Degenerate Four-Wave Mixing in Phycoerythrin Dye-Doped Nanoparticles

We have generated a phase-conjugate (PC) wave from nanoparticles with a new microscopic system proposed. The microscope includes a confocal system with a degenerate four-wave mixing (DFWM) system, which plays a major role in generating the phase-conjugate wave to compensate phase distortion in the optical path toward targets. The proposed optical system detects feeble PC wave and imagines 3D particles while improving the inplane contrast resolution of the microscopic image.

Entropy

This chapter explores irreversibility, disorder, and ignorance as manifestations of entropy. Entropy measures irreversibility. The inevitable increase of entropy was discovered by analyzing a reversible heat engine, and implied the heat death of the Universe. Entropy measures disorder. Osmotic pressure is the entropy of ions in water; the residual entropy of glasses measures their atomic disorder. Entropy measures our ignorance about the world. Information entropy is used to compress messages and files on the Internet. Exercises span information entropy (burning information and Maxwell’s demon, reversible computation, card shuffling, Shannon entropy, entropy of DNA and aging, entropy of messy bedrooms, data compression), fundamentals of equilibration (Arnol’d cat map, proofs for and against entropy increase, phase conjugate mirrors), materials science (rubber bands and glasses), and astrophysics and cosmology (life at the end of the Universe, black hole entropy, Dyson spheres, cosmic nucleosynthesis and the arrow of time).