Custom Diffraction Gratings
Enabled through production on one of several in-house environmentally and interferometrically controlled ruling engines, or within one of our master holographic diffraction grating recording laboratories, this capability uniquely positions us as a reliable resource of many forms of surface relief custom diffraction gratings. These master diffraction gratings support our production of consistent high quality, low cost replicas for both reflection and transmission gratings and also allow us to provide gratings for use within high damage threshold laser applications.
If one of our standard diffraction gratings does not provide the ideal dispersion or diffraction efficiency profile necessary to optimize your performance goal, we offer the engineering and manufacturing expertise to design and build what you need to differentiate your product with winning performance.
Enabled through production on one of several in-house environmentally and interferometrically controlled ruling engines, or within one of our master holographic diffraction grating recording laboratories, this capability uniquely positions us as a reliable resource of many forms of surface relief diffraction gratings. These master diffraction gratings support our production of consistent high quality, low cost replicas for both reflection and transmission gratings and also allow us to provide gratings for use within high damage threshold laser applications.
If you need help determining what grating parameters you need contact us for assistance.
Ruled Grating Capability
The ini
tial steps in ruling an original or master grating includes the selection of an appropriate substrate, usually glass or copper, polishing the substrate to a high degree of flatness, and coating it with a thin layer of aluminum by vacuum deposition. The ruling of parallel, equally spaced grooves is a slow process that can require several days of set-up and testing prior to the actual ruling. The ruling engine must be able to retrace the exact path of the diamond forming tool on each stroke and to index (advance) the substrate a predetermined amount after each cut. Both groove parallelism and displacement must be controlled with great precision. A series of “test” rulings are made and the grating is checked for efficiency, groove profile and stray light.
After each test, a minor mechanical adjustment may have to be made. It can take a week or more of repeated testing to optimize the groove profile for specific optical characteristics. After exhaustive testing, an original grating is ruled on a large substrate. An original grating is obviously very expensive and, consequently, gratings saw only limited use until after the development of the replication process.
Holographic Grating Capability
Like a ruled grating, the first step in the production of a holographic grating is the selection of an appropriate polished substrate. The substrate for a holographic grating is, however, coated with a photosensitive (photoresist) material rather than the reflective coating used in ruled gratings. The photoresist is exposed by positioning the coated blank between the intersecting beams of monochromatic and coherent light produced by a laser. The intersecting laser beams generate a series of parallel, equally spaced interference fringes whose intensities vary in a sinusoidal pattern. This fringe pattern exposes the resist differentially. Since the solubility of the resist is dependent on its exposure to light, the development process transfers the varying intensities of the interference fringes to the surface of the resist. The substrate is then coated with a reflective material and can be used as is, or replicated by the same process used for ruled originals.
Since holographic gratings are produced optically, groove form and spacing are perfectly consistent. Holographic gratings are, therefore, free from the periodic and random spacing errors responsible for “ghosts” and stray light in ruled gratings. The result is that holographic gratings generate much less stray light than ruled gratings.
The Replication Process
Our replication process allows numerous “replica” gratings to be produced from a single master, either ruled or holographic. It is a procedure that results in the transfer of the three dimensional topography of a master grating to another substrate, allowing reproduction of a master in full relief to extremely close tolerances. As a result, this reliable, cost effective and repeatable process facilitates the widespread use of gratings in spectroscopic and laser applications.
Filtered Diffraction Gratings
Optometrics’ patented process for filtered diffraction gratings integrates a spectral filtering component within the grating construction. Integration of the filtering component enables a unique high level of control over primary or unwanted wavelength bands, providing an OEM the opportunity of superior system level dynamic range.
Quality is assured through state-of-the-art testing & metrology.