Semiconductor lasers: innovations, applications, and directions

An article written by Maurizio Di Paolo for EETIMES EUROPE, based on an interview by Martin Vallo, and Pierrick Boulay from Yole Développement (Yole) – Since the invention of lasers in the 1960s, a wide range of devices have been utilized in a growing number of applications. Laser technologies are now widely used in a wide range of classic and new applications. Material processing, optical communications, automobile front illumination, medical surgery, and 3D sensing are just a few of the applications. There are many different types of lasers, such as diode lasers, fiber lasers, DPSSLs, CO2 lasers, and excimer lasers, in the laser landscape. Traditional uses include industrial, scientific, and consumer sectors, but there are also a number of  applications, such as military and medicinal industries, that replace traditional approaches.

Semiconductor lasers are quantum generators based on active medium of single crystal semiconductor material, in which optical amplification is created by stimulated emission at the transition between quantum energy levels at high concentration of free charge carriers in the region. In an interview with EE Times Europe,Martin Vallo, Ph.D., Technology & Market Analyst, Solid-state Lighting, and Pierrick Boulay, Senior Technology & Market Analyst, Solid-state Lighting, both at Yole Développement (Yole), highlighted the main technology for semiconductors laser such as edge-emitting laser (EEL) and Vertical Cavity Surface-Emitting Laser (VCSEL).

The edge-emitting laser is a well-established semiconductor laser idea that has been in use for decades. Light is emitted from the edges of the semiconductor chip, which act as cavity mirrors, in a waveguide structure parallel to the semiconductor surface. A considerable amount of gain and high output powers may be produced with a relatively lengthy active area of hundreds of micrometers to a few millimeters. Electrically pumped EELs are small and cost-effective laser emission sources that may be used in a variety of applications.

VCSELs produce light perpendicular to the semiconductor surface, unlike edge-emitting lasers. Two distributed Bragg mirrors with alternating layers of high- and low-refractive index material with thicknesses of a quarter of the laser wavelength form the vertical cavity. Electrically pumped quantum wells or quantum dots in the active area between monolithically produced semiconductor mirrors give gain, resulting in single-longitudinal mode operation. Because oxide apertures confine both the current and the optical field, the VCSEL may operate in single-transverse mode, making it a small and efficient source of laser emission with high beam quality.

EET: Why are VCSELs so well-suited for 3D sensing?

Yole: Various infrared light sources could be used: LEDs, edge emitters, and VCSELs. LEDs are mature, cheap components, and easy to manufacture. Most of the time, they are used for 2D sensing as in a driver monitoring system. On the other hand, edge emitters and VCSELs are perfect light sources for 3D sensing, and the choice of one source or another will depend mainly on the output power needed for the application. But VCSELs are particularly well-suited for 3D sensing in smartphones due to their compact size, ease of manufacture, and the ability to use pulse speeds in the order of a nanosecond, which is needed for Time-of-Flight (ToF) applications. As a result, Yole Développement (Yole) is forecasting the VCSEL market will grow from US$794 million in 2021 to US$1,742 million in 2026.

EET: What are the challenges facing VCSELs?

… Read the full article on pages 56, 57 and 58.

Source: https://www.eetimes.eu/

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