High-power Semiconductor Lasers Research Articles

Conservation of quantum efficiency in quantum well intermixing by stress engineering with dielectric bilayers

In semiconductor lasers, quantum well intermixing (QWI) with high selectivity using dielectrics often results in lower quantum efficiency. In this paper, we report on an investigation regarding the effect of thermally induced dielectric stress on the quantum efficiency of quantum well structures in impurity-free vacancy disordering (IFVD) process using photoluminescence and device characterization in conjunction with microscopy. SiO2 and SixO2/SrF2 (versus SrF2) films were employed for the enhancement and suppression of QWI, respectively. Large intermixing selectivity of 75 nm (125 meV), consistent with the theoretical modeling results, with negligible effect on the suppression region characteristics, was obtained. SixO2 layer compensates for the large thermal expansion coefficient mismatch of SrF2 with the semiconductor and mitigates the detrimental effects of SrF2 without sacrificing its QWI benefits. The bilayer dielectric approach dramatically improved the dielectric–semiconductor interface quality. Fabricated high power semiconductor lasers demonstrated high quantum efficiency in the lasing region using the bilayer dielectric film during the intermixing process. Our results reveal that stress engineering in IFVD is essential and the thermal stress can be controlled by engineering the dielectric strain opening new perspectives for QWI of photonic devices.

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

大功率半导体激光器驱动电源及温控系统设计

In order to solve the output wavelength and power stability of high power semiconductor laser, high power semiconductor laser constant current driver and temperature control system were designed. Deep negative feedback circuit was used to control the laser drive current, the analog Proportional-Integral (PI) circuit and constant current driver were adopted to control the working current of Thermoelectric Cooler (TEC), the laser working temperature can be kept accurately. The design can realize the linear adjustment of output current from 0-12.5 A, and has the function of current detection, over-current protection and Transistor-Transistor Logic (TTL) modulation. The control precision of the temperature control system can achieve 0.05℃. Temperature can be adjusted continuously and can be monitored in real time. Experiment results show that the design can guarantee the output current and temperature control stably, which satisfies the requirement of high power semiconductor laser.

Design of active region for GaAsP/AlGaAs tensile strain quantum well laser diodes near 800 nm wavelength

As an active region, the tensile strain GaAs1-xPx quantum well plays an important role in the high power semiconductor laser diode with a wavelength of about 800 nm. Accompanied with the improved stability due to the Al-free active region, the GaAs1-xPx quantum well laser also shows a high level of catastrophic optical mirror damage because of the non-absorbing window at the facet, which is formed automatically by the relaxation of the tensile strain GaAs1-xPx material. On the other side, the GaAs1-xPx quantum well laser can provide a transverse magnetic (TM) polarized light source which is important for many solid state laser systems. However, the energy band structure of the tensile strain GaAs1-xPx quantum well is more complicated than that of the compressed or lattice matched quantum well. Although the light hole band is on the top of the heavy hole band for the bulk tensile strain GaAs1-xPx material, the situation may be different from the tensile strain GaAs1-xPx quantum well, in which the first light hole subband lh1 can be either on the top of the first heavy hole subband hh1 or reversed, that will cause the laser to generate either TM or transverse electric (TE) polarized light according to the well structure. So it is meaningful to optimize the tensile strain GaAs1-xPx quantum well structure based on the analysis of the energy band structure. Firstly, according to the 6×6 Luttinger-Kohn theory, the energy band structure of the tensile strain GaAs1-xPx quantum well is calculated by the finite difference method. The relationship between the interband transition energy and the well structure parameters is established. It is found that the well composition x and the well width should increase simultaneously, in order to fix the first subband transition wavelength at about 800 nm. Special attention is paid to the 808 nm quantum well, the valence structures of different well widths are calculated, the detailed analysis of the envelope function shows that the top valence subband is lh1 for wider well width, while it is changed to hh1 for narrower well width. Meanwhile, both the TE and the TM momentum matrix element are calculated as a function of the transverse wave vector for the subband transition from c1 to lh1, lh2, hh1 and hh2, respectively. Further, the threshold optical gains of different well widths are simulated for 808 nm laser diode with the tensile strain GaAs1-xPx quantum well as an active region, the wider well width benefits the TM mode, while the narrower one is favor of TE mode. Finally, according to the threshold carrier density, the relationship between the threshold current density and the well width is analyzed for 808 nm laser diode by considering both the spontaneous and the Auger recombination, an optimum combination of the well width and the well composition exists. For wider well width, the threshold current density will be higher because of the high energy subband carrier filling effect. For narrower well width, the decrease of the optical confinement factor will lead to the increase of threshold current density.

