Mode-locking (lasers)

The Shockley–Queisser limit is the maximum theoretical efficiency for a single p-n junction solar cell. It considers only radiative recombination and black-body radiation losses. For a single-junction cell with an optimal bandgap of 1.34 eV under standard solar illumination (AM1.5G), the maximum efficiency is approximately 33.7%. This fundamental limit guides solar cell research and design.

Q-switching is a technique for producing high-intensity, short-duration laser pulses. It works by temporarily preventing laser action, allowing the gain medium to store a large amount of energy via population inversion. The laser's quality factor (Q-factor) is then rapidly switched to a high value, causing the stored energy to be released in a single, powerful nanosecond pulse.

The CIE D-series illuminants are a set of standard spectral power distributions (SPDs) representing various phases of natural daylight. The most common is D65, which has a correlated color temperature of approximately 6504 K and represents average noon daylight. D50 (5003 K) is another key standard, often used in graphic arts. These standards enable consistent color reproduction.

Top-down synthesis involves creating nanomaterials by starting with a larger, bulk material and breaking it down or patterning it to the nanoscale. Key techniques include mechanical methods like ball milling and lithographic methods like photolithography, electron-beam lithography, and nanoimprint lithography. These methods are often used for creating structured surfaces and integrated circuits, but can suffer from surface imperfections.

Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational kinetic energy. The energy stored is proportional to the square of the rotational speed. When energy is extracted, the flywheel's rotation slows down. The formula for stored energy is \(E = \frac{1}{2} I \omega^2\), where I is the moment of inertia and ω is the angular velocity.

Molecular electronics explores using individual molecules or nanoscale molecular collections as fundamental electronic components. This approach aims to build circuits at the ultimate limit of miniaturization, far beyond traditional silicon-based technology. Key components include molecular wires, switches, and rectifiers, leveraging quantum mechanical properties like electron tunneling through molecular orbitals for their function.

The first functional laser was the ruby laser, demonstrated in 1960. It is a solid-state laser that uses a synthetic ruby crystal (chromium-doped aluminum oxide) as its gain medium. The ruby is optically pumped by a powerful xenon flashtube, creating a population inversion in the chromium ions and producing a deep red beam of light at a wavelength of 694.3 nanometers.

A brushless DC (BLDC) motor is a synchronous motor that uses an electronic controller instead of mechanical brushes and a commutator to switch current in the windings. It typically features a permanent magnet rotor and a wound stator. The controller uses sensors (like Hall effect sensors) or sensorless algorithms to determine rotor position and energize the windings sequentially, creating a rotating magnetic field.

CMOS (Complementary Metal-Oxide-Semiconductor) is the dominant technology for constructing integrated circuits. It uses complementary pairs of p-type and n-type MOSFETs to build logic gates. Its primary advantage is very low static power consumption, as one transistor in the pair is always off during steady state, resulting in minimal current flow except during switching transitions.

The discovery that europium-doped yttrium vanadate (\(YVO_4:Eu^{3+}\)) could act as a brilliant red phosphor was a critical breakthrough for color television. Before this, red phosphors were weak, resulting in dull colors. The intense, narrow-band red emission from the \(Eu^{3+}\) ion allowed for bright, vibrant color displays, dramatically improving the quality of color TV and setting the standard for display technology.

Developed by French engineer Pierre Bézier for Renault in the 1960s, UNISURF was one of the first true 3D CAD/CAM systems. Its core innovation was the use of what are now known as Bézier curves and surfaces. These are parametric curves defined by a set of control points, allowing for the intuitive and mathematical creation of complex freeform shapes for car bodies.

Superconducting Magnetic Energy Storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil. The energy can be stored indefinitely as long as the coil is kept at superconducting temperatures, as there is virtually no energy loss due to electrical resistance. The stored energy is given by \(E = \frac{1}{2} L I^2\).

The Ganz-Griesser whiteness index is a linear formula widely used, particularly in the textile industry. It is derived from CIE tristimulus values and is defined as \(W_{GG} = Y - Px - Qy + C\), where P, Q, and C are constants specific to the illuminant and observer. For the D65/10° condition, the formula is \(W_{GG} = Y - 1868.322x - 3695.690y + 1809.441\).