## 3 Progress in Grating Fabrication Technology
### Mechanical Scribing Technology  
Mechanically scribed gratings are amplitude gratings. Mechanical scribing was the first method used for fabricating gratings, and it involves the process of scribing parallel and equal widths on a metal-coated substrate with a scribing machine. The process of equal spacing includes extruding and polishing the material. In the early years, mechanical scribing combined with ion-beam etching was traditionally used to create diffraction grating masters. However, the production of gratings by this method is a lengthy process. In the 1780s, [PERSON] made the first grating with dozens of metal wires on a 13 mm wide K9 substrate and performed corresponding diffraction experiments; [PERSON] did not employ gratings to see distinct spectra until the early 19 th century. [PERSON] then employed a hydraulically powered scribing machine to increase the precision of grating processing and successfully created a grating with 3500 grooves/mm, bringing diffraction grating processing technology to a new level. [PERSON] employed mechanical scribing technology in the early 20 th century to create infrared blazed gratings with a low scribe-line \begin{table}
\begin{tabular}{c c c c} \hline
**Years** & **Units** & **Structures/Contributions** & **Performance** \\ \hline
2006 & [PERSON], & Duty cycle 0.5, & \(\Lambda=1550\) nm, \\  & [PERSON], et al. [50] & etched groove depth 2500 nm, & DE \(>95\%\) \\  & & line density 674 lines/mm & \\ \hline  & & Scribed line density 1670 grooves/mm, & \(\Lambda=1064\) nm, \\
2008 & [PERSON], [PERSON], et al. [52] & duty cycle 0.57, & DE \(=95\%\) \\  & & groove depth 1440 nm, & \\ \hline
2009 & [PERSON], & Period 1216 nm, & Realize the dual function of 1 \(\times\) \\  & [PERSON], et al. [53] & groove depth 2314 nm & 2 beam splitter, \(-1\)st order \\  & & high-efficiency grating \\ \hline
2010 & [PERSON], & Duty cycle 0.67, & \(\lambda=800\) nm, \(\theta_{0}=41.5^{\circ}\), \\  & [PERSON], et al. [54; 55] & groove depth 1950 nm & DE \(>92\%\) (750–850 nm) \\ \hline  & & Line density 1250 lines/mm, & \(\theta_{0}=30^{\circ}\), TE mode, \\
2011 & [PERSON], [PERSON], et al. [56] & duty cycle 0.49, & \(\lambda=800\) nm, \\  & & groove depth 1380 nm & DE \(>90\%\) (750–850 nm) \\ \hline
2012 & [PERSON], & Deeply etched triangular & \(\lambda=1064\) nm \\  & [PERSON], et al. [57] & groove structure & \\ \hline
2013 & [PERSON], [PERSON] & Line density 1250 line/mm, & \\  & [PERSON], et al. [58] & groove depth 1450 nm, & DE \(=96\%\) \\  & & duty cycle 0.45 & \\ \hline
2013 & [PERSON], [PERSON], et al. [59] & Period 1100 nm, & \(\lambda=1550\) nm, \\  & & duty cycle 0.6, & DE \(>95\%\) \\ \hline
2020 & [PERSON], [PERSON], et al. [60] & Period 1624.6 nm, & \(\lambda=1550\) nm, \\  & & duty cycle 0.4 & \(-2\)st Bragg DE \(>95\%\) \\ \hline  & & Period 1270 nm, & \(\lambda=1550\) nm, \\  & & duty cycle 0.58 & \(-1\)st Littrow DE \(>95\%\), \\  & & irrelevant loss 0.0013 dB \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._density and flame effect [62]. [PERSON] and [PERSON] of Australia conducted experimental research on diffraction gratings with scribing densities of 1276 g/mm, 638 g/mm, and 425 g/mm in 1969, and the association between scribed grating grooves and flame angle, as well as grating diffraction effectiveness, was discovered [63]. In 1996, scientists at Bielefeld fabricated a 1200 lines/mm Mo-Si multilayer blazed grating by mechanical scribing. By optimizing the grating groove type, blaze angle and the best matching of Mo-Si bilayer film thickness, the maximum 1 st diffraction efficiency was 32% at a wavelength of 13.8 nm and blaze angle of 0.8\({}^{\circ}\). Compared with the 1 st diffraction efficiency of a blazed grating with a blaze angle of 1.6\({}^{\circ}\), the mechanical scribing error and reduction of the roughness in the groove were very important for high diffraction efficiency. The efficient scribing of gratings is of great significance [64].