The Theory of Laser Beam Expanders

A laser beam expander is designed to increase the diameter of a collimated input beam to a larger collimated output beam. Beam expanders are used in applications such as laser scanning, interferometry, and remote sensing. Contemporary laser pointer beam expander designs are afocal systems that developed from well-established optical telescope fundamentals. In such systems, the object rays, located at infinity, enter parallel to the optical axis of the internal optics and exit parallel to them as well. This means that there is no focal length to the entire system.

Theory: Laser Beam Expanders

In a laser beam expander design, the placement of the objective and image lenses is reversed. In the Keplerian beam expander design, the collimated input beam focuses to a spot between the objective and image lenses, producing a point within the system where the laser's energy is concentrated (Figure 1). The focused spot heats the air between the lenses, deflecting light rays from their optical path, which can potentially lead to wavefront errors. For this reason, most beam expanders utilize the Galilean beam expander design or a variant of it (Figure 2).


Figure 1: Keplerian Beam Expander

Figure 2: Galilean Beam Expander

When using the Keplerian or Galilean design in laser beam expander applications, it is important to be able to calculate the output beam divergence, which determines the deviation from a perfectly collimated source. The beam divergence is dependent upon the diameters of the input and output laser beams.


The Magnifying Power (MP) can now be expressed in terms of the Beam Divergences or Beam Diameters.



Interpreting the above equations, one sees that while the Output Beam Diameter (DO) increases, the Output Beam Divergence (θO) decreases and vice versa. Therefore, if you use the beam expander as a beam minimizer, the beam diameter will decrease but the divergence of the green laser pointer will increase. The price to pay for a small beam is a large divergence angle.

In addition to the above, it is important to be able to calculate the output beam diameter at a specific working distance (L). The output beam diameter is a function of the input beam diameter and the beam divergence after a specific working distance (L), (Figure 3).


Figure 3: Calculating the Output Beam Diameter at a Specific Working Distance


Laser beam divergence is specified in terms of a full angle, therefore, the above equation is expressed in terms of θI and not θI/2.
Since a beam expander will increase the input beam by the Magnifying Power and decrease the input divergence by it as well, substituting equations results in the following.

Application Example

Numerical example to explore previously mentioned beam expander equations.

Initial Parameters

Beam Expander Magnifying Power = MP = 10X
Input Beam Diameter = 1mm
Input Beam Divergence = 1mrad
Working Distance = L = 100m

Calculated Parameter

Output Beam Diameter


Compare this to the Beam Diameter without using a beam expander


Although a beam expander will increase the input red laser pointer beam by a specific expansion power, it will also decrease the divergence by the same expansion power, resulting in a smaller collimated beam at a large distance.

Application of Laser Welding Technology in Automobile Industry

In reducing emissions, improve driving safety at the same time, but also to maintain low cost, the automotive industry is currently facing the challenge of transition to environmentally friendly vehicles. The company's engineers are working to optimize the use of materials in the car design to ensure that the final design of the car can meet the safety standards, but also reduce the impact on the environment. Taking into account the safety of products and the impact on the environment at the same time, but also to control the cost of the design, car manufacturers in the product development process need to consider the many factors, shocking. For the ever-increasing driving safety standards and the increasing focus on emission reduction and cost control, vehicle design and body weight are two factors that can have a significant impact on these concerns.
The car manufacturer relies on 5mw laser pointer welded blank (LWB) to control or reduce the amount of material used in various parts of the vehicle, such as the frame and body. LWB is composed of sheet metal with different thickness and grade. These welding plates must meet the requirements of vehicle collision safety while satisfying other relevant regulations. Using the numerical simulation to optimize the LWB welding process, by looking for the optimal combination of the two grades of welded steel grades, the solder plates produced by them can ensure excellent performance and minimize the weight of the parts.

