Diffraction grating

About: Diffraction grating is a research topic. Over the lifetime, 24884 publications have been published within this topic receiving 372437 citations. The topic is also known as: grating.

Ultra-broadband terahertz perfect absorber by exciting multi-order diffractions in a double-layered grating structure.

Abstract: Terahertz (THz) perfect absorber, as a useful functional device, has attracted considerable attention. Traditional metamaterial perfect absorbers are usually in response to single-frequency or multi-frequency owing to the resonance features of the metal-based sub-wavelength structure. In this paper, a simple double-layered doped-silicon grating structure was designed to realize an ultra-broadband and polarization-independent THz perfect absorber. Both theoretical and experimental results demonstrate that the incident THz waves ranging from 0.59 to 2.58 THz can be efficiently absorbed with an absorptivity of more than 95% and a bandwidth of about 2.0 THz. The excellent characteristic of this broad-bandwidth THz perfect absorber is mainly resulted from the air gap mode resonance together with the first-order and the second-order grating diffractions.

External-cavity semiconductor laser with 15 nm continuous tuning range

Abstract: A 1.26 μm optical amplifier with a facet modal reflectivity below 0.0001 has been used in a 58 mm-long grating external cavity. The lasing wavelength has been continuously tuned without mode hopping over a range of 15 nm by combined translation-rotation of the diffraction grating. A linewidth of 20 kHz has been derived from heterodyne beat frequency measurements between two tunable external-cavity lasers.

Electrically controlled surface diffraction gratings in nematic liquid crystals

Abstract: Photorefractive diffraction gratings were studied in cells of homeotropically aligned pentyl-cyanobiphenyl liquid crystal. These holographic gratings were induced by the simultaneous and nonsimultaneous application of dc and coherent optical electric fields. The observed behavior was consistent with a predominantly surface-mediated photorefractive effect. Beam coupling was observed in all cases and led to a model involving screened and unscreened interfacial trapped charges driving a modulation of the easy axis. Holographic gratings could be switched on and off by the application of a small voltage.

High-power widely tunable Tm:fibre lasers pumped by an Er,Yb co-doped fibre laser at 1.6 mum.

Abstract: High-power and widely tunable Tm-doped silica fibre lasers cladding-pumped and core-pumped by a 1565 nm Er,Yb fibre laser are reported. Output power up to 19.2W was generated from the cladding-pumped cavity configuration for ~38.2W of launched pump power and with slope efficiency up to ~72% with respect to absorbed pump power. Wavelength tuning was realized by use of an external cavity containing a diffraction grating. A maximum output power of 17.4 W at 1941 nm was generated for 38.2 W of launched pump power and the operating wavelength could be tuned over 202 nm from 1859 to 2061 nm. In the core-pumped configuration, a maximum output power of 12.1 W was generated at 1851 nm for 23.1 W absorbed pump power using a simple free-running cavity configuration with only ~24 cm of Tm-doped fibre. By employing a tunable cavity configuration, the operating wavelength of the core-pumped Tm:fibre laser could be tuned over 250 nm from 1723–1973 nm at multi-watt power levels.

Monochromator beamline for FLASH

Abstract: The design of a high resolution monochromator for the vacuum ultraviolet free electron laser at Hamburg (FLASH), DESY, is described. The monochromator is constructed as a plane grating monochromator using collimated light. Modifications have been made to take into account the free electron laser (FEL) beam characteristics, in particular, the extremely high peak power density of the radiation. Ray tracing simulations yield a resolving power in the range of 10 000–70 000 depending on the photon energy and the grating in use. Our monochromator is equipped with a 200line∕mm grating for the energy range of 20–200eV—the operation regime of FLASH—and a high resolution 1200line∕mm grating for the energy range of 100–600eV, covering the higher harmonic radiation of the FEL.