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Vertical-cavity surface-emitting laser

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A vertical-cavity surface-emitting laser (VCSEL) is a semiconductor laser diode whose laser cavity is perpendicular to the wafer, so the light leaves the chip through its top or bottom surface instead of from a cleaved edge. The cavity is formed by two stacks of semiconductor Bragg mirrors with a thin active region between them, and it is only a few micrometers long.[1] Kenichi Iga of the Tokyo Institute of Technology conceived the device in 1977, and his group reported the first current-injected VCSEL in 1979.[2]

VCSELs can be tested on the wafer before it is diced, give a round, low-divergence beam, and can be packed into two-dimensional arrays with thousands of emitters.[1] Iga lists their applications as including high-speed local area networks, computer mice, parallel optical interconnects, laser printers, face recognition systems and various optical sensors.[3] In augmented reality and virtual reality hardware, VCSELs are the infrared emitters in several depth sensing systems, including the structured light projector behind Apple's Face ID and the direct time-of-flight LiDAR Scanner that Apple uses for AR on the iPad Pro and in the Apple Vision Pro.[4][5][6] A VCSEL was also the light source of Intel's Vaunt retinal-projection smart glasses prototype, and researchers are developing VCSEL-based laser sensors for eye tracking in AR glasses.[7][8]

Reviewed 13 October 2026. Claims re-checked against the cited IEEE Milestone, RP Photonics, Iga, Laser Focus World, Apple, EE Times Asia, TechInsights, Verge, Fortune and patent pages, with paper metadata via Crossref and key abstracts. About review dates.

How it works

A conventional edge-emitting laser diode uses the two cleaved facets of a chip as mirrors, so its cavity runs parallel to the wafer and is typically a few hundred micrometers long. In a VCSEL the layers, including the active layer, are grown monolithically and the cavity is perpendicular to the wafer surface.[9] The resonator consists of two distributed Bragg reflectors (DBRs), stacks of alternating semiconductor layers of different refractive index, with an active region of (typically) several quantum wells between them, only a few micrometers thick in total.[1] Because the gain over such a short path is small, the mirrors must be highly reflective: the bottom mirror usually exceeds 99.9 percent reflectivity and the top mirror, which couples out the beam, is typically 99.5 to 99.9 percent.[1]

Current is often fed through a ring-shaped electrode, and the output beam leaves through the opening in the ring. The current is confined to the area of the laser mode by conductive mirror layers surrounded by insulating material.[1] One way of forming such an aperture is with a native oxide; D. L. Huffaker, D. G. Deppe and colleagues described a native-oxide defined contact for low-threshold vertical-cavity lasers in 1994.[10] Iga lists AlAs oxidation, along with quantum wells and semiconductor Bragg reflectors, among the technologies that later became essential to the device.[9]

Typical single VCSELs are electrically pumped with a few tens of milliwatts and emit 0.5 to 5 mW, with more from multimode devices. A low-power VCSEL has a symmetric beam profile and lower divergence than an edge-emitting diode, so a simple lens can collimate it. The very short cavity makes single-frequency operation easy and lets the laser be modulated at gigahertz rates. The trade-off is power: good beam quality is possible only with mode diameters of a few micrometers, and larger apertures excite higher-order transverse modes.[1]

The most common wavelengths are 750 to 980 nm (often around 850 nm), produced with the GaAs/AlGaAs material system. Longer wavelengths such as 1.3 and 1.55 micrometers, or beyond 2 micrometers for gas sensing, use dilute nitrides on GaAs or indium phosphide based materials.[1] Gallium nitride based VCSELs for shorter wavelengths were reported in 2008, including continuous-wave lasing of a current-injected blue device at 77 K by Tien-Chang Lu and colleagues and room-temperature continuous-wave lasing by current injection by Yu Higuchi and colleagues.[11][12]

Manufacturing and arrays

Iga has written that his dissatisfaction with edge-emitting lasers motivated the design. Their cavities were made by cleaving the wafer, so devices could only be characterized after cleaving, wafer-scale testing was impossible, and two-dimensional laser arrays were hard to build. Around 1976 he had also concluded from simulations that a cavity shorter than 50 micrometers would widen the spacing between longitudinal modes enough to keep the laser in a single mode.[9]

A VCSEL wafer can be tested and characterized right after growth, before it is diced. It can also be combined with a wafer of optical elements, such as collimating lenses, and diced as a unit, which lowers the cost of mass production. Because the optical intensity at the output surface is much lower than at the facet of an edge emitter, VCSELs are not at risk of catastrophic optical damage, even when pulsed at high peak power.[1]

