polarization

History

Polarization was discovered by the French engineer Étienne-Louis Malus in 1808, while looking through a calcite crystal at light reflected from a window. Later, James Clerk Maxwell in 1865 created the unified theory of the electromagnetic field, showing that light is waves with vector fields, and laid the precise foundation for understanding polarization.

How it works

Light reflected from a horizontal surface is strongly horizontally polarized. Polarizing glasses contain a filter that only passes vertical oscillations. It's like microscopic blinds that cut out stray light—glare disappears, while the rest of the scene remains bright.

History

Polarization was discovered by the French engineer Étienne-Louis Malus in 1808, while looking through a calcite crystal at light reflected from a window. Later, James Clerk Maxwell in 1865 created the unified theory of the electromagnetic field, showing that light is waves with vector fields, and laid the precise foundation for understanding polarization.

How it works

Light reflected from a horizontal surface is strongly horizontally polarized. Polarizing glasses contain a filter that only passes vertical oscillations. It's like microscopic blinds that cut out stray light—glare disappears, while the rest of the scene remains bright.

History

Étienne-Louis Malus discovered polarization by reflection in 1808, while observing light through a calcite crystal from the window of his home in Paris. In the 1810s, Augustin Fresnel and François Arago supplemented the wave theory of light with transverse oscillations and investigated the interference of polarized rays. James Clerk Maxwell in 1865 derived equations that explained polarization as the directionality of the electromagnetic field vectors. Quantum electrodynamics later linked polarization to photon spin, and Alain Aspect in 1982 conducted the famous experiment with polarization-entangled photons, violating Bell's inequalities.

How it works

According to Maxwell's equations, an electromagnetic wave consists of mutually perpendicular electric and magnetic fields oscillating in phase. The type of polarization is determined by the trajectory of the end of the E vector: if it oscillates along a line—linear polarization; if it rotates with constant amplitude—circular; the general case is elliptical. The intensity of light transmitted through a polarizer is described by Malus's law: I = I₀ cos²θ. Wave plates introduce a phase shift between orthogonal components, changing the polarization type. In quantum optics, a single photon exists in a superposition of two basis states, and measurement is projective and described by density matrices.

Open problems & fun facts

Creation of deterministic single-photon sources with controlled polarization for quantum repeaters; Overcoming depolarization in scattering media without active compensation; Integration of polarization qubits into scalable quantum networks with error correction

💡 The screen of a liquid crystal display (LCD) manipulates polarization. Each pixel contains a liquid crystal that, under voltage, rotates the polarization of backlight. The system of two polarizers at the input and output turns this rotation into a change in brightness.