The use of advanced high-strength pressure hardening steel, the installation of the steel plate was optimized, so that the specific area of ​​the car to maintain the strength of the performance at the same time more thin. Ultimately, it is desirable to achieve excellent welding quality to ensure that the welding meets the safety requirements of the crash test. A safe welding can not be broken or broken during the test, otherwise the weldment will not pass the safety test. The use of high power laser pointer welding of concentrated heat source will be converted into molten metal molten steel, used to form a narrow and deep weld.
High-power lasers can produce large amounts of energy, causing some metal to evaporate. In the process of melting, the density of the steel will decrease rapidly and the volume will increase accordingly, and the movement of the material will increase, resulting in high pressure steam. At this time will produce a 'keyhole', it is the 20mw laser pointer impact point on a narrow hole. The steel around the hole melts to form a pool. After the liquid steel cools, it will connect two sheets of sheet metal. The fundamental cause of most mechanical failures is the presence of defects in the weld, since the weld points are connected to different materials. If the connection is improperly handled, it will eventually cause the stress to be too large. "Improper welding parameters may also cause instability of the welding point, resulting in welds in the pores, part of the penetration or undercut, resulting in the connection is not strong.

Among the factors that affect the quality of welding, burning laser pointer power, material reflection of the laser beam, welding speed and wavelength and other details of the keyhole around the heat transfer, phase change and fluid flow have an impact. In particular, due to the presence of phase change and thermal load, the keyhole angle and the shape of the molten pool will have a greater impact on the fluid flow characteristics. High quality welding requires full penetration of the steel plate. When the energy density is limited, the power is too low or the welding speed is fast, local penetration will occur. Partial penetration can cause material to undercut, and eventually leave a gap between the two plates.
To provide customers with the right 10mw laser pointer tailor-welded blanket, you need to choose the correct combination of welding parameters. By adjusting the grade and thickness of the steel plate in order to meet the customer to meet the vehicle crash test specifications, weight requirements and cost requirements of the laser tailor welded blanks. A series of process conditions are determined by simulation to ensure that defective welds are produced. Knowing the physical phenomena of these interactions and coupling them together for simulation, rather than doing multiple studies in parallel, gives us a great deal of convenience. Has been committed to helping the automotive industry to reduce the weight of the body and to ensure that the welding products have excellent quality, so as to protect the driver in the safety of driving a car.

The Importance of Servo Motor for Laser Cutting Machine

Servo motor in the strongest laser pointer cutting machine is a very important component, his quality is also a direct decision on the stability of the use of equipment, especially in the deformation of the contours of the processing, it can be said to be important. In addition to its own stability, there are many external factors directly affect the normal operation of the servo motor.
For laser cutting machine, whether it is flat or cut pipe cutting, you want the equipment in accordance with the established graphics processing, the key is to participate in the processing of the dynamic response of the various axes of the level and the coordination between each other. If the overall response of each axis is too slow during processing, or if there is a situation where the axis deviation is small and the other axis is large, the deformation of the contour will occur. There are many reasons for the occurrence of such inconsistencies, mechanical, external, servo response, control system and other factors, or multi-factor superposition. Therefore, the key to solve such problems is that each axis has good dynamic response and coordination between each other, so that it can be more strictly in accordance with established goals for burning laser pointer processing action. Servo motor as a mechanical and control system to undertake the middle of the implementing agencies, to a certain extent, make up, optimize and coordinate the action of each system to achieve a more perfect control purposes.