Holger Mönch of TRUMPF Photonic Components wrote in 2017 that single VCSELs are limited to about 10 micrometers of emitting diameter and about 10 mW of output, but can be packed into dense arrays of tens to thousands of emitters on one chip, and that pulsed arrays of 500 to 1,000 elements can deliver several tens of watts from an area of 1 to 2 square millimeters.[13] Large two-dimensional arrays can emit tens or hundreds of watts continuous-wave, although beam quality drops as more emitters are added unless their emission is made coherent.[1]

History

Iga sketched the vertical-cavity concept in a research note dated 22 March 1977 and presented it at meetings of the Japan Society of Applied Physics in 1978. The first current-injected VCSEL, a pulsed GaInAsP/InP device operating at 77 K, was demonstrated in 1979 by Haruhisa Soda in Iga's group.[2][14] Tokyo Tech filed its patent application on 9 January 1980. Xerox researchers Burnham, Scifres and Streifer had filed independently on 13 September 1979, and their application was granted as US patent 4,309,670 in 1982.[2]

In 1988 Fumio Koyama of Iga's group achieved room-temperature continuous-wave operation of an AlGaAs/GaAs VCSEL, and the group demonstrated the first VCSEL with semiconductor (AlGaAs/AlAs) Bragg mirrors. The same year Iga, Koyama and S. Kinoshita published a review of surface-emitting semiconductor lasers in the IEEE Journal of Quantum Electronics.[2][15] In 1989 J. L. Jewell and colleagues reported low-threshold, electrically pumped vertical-cavity surface-emitting "microlasers" in Electronics Letters.[16]

Year Milestone
1977 Iga conceives the VCSEL at the Tokyo Institute of Technology (research note of 22 March 1977)[2]
1979 First current-injected VCSEL (GaInAsP/InP, pulsed, 77 K)[2][14]
1982 Single-frequency operation with a cavity about 10 micrometers long[2]
1985 2 by 2 VCSEL array reported by Uchiyama and Iga[2]
1987 Multiple-quantum-well active regions introduced into VCSELs[2]
1988 Room-temperature continuous-wave operation; first semiconductor Bragg mirror VCSEL; 5 by 5 array[2]
1992 Continuous wavelength tuning over 40 angstroms at 77 K with a mechanically movable external mirror[2]
1993 First room-temperature continuous-wave operation of a long-wavelength VCSEL, by T. Baba of Iga's team[2]
1994 Native-oxide defined current aperture for low-threshold VCSELs[10]
1995 Threshold current of 70 microamperes reported by Iga's team[2]
2001 Two-dimensional VCSEL arrays used in laser printers[17]
2004 Laser computer mice with VCSEL light sources appear[17]
2017 Apple announces the iPhone X, whose Face ID TrueDepth camera uses VCSELs[4]
2025 IEEE Milestone dedicated on 28 October 2025; the plaque is at the Suzukakedai campus of the Tokyo Institute of Technology in Yokohama[2]

The IEEE Milestone citation describes the VCSEL as "notable for its single-mode operation, easy monolithic manufacturability, and frequency tunability" and says it became widely used in data communications, laser printing, facial recognition and LiDAR.[2] Iga's honors listed in the Milestone record include the 2021 IEEE Edison Medal and the 2013 Franklin Institute Bower Award and Prize in Science.[2][17]

General applications

Short-range optical communication is a major application. Because the short cavity allows modulation well into the gigahertz range, 850 nm VCSELs paired with multimode fiber carry data over distances of a few hundred meters.[1] A 2021 review in the IEEE Photonics Journal gave the highest data rates achieved by then for single-VCSEL optical links as 80 Gbit/s with simple on-off keying in back-to-back tests and 168 Gbit/s with PAM-4 modulation over 150 m of OM5 multimode fiber.[18]

The IEEE Milestone proposal suggests that the first high-volume use may have been as the light source of laser computer mice, which appeared in 2004. It also cites VCSEL arrays in laser printers from Fuji Xerox (an 8 by 4 array for 2,400 dpi printing) and Ricoh (a 40-channel array), and reports that Finisar, II-VI and Philips ULM Photonics together shipped 100 to 200 million VCSELs a year in 2013 or 2014.[17] Other uses include gas sensing with wavelength-tunable infrared VCSELs, miniature optical clocks in which the laser probes an atomic transition in cesium vapor, and pumping of solid-state lasers with high-power arrays.[1]

