Semiconductor Laser Packaging Research Articles

Review of Issues and Solutions in High-Power Semiconductor Laser Packaging Technology

In the past 20 years, semiconductor lasers have been widely used in medical, industrial, and communication applications, providing a revolutionary and powerful platform for the fifth generation and advanced manufacturing. Semiconductor laser has the advantages of small size, lightweight, high reliability and easy modulation, becoming increasingly popular. However, due to the laser diode emission mechanism limitation, the beam quality is inferior and cannot be directly applied and required to be handled by beam shaping. However, the packaging of multiple beam shaping optical components is accompanied by risks due to misalignment. The misalignment error of the optical components has a great hidden danger to the laser performance. As semiconductor lasers' power gradually increases, lasers' thermal management technology is also increasingly strict. Therefore, this article first reviews the beam shaping technology of semiconductor laser diode array. Secondly, the analysis of the influence of the array semiconductor laser optical device's misalignment is reviewed, and a feasible solution is proposed. Finally, it summarizes the researches on thermal management in high-power semiconductor lasers. This article aims to give readers a comprehensive and broad understanding of semiconductor laser packaging's technical difficulties and to recognize each corresponding solution.

Study and optimization of die-bonding technology for semiconductor lasers based on differential-analysis

This study proposed the method of “differential analysis” based on the study and analysis of the die-bonding technology in semiconductor laser packaging by using the analysis of ray tracing and thermal characteristics to explore the influence of the differential (Δx, the position error between the laser chip and the Submount) on the optical efficiency and heat dissipation performance of the device. Under the influence of the "underhang" effect, the value of Δx was controlled within 12 μm, which can effectively stabilize the output power of the device. Under the influence of the "overhang" effect, the Δx will not have substantial impact on the heat dissipation characteristics of the device. The submount which has the new chamfered structure is designed using this structure, COS (chip on submount) prepared in the semiconductor laser die-bonding technology was shown to exhibit higher stability and reliability.

Thermal management of graphene-induced high-power semiconductor laser package with bidirectional conduction structure

A graphene-based film acted as thermal dissipation channel is introduced to design the package of high-power single-emitter laser diodes. Here we show that heat conduction of high-power laser diodes can be greatly improved via introduction of additional transverse heat dissipation channel with graphene-based film through thermal management. The finite element analysis method is employed to analyse the heat dissipation performance of laser diodes. The epi-up package coupled with graphene is proposed to reduce the thermal stress of laser diodes. In order to increase the thermal dissipation while reducing thermal stress, the effect of the temperature of the active region on account of the thickness of graphene-based film of the package of high-power single-emitter laser diodes is discussed, and the relationship between the output power of semiconductor laser and the heat dissipation effect of graphene-based film is analyzed. The results show that the junction temperature of the active region of graphene-induced package structure is reduced by 9.1 K and the thermal resistance is reduced by 1.52 K/W by using bidirectional conduction graphene-based film compared with the non-graphene-based structure.

基于ANSYS Workbench半导体激光器封装热特性分析

基于ANSYS Workbench半导体激光器封装热特性分析

Laser beam shaping with an ellipsoidal lens

This paper presents a semiconductor laser beam shaping system that can collimate the irradiance profile effectively by using an ellipsoidal lens. Geometrical optics analysis based on the ray tracing method is done and the formulas to calculate the shape of ellipsoidal lens are given. Both the theoretical and experimental result show that the laser beam system works effectively; the divergence angle is reduced to less than 1° in the fast-axial direction. By using epoxy resin, this shaper collimates a semiconductor laser beam and packages the laser diode (LD) at the same time, which simplifies the manufacturing process and greatly reduces the LD volume. Because of the small volume, low-cost, high rigidity and easy fabrication, the shaper is of great value in the field of semiconductor laser diode applications.

Simplified light transport model for irradiation dose calculation of photodynamic therapy

A proper combination of photosensitising agent, oxygen, and a specific wavelength of light is necessary for the cytotoxic destruction of cancerous cells by Photodynamic Therapy (PDT). For a light source, semiconductor lasers are suggested for the light delivery system, however packaging of semiconductor lasers for optimal optical power output is challenging. In this paper an optimal design of a semiconductor laser package with De-Ionised (DI) water-cooling system is described and analysed. A microwave antenna is designed to provide local heating of the esophagus, leading to an increase in local oxygenation of the tumor to generate singlet oxygen for cellular death.