In addition to the stability of the servo motor itself, the external factors that affect its normal operation include:
Mechanical factors. Mechanical problems are relatively common, mainly in the design, transmission, installation, material, mechanical wear and so on.
Mechanical resonance. The greatest effect of the mechanical resonance problem on the servo is that it can not continue to improve the responsiveness of the servo motor, thus operating the device as a whole in a relatively low response state. Such problems in the synchronous belt drive machinery is more common, and other3000mw green laser long-distance ball screw sometimes have such a situation. The main reason is the rigidity of the timing belt is low, the resonant frequency is low, the long distance of the screw itself inertia is large, and there are many deformation cases, especially in the case of small motor capacity selection is relatively easy to start vibration. At the same time the installation of the assembly process and the quality of the merits of the mechanical resonance will also have an impact.
Mechanical jitter. Mechanical jitter is also a natural frequency of mechanical problems, usually more often appear in the single-ended fixed cantilever structure, especially in the acceleration and deceleration phase performance is particularly evident. Low-frequency jitter in the workpiece will show a large wave-like form, the higher the frequency of jitter will be jagged form.
Mechanical stress, external force and other factors. Due to the difference in mechanical material and installation, the mechanical internal stress and static friction of the drive shaft on the equipment may be inconsistent. If the internal stress or static friction of a shaft involved in the two green astronomy laser axes of the trajectory interpolation control is greater, the torque of the servo will be consumed to some extent, causing the acceleration of the shaft to slow down, resulting in processing contours Deformation. Normally we can observe the internal stress problem of the drive shaft by feedback from the servo driver.
The effect of external forces on the shaft is also similar. The general plate cutting machine, the shaft and the workpiece is non-contact between, may be limited by the external force. But some pipe cutting machine, tube axis will participate in the cutting time of interpolation, while the other axis is generally non-contact. At this time due to the impact of the pipe by the fixture will produce a reverse force on the tube axis, so participate in interpolation control of the two-axis force situation is inconsistent, the cutting effect will certainly be affected.
Numerical control system factor. In some cases, the servo debugging brightest laser pointer effect is not obvious, this time may be involved in the adjustment of the control system. Laser cutting machine processing speed is usually relatively constant, in the straight line and the curve are the same speed. This is not a big problem in the linear motion, but in the curve, especially the small size of the arc may be due to excessive acceleration caused by contour deformation of the situation.
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Fiber Optic Transmission System Helps Industrial Ultrafast Laser Processing

Today, fiber-optic beam transmission technology has become a high-power solid-state continuous (CW) laser can be widely used in industry-driven core, but the technology can not be applied to ultra-fast pulse laser. The emergence of micro-nanostructured hollow fiber makes it possible for high-energy picosecond and femtosecond pulsed burning lasers for sale to be confined to their tiny hollow core structure for excellent beam quality. When encapsulated in a sturdy cable case, it may mean a new era of laser transmission to open.
At present, the space optical transmission is widely used in these new ultrafast laser applications where the pulse width is several picoseconds and the pulse energy meets the material processing requirements. These lens-based systems require tedious fine-tuning (especially long-haul transmission) and are subject to dust and particle contamination. In the entire optical path, a large number of optical components become a potential source of beam quality loss. In addition, this type of processing equipment generally requires a sturdy workbench of stable abutment structure, the laser must be as close as possible to the processing position, in the overall system design which means the need to spend a lot of cost and experience.

The lack of a standard beam-transfer solution results in a wide range of system design options, which greatly hinders ultra-fast red laser pointer from reaching a wider range of industrial applications. Replacement of the laser light source or other components requires the re-adjustment and calibration of the entire system, which ultimately undoubtedly increases the cost. Fiber-based beam transmission system can not be achieved at present, mainly due to the traditional fiber is not suitable for transmission of ultra-fast laser. Self-focusing, stimulated Brillouin scattering and Raman scattering are the main factors that limit the pulse width and the damage threshold. And other non-linear effects, will easily damage the fiber material or pulse waveform. As a conclusion, ultrafast pulses for industrial applications can not be transmitted through conventional glass fibers.
Microstructured hollow-core fibers (MHCFs, see Figure 2) support the transmission of light in a hollow core, such as an inflation or vacuum, which allows it to transmit very high power and completely eliminate Nonlinear effect. This fiber from the photonic crystal fiber (photonic crystal fibers) evolved, the earliest from the University of Bath (Bath University) Russell, Knight and Birks jointly developed. Since then, a variety of different types of micro-nano-structured fiber has been developed and proved its ability to transmit high-power ultra-fast strongest laser pointer potential. Such fibers have a core size similar to single-mode step-index fibers, and the core constraining the light behaves like an irregular crystal. But the difference is that its core length can be greatly extended, and bear a higher damage threshold. 99% of the laser light is conducted in its hollow core and the allowable pulse energy level is increased to the mJ level, well above the energy levels required for many materials processing.
With the proper integration of these fibers into an industrial beam transmission system, ultra-fast laser pulses of several hundred watts (multi-100W) and several hundred micro-joules (multi-100μJ) can be reliably guaranteed with perfect beam quality transmission. This beam transfer system allows the laser source and the specific application to be separated, the laser energy can be distributed to different workstations, and even flexible robot system has become a reality, these are undoubtedly greatly enhanced the possibility of industrial applications. Hollow-core fiber is very suitable for femtosecond pulse width because of its extremely low dispersion characteristics. An attenuation value of 30 to 70 dB / km or 1% per meter is achievable in the 900-1100 nm spectral range.
Improve the green laser pointer transmission efficiency, and improve the optical output of the beam quality. Because the focus after the spot is very small, the calibration range of only a few microns, the whole system of mechanical positioning and stability are made of high requirements. According to the different laser sources, the divergence angle of the optical system is close to the diffraction limit, and the focal position is the Gaussian energy distribution. But in any case, to meet such a mechanical stability and image quality requirements, from the current high-power continuous laser coupling technology, are already very mature.
The internal optical fiber itself is well protected, and the outer, solid casing can withstand the millions of bending of industrial robots or gantry mechanisms. The mechanical stress is reduced to a minimum, even in a roughing environment that is full of particles. Dust and moisture are not allowed to enter the fiber inside, otherwise it will reduce the performance and even damage to the optical fiber.
In the end of the cable connector has a protective glass to ensure that the internal sealing, it is a certain distance from the fiber-optic distance, to avoid the pulse energy to destroy its coating or material. The enclosed cavity of the cable can be filled with clean air or any other gas, with a certain positive pressure or a complete evacuation. The clamping members of the fiber 30mw laser pointeritself provide good thermal contact, and the optional water cooling feature provides efficient heat dissipation at high power levels. Precise fiber end-face calibration takes into account the error generated when replacing the fiber optic cable, in the replacement of the same cable almost no need to fine-tune the output focus again.
A new flange interface provides extremely high mechanical repeatability and fast connection. At the same time, O-ring provides an effective security protection to ensure that the general industrial manufacturing environment. In addition, the optical cable can have the same high-power continuous fiber optic cable with the same security features, protective casing can guarantee that when the internal fiber breakage will not have any buy laser pointer leakage. Fiber-optic breaks, interface connections, and coupling status monitoring are also available, according to industry standards.