Applications in VR and AR

Depth sensing

VCSELs, often as arrays, are the light source in many structured light and time-of-flight depth sensors. They can switch in nanoseconds at high peak power, and their narrow spectral width lets the receiver filter out background light.[1] Mönch named augmented reality and virtual reality among the reasons that phones, laptops, drones, robots and cars increasingly map the 3D space around them. He recommended 940 nm over the 850 nm wavelength common in data links because sunlight is weaker at 940 nm, the red glow of the emitter is less visible, and silicon CMOS sensors are still sensitive there.[13]

Apple introduced the TrueDepth camera with the iPhone X on 12 September 2017. It combines a dot projector, an infrared camera and a flood illuminator, and Apple states that Face ID "projects more than 30,000 invisible IR dots".[19] In December 2017 Apple announced a US$390 million award from its Advanced Manufacturing Fund to Finisar to expand VCSEL research and production at a plant in Sherman, Texas. In the announcement Apple said VCSELs power Face ID, Animoji and Portrait mode selfies with the TrueDepth camera, as well as the proximity sensing in AirPods, and that in the fourth quarter of 2017 it would buy "10 times more VCSEL wafers than were previously manufactured worldwide over a similar time period."[4]

On 18 March 2020 Apple introduced an iPad Pro with a LiDAR Scanner that measures distances up to 5 meters away. Apple said that the scanner, together with the tablet's cameras, motion sensors and other hardware, "extends the lead of iPad Pro as the world's best device for augmented reality (AR)."[20] A teardown by System Plus Consulting, reported by EE Times Asia, found a Lumentum VCSEL emitter with separately connected groups of emitters, a diffractive optical element from Himax on top of it to generate the dot pattern, and a Sony single-photon avalanche diode (SPAD) sensor that measures time of flight directly.[6]

The Apple Vision Pro lists both a TrueDepth camera and a LiDAR Scanner among its sensors.[21] According to TechInsights, the headset's LiDAR reuses the iPad Pro 11 design, with a Texas Instruments VCSEL array driver and a Sony SPAD array, and works at 940 nm. TechInsights also reports that the headset's TrueDepth system uses a VCSEL to project a dot pattern read by an infrared camera, an evolution of the iPhone X design.[5][22]

Retinal projection displays

VCSELs have also been tried as light sources for near-eye displays. Intel's Vaunt smart glasses prototype, shown to The Verge in February 2018, used a very low-power VCSEL powered by electronics in the right stem of the frame. It drew a red, monochrome image of about 400 by 150 pixels onto a holographic reflector in the right lens, which reflected it onto the wearer's retina, a form of retinal projection. Mark Eastwood, industrial design director of Intel's New Devices Group, called it a class one laser "at the very bottom end" of that class, and Jerry Bautista, who led the group's wearables team, said the design used MEMS devices to paint the image.[7] In April 2018 Fortune reported that Intel was ending Vaunt and shutting down the New Devices Group behind it.[23] Other scanned-laser near-eye displays are covered under laser beam scanning and virtual retinal display.

Eye tracking

A laser beam that is reflected back into a VCSEL interferes with the light inside the cavity. This self-mixing interference (also called laser feedback interferometry) changes the laser's output, and a sensor can derive the optical path length to the reflecting surface and, from the Doppler shift, its velocity.[8][24] TRUMPF Photonic Components makes single-mode VCSELs at around 850 nm with an integrated photodiode for this purpose (sold as ViP). Writing for Laser Focus World in 2023, TRUMPF's Holger Mönch said the company had sold many tens of millions of these devices, that the technique can sense the velocity of the rotating eye, and that AR/VR glasses would be the next mass application.[8]

Johannes Meyer, Thomas Schlebusch and colleagues presented a self-mixing eye-tracking sensor for AR glasses at the 2020 ACM Symposium on Eye Tracking Research and Applications (ETRA). They described the sensor as "as small as a grain of sand" and reported exceptional robustness against ambient light compared with conventional camera-based eye trackers.[25] In a 2022 paper the same group reported a scanned laser feedback interferometry sensor for retinal-projection AR glasses that reached a gaze accuracy of 1.62 degrees with lower power consumption than video-based eye tracking.[26] Meyer, Schlebusch, Spruit and Hellmig are among the inventors on a patent originally assigned jointly to Robert Bosch GmbH and TRUMPF Photonic Components (US 11,513,594 B2, granted 29 November 2022), which describes smart glasses that detect eye movement by laser feedback interferometry and in which the laser device preferably has a VCSEL with an integrated photodiode.[24] Apple holds a patent on eye tracking with self-mixing interferometry sensors mounted on a head-mountable frame, in which the light emitter may be a VCSEL or another source such as an edge-emitting laser or LED; the application was published in October 2023 and granted on 3 February 2026 as US 12,541,100 B2.[27] A patent or prototype does not mean that a shipping headset uses the technique.

