Concave Blazed Holographic Gratings
A concave grating has the advantage of setting up a spectroscopic system without any imaging optics like concave mirrors. For this reason, the concave grating is used in a wide range of applications, such as analytical instruments, optical communications, biotechnology, and medical instruments. Spectroscopes incorporating concave gratings are classified roughly into two categories: polychromators or monochromators. Shimadzu offers concave gratings for applications in (1)flat-field polychromators and (2)constant deviation monochromators.
Features
- As a concave grating itself has the aberration correction function, it is possible to design a compact spectroscopic system by a concave grating in higher resolution than by a mechanically ruled grating.
- Concave gratings with small radius of curvatures are available. It is also possible to make concave gratings with high aperture ratios for fluorescence analysis and optical communication applications.
- All the concave gratings for flat-field polychromators and constant deviation monochromators are aberration corrected by the optimum exposure method of Shimadzu's Aspherical Wave Exposure Technology and have excellent imaging performance.
- The grating grooves are formed by a holographic exposure method which applies two-laser-light interference. This holographic method ensures that the stray light ,due to periodical errors of grooves, of concave gratings is much smaller than that of mechanically ruled gratings.
- Blaze angle is formed by an ion-beam etching technology which easily makes blazed holographic gratings with various blaze angles (blaze wavelengths).
- High groove density and high resolution gratings can be manufactured easily and at competitive price.
Fig.3 Shape of Concave GratingsStandard Specifications
| Grating Type | Unequally spaced curved-groove replica grating*1 |
|---|---|
| Blank material | Soda glass |
| Dimensional tolerances Width(W) and hegiht (H) of rectangular blanks Diameter(Φ) of round blanks Thickness(T) |
±0.2mm 0/-0.2mm ±0.5mm |
| Effective area | Total area less a 2mm strip around the perimeter |
| Groove density tolerance (at center of grating) | ±2 grooves/mm |
| Coating (vacuum evaporation) | Aluminum (Aℓ) |
| Scratches and digs | 80-50 (in accordance with MIL-O-13830A) |
Special Specifications
- When you need special concave gratings other than our standard, please contact us.
- Holographic gratings (HG) are also available.