Fix dollar signs + add descendants section

# [TECH] Semiconductor Lasers & LEDs

**Semiconductor Lasers** (laser diodes) and **LEDs** (light-emitting diodes) are optoelectronic devices that convert electrical current to light, enabling optical communications, displays, lighting, and optical storage.

## Overview

Nick Holonyak demonstrated the first visible LED (red, 1962, GE). Semiconductor laser diodes achieved room-temperature continuous-wave operation (1970, Alferov/Kroemer type double heterostructure; **Nobel 2000**). Blue LEDs (Nakamura, Akasaki, Amano, 1993–1994; **Nobel 2014**) completed the RGB triad and enabled white LED lighting. Vertical-cavity surface-emitting lasers (VCSELs) enabled optical mice and 3D sensing. Distributed feedback (DFB) lasers are the workhorses of optical fiber networks.

## Key Actors

- **Companies**: Nichia (Nakamura's LEDs), Osram, Cree, II-VI/Coherent, Lumentum, Sony (optical storage lasers)
- **Inventors**: Nick Holonyak Jr. (1928–2022), Shuji Nakamura (1954–, **Nobel 2014**)

## Key Patents

- Nakamura, S. US Patent 5,578,839 (1996) — blue InGaN LED (Nichia)

## Economic Value

Global LED market: **\$75 billion/year** (2023, MarketsandMarkets). LED lighting alone saves ~\$50B/year in electricity costs globally vs. incandescent. Semiconductor laser/optical comms: \$20B/year hardware.

## Notes

LED lighting energy savings from IEA *Tracking Clean Energy Progress* 2023. MarketsandMarkets *LED Market* 2023.

## What This Enables
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- **[TECH] Optical Fiber Communications** — DFB (distributed feedback) laser diodes operating at 1310/1550 nm are the transmitters in every fiber link.
- **[TECH] Mobile Phones & Smartphones** — LED displays, infrared face-ID lasers, and LiDAR depth sensors in smartphones are semiconductor laser devices.
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# Parents

* [SCI] Semiconductor Physics
* [SCI] Semiconductor Physics
* [SCI] Condensed Matter & Topological Physics
* [TECH] Integrated Circuit