Tomas Plettner

Continuous-wave 532-nm-pumped singly resonant optical parametric oscillator based on periodically poled lithium niobate.

We report a continuous-wave (cw) 532-nm-pumped singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate. The pump source is a commercial 5-W cw diode-pumped, multilongitudinal-mode, intracavity-doubled Nd:YVO(4) laser. Using a four-mirror ring SRO cavity and single-pass pumping, we achieved subwatt internal oscillation threshold, 56% quantum efficiency, and output tuning from 917 to 1266 nm.

Self-phase-locked degenerate femtosecond optical parametric oscillator

We demonstrated a stable degenerate synchronously pumped femtosecond optical parametric oscillator (SPOPO) as a divide-by-2 subharmonic generator. The SPOPO exhibited passive all-optical self-phase-locking between the pump and signal/idler and thus required no external electronic feedback to produce the phase-locked subharmonic. We employed a type I phase-matched, 1-mm-long, periodically poled MgO:LiNbO3 crystal as the nonlinear gain element and an 80 MHz mode-locked Ti:sapphire laser with 180 fs pulses tuned at 775 nm as the pump. The SPOPO generated transform-limited 70 fs phase-locked output pulses centered at 1550 nm. The self-phase-locking operation was confirmed by separate beat-note measurement techniques with respect to the pump laser and with respect to an external cw laser.

Gamma radiation studies on optical materials

Results for the effects of /spl gamma/s on materials for a new laser-driven accelerator are presented. Various optical and laser materials are compared. While Si and fused c-SiO/sub 2/ appear ideal for subbandgap laser wavelengths, other interesting candidates include certain fluorides and compound semiconductors.

Electromagnetic forces in the vacuum region of laser-driven layered grating structures

Symmetric multilayer grating structures that have an embedded vacuum channel and that are powered by external laser beams are analyzed for their ability to manipulate charged particle beams. It is shown that acceleration, deflection and focusing forces can all be generated in a controlled fashion from the same grating architecture and by adjustment of phase of the incoming laser beams

The impact of Einstein's theory of special relativity on particle accelerators

We describe the consequences of the theory of special relativity on particle accelerators and present a historical overview of their evolution and contributions to science and the present limitations of existing accelerator technology. We report recent results of our experiment where we succeeded in accelerating relativistic electrons with visible light in vacuum. The experimental demonstration is the first of its kind and is the proof of principle for future linear laser-driven particle acceleration schemes in vacuum that may lead to the realization of electron–positron colliders beyond the TeV scale.

Experiment to Detect Accelerating Modes in a Photonic Bandgap Fiber

An experimental effort is currently underway at the E‐163 test beamline at Stanford Linear Accelerator Center to use a hollow‐core photonic bandgap (PBG) fiber as a high‐gradient laser‐based accelerating structure for electron bunches. For the initial stage of this experiment, a 50 pC, 60 MeV electron beam will be coupled into the fiber core and the excited modes will be detected using a spectrograph to resolve their frequency signatures in the wakefield radiation generated by the beam. We will describe the experimental plan and recent simulation studies of candidate fibers.

The proposed interferometric-type laser-driven particle accelerators

In a crossed-laser-beam accelerator, two properly phased laser beams, forming an interferometric configuration, may provide an adequate particle acceleration field over a phase matching distance. The two laser beams can be obtained by dividing a full, Gaussian laser beam equally in amplitude or in wavefront. We show in this paper that a wavefront-splitting laser-driven accelerator is relatively simple to set up and provides an acceleration gain comparable to that of an amplitude-splitting accelerator under the same laser damage fluence. We also present the noise characteristics measured from various interferometers, which may be useful for implementing interferometric-type accelerators.

Proposed tabletop laser-driven coherent X-ray source

We describe the concept of an all-dielectric laser-driven undulator for the generation of coherent X-rays. The proposed laser-driven undulator is expected to produce internal deflection forces equivalent to a several-Tesla magnetic field acting on a speed-of-light particle. The key idea for this laser-driven undulator is its ability to provide phase synchronicity between the deflection force and the electron beam for a distance that is much greater than the laser wavelength. A possible conceptual tabletop SASE-FEL device composed by such an integrated laser-driven accelerator-undulator system is explored.

Proposed few-cycle laser-particle accelator structure

We describe a transparent dielectric accelerator structure that is designed for ultra-short laser pulse operation. The structure is based on the principle of periodic field reversal to achieve phase synchronicity for relativistic particles. To preserve the possibility of ultra-short pulse operation it does not resonate the laser field in the vacuum channel, which enables the structure to support higher peak electric fields. Gradients on the order of a few GeV/m are expected to be possible with 10 fsec laser pulses. The proposed structure has a two-dimensional geometry which is ideally suited for micro-fabrication techniques and for integration with other optical MEMs components.

Optical wakefield from a photonic bandgap fiber accelerator

Photonic Bandgap (PBG) structures have recently been proposed as optical accelerators for their high coupling impedance and high damage threshold. As a first step in preparing a PBG accelerator, we propose to observe the optical wakefield induced by an electron beam traversing the structure in the absence of a coupled laser pulse. The electrons are focused into the fiber via a permanent magnet quadrupole triplet. The electrons excite fiber modes with speed-of-light (SOL) phase velocities. By observing the wakefield using a spectrometer, the SOL mode frequencies are determined.