See also

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Rüdiger Paschotta. "Vertical Cavity Surface-emitting Lasers". RP Photonics Encyclopedia. RP Photonics AG. doi:10.61835/qcg. https://www.rp-photonics.com/vertical_cavity_surface_emitting_lasers.html. Retrieved 2026-10-13.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 "Milestones:Vertical-Cavity Surface-Emitting Laser, 1977-1992". Engineering and Technology History Wiki. IEEE History Center. https://ethw.org/Milestones:Vertical-Cavity_Surface-Emitting_Laser,_1977-1992. Retrieved 2026-10-13.
  3. ↑ Kenichi Iga (2018-07-03). "Forty years of vertical-cavity surface-emitting laser: Invention and innovation". Japanese Journal of Applied Physics, vol. 57, no. 8S2, 08PA01. doi:10.7567/JJAP.57.08PA01. https://doi.org/10.7567/JJAP.57.08PA01. Retrieved 2026-10-13.
  4. ↑ 4.0 4.1 4.2 "Apple awards Finisar $390 million from its Advanced Manufacturing Fund". Apple Newsroom. Apple. 2017-12-13. https://www.apple.com/newsroom/2017/12/apple-awards-finisar-390-million-from-its-advanced-manufacturing-fund/. Retrieved 2026-10-13.
  5. ↑ 5.0 5.1 "LiDAR Technology in Apple Vision Pro". TechInsights. https://www.techinsights.com/blog/lidar-technology-apple-vision-pro. Retrieved 2026-10-13.
  6. ↑ 6.0 6.1 Junko Yoshida (2020-06-08). "Look Inside iPad Pro 11's LiDAR Scanner". EE Times Asia. https://www.eetasia.com/look-inside-ipad-pro-11s-lidar-scanner/. Retrieved 2026-10-13.
  7. ↑ 7.0 7.1 Dieter Bohn (2018-02-05). "Intel made smart glasses that look normal". The Verge. https://www.theverge.com/2018/2/5/16966530/intel-vaunt-smart-glasses-announced-ar-video. Retrieved 2026-10-13.
  8. ↑ 8.0 8.1 8.2 Holger Mönch (2023-03-15). "Full sensor functionality integrated into tiny VCSELs". Laser Focus World. https://www.laserfocusworld.com/lasers-sources/article/14290703/full-sensor-functionality-integrated-into-tiny-vcsels. Retrieved 2026-10-13.
  9. ↑ 9.0 9.1 9.2 Kenichi Iga. "Invention of a Surface Emitting Laser and Its Realization (in Japanese)". Tokyo Institute of Technology. https://www.cent.titech.ac.jp/assets/img/professor-emeritus/iga-research.pdf. Retrieved 2026-10-13.
  10. ↑ 10.0 10.1 D. L. Huffaker, D. G. Deppe, K. Kumar, T. J. Rogers (1994-07-04). "Native-oxide defined ring contact for low threshold vertical-cavity lasers". Applied Physics Letters, vol. 65, no. 1, pp. 97-99. doi:10.1063/1.113087. https://doi.org/10.1063/1.113087. Retrieved 2026-10-13.
  11. ↑ Tien-Chang Lu, Chih-Chiang Kao, Hao-Chung Kuo, Gen-Sheng Huang, Shing-Chung Wang (2008-04-07). "CW lasing of current injection blue GaN-based vertical cavity surface emitting laser". Applied Physics Letters, vol. 92, no. 14, 141102. doi:10.1063/1.2908034. https://doi.org/10.1063/1.2908034. Retrieved 2026-10-13.
  12. ↑ Yu Higuchi, Kunimichi Omae, Hiroaki Matsumura, Takashi Mukai (2008-12-05). "Room-Temperature CW Lasing of a GaN-Based Vertical-Cavity Surface-Emitting Laser by Current Injection". Applied Physics Express, vol. 1, 121102. doi:10.1143/APEX.1.121102. https://doi.org/10.1143/APEX.1.121102. Retrieved 2026-10-13.
  13. ↑ 13.0 13.1 Holger Mönch (2017-10-12). "Vertical-cavity Surface-emitting Lasers: VCSEL arrays provide leading-edge illumination for 3D sensing". Laser Focus World. https://www.laserfocusworld.com/lasers-sources/article/16548239/vertical-cavity-surface-emitting-lasers-vcsel-arrays-provide-leading-edge-illumination-for-3d-sensing. Retrieved 2026-10-13.
