Navy laser weapon deployment

The U.S. Navy will deploy a high-energy laser weapon on the USS Ponce in fiscal 2014, chief of Naval Research Rear Admiral Matthew Klunder announced April 8, 2013 at the Sea-Air-Space exposition. The Navy Laser Weapon System (LaWS) will be the first high-energy laser deployed for field use by the armed services. The Navy has tested the laser system against its prime targets, moving small surface boats, and remotely piloted vehicles.

The at-sea deployment comes two years earlier than the Navy had planned. That may be a first in laser weapon development, where schedule slippage and cost overruns have been common. The New York Times reports LaWS cost just under $32 million, roughly two orders of magnitude less than the Airborne Laser, dropped from the fiscal 2011 budget after it failed to reach the required 200 km range.

NAVY LaWS on board a ship during tests of the laser weapon. (Image courtesy of the US Navy)

LaWS is part of the new generation of electrically powered solid-state laser weapons, which Navy officials say offer two advantages. One is a "deep magazine," the ability to fire pulses as long as electrical power is available--and ships have plenty of power. The other is cost. Klunder said, "Our conservative data tells us a shot of directed energy costs under $1," compared to $100,000 or more to fire a missile.

The choice of LaWS marks a big success for fiber lasers. When the Pentagon launched the Joint High Power Solid-State Laser (JHPSSL) program in 2002, developers focused on diode-pumped slab lasers, which at the time seemed the technology most likely to reach the 100 kW sought for defense against rockets, artillery, and mortars. JHPSSL reached that level in 2009, but fiber lasers have been catching up. The Naval Sea Systems Command reached 30 kW by combining the beams from six 5.5 kW industrial fiber lasers to shoot down a drone in 2010. LaWS has been upgraded since then, but Navy officials did not disclose the output power of the current system.

The laser is not the only challenge. For the current version of LaWS, L-3 Integrated Optical Systems (Pittsburgh, PA) upgraded the pointing and tracking system, improving accuracy of the fine steering mirror and controls, and improving the software and user interface. "We took scientists out of the loop to make it operable by seamen," said Don Linnell, director of business development and strategy. The Navy considers that a must for fielding laser weapons.

Directed self-assembly

One reward of exploring "Photonic Frontiers" every month for Laser Focus World is discovering new and emerging technologies that could have important impact. In investigating extreme-ultraviolet (EUV) lithography for my May Frontiers article, I discovered an intriguing concept called "directed self-assembly" which has surfaced since I last covered EUV development four years ago. Practical applications of directed self-assembly remain a ways off, but it could be crucial to sustaining the Moore's Law trend of shrinking electronic components on semiconductor chips.

Simple self-assembly builds structures from the bottom up. On a nano-scale, it starts with molecular building blocks that assemble themselves into larger structures. An example is atoms or molecules adding themselves to bonding sites on the edge of a growing crystal. DARPA has studied ways to self-assemble small building-block modules into robots that could reassemble themselves in different configurations for other purposes, like how children reassemble Lego blocks into new structures.

Robotic modules can be programmed to build desired structures, but external controls are needed to make atoms and molecules grow specific nanostructures. Directed self-assembly does that by applying forces from the top down to control assembly. For making semiconductor chips, the top-down control would come from patterns written by the photolithographic light source onto the material.

Dan Herr became intrigued by the idea of the functional self-assembly of materials while working on lithographic photoresists at Research Triangle Park, NC-based Semiconductor Research Corp. Resists are central to photolithography, and their chemistry can limit the minimum feature size, edge roughness, and writing speed. Conventional resists were designed to match visible and near-ultraviolet light sources, but EUV lithography poses additional challenges because the photons carry an order of magnitude more energy, enough to blast cascades of electrons from the resist.

"Directed self-assembly is a replacement for conventional resists," says Herr, who is now developing the materials at the University of North Carolina, Greensboro (Greensboro, NC). It's based on combining two polymers--one water-soluble, the other oil-soluble--which arrange themselves in regular patterns so the oil- and water-soluble parts can keep apart from each other. Light sources then direct their assembly by writing lines on the substrate for the polymers to start building upon.

Directed self-assembly involves three steps: writing a pattern, depositing the two block copolymers, and removing one to form a pattern. (Courtesy of Wikipedia)

The short-term focus is finding an alternative to conventional photoresists. But Herr says "the holy grail would be materials that self-assemble into shapes and structures that define active components of the circuit." That could change the rules for light sources as well as lithography.