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Introduction:
Light has always played a fundamental role in our lives, providing illumination, enabling communication, and driving technological progress. In recent years, semiconductor laser technology has emerged as a game-changer, revolutionizing various industries and opening up new possibilities. In this article, we explore the fascinating world of semiconductor laser technology and its profound impact on illuminating our world.
Understanding Semiconductor lasers
Semiconductor lasers, also known as diode lasers, are a type of laser that uses a semiconductor material as the gain medium. They are widely used in a variety of applications, such as optical communications, data storage, sensing, and materials processing.
The structure of a semiconductor laser consists of several layers of semiconducting materials, including p-type and n-type regions, with an active region in between. When an electrical current is applied to the semiconductor material, it stimulates the emission of photons from the active region, which then produce laser light.
One of the main advantages of semiconductor lasers is their small size and efficiency. Semiconductor lasers make powerful, precise beams of light (like ordinary lasers), but they’re about the same size as simple LEDs. Semiconductor lasers are advanced and efficient as compared to conventional lasers as they use active semiconductor materials for light amplification.
These lasers are small in size, require less power and are much more efficient than conventional lasers, which make them the smarter choice in the manufacturing of laser-based system. Moreover, semiconductor lasers cost less than conventional lasers. In telecommunication industry, semiconductor lasers are mostly used in fiber optic cables to enable fast and efficient communication.
They can be fabricated in very small sizes, making them ideal for use in compact devices such as optical communication systems, laser printers, and barcode scanners. Additionally, they require less power than other types of lasers, making them more energy-efficient.
Semiconductor lasers have a broad range of applications in various fields, such as telecommunications, information technology, and materials processing. They are commonly used in fiber-optic communications to transmit data over long distances, and they are also used in data storage devices such as CD and DVD players. In materials processing, they are used for cutting, welding, and engraving.
Overall, semiconductor lasers have become an integral part of modern technology and have enabled many important applications that have improved our lives. As the technology continues to advance, we can expect to see even more innovative uses of semiconductor lasers in various fields.
For fundamentals on lasers please visit: Laser Technology and its Applications: A Practical Guide
Most semiconductor lasers are laser diodes, which are pumped with an electrical current in a region where an n-doped and a p-doped semiconductor material meet. However, there are also optically pumped semiconductor lasers, where carriers are generated by absorbed pump light, and quantum cascade lasers, where intraband transitions are utilized.
Semiconductor laser technology
A semiconductor laser is a specially fabricated pn junction device (both the p and n regions are highly doped) which emits coherent light when it is forward biased. p region is rich in “holes” or, in other words, slightly lacking electrons, the tiny negatively charged particles inside atoms and and n-type has slightly too many electrons.
Electrons are injected into the diode, they combine with holes, and some of their excess energy is converted into photons, which interact with more incoming electrons, helping to produce more photons—and so on in a kind of self-perpetuating process called resonance. This repeated conversion of incoming electrons into outgoing photons is analogous to the process of stimulated emission that occurs in a conventional, gas-based laser.
In a conventional laser, a concentrated light beam is produced by “pumping” the light emitted from atoms repeatedly between two mirrors. In a laser diode, an equivalent process happens when the photons bounce back and forth in the microscopic junction (roughly one micrometer wide) between the slices of p-type and n-type semiconductor, which is technically known as a Fabry-Perot resonant cavity (a kind of interferometer). The amplified laser light eventually emerges from the polished end of the gap in a beam parallel to the junction.
It is made from Gallium Arsenide (GaAs) which operated at low temperature and emits light in near IR region. Now the semiconductor laser are also made to emit light almost in the spectrum from UV to IR using different semiconductor materials. They are of very small size (0.1 mm long) as simple LEDs, efficient, portable and operate at low power. These are widely used in Optical fibre communications, in CD players, CD-ROM Drives, optical reading, laser printing etc.
