High-power Semiconductor Lasers Research Articles

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

传导冷却单巴高功率半导体激光器热应力和smile研究

传导冷却单巴高功率半导体激光器热应力和smile研究

Theory of direct and indirect effect of two-photon absorption on nonlinear optical losses in high power semiconductor lasers

The effect of the transverse laser structure on two-photon absorption (TPA) related effects in high-power diode lasers is analysed theoretically. The direct effect of TPA is found to depend significantly on the transverse waveguide structure, and predicted to be weaker in broad and asymmetric waveguide designs. The indirect effect of TPA, via carrier generation in the waveguide and free-carrier absorption, is analysed for the case of a symmetric laser waveguide and shown to be strongly dependent on the active layer position. With the active layer near the mode peak, the indirect effect is weaker than the direct effect due to the population of TPA-created carriers being efficiently depleted by their diffusion and capture into the active layer, whereas for the active layer position strongly shifted towards the p-cladding, the indirect effect can become the dominant power limitation at very high currents. It is shown that for optimizing a laser design for pulsed high power operation, both TPA related effects and the inhomogeneous carrier accumulation in the waveguide caused by diffusive current need to be taken into account.

Narrowing of the emission spectra of high-power laser diodes with a volume Bragg grating recorded in photo-thermo-refractive glass

The spectral characteristics of a high-power semiconductor laser with an external cavity in which longitudinal-mode selection is implemented by means of a holographic volume Bragg grating recorded in photo-thermo-refractive glass are investigated. Mode selection leads to narrowing of the spectrum of the laser diode from an initial width of 6 nm to 5 A. In the narrowed spectrum, a fine structure representing a set of eigenmodes that correspond to the length of a laser chip is resolved. The number of these modes is limited by the width of the spectral selectivity curve of the grating. It is shown that insertion of the grating into the cavity leads to severalfold enhancement of the grating selectivity. It is demonstrated that the implemented external-cavity design makes it possible to smoothly tune the laser emission wavelength in a 10-nm range.

Spectrum Improvement of a High-Power Broad-Area Laser Diode Based on a Grating Semi-Feedback External Cavity Scheme

We propose a grating semi-feedback external cavity (GSFEC) scheme for high-power broad-area laser diodes for improving the spectrum characteristics of high-power semiconductor lasers. We design this scheme as two crossed cylindrical resonators employing a holographic diffraction grating and a rectangular highly reflecting mirror. In our experiments, we obtain stable spectrum characteristics over a tuning range of 5 nm, with maximum output power up to 764 mW at an operating current of 3.5 A. The wavelength drift rate with injection current decreases from 0.59 nm/A of free-running condition to 0.2 nm/A, and the laser bandwidth is compressed to 21.5% at 2 A.

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.

High Wall-Plug Efficiency 1060 nm High Power Semiconductor Laser

By analyzing the factors which affect the wall-plug efficiency of semiconductor Laser Diodes (LDs), a high efficiency 1060 nm LD was designed, including active region, waveguide layers, and cladding layers. The simulation result shows that the component of In in InGaAs in the active region cannot be too small, otherwise the thickness of InGaAs active layer will exceed the critical thickness, meanwhile the asymmetric large optical cavity can decrease the cavity loss effectively. The epitaxial structure was grown by MOCVD, experimental results of varying cavity length showed that the internal quantum efficiency reached 98.57%, and the cavity loss was only 0.273 cm?1. Devices with 4 mm-cavity-length and 100 μm-strip-width were fabricated, 47.4% wall-plug efficiency was reached under QCW pulse condition at room temperature, and the peak wavelength was 1059.4 nm.

大功率低阈值半导体激光器研究

大功率低阈值半导体激光器研究

高功率半导体激光器陶瓷封装散热性能研究

高功率半导体激光器陶瓷封装散热性能研究

Analysis of origin of measured 1/f noise in high-power semiconductor laser diodes far below threshold current

The 1/f noise is measured under the bias one tenth the threshold current of the InGaAs quantum well high-power semiconductor laser diodes (LDs). The noise origin is analyzed using the current and voltage 1/f noise and dynamic resistance characteristics. Then the relationship between the noise and the internal defect is analyzed according to the differences of LDs in the noise intensity and the fluctuation near the initial electrical derivative peak. The result shows that with currents 0.13mA–1mA, the dynamic resistance of the LDs is in the magnitude of hundreds of ohms, when the changing rates of both the noise intensity and the resistance reflect the typical features of the active region, while with currents 8mA–32mA, the dynamic resistance drops under 10Ω and its changing rate slows down, when the 1/f noise intensity trend shows the features of the contact resistance. Moreover, the electrical derivative of LDs with weaker noise fluctuates milder and has more conspicuous initial peaks, while the electrical derivative of other LDs fluctuates acuter and hardly shows distinct initial peaks. The results indicate that the 1/f noise from the active region can be measured under bias currents far lower than the threshold currents of the LDs, and it can indicate the defects in the active region and further the reliability of the device.

Electro-optical modeling of high power semiconductor laser based on an InGaAs/GaAs/InGaP heterostructure

We present the electrical-optical modeling of a high power semiconductor laser diode for emission at 800 nm wavelength. We describe a thorough detailed procedure for the modeling of a semicondutor laser device with a Separate Confinement Heterostructure (SCH), based on the material alloys of III-V compounds families, InGaAsP/InGaAsP/InGaP on GaAs substrates. The heterostructure active region produces a peak emisson at 0.8 nm. The SCH heterostructure comprises a quntum well 100 A thick of InxGa1-xAsyP1-y (x = 0.14, y = 0.73) alloy. The quantum barriers layers comprise quaternary materials of composition InxGa1-xAsyP1-y (x = 0.39, y = 0.2). The confining layers of the quaternary SCH heterostrucure may involve higher gap materials, such as ternary InGaN or quaternary AlGaInP. Band gaps of quaternary materials in the well and confining layers of the SCH heterostructure correspond to wavelengths of 0.8 m (Eg = 1.55 eV) and 0.69 m (Eg = 1.8 eV), respectively.

