Research Roundup

| 10 September 2009

Berkeley Unified’s integration plan: A nationwide model?

The Berkeley Unified School District’s plan to maintain diversity could serve as a model for other public schools nationwide that are seeking constitutionally sound desegregation programs, according to a new report by researchers at Berkeley and UCLA.

In 2004, the Berkeley district adopted its newest “controlled choice” plan to assign students to elementary schools, dividing the city into more than 440 micro-neighborhoods, called “planning areas.” Each area was assigned a diversity code based upon its average household-income level, the highest level of education obtained by adults, and the percentage of students of color enrolled in public-school grades K-5.

All students in a planning area are assigned the same diversity code regardless of their individual race — a key difference between the Berkeley plan and others recently struck down by the U.S. Supreme Court, which assigned such codes to individual students.

New era in optical science heralded by advanced laser

Berkeley researchers have reached a new milestone in laser physics by creating the world’s smallest semiconductor laser, capable of generating visible light in a space smaller than a single protein molecule. The Berkeley team not only successfully squeezed light into such a tight space, but found a novel way to keep that light energy from dissipating as it moved along, thereby achieving laser action.

The achievement helps enable the development of such innovations as nanolasers that can probe, manipulate, and characterize DNA molecules; optics-based telecommunications many times faster than current technology; and optical computing in which light replaces electronic circuitry, with a corresponding leap in speed and processing power.

The Berkeley researchers used a cadmium sulfide nanowire separated from a silver surface by only 5 nanometers to trap and sustain light energy within an area 20 times smaller than its wavelength. This innovative design which uses semiconductor materials and fabrication technologies commonly employed in modern electronics manufacturing, enabled researchers to sustain the strongly confined light long enough that its oscillations stabilized into the coherent state that is a key characteristic of a laser.

“Plasmon lasers represent an exciting class of coherent light sources capable of extremely small confinement,” said Xiang Zhang, a professor of mechanical engineering and director at Berkeley of an NSF Nanoscale Science and Engineering Center. “This work can bridge the worlds of electronics and optics at truly molecular-length scales.”

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