封装对大功率半导体激光器阵列热应力及Smile的影响

封装对大功率半导体激光器阵列热应力及Smile的影响

大功率半导体激光器波导热透镜效应及对慢轴光束发散角的影响

大功率半导体激光器波导热透镜效应及对慢轴光束发散角的影响

烧结空洞对半导体激光器热分布的影响

烧结空洞对半导体激光器热分布的影响

Pulse Power Supply for High-Power Semiconductor Laser Diode Arrays With Micro-Current Pre-Start Control

This paper mainly introduces a pulse power supply for high-power semiconductor laser diode arrays with a novel micro-current pre-start control method. According to the operating characteristics of the semiconductor laser, the output current of the pulse power supply is required to be smooth, stable, and without overshoot. In the method of normal direct pulse start control, semiconductor laser is damaged easily by the overshoot and oscillation of pulse current caused by the switching threshold voltage of MOSFET. And the time delay between the current reference signal and the output pulse current makes the design of closed loop more complicated. Based on the above problems, the method of micro-current pre-start control is proposed. The method is simple to operate and it can solve the nonlinear problem of MOSFET caused by the switching threshold voltage. Therefore, it solve the problems of time delay between the current reference signal and the output pulse current and the overshoot and oscillation of output pulse current in the rising process. A 25.6-kW prototype is intended for verifying the effectiveness of the micro-current pre-start control.

A Highly Stable Source of Current Pulses with an Adjustable Amplitude of up to 350 A for a Nonlinear Complex Load

The application of high-power semiconductor lasers for creating a population inversion in active gaseous media is an integral part of studies that are aimed at the achievement of a sufficient level of laser-radiation energy to initiate a thermonuclear reaction. The stability of the laser radiation and, thus, the repeatability of experimental results, depend on the stability of the parameters of current pulses for pumping laser-diode arrays with a pulse amplitude of up to several hundred amperes. The flow of current pulses with such an amplitude through a cable that connects the load to the output of the current-pulse source must not lead to the formation of voltage pulses of opposite polarity across the load, which can damage it. This can be prevented by correcting the current pulse edges. It is proposed to develop a source of current pulses with a high amplitude on the basis of several modules of fast linear current amplifiers with individual control loops, whose outputs are connected in parallel. It is established that a compensation-type current sensor on the basis of the Hall effect is operable at high frequencies and can be used in these modules, but it has pronounced resonance properties, which must be canceled. It is shown that analog driving pulses of each module can be formed using aperiodic chains with parameters that eliminate oscillatory processes in the load circuit. A dynamic model of a module of the linear current amplifier and the calculation relationships for the parameters of its components, which follow from this model, are presented. The experimental results that confirm stability of the parameters of the formed current pulses are presented.

Modulation system and modulation characteristics of high power semiconductor laser

In this paper, we studied the factors that affect the high frequency modulation performance of semiconductor laser in the process of direct modulation. The equivalent circuit model of LD is derived from the rate equation of semiconductor laser, which was established by using PSpice. We analyzed the effects of the parasitic parameters, the DC bias and the current modulation intensity on modulation characteristics of the laser, and put forward the corresponding methods to improve the performance of modulation. We designed a direct modulation system of semiconductor laser and simulated the system by OrCAD/PSpice. This system can output modulation semiconductor laser with frequency of 1 MHz and average power of 1.1 W.