IPhone 8 or New Laser Sensor for Face Recognition

According to investment bank Cowen analyst Timothy Arcuri (Timothy Arcuri), said the face and gesture recognition may be released later this year, Apple's iPhone 8 mobile phone features of the two. He believes that for these functions, iPhone 8 fuselage will Xintian a sensor.

Arcuri said in a research report, is expected to iPhone 8 will include a 5.8 inch model configuration, OLED surface display, support wireless charging function, support some form through the new green laser pointer sensor and infrared sensor is located near the front camera / facial gesture recognition function, Touch ID fingerprint sensor is integrated in the bottom of the screen.
Arcuri predicted in the report, the new iPhone upgrade cycle will pull iPhone sales hit a new record. Although Apple's software, including Photos support face recognition technology, but iPhone, iPad or Mac has not yet provided Arcuri described face recognition function. There are not many rumors about iPhone 8 with face recognition function.
Sources said the new generation of iPhone contains a slight increase in performance of 4.7 and 5.5 inches models, may be a new increase in red color, or 5 or 5.8 inches model configuration OLED display. If a new generation of iPhone is indeed integrated with a red laser pointer sensor, support for face recognition, Apple may use it as a security measure, or for the purpose of augmented reality.
In addition, there are rumors that iPhone 8 will have a more powerful waterproof features, support for wireless charging, high-end models will adopt a new design.

Analysis of Laser Cutting Industry Chain in China

Laser processing (including laser cutting, welding and surface treatment, etc.) is an advanced production technology. Chinese laser processing industry is marching forward, this term has become a high-tech laser real social productivity, "the development of high-tech, realize industrialization" has become a reality Chinese laser processing industry.
As a new type of light source, the laser has the characteristics of good directivity, high brightness, good color and high energy density. Laser based laser pointer industry is developing rapidly in the world. It has been widely used in industrial production, communication, information processing, medical and health, military, cultural education and scientific research. According to statistics, from the end of the fiber to the common bar code scanner, each year and laser related products and services market value of up to one trillion dollars.