Mapping of laser diode radiation intensity by atomic-force microscopy

The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

Optical-cell model based on the lasing competition of mode structures with different Q-factors in high-power semiconductor lasers

A model describing the operation of a completely optical cell, based on the competition of lasing of Fabry-Perot cavity modes and the high-Q closed mode in high-power semiconductor lasers is proposed. Based on rate equations, the conditions of lasing switching between Fabry-Perot modes for ground and excited lasing levels and the closed mode are considered in the case of increasing internal optical loss under conditions of high current pump levels. The optical-cell operation conditions in the mode of a high-power laser radiation switch (reversible mode-structure switching) and in the mode of a memory cell with bistable irreversible lasing switching between mode structures with various Q-factors are considered.

Preparation for Bragg grating of 808 nm distributed feedback laser diode**Project supported by the National Natural Science Foundation of China (No. 11474036), and the National Key Lab of High Power Semiconductor Lasers Foundations (No. 9140C310103120C3101).

The second-order Bragg grating structure of an 808 nm distributed feedback semiconductor laser diode was designed and optimized. The grating with a period of 240 nm was fabricated on GaAs substrate by holographic photolithography and wet etching. Images of optical microscopy, scanning electron microscopy and atomic force microscopy show that the grating has a period of 240 nm, duty cycle of 0.25, depth of 80 nm, with perfect surface morphology, good fringe continuity and uniformity.

Design and Simulation of Fractional Order Control Systems Based on Bode's Ideal Transfer Function

The fractional order calculus theory and its modeling methods have been applied widely in control field. And design of fractional order control systems become hot point of recent years. This paper establishes fractional order systems which parameters are obtained by Bode’s ideal transfer function method to get the desired frequency response. Apply this method a new control structure of fractional order pseudo-derivative feedback (FOPDF) is suggested. Control methods are designed for integral first order system and for fractional first order system, and apply to a real high power semiconductor laser diodes constant temperature controlling system and the hydraulic servo systems and the electric drive system, the simulation results indicate that the effectiveness and validity of this method.

Suppressing the process of charge carrier delocalization in high-power pulse-pumped semiconductor lasers

The process of charge carrier delocalization in high-power semiconductor lasers is examined under high current, pulse-pumped operation conditions. It is established that the carrier delocalization process is mostly determined by the injection of electrons (rather than holes) into the waveguide. Two methods of suppression of carrier delocalization are experimentally demonstrated, which are based on increasing the waveguide bandgap width and on using the waveguide containing a potential energy barrier for electrons in the p-region.

Effect of Pt diffusion barrier layer in Ni/AuGe/Pt/Au on ohmic contact to n-GaAs**Project supported by the National Natural Science Foundation of China (No. 11474036), and the National Key Laboratory of High Power Semiconductor Lasers Foundations (No. 9140C310103120C31114).

The multi-layer metals of Ni/AuGe/Pt/Au with a Pt diffusion barrier layer of ohmic contact to n-GaAs were studied. The surface morphology and ohmic contact resistivity of multi-layer metals were characterized, with and without the Pt diffusion barrier layer for comparison. The SEM and EDS measurements show the Pt diffusion barrier layer can block the interdiffusion of atoms in multi-layer metals, and improve the surface morphology. The TLM results show that the samples with a Pt diffusion barrier layer have uniform ohmic contact resistance, indicating that the Pt diffusion barrier layer can increase the repetition and uniformity of ohmic contact to n-GaAs, and improve the thermal stability and reliability of GaAs-based devices.

A Design of Fuzzy-PID Controller of Constant Temperature for Semiconductor Laser Diodes

The paper introduces two types of precise temperature controllers for high power semiconductor laser diodes. We apply a category of self-tuning parameter fuzzy-PID controller and a kind of neuronal network optimized rules fuzzy-PID controller to realize stable temperature controlling. Also we simulate this two methods using Matlab. The result proves that the new method has more superiority than traditional means, such as PID controlling, etc. And further improvement on constant temperature control will inevitably promote the reliability of LD.

Optical investigation of ultrathin Al2O3 films grown on GaAs(100) substrates

The optical and structural properties of ultrathin aluminum oxide films grown on GaAs(100) substrates are studied by means of IR and UV spectroscopy. It is shown experimentally that such films are highly transparent to optical radiation in the infrared, visible, and ultraviolet regions, and are potentially of value in creating antireflection coatings for mirrors of high-power semiconductor lasers based on AIIIBV.

Surface activated bonding of GaAs and SiC wafers at room temperature for improved heat dissipation in high-power semiconductor lasers

Thermal management of high-power semiconductor lasers is of great importance since the output power and beam quality are affected by the temperature rise of the gain region. Thermal simulations of a vertical-external-cavity surface-emitting laser by a finite-element method showed that the solder layer between the semiconductor thin film consisting of the gain region and a heat sink has a strong influence on the thermal resistance and direct bonding is preferred to achieve effective heat dissipation. To realize thin-film semiconductor lasers directly bonded on a high-thermal-conductivity substrate, surface-activated bonding using an argon fast atom beam was applied to the bonding of gallium arsenide (GaAs) and silicon carbide (SiC) wafers. The GaAs/SiC structure was demonstrated in the wafer scale (2 in. in diameter) at room temperature. The cross-sectional transmission electron microscopy observations showed that void-free bonding interfaces were achieved.