830-nm InGaAs Quantum Well Lasers With Very Low Beam Divergence

We report on our design and fabrication of 830-nm high-power semiconductor lasers with very low beam divergence. Here, we propose a novel approach in which by combining asymmetric waveguide and a feature called “pins” together, we were able to design an optimize epi structure, which not only produces a beam divergence of less than 16°, which is measured at the full width at the half maximum, but also has very good growth tolerance as well. Device test shows the beam divergence is as small as 13°, yet they still retain high slope efficiency of around 1.15 W/A and low threshold current of 400 mA for the devices with cavity length being 2 mm long, and ridge width being 40 μm wide.

Advances in high power high beam quality diode lasers

Semiconductor laser enjoys its benefits such as small volume, light weight, long operation life, various selectable wavelength and direct current driving, meanwhile suffers from its beam quality which is making it hard for direct applicdations. Researchers around the world realize that it is beam quality has the same importance as power, and acquiring high power and high beam quality is the key issue in semiconductor laser induxtry. The question of how to improve the beam quality of high power semiconductor lasers is attracting increasing attention from researchers home and abroad. Considering the application fields which require high power high beam quality, such as industry processing and national defense, this paper discussed the research progress on both diode laser unit devices and laser beam combining sources. First of all, the relationships between single laser emitter′s structureand themodeof laser units, including lateral mode, transverse mode and longitudinal mode, are analyzed. Lateral mode is the main factor which limits the high beam quality for high power semiconductor lasers. Ridge waveguide is the main method adopted to realize single lateral mode. A method called longitudinal photonic bandgap crystal is introduced to manipulate the transverse mode of a single laser unit, which can acquire large optical near field and high beam quality even in high current input. To control longitude mode, usually to acquire single longitude mode in single semiconductor laser unit, distribute Bragg reflectors and distribute feedback structures using gratings in fabrication is also introduced in this section. And then we summarize the methods and some results of controlling modeusedinternationalresearchers. Further more, we introduced the lasers beam technology, including beam shaping and beam combining, considering all conditions of single emitters beam combining, mini bar beam combining, centimeter bar beam combining, laser stacks beam combining and laser systems beam combining. In beam combining technology, we introducted the method of traditional beam combining, including polarizetion beam combining and wavelength beam combining. Then the method of using dense wavelength division multiplexing with volume Bragg gratings to realize beam combinign is also introduced. Spectrum beam combining method using a Bragg diffractive grating is then introduced, which may realize a high beam quality of a single emitter′s beam spot with a laser bar′s optical power. Furthermore, coherent beam combining considering each laser unit′s wavelength, polarization and phase to realize high power high intensity farfield is also introduce. Then, the lastest international reported of high power, high beam quality diode laser combining sources are introduced, and characteristics of laser beam technology and development trends arediscussed and analyzed. Finally, the developments of high power high beam quality diode lasers are prospected. Right now, our country still have a distance below internal research in high quality semiconductor laser chip and beam combining source. The semiconductor laser chips′ power and beam quality needed to be improved. The technology of 10 kW level beam combining and optical fiber coupling technology is still urged to be acquired. Grating fabrication in optical beam combining technology and chip fabrication are also needed to be conquered.

Analysis of thermal characteristics based on a new type diode laser packaging structure

In order to improve the thermal characteristics of single-chip semiconductor lasers and increase the output power of the device, a new type of vertical packaging structure of heat sink is proposed and analyzed. The heat sink retains the advantages of simplicity and being easy to apply, and the performance of heat dissipation has been improved obviously. The new heat sink structure is believed to be more suitable for packaging of the high-power semiconductor laser chips by heat conduction. Finite-element thermal analysis was used to simulate the thermal field distribution and thermal vector distribution in the conventional structure and the new structure. The simulation results show that the thermal resistance of the conventional structure is 2.0 K/W and the thermal resistance of the new heat sink is less than 1.6 K/W. The theoretical calculation results show that the output power of the packaged laser by new heat sinks can be significantly improved.

