pumping profile operating at 912 nm is presented. The maximum output power of 7.82 W is obtained, with a slop efficiency of 24.7% and beam quality factors of M 2 ∼ 20, M 2 ∼ 1.3. To the best of our knowledge, this is the first laser diode bar directly pumped Nd:GdVO4 slab laser based on the quasi-three-level 4 F 3/2 → 4 F 9/2 transition in neodymium. Furthermore, we disclose that the experimental setups can be improved by inserting a plano-concave cylindrical lens in the cavity to form a new quasi-concentric resonator to improve die mode-matching in x-direction.

High-Throughput Cell Elastic Modulus Cytometry using Single Diode Laser Bar Optical Stretchers

Cellular elastic properties can be measured by trapping and deforming them using optical stretchers. Dual optical traps were recently shown to be an efficient experimental method to identify cell types and detect disease states from the measured elastic modulus.However, the low throughput associated with such dual optical traps has significantly limited its utility and application due to the need to sequentially isolate and probe individual cells. We have implemented a pseudo steady-state high-throughput optical stretcher that uses single inexpensive diode laser bar to impart anisotropic forces and stretch osmotically swollen bovine erythrocytes in a continuous microfluidic flow at a rate of ∼ 1 cell/second. This measurement rate is a factor of 10-100 higher than previous demonstrations of optical stretching. We also implemented a numerical model, dynamic ray tracing, to simulate the deformation of elastic capsules induced by the single diode laser bar optical stretcher in flow conditions. Finally, we demonstrated how the numerical model is used to determine the elastic modulus of individual cells from experimental measurements of the steady-state deformation. This new optical approach has the potential to be readily integrated with other cytometric technologies, and with the capability of measuring cell populations, thus enabling true mechanical-property based cytometry.

Narrow line width operation of a 980 nm gain guided tapered diode laser bar

We demonstrate two different schemes for the spectral narrowing of a 12 emitter 980 nm gain guided tapered diode laser bar. In the first scheme, a reflective grating has been used in a Littman Metcalf configuration and the wavelength of the laser emission could be narrowed down from more than 5.5 nm in the free running mode to 0.04 nm (FWHM) at an operating current of 30 A with an output power of 8 W. The spectrum was found to be tunable within a range of 16 nm. In the second scheme, a volume Bragg grating has been used to narrow the wavelength of the laser bar from over 5 nm to less than 0.2 nm with an output of 5 W at 20 A. To our knowledge, this is the first time spectral narrowing has been performed on a gain guided tapered diode laser bar. In the Littman Metcalf configuration, the spectral brightness has been increased by 86 times and in the volume Bragg grating cavity the spectral brightness has been improved over 18 times when compared to the free running operation. These schemes could be also extended for other wavelengths of interest in the future.

808 nm大功率半导体激光器阵列的优化设计

808 nm大功率半导体激光器阵列的优化设计

两相冲击强化换热激光二极管用单片热沉

两相冲击强化换热激光二极管用单片热沉

101 W of average green beam from diode-side-pumped Nd:YAG/LBO-based system in a relay imaged cavity

Studies on intracavity frequency doubling of acousto-optically Q-switched Nd:YAG rod laser using 18 mm long type-II phase-matched LBO crystal in a relay-imaged cavity is reported. A single pump head comprised of Nd:YAG rod, diffusive reflectors and linear array laser diode bars is used. 101 W of average green power at a total diode pumping power of 700 W is obtained corresponding to 14.4% optical-to-optical conversion efficiency. The pulse repetition rate is 30 kHz with an individual pulse duration of 200 ns.

808-nm laser diode bars based on epitaxially stacked double heterostructures

We have fabricated and investigated linear arrays of single laser diodes (LDs) and epitaxially stacked double LDs based on AlGaAs/GaAs heterostructures emitting in the 808-nm range. The power — current characteristic of the double-LD bars has a slope of 2.18 W A-1, which is almost twice that of the single-LD bars (1.16 W A-1). The voltage drop across the former bars is also larger. At a pump current of 60 A, the output power of 5-mm-long arrays of LDs based on epitaxially stacked double heterostructures is 100 W under quasi-cw pumping, which is a factor of 1.8 above that of the single-LD bars under identical conditions.

A novel prism beam-shaping laser diode bar end-pumped TEM00 mode Nd:YVO4 laser

A beam-shaping diode end-pumped TEM00 mode CW Nd:YVO4 laser is presented. A special beam-shaping element made up of isosceles right-angled prism pieces is adopted to realize beam symmetric. Two cylinder lenses are used to couple the shaped beam into a 3 × 3 × 9 mm Nd:YVO4 crystal with 0.3 at % neodymium doping. By using this laser system, we have achieved 6.1 W CW laser operated in single transverse mode at 1064 nm with 95.2% reshaping efficiency and 25.6% optical-optical conversion efficiency.

