Friday, August 24, 2012

LIBS on Mars: nice plasma indeed

While everyone knows that ambient conditions on Mars are vastly different than those on Earth, it's interesting to see the practical results of this fact. For example, when laser-induced-breakdown spectroscopy (LIBS) is done on Mars, as with the ChemCam on NASA's Curiosity rover, the process unfolds differently than it does here in the great out-of-doors. The photo below shows this (but for now please put aside the fact that these images were taken of laser plasmas in a Los Alamos National Laboratory test chamber under atmospheric pressures typical of Earth and Mars). The image size is 75 x 75 mm; the target in both cases is a piece of metal. The Mars-like atmospheric pressure is about one-hundredth of the Earth-like pressure.

(Image: LANL)

And now the results, please. The ChemCam's LIBS setup has three spectrometers that work in the UV, the violet, and the visible and near-IR, respectively. The first analyzed rock, dubbed Coronation, is (or maybe by now, was) 2.7 m away from Curiosity. The resulting spectrum of 30 laser shots, seen below in squashed form (the larger version can be found at shows many lines of metals and other elements, including carbon and hydrogen. Interestingly, the hydrogen only showed up in the first laser shot, indicating that it was only on the rock's surface. Note the sensitivity (very small peaks for titanium and manganese) as well as the fact that the x-axis scale is somewhat nonlinear.


However, as I mentioned earlier, conditions are quite different here on Earth: instead of vaporizing rock, curiosity merely killed the cat.

Monday, August 20, 2012

Petawatts proliferate

Borrowing a phrase from a 2006 Laser Focus World petawatt article, it is even more true today that "petawatts proliferate." All petawatt lasers aim to deliver petawatt-power-level pulses. But to understand just why so many petawatt-class (or sub-petawatt-class) laser systems are either in operation or being developed, it's necessary to understand the petawatt pulse itself and the groundbreaking applications that are causing these laser powerhouses to proliferate. What is the petawatt pulse width, the pulse duration, the peak power level, and the frequency at which these petawatt pulses are delivered? And just what type of light-matter interaction studies and other applications make petawatt-level pulses so appealing?

In mid July, Laser Focus World reported that the National Ignition Facility (Livermore, CA) delivered 500 terawatts (0.5 petawatts or PW) to its target in a step towards laser-initiated fusion. The 1.85 MJ energy is generated by NIF's 192 laser beams in a football-field-sized structure. And just a month prior, we reported on Ohio State University's Science Center for Advanced Research on Lasers and Engineered Targets (SCARLET), which aims to deliver the same 0.5 PW power-level pulses from a much smaller facility with a one-shot-per-minute repetition rate (see image below). However, compared to NIF, the 30 fs pulsewidth SCARLET creates sub-millijoule pulses that have a lot of power, but cannot compare to NIF's 1.85 MJ peak.

At the extreme of the petawatt-class-laser craze is definitely the Extreme Light Infrastructure (ELI)--Europe's project that will increase the peak power of ultrashort-pulse lasers to a whopping 200 PW and peak intensities of 10exp25 Watts per square centimeter. Not yet built, the ELI will begin with a more modest 10 PW laser and advance to 200 PW by 2017. In his Photonics Frontiers article in Laser Focus World in January 2011, Jeff Hecht described some of the applications that make ELI and all petawatt-class lasers so exciting; for example, proton acceleration to the 70-250 MeV range is needed for cancer therapy and ultrahigh-energy ultrashort pulses enable photonuclear physics studies that could lead to nuclear waste disposal.

This year's OSA CLEO conference included a special Petawatt Lasers Technologies (CMD4) series of sessions, which detailed the following petawatt-class laser systems (a reference paper is linked for each):

CAEP China:


LLE University of Rochester, USA:

In addition to these CLEO presenters, petawatt laser systems are proliferating worldwide; here are a few more examples of systems in operation or systems planned to be built:

Texas Petawatt Laser, The University of Texas at Austin, USA:

Hercules Petawatt Laser, University of Michigan, USA:

Z-Petawatt, Sandia National Laboratories, USA:

Vulcan laser, Rutherford Appleton Laboratory, England:

XCELS, Russia:

PHELIX laser, Germany:

One of the best YouTube videos available on the how petawatt lasers work and their many applications is from Todd Ditmire on the Texas Petawatt laser team. check it out, and I'm sure you'll see why petawatts proliferate and will continue to do so (at least until exawatt lasers arrive!).