Heat dissipation in high-power semiconductor lasers with heat pipe cooling system

This study focuses on the application of heat pipes in thermal management for high-power semiconductor lasers. The heat pipe cooling systems are used for heat dissipation in high-power semiconductor lasers. These systems are used instead of water cooling machines to realize a compact and lightweight laser module. The n-shaped heat pipe cooling system, which consists of eight 6 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 73 W from a single-laser unit. The fabricated U-shaped heat pipe cooling system, which consists of ten 12 mm copper heat pipes with sintered powder wicks, can easily handle a heat load of up to 300 W from five laser units. The optical power of the multi-laser module cooled by the U-shaped heat pipe cooling system reaches 210 W. These results indicate that high-power semiconductor lasers can be cooled using heat pipe cooling systems instead of water cooling machines.

Electrical Derivative Measurement of High‐Power InGaAs LDs Under Scanning Current with Variable Step

For the large driving current of high-power semiconductor Laser diodes (LDs), a modified method to measure the electrical derivative of LDs under scanning driving current with variable step length is proposed, which is to achieve the fast and accurate measurement of optical and electrical characteristic parameters of LDs with a relatively small data acquisition. The experimental results show that, with fewer measurements, this method can effectively and accurately measure and extract the LDs corresponding parameters including threshold current (Ith ), voltage-current characteristic (V-I ), luminous power-current relation (P-I ), electrical derivative curve (IdV/dI-I ). The wavelet transformation singularity testing results of the threshold current also verify the accuracy, reliability, and advantage of this method.

Two-state operation of high-power semiconductor lasers with a thick quantum well

We have examined the two-state operation process of the high-power edge-emitting lasers based on AlGaAs/InGaAs/GaAs heterostructure with a thick (90 Å) quantum well in the active region. It has been demonstrated that the laser emission spectrum can be switched between spectral lines corresponding to different optical transitions between the quantum states in the active region. The switching process is governed either by pump current or by temperature. The dynamic characteristics of the switching laser pumped with 100 ns current pulses have been investigated and explained. It has been shown that the current density dependence of internal optical loss can cause the current-initiated switching. The temperature impact is much more important and consists in the charge carrier redistribution in the quantum well. The registered optical power near the switching point was near 2 W in continuous wave and 15 W in pulse mode of operation.

Tunable high-power blue external cavity semiconductor laser

A commercially available high-power GaN-based blue laser diode has been operated in a simple Littrow-type external cavity (EC). Two kinds of EC configurations with the grating lines perpendicular (A configuration) and parallel (B configuration) to the p-n junction are evaluated. Good performance has been demonstrated for the EC laser with B configuration due to the better mode selection effect induced by the narrow feedback wavelength range from the grating. Under an injection current of 1100mA, the spectral linewidth is narrowed significantly down to ∼0.1nm from ∼1nm (the free-running width), with a good wavelength-locking behavior and a higher than 35dB-amplified spontaneous emission suppression ratio. Moreover, a tuning bandwidth of 3.6nm from 443.9nm to 447.5nm is realized with output power of 1.24W and EC coupling efficiency of 80% at the central wavelength. The grating-coupled blue EC laser with narrow spectral linewidth, flexible wavelength tunability, and high output power shows potential applications in atom cooling and trapping, high-resolution spectroscopy, second harmonic generation, and high-capacity holographic data storage.

Numerical study of high-power semiconductor lasers for operation at sub-zero temperatures

We present results on the impact of the Al-content in the waveguide structure on the electro-optical characteristics of 9xx nm, GaAs-based high-power lasers operated at room (300 K) and at sub-zero (200 K) heat sink temperatures. Experimentally a strong improvement of conversion efficiency and output power has been found if the lasers are cooled down. Numerical simulations using a software tool which solves the thermo-dynamic based drift-diffusion equations are able to reproduce the experimental findings. The reasons for the improved performance at lower temperatures are the enhancement of the modal gain and the reduced accumulation of electrons in the p-confinement layers resulting in a reduction of the leakage current. The latter allows the realization of lasers with a reduced Al content having a smaller series resistance and thus further enlarged conversion efficiency at sub-zero temperatures.

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.

大功率半导体激光器性能改善的研究

大功率半导体激光器性能改善的研究