Single focusing/dispersing optic for cost-effective VUV optical systems
The holographic recording process – a non-contact manufacturing technique – allows for the patterning of gratings on aspheric surfaces. HORIBA Jobin Yvon has developed manufacturing methods to define, produce, and test diffraction gratings on toroidal substrates. Toroidal gratings combine the off-axis focusing properties of a toroidal reflector and the dispersive properties of a grating into a single optic, allowing for simplified, high-throughput monochromator and spectrograph designs.
Toroidal diffraction gratings are recorded with a varying groove density along the grating length, which is defined and optimized for correcting aberrations in a particular instrument. This non-uniform groove density is holographically generated by interfering two spherical wavefronts on a photoresist layer deposited on the toroidal surface. The grating pattern is then transferred directly into the substrate bulk using an ion etching process; this technique (used in the semiconductor industry) creates a lamellar groove structure that minimizes unwanted harmonic contamination.
Our toroidal substrates are polished and tested in our own optics fabrication laboratory, allowing us to maintain strict quality control.