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The Miracle of Semiconductor Lasers: Why Can VCSELs Run on Thousands of Wafers Simultaneously?
In today's rapidly changing technological environment, vertical cavity surface emitting lasers (VCSELs) are leading the innovation trend of semiconductor lasers. Unlike traditional edge-emitting lasers, VCSEL's laser beam is emitted vertically from the top of the chip, a feature that makes it extremely important in many applications. Today, VCSEL is widely used in products such as computer mice, optical fiber communications, laser printers, facial recognition technology, and smart glasses.
"In the production process of VCSEL, the advantages of process controllability and high output are obvious."
Production advantages
The VCSEL production process has several distinct advantages. Traditional edge-emitting lasers can usually only be tested after production, and if a fault is discovered, a lot of production time and materials will be wasted. VCSEL can be tested at multiple stages, so that material quality and process problems can be detected early. For example, temporary testing can detect that metal layers are not joining properly when the circuit's connecting channels have not been completely cleared of printed material. Thanks to the vertical emission characteristics of VCSELs, hundreds of thousands of VCSELs can be processed simultaneously on a three-inch gallium arsenide wafer. Although the VCSEL production process is more labor-intensive relative to edge-emitting lasers, its predictability and final yield are significantly improved.
Structure and Characteristics
The laser resonant cavity of a VCSEL consists of two distributed Bragg reflectors (DBRs) parallel to the wafer surface, while the active region consists of one or more quantum wells. This design results in each layer being exactly one-quarter the laser wavelength, achieving a reflection intensity of over 99%. This becomes particularly important since VCSELs require high reflectivity to balance the short axial length of the gain region. In addition, due to the small active area characteristics of VCSEL, its startup current is also relatively low, which leads to higher energy efficiency and a significant reduction in power consumption.
"VCSEL can be tested on a wafer due to its upper surface emission characteristics, which reduces the manufacturing cost of the device."
Applications of high-power VCSEL
With the advancement of technology, major breakthroughs have been made in the production of high-power VCSELs. Scientists have successfully achieved higher power output by increasing the emission aperture of a single device or combining multiple elements into large two-dimensional arrays. For example, as early as 1993, reports showed that a single VCSEL device with a large aperture reached a power of about 100 mW, and by 1998, this number exceeded hundreds of mW. These high-power VCSELs have shown great application potential in various fields such as medical, beauty and industrial fields.
Historical background
The development history of VCSEL is equally amazing. In 1965, Ivars Melngailis reported the surface emission phenomenon of semiconductors at ultra-low temperatures, and Kenichi Iga proposed the concept of short-cavity VCSEL in 1977. After decades of development, VCSEL has now replaced many short-distance optical fiber communication applications and has become one of the indispensable technologies today.
Future Outlook
With the rapid growth in demand for optical fiber communications, laser applications and consumer electronics products, the market potential of VCSEL is still huge. Whether it is medical beauty or autonomous driving technology, VCSEL has shown strong vitality and stability. As technology continues to advance, we have reason to believe that VCSEL will lead more innovations in the future.
In this rapidly developing ocean of technology, how will the new possibilities of VCSEL affect our lives and technological progress?