While the most common semiconductor lasers are operating in the near-infrared spectral region, some others generate red light (e.g. in GaInP-based laser pointers) or blue or violet light (with gallium nitrides). For mid-infrared emission, there are e.g. lead selenide (PbSe) lasers (lead salt lasers) and quantum cascade lasers.
Stacked laser diodes
Early laser diodes could fire out only a single, relatively puny beam, but ingenious electronics engineers soon found ways to make them considerably more powerful. Since the 1990s, one common approach has been to mount a number of laser diodes on top of one another (like an apartment building) and then focus their individual beams into a single output beam using a collimator and/or lens. This kind of arrangement is variously called a semiconductor laser stack, stacked laser diode, or just a diode stack. Apart from making more power than a single laser diode, a stack opens up the possibility of generating multiple different wavelengths at the same time (because each laser in the stack can make a different one). Instead of a single P-N junction, there are multiple ones, and the laser light beams emerge from the active layers in between them; typically, there’s also at least one tunnel junction between the stacked layers. A single pair of terminals (sometimes called Ohmic contacts) feeds electrical power to the entire stack.
Types of Semiconductor Lasers
There is a great variety of different semiconductor lasers, spanning wide parameter regions and many different application areas:
- Small edge-emitting laser diodes generate a few milliwatts (or up to 0.5 W) of output power in a beam with high beam quality. They are used e.g. in laser pointers, in CD players, and for optical fiber communications.
- External cavity diode lasers contain a laser diode as the gain medium of a longer laser cavity. They are often wavelength-tunable and exhibit a small emission linewidth.
Both monolithic and external-cavity low-power levels can also be mode-locked for ultrashort pulse generation.
Monolithic mode-locked lasers are typically fabricated using a single chip, with the laser cavity, gain medium, and modulator all integrated onto the chip. This makes them very compact and stable, with a low noise and low jitter performance. Monolithic mode-locked lasers are commonly used in applications such as optical communications, optical clocks, and optical spectroscopy.
External-cavity mode-locked lasers, on the other hand, use an external cavity to provide feedback to the laser and generate the ultrashort pulses. This external cavity can be adjusted to tune the laser output and to compensate for any thermal or mechanical instabilities in the laser. External-cavity mode-locked lasers can be more versatile than monolithic lasers, but they are typically larger and more complex.
In both cases, mode-locking generates a train of short optical pulses by locking the laser oscillation to the round-trip time of the laser cavity or the external cavity. These ultrashort pulses can have durations ranging from picoseconds to femtoseconds, and can be used in a variety of applications including microscopy, spectroscopy, material processing, and more.
- Broad area laser diodes generate up to a few watts of output power, but with significantly poorer beam quality.
- High-power diode bars contain an array of broad-area emitters, generating tens of watts with poor beam quality.
- High-power stacked diode bars can generate extremely high powers of hundreds or thousands of watts.
Semiconductor lasers have continued to evolve since their invention in the 1960s, with new technologies and applications emerging. Some recent advancements in semiconductor laser technology include:
- High-power lasers: Advances in semiconductor materials and cooling techniques have allowed the development of high-power semiconductor lasers that can produce output powers in the kilowatt range. These lasers are used in materials processing applications such as cutting, welding, and drilling.
- Tunable lasers: Tunable semiconductor lasers can be adjusted to emit light at different wavelengths, making them useful for a range of applications such as spectroscopy, sensing, and optical communications.
- Vertical-cavity surface-emitting lasers (VCSELs): Surface-emitting lasers (VCSELs) emit the laser radiation in a direction perpendicular to the wafer, delivering a few milliwatts with high beam quality. They are widely used in optical communications and sensing applications due to their high efficiency, low power consumption, and ability to be integrated into complex optical systems.
Optically pumped surface-emitting external-cavity semiconductor lasers (VECSELs) are capable of generating multi-watt output powers with excellent beam quality, even in mode-locked operation. Electrically pumped photonic crystal surface-emitting lasers promise to reach similar performance. - Quantum cascade lasers: Quantum cascade lasers are a type of semiconductor laser that use quantum mechanics to produce light. Quantum cascade lasers operate on intraband transitions (rather than interband transitions) and usually emit in the mid-infrared region, sometimes in the terahertz region. They have unique properties that make them ideal for applications such as trace gas sensing, spectroscopy, and imaging.