Simulation and design of applied hollow-duct used for side-pumped cutting-edged of high power disk laser

In this article a ray tracing method is used to design a specific hollow-duct whereby we show that it will be the best choice for pumping the gain medium that has inclined sides or cutting edges used for edge-pumped high power disk laser due to several advantages of the shape of this gain medium. This kind of hollow-duct which is called non-symmetric hollow-duct in this paper includes inclined output facet that compresses and homogenizes the emission of laser diode arrays which are coupled to the entrance-inclined surface of the gain medium. In this paper, the goals of designing this kind of hollow-duct are based on two important criteria: First, homogeneity of pump light distribution due to the beam concentration of laser diode bars according to the edge-pumped disk laser. Second, uniform distribution of pump light in non-symmetric hollow-ducts deducing uniform temperature distribution in the gain medium.

Linear diode laser bar optical stretchers for cell deformation

To investigate the use of linear diode laser bars to optically stretch cells and measure their mechanical properties, we present numerical simulations using the immersed boundary method (IBM) coupled with classic ray optics. Cells are considered as three-dimensional (3D) spherical elastic capsules immersed in a fluid subjected to both optical and hydrodynamic forces in a periodic domain. We simulate cell deformation induced by both single and dual diode laser bar configurations and show that a single diode laser bar induces significant stretching but also induces cell translation of speed < 10 µm/sec for applied 6.6 mW/µm power in unconfined systems. The dual diode laser bar configuration, however, can be used to both stretch and optically trap cells at a fixed position. The net cell deformation was found to be a function of the total laser power and not the power distribution between single or dual diode laser bar configurations.

Compact beam collimator for laser diode bar

A compact beam collimator for a laser diode (LD) bar fabricated by a simple method is presented. It consists of a single set of microlenses and a cylindrical lens, which are fabricated from SiO2 rods using a fiber-drawing tower. The principle and parameter optimization of this device are investigated numerically using ZEMAX software and illustrated experimentally for a specific LD bar. It is shown that the output beam is well collimated in both the fast-axis and slow-axis directions; the beam quality is greatly enhanced via the redistribution of intensity in the two directions and by eliminating the fill factor for the LD bar.

Spectral beam combining of a 980 nm tapered diode laser bar

We demonstrate spectral beam combining of a 980 nm tapered diode laser bar. The combined beam from 12 tapered emitters on the bar yielded an output power of 9.3 W at 30 A of operating current. An M2 value of 5.3 has been achieved along the slow axis. This value is close to that of a free running single tapered emitter on the bar at the same current level. The overall spectral beam combining efficiency was measured to be 63%.

窄线宽、高光束质量的外腔双反馈激光二极管阵列

An off-axis external cavity with double feedback is designed to simultaneously reduce spectral bandwidth and improve the beam quality of the laser diode bar. The external cavity is made up of a high-reflection mirror and a blazed grating, where the selected spatial mode can be amplified. The grating can also provide a spectral-sensitive feedback to the laser diode bar. In addition, a half-wave plate is inserted into the grating-feedback branch to control the feedback light amount, and the output laser is taken from the grating-feedback branch. The bandwidth and the beam parameter product are respectively reduced to 0.15 nm and 283 mm·mrad for laser diode bar with the external cavity at a drive current of 16 A. The center wavelength is almost unchanged as the temperature varies, the laser

高亮度窄线宽的激光二极管阵列研究进展

高亮度窄线宽的激光二极管阵列研究进展

Dual-axis beam correction for an array of single-mode diode laser emitters using a laser-written custom phase-plate

A single optical component for a diode laser bar combines fast-axis smile and lens error correction with slow-axis collimation. Produced by laser-machining/polishing, it provides 0.9 mm focal length, 200 microm pitch slow-axis collimation on the same surface that corrects fast-axis errors. Custom fabrication enables fill-factor optimization for the 49 single-mode beams and gives parallel collimation with rms pointing errors of 3% and 6% of the far-field divergence for the fast- and slow-axis array respectively. Sub-micron pitch mismatch between the slow-axis lens and emitter arrays, and beam pointing changes by thermal expansion of the laser bar are detected.

Dependence of Junction Voltage Saturation on Uniformity and Quality of Laser Diode Bars

The dependence of the sinkage at the threshold of the electric derivative curve (IdV/dI – I) on the uniformity and the quality of the laser diode bar is analyzed. By using the equations derived from the equivalent circuits of the bars, the influence of the bar uniformity on the depth of the dip is investigated in theory under certain conditions. Furthermore, the experimental results based on the presented technique indicate that the depth of the dip is interrelated to the uniformity and the quality of the corresponding bar. The present technique can be used conveniently and effectively to measure the laser diode bars in practice.