Practical Design of Lensed Fibers for Semiconductor Laser Packaging Using Laser Welding Technique

We propose a set of guidelines for the practical design of lensed fiber for the optical coupling of semiconductor lasers in butterfly packages using laser welding. These guidelines have optimized the tradeoff between coupling efficiency and alignment tolerance. Moreover, a radius of curvature of 11 mum is shown to be optimal for semiconductor lasers whose divergence angles range from 5deg to 30deg. To experimentally evaluate the design, lensed fibers were assembled by a Nd:YAG laser welding technique in conventional butterfly packages and their coupling efficiencies were 28%-72% without horizontal misalignment compensation.

Direct De-Ionized Water-Cooled Semiconductor Laser Package for Photodynamic Therapy of Esophageal Carcinoma: Design and Analysis

Effective delivery of the activation light for photodynamic therapy (PDT) of internal organs is a challenge. In this paper, we present a direct de-ionized water-cooling semiconductor laser package design for PDT of esophageal carcinomas. This self-sustained photonic light delivery system is designed to provide the correct amount of light dose for optimal treatment. The direct de-ionized water-cooling technique discussed in this paper not only removes heat efficiently but also results in a high optical power output. Voltage-current and power-current characteristics, and near field optical patterns for unidirectional and direct de-ionized water-cooling, are used to show the validity of the technique. Modeling of fluid flow is conducted to investigate the effect of flowing water over the laser package.

非制冷980 nm半导体激光器封装设计与热特性分析

非制冷980 nm半导体激光器封装设计与热特性分析

Thermal stresses in box-type laser packages

The effect of Au coating on thermally induced stresses in box-type semiconductor laser packages was investigated by a finite-element method (FEM). The simulated results showed that Invar–Invar joints with Au coating have maximum stresses two times higher than joints without Au coating. This is due to the different coefficients of the thermal expansion (CTE) between dissimilar materials of Invar and Au, resulting in higher stresses. Maximum stresses were also found to be increased as the Au thickness increased. This effect is attributed to the increase in the thermal gradient in the welded region provided by the increased thermal conduction of the thicker Au coating layer. These results suggest that both the difference in CTE between dissimilar materials and higher thermal conduction of Au coating layer have an important impact on thermally induced stresses for optoelectronic packages having laser-welded Au coated materials.

Crack formation mechanism in laser-welded Au-coated Invar materials for semiconductor laser packaging

Crack formation mechanism in laser-welded Au-coated Invar materials for semiconductor laser packaging is investigated experimentally and numerically. Experimental results obtained from metallography, scanning electron microscope (SEM), SEM mapping, and energy dispersive spectrometer (EDS) line profile show that high concentration of Au composition accumulate near the crack region. The cause of Au accumulation may come from the segregation of Au along the track region. A finite-element method (FEM) is performed on the calculation of thermal stresses during spot-welding for Au-coated Invar materials. Numerical results show that the high tensile stresses of the Au segregation layer generated by rapid solidification shrinkage is the possible cause for crack formation. Both experimental and numerical results suggest that the crack formation mechanism in laser-welded Au-coated optoelectronic materials is directly related to the combined effects of the Au segregation and high tensile stresses induced by the strain shrinkage during the final stage of solidification.

Direct evidence of au segregation in laser welded au-coated invar material

Evidence of the Au segregation within the crack region in laser welded Au-coated Invar material for semiconductor laser packaging is investigated. Results obtained from the metallography, scanning electron microscope (SEM) mapping, energy dispersive spectrometer (EDS) line profile, and Auger electron spectroscopy find that the cracks in the welded joints occur around the Au rich boundaries. The SEM Au mapping and EDS line profiles show that Au accumulates at the crack region. This direct observation indicates that one of the primary causes of cracks in laser welded Au-coated materials is due to the segregation of Au in the final stage of solidification. Detailed knowledge of the defect formation mechanisms in laser welded Au-coated materials is important for the practical design and fabrication of reliable optoelectronic packaging.

