Advanced, Ultrafast SLIDER Deflector
The SLIDER deflector is capable of sweeping a beam of light at world record deflection rates. When coupled with an ordinary camera, SLIDER can record waveforms with picosecond resolution and high dynamic range. With a rad-optic transcoder added to its front-end, the system can be used to record X-ray signatures and optimize laser fusion energy systems such as the National Ignition Facility at Lawrence Livermore National Laboratory.
Transcript
00:00:01 At the National Ignition Facility, experiments are being conducted using 192 laser beams that converge on a tiny fuel pellet to create fusion ignition. It's been a challenge to record the events during the billionths of a second timeframes it takes for the implosion to occur. Traditional imaging devices such as oscilloscopes or streak cameras have proven too slow to record the picosecond events. The Serrated Light Illumination for Deflection Encoded Recording, or SLIDER, device has been created to solve this problem. The following animation shows how it works. Here is an ultrafast optical signal that we wish to record. There are features on this signal that we would like to measure both with fine time-resolution and with high fidelity or dynamic range. A top-of-the-line oscilloscope would produce
00:00:55 poor resolution and poor fidelity. A top-of-the-line streak camera would perform better. But there would be a tradeoff between resolution and fidelity. Using our advanced concept called SLIDER, we can achieve both fine resolution and high fidelity. The heart of SLIDER is its solid-state all-optical deflector. The signal being measured is collimated by a simple lens and then focused by a cylindrical lens so that it can be injected into a thin, broad semiconductor waveguide. Once the signal is fully contained within the waveguide, an auxiliary pump beam is introduced from the top. A serrated gold mask deposited on top of the waveguide cladding, patterns the pumped beam profile. Much like a film exposure, the patterned
00:01:49 beam then imprints its intensity profile into the refractive index of the waveguide. The signal propagating through the waveguide experiences the patterned refractive index as a series of prisms. Because the later portions of the signal experience more activated prisms than the earlier portions, they undergo a larger deflection angle. The signal exiting the waveguide is collimated by a cylindrical lens and then focused by a final lens to a spot on a pixelated camera. The deflection encoded signal is manifested as a sweep at the focal plane. Here, an ordinary CCD array can be used to record the signal. The camera can be high fidelity but need not be fast, since the signal has been swept across the pixels and effectively shuttered by the deflection encoding.
00:02:48 Finally, the imprinted prisms continue to persist for a few billionths of a second and reset for the next repetition. SLIDER is a unique device that can effectively record with high resolution and fidelity, optical signals in the picosecond range that is needed for fusion ignition implosion characterization. In order to measure x-rays, a rad-optic transcoder can be inserted in front of the SLIDER system to convert the x-ray signal into an optical signal that SLIDER can then record. This enables SLIDER to be used as a diagnostic for recording the details of the burning plasma on NIF. SLIDER can record up to 20 signals in parallel, each being multiplexed along a different wavelength channel. The signals can be multiplexed in and demultiplexed out via ordinary diffraction gratings. SLIDER is the latest example of the R&D work
00:03:45 being developed at Lawrence Livermore National Laboratory's National Ignition Facility.