- Semiconductor disk lasers: Semiconductor disk lasers use a unique design that allows for high output powers while maintaining high beam quality. They are used in a range of applications, including materials processing, medical treatments, and scientific research.
Overall, the continued evolution of semiconductor laser technology has opened up new possibilities in many fields, enabling new technologies and advancements that were once thought impossible. As research and development continue, we can expect to see even more innovative uses of semiconductor lasers in the future.
Typical Characteristics and Applications
Some typical aspects of semiconductor lasers are:
- Electrical pumping with moderate voltages and high efficiency is possible particularly for high-power diode lasers, and allows their use e.g. as pump sources for highly efficient solid-state lasers (→ diode-pumped lasers) and even as direct diode lasers.
- A wide range of wavelengths are accessible with different devices, covering much of the visible, near-infrared and mid-infrared spectral region. Some devices also allow for wavelength tuning.
Small laser diodes allow fast switching and modulation of the optical power, allowing their use e.g. in transmitters of fiber-optic links. - Such characteristics have made semiconductor lasers the technologically most important type of lasers. Their applications are extremely widespread, including areas as diverse as optical data transmission, optical data storage, metrology, laser spectroscopy, laser material processing, pumping solid-state lasers (→ diode-pumped lasers), and various kinds of medical treatments.
Lighting the Way:
Semiconductor lasers have also ushered in a new era of lighting solutions. Solid-state lighting, including light-emitting diodes (LEDs) and laser diodes, has become increasingly prevalent due to its energy efficiency and longevity. These lighting technologies find applications in various sectors, from residential and commercial lighting to automotive lighting systems. Semiconductor lasers enable adaptive headlights, laser projectors, and high-precision LiDAR sensors, driving advancements in the automotive industry and contributing to safer and more efficient transportation.
Revolutionizing Telecommunications:
The telecommunications industry has greatly benefited from semiconductor laser technology. By enabling high-speed data transmission over long distances through optical fibers, these lasers have transformed the way we communicate. They form the backbone of optical fiber networks, facilitating fast and reliable connections that power our digital world. With the advent of 5G and beyond, semiconductor lasers will continue to play a crucial role in enabling faster and more advanced wireless communication systems.
Advancements in Medicine and Biotechnology:
The impact of semiconductor laser technology extends to the field of medicine and biotechnology. Laser-based medical treatments, such as laser surgery and cosmetic procedures, have revolutionized the way certain medical conditions are treated. Semiconductor lasers provide precise control and enable minimally invasive procedures with reduced patient discomfort and faster recovery times. In addition, these lasers are instrumental in diagnostic imaging techniques, offering high-resolution and real-time visualization for improved medical diagnoses.
In the realm of bioanalysis and genomics, semiconductor lasers have become essential tools. They power bioanalytical technologies like DNA sequencing and flow cytometry, allowing researchers to analyze genetic material and biological samples with unparalleled speed and accuracy. This paves the way for advancements in genomics, personalized medicine, and disease diagnosis.
Application: Defense
Because of their compact size and lightweight and ruggedness, semiconductor lasers are ideal for military and aerospace applications. Used directly or as pumps for other lasers, semiconductor lasers are used in a wide variety of applications including both the transmission optical energy to a target and receiving a portion of it back in order to measure various physical properties of the target in a remote fashion.
Defense lasers that transmit energy to the target are common at both low and high power levels. On the low power end (<500mW), direct diode lasers are used for free-space communications for line of sight transmission. At slightly higher power, direct diode lasers are used to initiate ordinances. For even higher powers and long wavelengths, diode lasers can be used directly or to pump solid state lasers which disable incoming heat seeking missiles. At the highest power levels of 50-100kW, high energy solid state lasers for missile defense are being developed. These lasers use >100kW of diode pump light per laser and are expected to be deployed by land, sea, and air in the years to come.