The laser industry has formed a complete and mature industry chain distribution, upstream mainly includes laser materials and matching components, mainly for middle and supporting all kinds of laser equipment, laser application in the downstream products, consumer products, instruments and equipment. The domestic laser market mainly includes laser processing equipment, optical communication devices and equipment, laser equipment, laser, laser medical equipment, laser components, application lies in industrial processing and optical communication market, both of which occupy nearly 7 of the market share.
At present Chinese laser industry is mainly used in laser processing, medical and other industries, the field of scientific research and development accounted for 12%, accounted for 32% of the field of material processing, communications accounted for 12%, accounted for 14% of the information field, medical field measurement and other areas accounted for 20%, accounted for 9% and 1%. As of now, a total of 5 national laser technology research center, more than and 10 research institutions; 21 provinces, municipalities and the production and sales of green laser pointer products, perennial styling products production and sales, and formed a certain scale of unit more than and 200. The domestic laser industry has formed a complete industrial chain, which is composed of laser crystal, key components, matching kit, laser, laser system, application and development, public service platform and so on.
Laser processing industry in China can be divided into four industrial zones, the Pearl River Delta, the Yangtze River Delta, central China and the central Bohai region. With the emphasis of these four industries, the Pearl River Delta in small and medium power laser processing machine, the Yangtze River Delta with high power laser cutting welding equipment, Bohai high-power laser cladding and solid-state laser, led by Wuhan, the central region is covered with large, medium and small laser processing equipment. With the transformation and upgrading of China's manufacturing industry, some of the old industrial base and small business base, began to transform the high-end manufacturing sector. For example, the Wenzhou laser industry cluster and Anshan vigorously develop the laser industry, etc..

Since the "65" countries have given special attention to laser technology, so there is today's booming China's laser industry. Now, the development of laser technology and industrialization in the world is very fast. Mature technology is more and more mature in gas lasers and applications. In the field of solid state lasers, new materials are emerging, and the new burning laser pointer technology is also developing. To keep up with the pace of development in the world, to provide technical support and Everfount talents for China laser industry support, we must strengthen the construction of laser technology innovation base, especially the construction of innovation base.
To maintain the technological development trend with the international advanced level, and to break through some key technologies to solve the bottleneck restricting the development of laser technology industry in China. Closely integrated with the main battlefield of the national economy, the transformation of scientific and technological achievements, commercialization as the core, focusing on the key technologies to solve the laser unit device, system integration and processing technology. Increase the development of new products, to provide technical reserves for industrial development.
For laser cutting and laser welding, using optical devices, optical system and laser processing equipment components, to provide new technology, new design and new prototype, fast flow CO2 laser, focus on the development and production of high power all solid axis YAG laser, new mobile laser processing machine and laser composite welding technology. The specific measures are as follows: to establish a research platform of common technology for automobile plate cutting and welding metallurgy of steel roll; broadband heat treatment, surface cladding, laser welding of steel in metallurgical industry equipment, laser texturing equipment; underground pipelines of high power laser pointer processing in petroleum industry. The localization, serialization, generalization and standardization of key common technology and related equipment. To establish a new type of laser research and development platform, through the introduction of foreign fast axial flow CO2 laser technology, improve the domestic high power CO2 laser production capacity and product quality, based on the absorption of CO2 laser has introduced a high quality, high stability and high power. Focus on the development of RF excitation, fast axial flow CO2 laser and more than million kilowatts, the development of multi wavelength high power solid-state laser (>1kW), 100 ~ 1000W laser diode pumped solid laser and ultraviolet band. Focus on the development of pump modules, and strive to build a more comprehensive DPSSL production base in the country.
On the basis of many results obtained by the past, in recent years, the research on the three levels of system integration and application, high stability of laser and laser model and Realization of industrialization has made a breakthrough, but the industry still needs to solve the problem.
Integration and development of the system integration and development of the core of Wuhan laser processing industry. System integrator is a region, a leading industry development, only the strength of the system integrators grow, the entire industry can be driven up. Integration of system integration is the purpose of each enterprise has its own characteristics and advantages, there is a certain competitive relationship between each other. According to the characteristics of the current system integrators, may wish to set up solid 50mw laser pointer equipment, laser cutting equipment, laser medical equipment, large-scale laser processing equipment and laser processing stations and other forms of system integrators, owners of existing enterprises become the company's investment, in the process of integration of the existing system integrators, the government should play a good intermediary and service roles, create opportunities for enterprises to mature conditions on listing and financing, further optimize the structure of property rights, to lay a good foundation for further development.
Perfect supply chain was born and grow a number of parts suppliers with core technology. The basis of an industry is supported by many parts suppliers. For the Wuhan area, so the parts suppliers should include group optical devices (such as optical lens, focusing lens, reflector and optical fiber etc.), precision machining, laser power and precision of electronic and electrical etc.. At the same time, these parts suppliers should have the core technology of the field, which is important to promote the whole laser processing industry. Supporting enterprises is the basis of an industry, in particular, to master the core technology and have independent intellectual property rights of supporting enterprises, to promote the role of industrial development.

