LONG BEACH, Calif., May 21 -- The best test of special relativity yet, detecting cervical cancer with light, sodium guide starts, how to make better clocks with calcium, and practical applications of stopped light: North America's largest conference on lasers, electro-optics and quantum electronics features a gathering of the latest research and technology involving lasers, a broad range of electrical and optical devices and various systems in which the wave nature of atoms and electrons becomes important. Following are some highlights from technical sessions held at the conference, which is being held through Friday at the Long Beach Convention Center: Lasers When it was introduced in the latter half of the 20th century, the laser was an invention in search of an application. Lasers produced narrow beams of single-color light, made of waves which line up with each other in a perfectly defined, "coherent" fashion. Scientists thought they would be useful for studying energy jumps in atoms, but other applications remained undetermined. Nowadays, lasers are everywhere -- they scan your grocery items at checkout, they play your CDs and DVDs, they perform state-of-the-art laser surgery. And the story of lasers is just beginning, as new applications loom on the horizon. Continuing advances in lasers will help bring about faster Internet transmissions, safer and better ways of detecting diseases such as cancer, new and presently unimagined entertainment applications, and they will continue their original mission of exploring the frontiers of quantum physics. Quantum Electronics Much of our present-day technology is based upon the electron, the particle that carries electricity in devices such as stereos and hair dryers. At its most basic level, quantum electronics deals with our modern understanding of the electron in various settings, from the semiconductors that make up computer chips to LEDs (light-emitting-diodes) which illuminate the latest video screens to the lasers that we find everywhere. Whenever the negatively charged electrons accelerate, or shed their energy, or combine with positively charged "holes" in electronic devices, they produce light or some other form of electromagnetic radiation, and therein lies the electron's connection to optical science. Electro-optics is the study of all of the wavelengths of electromagnetic radiation, from x-rays to the far infrared through the use of electronic and optical devices. Microwave ovens, radios, cell telephones were all made possible through the use of devices which manipulate electromagnetic energy. Just as the spectrum of electromagnetic radiation is infinite, so are the possibilities for electro-optics applications. Wireless communications, solar-energy cells and many other important technologies will depend upon advances in electro-optics.