Another class of defense laser is those which are used to extract information from a target. At the low power end, for example, range finding lasers enable the user measure distance and illuminators enable the user to view unprecedented levels of detail. At higher power, remote sensing and LIDAR lasers allow the user to detect bio-chemical agents, clear air turbulence and other atmospheric conditions.This new class of direct diode rangefinders and compact LIDAR systems is based on QPC’s proprietary high efficiency material design around the Eyesafe wavelength of 1550nm and unique high power single mode laser designs exceeding 1W CW.
A new class of non-lethal laser weapons use high brightness green light to warn targets at a distance that is far enough to allow escalation of force and even suppress a potential threat while decreasing the risk for potential collateral damage. QPC’s visible laser product line, based on integrated diode wavelength stabilization technology, allows integration of compact and efficient green lasers on various platforms from rifles to airborne and ground vehicles.
Semiconductor Laser Market
The semiconductor laser market size was valued at USD 7.22 billion in 2021 and USD 7.69 billion in 2022. The market is expected to reach USD 13.25 billion by 2029 with a CAGR of 8.1% during the forecast period. Rising applications in various sectors such as automotive, consumer electronics, and others are predicted to boost the demand for semiconductor lasers. Asia Pacific held the largest market share USD 3.08 billion in 2021, owing to the robust manufacturing sector. Increasing investments in smart connected devices are set to drive market growth.
The semiconductor laser market has experienced significant growth in recent years due to the increasing demand for high-speed data communication, industrial and medical applications, and the rise of autonomous vehicles and LiDAR technology.
The increasing adoption of fiber optic lasers in the telecommunication industry and the rising preference of semiconductor lasers as compared to other light sources are driving the semiconductor lasers market globally. Also, the increasing use of 3D printing in the architectural and healthcare sector is likely to augment the demand and popularity of semiconductor lasers.
Furthermore, factors such as compact size, low cost, and long life are expected to contribute to the growth semiconductors lasers during the forecast period. However, low packing tolerance, delicate design and low reliability are expected to inhibit the growth of semiconductor lasers market in the near future. On the other hand, increase in research and development activities coupled with increased demand of data storage is expected to create lucrative opportunities in the market over the forecast period.
There is a rapid increase in the use of semiconductor lasers for different applications. The semiconductor laser is vital in the healthcare sector due to their extensive use for cosmetic procedures, medical diagnosis, and therapies. On the basis of application, the Global Semiconductor Laser market has been segmented into: Optical Storage & Display, Telecom & Communication, Industrial Applications, and Medical Application
Moreover, they are ideal for military and defense applications due to their compact size, lightweight, and ruggedness. In the defense sector, the new high brightness semiconductor laser technology is permitting diode lasers to be used directly in applications where DPSS lasers were the only solution. i.e., target designation, countermeasures, and potentially even high energy lasers. Semiconductor diode lasers are offering advantages over other light sources for applications in dentistry, dermatology and other applications.
In addition, the launch of 3D printers has further increased the demand in this market as this technology is widely used in healthcare to produce fabricated prosthetic limbs and various other life-sciences applications. With the increase in sales of smarpthone, technologies like OLED and VCEL in the smartphone segment are also propelling the growth of semiconductor laser market. Also, the growth in the semiconductor industry may fuel the growth of the market.
Segments
Fiber Optic Laser (FOL) to Lead Due to Increasing Adoption
On the basis of type, the market is divided into Fiber Optic Lasers (FOL), Vertical Cavity Surface Emitting Lasers (VCSEL), blue laser, red laser, green laser, infrared laser, and others (compact disc laser). Fiber Optic Lasers (FOL) segment is anticipated to have the dominant part due to increasing adoption of edge-emitting diodes in optical device manufacturing.