Effects of Au coating on thermal stresses in stainless-to-Kovar packages

A finite-element method (FEM) analysis has been carried out on the thermally-induced stresses generated when stainless steel covers are laser-welded to Au-coated Kovar TO headers during the packaging of semiconductor lasers. In particular, the effect of varying the Au coating thickness of these stresses was investigated. Maximum stresses were found to be reduced as the Au thickness increased. This effect is attributed to the reduction in thermal gradient in the weld region provided by the increased thermal conduction of thicker Au. The result suggests that adequate Au coating thickness is important for ensuring good reliability of opto-electronic packages having laser-welded caps.

Effect of Au thickness on laser beam penetration in semiconductor laser packages

Comprehensive measurements of the dependence of the weld width, penetration depth, and joint strength on the Au coating thickness in laser welding techniques for semiconductor laser packages are presented. The results obtained from the Invar-Invar joints show that the welded joints with thick Au coating exhibit narrower weld width, shallower penetration, and hence less joint strength than those the package joints with thin Au coating. A finite-element method (FEM) has been carried out on the effect of Au thickness on laser beam penetration in Invar-Invar joints. This method has been employed successfully to predict the laser beam penetration in laser welded Au-coated materials that the weld width and the penetration depth are reduced as the Au coating thickness increases. The likely cause for the reduction is the increased thermal conduction of thicker Au in the welded region. In addition to Au coating, the effect of Ni coating on laser beam penetration is also presented. Detailed knowledge of the effect of Au coating thickness on laser beam penetration is important for the practical design and fabrication of reliable optoelectronic packaging having laser welded Au-coated materials.

Reduction of post-weld shift in semiconductor laser packaging

A reduction of post-weld shift (PWS) in semiconductor laser packaging using a laser welding technique is presented. It is found that the PWS and its association with the power coupling loss of the laser packaging can be reduced under proper pressure constraint. Characteristics of defect mechanisms in laser welding techniques for semiconductor laser packaging are also investigated experimentally. The results in the stainless-to-Kovar joints show that the surface cracks are dependent on the Au thickness on the Kovar material. The low solubility of gold in the Kovar is identified as the defect mechanism for surface cracks. Preliminary reliability data demonstrated that these laser packages without crack defects in the welded joints are reliable.

Turn-key, liquid-nitrogen-cooled 3.9 [micro sign]m semiconductor laser package with 0.2 W CW output

A CW 3.9 µm diode-pumped InAsSb/GaSb laser yielded 0.2 W at 84 K and 0.26 W at ~68 K in a collimated beam, limited only by the pump power. The beam exhibited 62% coupling efficiency into a 250 µm core, 0.2 NA infrared fibre.

Defect formation mechanisms in laser welding techniques for semiconductor laser packaging

In this work, the authors experimentally investigate defect formation mechanisms in spot-welding techniques for semiconductor laser packaging. Results obtained from the stainless-to-stainless steel joints indicate that the dimension of hole formation depends on the laser power density, and the hole disappears as the power density is below 3/spl times/10/sup 5/ W/cm/sup 2/. In the stainless-to-Kovar/sup TM/ joints, surface cracks are eliminated by reducing the gold thickness from the Kovar/sup TM/ before welding, while the centerline cracks in the fusion zone are eliminated by the air gap tightness between the Kovar/sup TM/ and stainless steel. The excess laser energy is the possible cause for hole formation. The low solubility of gold in the Kovar/sup TM/ and the large air gap between the joints are the possible causes for surface cracks and enhancing centerline crack propagation, respectively. A technique for reduction of post weld shift (PWS) in semiconductor laser packaging is also presented. Preliminary reliability data demonstrated that these laser packages, which do not have hole and crack defects in the welded joints, are reliable.

Capillary bonded components for injection laser transmitter modules

The packaging of semiconductor lasers with fibre-optic and electronic components is described, based on the use of an Si chip as a common substrate. The components are attached by flowing solder in grooves underneath the components by capillary action. The modules are small in dimension, and fabricated using automatable techniques for low cost.

Wavelength sensed mode control of semiconductor lasers

A wavelength detector suitable for use with semiconductor laser packages has provided control of laser emission wavelengths to better than 0.1 A. Special features of the detector have also enabled mode hopping, gain profile shift and end of single-mode lifetimes to be observed.