Wideband All-Dielectric Diffraction Grating on Chirped Mirror

Broadband pulse compression gratings with measured 997% diffraction efficiency

“…Grating mirror designs with diffraction efficiencies of >99.7%, for a spectral bandwidth of more than 65 nm centered at 1030 nm can be obtained, while the same separation between incident beam and diffracted beam of ∼7.6°is kept. This corresponds to the same spectral bandwidth of high diffraction efficiency as demonstrated in the simulation presented in [17], which was, however, centered at 770 nm wavelength. Additionally, for our laser pulses centered at 1030 nm, which were used in the experiments reported above, a grating mirror with 1700 lines∕mm and angular separation of 15°could be realized.…”

“…Reflective grating designs, which allow high diffraction efficiencies over especially large spectral ranges, have been proposed by several authors [4,15,16], where structures based on a leaky mode waveguide on top of a highly reflective (HR) mirror have been studied with major interest [17][18][19][20][21][22]. A design study by Kalinchenko and Lerer [17] proposed the use of chirped mirrors in order to further increase the spectral width of high diffraction efficiency, as well as to have constant group delay dispersion over the same range.…”

“…The remaining four layers are a 175 nm thick layer of SiO 2 , followed by 144 nm of Ta 2 O 5 , followed by 48 nm SiO 2 , and finally 284 nm of Ta 2 O 5 . The function of these four layers is to obtain high diffraction efficiency in the −1st order for TE polarization also off the Littrow configuration [17,19]. The complete layer sequence is shown schematically in Fig.…”

Design of high-efficiency ultrabroadband dielectric gratings

“…Furthermore, the ideal layer thicknesses for the TF layers are not the same as in the case of using them as dielectric mirrors in air. Maximum reflection and bandwidth can be obtained by choosing an angle of incidence and calculating the corresponding λ∕4 thicknesses of the high-and low-index layers [10,13], but these optimum values can be modified by the presence of a grating above the multilayer stack. Therefore, the stack of layers has to be optimized together with other grating parameters.…”

“…This structure was achieved by computer optimization using a corrugated hafnia (HfO 2 ) grating structure, a low-index silica (SiO 2 ) layer below, and a silica-hafnia quarterwave multilayer mirror. One possibility to increase the bandwidth of the DE curve is to introduce a chirped mirror below the grating structure, achieving this way a 20-30 nm wider bandwidth [10]. The quarterwave stack design with one resonant layer above has been studied using hafnia and silica by the optimization of the resonant silica layer and the grating parameters, such as filling factor (f ), grating thickness (t), and period (Λ), and also the angle of incidence (α) [11].…”