  14. ↑ 14.0 14.1 Haruhisa Soda, Ken-ichi Iga, Chiyuki Kitahara, Yasuharu Suematsu (1979-12). "GaInAsP/InP Surface Emitting Injection Lasers". Japanese Journal of Applied Physics, vol. 18, no. 12, pp. 2329-2330. doi:10.1143/JJAP.18.2329. https://doi.org/10.1143/JJAP.18.2329. Retrieved 2026-10-13.
  15. ↑ K. Iga, F. Koyama, S. Kinoshita (1988-09). "Surface emitting semiconductor lasers". IEEE Journal of Quantum Electronics, vol. 24, no. 9, pp. 1845-1855. doi:10.1109/3.7126. https://doi.org/10.1109/3.7126. Retrieved 2026-10-13.
  16. ↑ J. L. Jewell, Y. H. Lee, S. Walker, A. Scherer, J. P. Harbison, L. T. Florez, S. L. McCall (1989-08-17). "Low-threshold electrically pumped vertical-cavity surface-emitting microlasers". Electronics Letters, vol. 25, no. 17, pp. 1123-1124. doi:10.1049/el:19890754. https://doi.org/10.1049/el:19890754. Retrieved 2026-10-13.
  17. ↑ 17.0 17.1 17.2 17.3 "Milestone-Proposal:Vertical-Cavity Surface-Emitting Laser, 1977". IEEE Milestones Wiki. IEEE History Center. https://ieeemilestones.ethw.org/Milestone-Proposal:Vertical-Cavity_Surface-Emitting_Laser,_1977. Retrieved 2026-10-13.
  18. ↑ Chih-Hsien Cheng, Wei-Chi Lo, Borching Su, Chao-Hsin Wu, Gong-Ru Lin (2021-10). "Review of VCSELs for Complex Data-Format Transmission Beyond 100-Gbit/s". IEEE Photonics Journal, vol. 13, no. 5. doi:10.1109/JPHOT.2021.3104647. https://doi.org/10.1109/JPHOT.2021.3104647. Retrieved 2026-10-13.
  19. ↑ "The future is here: iPhone X". Apple Newsroom. Apple. 2017-09-12. https://www.apple.com/newsroom/2017/09/the-future-is-here-iphone-x/. Retrieved 2026-10-13.
  20. ↑ "Apple unveils new iPad Pro with breakthrough LiDAR Scanner and brings trackpad support to iPadOS". Apple Newsroom. Apple. 2020-03-18. https://www.apple.com/newsroom/2020/03/apple-unveils-new-ipad-pro-with-lidar-scanner-and-trackpad-support-in-ipados/. Retrieved 2026-10-13.
  21. ↑ "Apple Vision Pro - Technical Specifications". Apple. https://www.apple.com/apple-vision-pro/specs/. Retrieved 2026-10-13.
  22. ↑ "Apple Vision Pro: Revolutionizing Face ID with TrueDepth Technology". TechInsights. https://www.techinsights.com/blog/apple-vision-pro-revolutionizing-face-id-truedepth-technology. Retrieved 2026-10-13.
  23. ↑ David Meyer (2018-04-19). "Intel Is Killing Its Google Glass-Like Project, Vaunt". Fortune. https://fortune.com/2018/04/19/intel-new-devices-group-shuts. Retrieved 2026-10-13.
  24. ↑ 24.0 24.1 "US11513594B2 - Method for operating a pair of smart glasses". Google Patents. Robert Bosch GmbH, Trumpf Photonic Components GmbH. 2022-11-29. https://patents.google.com/patent/US11513594B2/en. Retrieved 2026-10-13.
  25. ↑ Johannes Meyer, Thomas Schlebusch, Hans Spruit, Jochen Hellmig, Enkelejda Kasneci (2020-06-02). "A Novel Eye-Tracking Sensor for AR Glasses Based on Laser Self-Mixing Showing Exceptional Robustness Against Illumination". ACM Symposium on Eye Tracking Research and Applications (ETRA '20 Short Papers). ACM. doi:10.1145/3379156.3391352. https://doi.org/10.1145/3379156.3391352. Retrieved 2026-10-13.
  26. ↑ Johannes Meyer, Thomas Schlebusch, Enkelejda Kasneci (2022-05-13). "A Highly Integrated Ambient Light Robust Eye-Tracking Sensor for Retinal Projection AR Glasses Based on Laser Feedback Interferometry". Proceedings of the ACM on Human-Computer Interaction (ETRA). ACM. doi:10.1145/3530881. https://doi.org/10.1145/3530881. Retrieved 2026-10-13.
  27. ↑ "US20230333371A1 - Eye Tracking Using Self-Mixing Interferometry". Google Patents. Apple Inc.. 2023-10-19. https://patents.google.com/patent/US20230333371A1/en. Retrieved 2026-10-13.
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