ABSTRACT
We have demonstrated broad bandwidth large area (229 mm x 114 mm) multilayer dielectric diffraction gratings for the efficient compression of high energy 800 nm laser pulses at high average power. The gratings are etched in the top layers of an aperiodic (Nb0.5Ta0.5)2O5-SiO2 multilayer coating deposited by ion beam sputtering. The mean efficiency of the grating across the area is better than 97% at the center wavelength and remains above 96% at wavelengths between 820 nm and 780 nm. The gratings were used to compress 5.5 J pulses from a Ti:sapphire laser with an efficiency above 80 percent.
Subject(s)
Lasers , Lighting/instrumentation , Refractometry/instrumentation , Computer-Aided Design , Equipment Design , Equipment Failure AnalysisABSTRACT
We describe the advantages of using diffractive (Fresnel) lenses on thin membranes over conventional optics for, among others, future space telescope projects. Fabrication methods are presented for lenses on two types of freestanding membrane up to 50 cm in size. The first is a Fresnel lens etched into a thin (380-microm) glass sheet, and the second is an approximately 50-microm-thick polymer membrane containing a Fresnel lens made by replication process from a specially made fused-silica master. We show optical performance analysis of all the lenses that are fabricated, including a diffraction-limited Airy spot from a 20-m- focal-length membrane lens in a diffractive telescope system.
ABSTRACT
We have developed a hybrid Ti:sapphire-Nd:glass laser system that produces more than 1500 TW (1.5 PW) of peak power. The system produces 660 J of power in a compressed 440+/-20 fs pulse by use of 94-cm master diffraction gratings. Focusing to an irradiance of >7x10(20) W/cm (2) is achieved by use of a Cassegrainian focusing system employing a plasma mirror.
ABSTRACT
We combined functionalities of two diffractive optics with almost 100x lateral and vertical scale-length difference onto a single fused-silica surface. Fine-scale (2-mum-period) gratings for beam sampling were printed in photoresist by interference lithography and transferred to the substrate by a hydrofluoric acid etch. Subsequently, 115-mum-linewidth stairstep gratings for color separation at focus were proximity printed and wet etched in a two-mask process. Line shapes of the lamellar sampling grating are remarkably preserved following etching of the much deeper color separation grating structures with this nominally isotropic etch process. Model simulations of isotropic etching of topographical features show good agreement with the measured shape evolution of the sampling grating profiles, and the simulations reveal the sensitivity of the final feature shape to its initial aspect ratio. As a rule of thumb, lamellar grating profiles can be etched approximately 0.08A(-2) times their modulation depth, where A is their initial aspect ratio (height/width), before they evolve into a cusplike shape and begin to lose height.
ABSTRACT
We describe the design, fabrication, and performance of high-efficiency transmission gratings fabricated in bulk fused silica for use in high-power ultraviolet laser systems. The gratings exhibit a diffraction efficiency of 94% in order m=-1 and a damage threshold greater than 13>J/cm( 2) for 3-ns pulses at 351 nm. Model calculations and experimental measurements are in good agreement.
ABSTRACT
We have demonstrated a Ti:sapphire/Nd:glass laser system that produces up to 51 J of energy in 395-fs pulses (125TW). Focusing at f/3 to a 2.5-times diffraction-limited spot results in a peak irradiance greater than 10(20) W/cm(2) . Our 40-cm-diameter gold diffraction gratings have a damage threshold of 0.42 J/cm(2) for 320-fs pulses.
ABSTRACT
We have developed a holographically produced master metallic grating that achieves >91% diffraction efficiency over the wavelength range 800-1100 nm and a maximum diffraction efficiency at 1053 nm greater than 93% when used with TM polarization near the Littrow angle. The near-uniform diffraction efficiency with laser wavelength makes this design attractive for use in chirped-pulse amplification systems employing Ti:sapphire, Cr:LiSAF, or Nd:glass and permits high-fidelity stretching and compression of extremely short (10-fs) pulses.
ABSTRACT
The design and performance of a new type of high-efficiency diffraction grating for use in either transmission or reflection are described. The gratings are produced in a multilayer dielectric coating deposited upon optically flat substrates. By proper design of the multilayer stack and grating structure, a diffraction efficiency in excess of 96% for polarized light in the m = -1 order in reflection has been achieved.
ABSTRACT
The design and fabrication of large-area, high-efficiency metallic gratings for use in high-power laser systems is described. The gratings exhibit a diffraction efficiency in excess of 95% in the m = -1 order (Littrow mount) and have a high threshold for laser damage. Computations and experimental measurements are presented that illustrate the effect of grating shape and polarization on efficiency. A simple theory for optical damage to metallic diffraction gratings is developed and compared with experimental measurements of the laser-damage threshold over the pulse range from 400 fs to >1 ns.
ABSTRACT
Delayed post-traumatic erosion of the skull base is reported in three patients who presented as adults with cerebrospinal fluid fistulae and a history of recurrent meningitis. These skull defects were associated with herniation of the subarachnoid space into the diploe of the skull base, the paranasal sinuses and the orbit. This rare complication of head injury is assumed to have occurred as the result of a dural tear at the time of trauma. Its site probably determines whether a resulting meningocele widens the intradiploic space or broaches the cranial floor.