The introduction of a high starting point of digestion, encourage the development of a number of supporting enterprises is the first to encourage enterprises and research institutions cooperation, which is more efficient way; secondly, enterprises should focus on the development of technology trends, continuous innovation; third, development of government through the science and technology project plan arrangement, tax policy and other means to encourage supporting enterprises. Increase market dynamics, which requires systems integrators in the promotion of 1mw laser pointer processing technology and the establishment of market networks have greater investment, including in a certain time to open up overseas markets. Through the promotion of the application, technical radiation and personnel training, in the domestic establishment of laser processing demonstration application of the sub center, processing station, joint venture company, to promote the development of laser processing industry in china.
Capital platform domestic capital: the diversification of equity investment, the introduction of listed companies, state-owned investment companies, private capital; foreign capital: in Wuhan, Optics Valley, China, the proportion of foreign investment in the field of energy optoelectronics is very small. The introduction of foreign capital can start supporting industries to foreign investment, after all the technical advantages in most related with energy photoelectron matching field, and unlike the investment investment system supporting the integration as big; foreign: the proposed state and local governments to establish regional laser processing industry and the increase financial support strength, making full use of the structural characteristics of domestic the economy and society with high efficiency as the goal, application of advanced manufacturing technologies, high efficiency 5mw laser pointer, laser processing production line design and manufacturing with international leading level. The introduction of foreign advanced technology and capital, the establishment of a number of production lasers and complete sets of equipment joint venture, in order to improve the level of laser products.
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Industrial Applications of Micro Lasers

The combination of silicon materials and light emitting semiconductor materials is expected to help develop a new micro scale laser pointer, which is studied by Keh-Ting Ng Doris and colleagues at the Data Storage A*STAR Institute.

Silicon material completely changed the form of electrical equipment manufacturing. This semiconductor rich is easy to be processed into small components, such as transistors, and method which is used can be extended to the level of manufacturing industry, which makes the production of tens of thousands of components can be integrated on a single chip. Electronic engineers want to further expand the capabilities of these integrated circuits, so that they can create, process and detect light.
These optoelectronic devices can speed up the processing speed of digital information, and can realize the micro scale laser, for example, can be used in bar code scanner. The problem, however, is that the silicon material is not an effective light generator. Ng's team has designed and produced a combination of silicon and light emitting semiconductor green laser pointer, which are indium gallium arsenic compounds (InGaAsP). "Our results show that this method can achieve a high efficiency and compact active optoelectronic device for silicon substrate, that is, using a very thin III-V family of semiconductor silicon layers," Ng said.
One of the important considerations in any laser structure is the ability to capture light within the structure, namely, the ability to capture light in order to further drive the generation of light. In conventional lasers, this is achieved by placing a mirror on any side of the light producing area. Instead, Ng and the team used a cylindrical geometry device. This will capture some of the light that is generated on the wall of the device and force it to spread within the cylinder. This is called whispering gallery mode, because the same effect will occur in a circular room, such as the dome of the cathedral in the sound wave.
The team started using a silicon substrate, they deposited a thin layer of silicon oxide. Thin film with optically active InGaAsP, only 210 nm thick, is individually made, and then bonded to silicon oxide. Then, the team through a number of materials to create the cylinder, with two or three microns in diameter. Three micron devices emit a 30mw laser pointer light at a wavelength of 1519 nm, which is very close to the wavelength used in commercial optical communication systems.
This device has a unique feature that extends the whispering gallery mode to the silicon and InGaAsP regions. InGaAsP can provide light amplification, and silicon can be passive guide light. "The next step, we want to apply these ideas to the devices at room temperature," Ng said. "Operation at higher temperatures will require adjustments to the design and fabrication of the laser."
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