Monday, August 6, 2012

Curiosity to Earth: the photonics have landed!

As we all know by now, the Mars Curiosity rover has landed -- congrats, NASA! I, along with millions of others, will be eagerly awaiting what Curiosity has to say.

Here is just a brief mention of some of the photonics companies and organizations that produced the lasers, sensors, and optics essential to Curiosity's misson.

One of the most important instruments carried by Curiosity is the ChemCam, originally developed by the Los Alamos National Laboratory (Los Alamos, NM); this instrument contains a laser-induced breakdown spectroscopy (LIBS) system that will spectroscopically analyze Mars' surface.

An early image taken by one of Curiosity's hazard avoidance cameras (NASA)

The spectrometers in ChemCam were produced by Ocean Optics (Dunedin, FL), while the plasma-producing Q-switched, diode-pumped solid-state laser at the heart of the instrument was developed by Thales Laser (Orsay, France). The Chemcam also contains laser diodes from 3S Photonics (Nozay, France).

Curiosity contains 17 cameras; some of these were developed by Malin Space Science Systems (San Diego, CA), a company specializing in systems for unmanned spacecraft. CCD cameras from Truesense Imaging (Rochester, NY; a former division of Eastman Kodak) will be used for high-resolution (up to 14.4 μm per pixel) photos of rocks and other surface material, while CCD cameras from Teledyne Dalsa (Waterloo, ON, Canada) will be used for navigation and hazard avoidance.

Many of the camera optics for Curiosity were provided by Optimax (Ontario, NY).

It should also be mentioned that radiation-hardened photovoltaic cells from Emcore (Albuquerque, NM) powered the spacecraft as it headed toward Mars (the Curiosity rover itself is powered by radioisotope thermal generators).

I'd like to thank these innovative photonics outfits, along with the many that I have not mentioned here, for a job well done! And I look forward to seeing the science results that Curiosity will be producing in abundance -- along with the sweeping vistas that make many of us want to put our own footprints into the surface of Mars.

Friday, August 3, 2012

Persistent surveillance pays off

During the SPIE Defense, Security + Sensing show in Baltimore, I had a very interesting conversation with John Marion, who is director of persistent surveillance at Logos Technologies, based in Fairfax, VA. Our talk was about surveillance imaging from aerostat balloons tethered to the ground to continuously observe what Marion said could be a “small-city size area”.
Aerostats made news in May with a New York Times article describing life in Afghanistan under the eye of the many spy balloons tethered at military bases and in cities. At a relatively low cost, such balloons provide the military with an unblinking, long-term view of important areas, helping to catch insurgents planting bombs and deterring ambushes.
In 2010, General David Petraeus, commander of allied forces in Afghanistan, had asked for help from all available intelligence, surveillance, and reconnaissance (ISR) assets. In partial response, a 300-ft-long, untethered hybrid airship called LEMV (long-endurance multi-intelligence vehicle) was developed by Northrop Grumman for the US Army. Its first flight has been repeatedly delayed and now may be scheduled for November, according to one report.
To enhance the imaging capabilities of the much smaller aerostats, Logos Technologies developed its Kestrel system, which is a wide-area persistent surveillance system for forward operating bases. Its development includes novel imaging and stabilization capability for day/night operation.

To date such aerostats have relied on narrow field-of-view ball gimbal sensors to identify targets of interest. The Kestrel sensor enables 360° coverage out to extended ranges at moderate resolution, while cueing a narrow field of view camera to provide high resolution imagery of targets of interest.
The ground station system enables operators to monitor multiple regions of interest in real time, and allows for backtracking through the recorded imagery while monitoring ongoing activity (see video). This backtracking capability allows operators to detect and understand threat networks and operations. Since July, ten of the full day/night surveillance systems have been deployed to Afghanistan, with six more available as spares.

This spring the US Department of Homeland Security tested the Kestrel system for border security around Nogales, Arizona. A Raven Aerostar aerostat was fitted out with a Wescam MX-15 hi-res, narrow-field camera from L-3 Communications and a Kestrel day/night medium-res, wide-area persistent surveillance system. Thanks to the system, authorities apprehended 30 suspects on the first night of the demonstration and made a total of 80 arrests over the course of the week.