Material Processing to Govern Owing to Rising Investments
Based on application, the market is categorized into medical & aesthetic, instruments & sensors, aerospace, defense, and military, materials processing, communications & optical storage, entertainment, displays, & printing, and others (printing, lithography). Material processing segment is expected to have a major part due to rising investment in manufacturing automotive component cutting. Instruments & sensors segment is projected to grow with the highest CAGR owing to increasing investments across IoT devices.
On the basis of product type, the Global Semiconductor Laser market has been segmented into:
- Blue Laser
- Red Laser
- Infrared Laser
Geographical Analysis
North America held the lion share of the market and is anticipated to continue holding the major market share throughout the forecast period. The initiatives taken by the U.S. Federal Government, in association with the International Electrotechnical Commission (IEC), endorses and encourages the usage of 3D printers particularly in the healthcare sector with specific mandatory directives, which is expected to drive the market in North America.
Asia-Pacific is also anticipated to register the highest growth rate over the forecast period, due to the high manufacturing and industrialization in the region. Also, government initiatives and investments in Asia-Pacific are promoting the growth of numerous sectors. The exponential growth in the communication industry in countries, such as Japan, China, South Korea, and India, is anticipated to drive the laser market in the region, during the forecast period. Moreover, countries like China, Taiwan, Korea, Japan are the house of smartphone manufacturers such as Apple, Oneplus, Vivo. Samsung, among others which makes semiconductor manufacturer around these regions to produce semiconductor laser to cater to smartphone manufacturers.
Key vendors operating in this market space include Sony, Nichia, Ushio, Osram, TOPTICA Photonics, Egismos Technology, Arima Lasers, Ondax, Panasonic, Sharp, ROHM, Hamamatsu, Newport Corp, Finisar, Mitsubishi Electric, Huaguang Photoelectric and QSI
Cutting-Edge Research and Future Directions:
Semiconductor laser technology continues to push the boundaries of innovation. It plays a critical role in the development of quantum technologies, including quantum computing, quantum communication, and quantum sensing. These technologies have the potential to revolutionize industries and solve complex problems that are beyond the reach of classical computing and communication systems.
Furthermore, ongoing research focuses on advancing laser materials and exploring new possibilities. Organic semiconductors and perovskites are being investigated for their potential to enhance the efficiency and versatility of semiconductor lasers. These advancements will further expand the scope of semiconductor laser technology and unlock new applications in various fields.
UTA Team Pioneering Semiconductor Photonics Advancements
Led by Weidong Zhou, a Distinguished University Professor in the Department of Electrical Engineering, a research initiative at the University of Texas at Arlington (UTA) is poised to revolutionize semiconductor chip technology. Zhou is spearheading a $2.7 million grant from the U.S. Department of Defense, exploring the potential of high brightness semiconductor photonic crystal surface-emitting laser (PCSEL) chip technology.
The research aims to harness the power of light to enhance the efficiency, potency, and luminosity of semiconductor chips. Zhou emphasizes that the applications of this research are vast, spanning self-driving cars, satellite technology, and even space exploration. Describing the endeavor as a convergence of chip and space sectors, Zhou underscores the multifaceted significance of their work.
A critical aspect of the project involves scaling laser power output while preserving high beam quality, a pivotal factor in various applications. Semiconductor lasers, crucial for advancements in numerous fields, have seen recent developments in large-area, surface-emitting lasers based on in-plane photonic crystal modulation and feedback. Zhou’s work delves into the design and development of these photonic crystal surface-emitting lasers, with a focus on future exploration avenues.
Conclusion:
Semiconductor laser technology has become a transformative force, illuminating our world and shaping the future of light. From revolutionizing telecommunications and lighting solutions to powering advancements in medicine, biotechnology, and cutting-edge research, these lasers have found applications in numerous industries. As ongoing research and innovation continue to improve efficiency and expand the capabilities of semiconductor lasers, we can look forward to a future where light plays an even more vital role in driving progress and improving lives.
References and Resources also include:
https://www.explainthatstuff.com/semiconductorlaserdiodes.html
https://www.photonicsonline.com/doc/semiconductor-lasers-for-defense-0001
