Description: Lasers are used or proposed for use in many areas of accelerator applications: as drivers for novel accelerator concepts for future colliders, in the generation, manipulation, and x-ray seeding of electron beams, in the generation of electromagnetic radiation ranging from THz to gamma rays, and in the generation of neutron, proton, and light ion beams. In many cases ultrafast lasers with pulse lengths well below a picosecond are required, with excellent stability, reliability, and beam quality. With applications demanding ever higher fluxes of particles and radiation, the driving laser technology must also increase in repetition rateand hence average powerto meet the demand.
b: Optical Coatings for Ultrafast Optics
Description: The cost and reliability of ultrafast laser systems depend in part on the optical robustness of coated optics such as mirrors and windows. R&D proposals leading to low loss, low scatter, ultra-high damage threshold broad bandwidth coatings that can sustain fluences exceeding >2 J-cm2 for 100 fs pulses. Coatings must also be stable at incident average powers exceeding 100 W, and provide high quality transmission or reflection properties over >10% bandwidth under both vacuum and in-air use.
c: Timing Synchronization and Feedback
Description: Lasers for accelerator applications must be synchronized to external timing sources, most often in the form of microwave reference signals. As experiments come to depend on increasingly shorter laser and particle bunch lengths, the timing requirement becomes increasingly challenging. Modern commercial laser systems lock with ~100 fsec RMS timing jitter. Applications to develop field-installable upgrades for widely used laser systems (eg. Ti:Sapphire) that can improve the timing jitter with respect to the external reference to 10 fsec are sought.
d: Stabilization of Complex Laser Systems
Description: Lasers for accelerator applications must produce laser pulses with excellent mode quality (M2<1.1) and precisely controlled spectral and temporal shape (Gaussian or flat-top being typical). The large number of optics involved in very high peak power ultrafast laser systems raises the likelihood of time-dependent mode and profile degradation, and requires considerable expertise and manual intervention to counteract.
Grant applications are sought for passive and active systems that automatically diagnose and mitigate transverse and longitudinal profile drift in ultrafast laser systems. The successful application will begin with a measurement and characterization phase on an existing TW-class laser system, design an appropriate combination of passive and active mitigations based on modern control theory, and implement and thoroughly test a prototype system. The prototype system must be designed as a retrofit kit for existing commercial Ti:Sapphire CPA systems and must not interfere with existing mode locking, timing synchronization, or carrier-envelop-phase locking feedback loops already in place.
e: Simulation and Modeling Codes for Diffractive Optics
Description: Designing diffractive optics requires high accuracy simulation codes. Computer software capable of designing high performance broadband diffractive optics is sought. Codes must support the development of beam combiners and high-efficiency multilayer diffraction gratings for ultrafast laser use. At a minimum, the code must support accurate far-field performance prediction and automated geometric optimization. Proposals for codes which also allow analysis of potential failure modes by local field strength calculation within and near optical surfaces are especially encouraged.
f: Robust Nonlinear Optical Materials
Description: Nonlinear optical materials for frequency conversion are key to producing a wide array of laboratory-scale sources of radiation. Materials supporting conversion of laser power to frequencies in the terahertz to EUV range (=3000.1 micron) at high conversion efficiency, high damage threshold, and at high average power (>100 W, cw) are sought.
Description: Periodically-poled materials provided engineered optical properties useful for a variety of laser applications, ranging from parametric oscillators and amplifiers to nonlinear frequency generation. Centimeter-thick optical-quality PPMgLN has been produced and used successfully in an OPCPA, but current commercial fabrication techniques remain limited in achievable thicknesses. Development and demonstration of techniques for producing optical-quality periodically-poled materials suitable for high-power use in OPCPA or other optical frequency conversion applications is sought.
h: Drive Lasers and for Photocathode Electron Sources
Description: Applications are sought for developing turn-key commercial laser systems and subsystems for driving high-brightness photocathodes.
a) A self-contained turn-key laser system (including environmental enclosure and controls) producing 50 Watts of 520nm light in 1 psec pulses at 1.3 GHz with no more than 100 fsec rms timing jitter with respect to an external microwave timing reference is sought. The resultant beam must be shaped temporally and spatially, as well as have the ability for producing varying pulse trains.
b) Practical and highly efficient (>90%) methods are sought for advanced laser shaping. The technique must allow a wide range of transverse shapes (elliptical to flattop) and spot sizes (0.3-3 mm) to be projected onto a photocathode to mitigate non-linear space charge effects and concomitant emittance degradation. The shaping system must preserve the laser beam quality and be usable with high powers (10s of Watts of average laser power).
Description: In addition to the specific subtopics listed above, the Department invites grant applications in other areas that fall within the scope of the topic description above.