# [SCI] Laser Physics & Stimulated Emission

**Laser Physics** is the theory and practice of stimulated emission of radiation — the coherent amplification of light by excited atomic systems — culminating in the invention of the laser (1960).

## Overview

Einstein (1917) derived the rate equations for stimulated emission: an excited atom can be triggered to emit a photon identical to an incident one, enabling amplification. Townes and Gordon built the first maser (microwave amplification, 1954). Schawlow and Townes (1958) proposed extending the principle to optical frequencies. Maiman built the first working laser (ruby, 694 nm, 1960). Within a decade, lasers spanned from femtosecond pulses to continuous-wave beams across all wavelengths.

Lasers provided a uniquely coherent, intense, monochromatic light source with no classical analogue, enabling holography, optical communications, precision measurement, surgery, and quantum optics.

## Key Figures & Recognition

- **Charles Townes** (1915–2015), **Nikolay Basov** (1922–2001), **Alexander Prokhorov** (1916–2002): Maser/laser. **Nobel Prize 1964**.
- **Theodore Maiman** (1927–2007): First working laser, 1960.
- **Arthur Schawlow** (1921–1999): Laser spectroscopy. **Nobel Prize 1981**.

## Seminal Papers

- Einstein, A. "Zur Quantentheorie der Strahlung." *Phys. Z.* 18 (1917).
- Schawlow, A. & Townes, C. ["Infrared and Optical Masers." *Phys. Rev.* 112 (1958)](https://doi.org/10.1103/PhysRev.112.1940)
- Maiman, T. "Stimulated Optical Radiation in Ruby." *Nature* 187 (1960).

## What This Enables

- **[TECH] Laser (Device)** — Stimulated emission theory gives engineers the gain medium, resonator design, resonator conditions, and threshold conditionsequations for every laser.
- **[SCI] Quantum Optics** — Coherent laser light is both the central experimental tool of quantum optics experiments and itsthe primary object of study in quantum optics.

# Parents

* [SCI] Quantum Mechanics
* [SCI] Atomic Structure & Spectroscopy
* [SCI] Quantum Mechanics