Development of Grating for the Optical Addressing of Sr⁺ Ions With Data Analysis Techniques

Abstract

In this study, SiN-based gratings with various radius of curvature (r) are designed and fabricated for the optical addressing of trapped Sr + ion. The beam width of the light coupled out from the gratings is investigated using a self-developed Pythonbased data analysis technique. It is found that the r values have insignificant influence on the beam width along x-axis; whereas the beam waist along y-axis reduces from 13.96 to 12.3 µm as r increases from 15 to 20 µm, then increases gradually to 20.51 µm as the r value further increases to 60 µm. The obtained results can provide a versatile solution on the optical addressing of trapped Sr + for applications in quantum engineering.

Modelling and Classification of Optical Beam Profiles using Vision Transformer

“…From our previous studies, we observed that changes in R values varies the shape of the corresponding beam profiles along y-axis, with limited impact on the beam profiles along x-axis (axis reference: Fig. 1(a)) [20,23]. As shown in Fig.…”

“…In optical addressing of trapped ions, the application of gratings, in place of traditional optical fiber, greatly reduces the formfactor of ion trap quantum computing devices, and further enhances the manufacturability of quantum computing chips. In our previous works, we have attempted to improve the focusing of chip-to-free-space light by modifying the grating designs, such as varying the radius of curvature (R) of the pitch structure in gratings [20,21], or introducing mixed pitch gratings for enhanced focusing [22]. The R values of grating couplers are illustrated in Fig.…”

“…2, the beam waist along y-axis reduces as R reduced from 15 to 20 µm, after that, the beam waist increases gradually as R increases from 20 to 60 µm. The details of the variation of beam profiles with changing R values are discussed in our previous works [20,23].…”

“…In a typical FDTD simulation, laser light with wavelength of 1,092 nm is input the grating via connecting waveguide. The wavelength of 1,092 nm is selected based on the energy levels in 88 Sr + ions, where 1,092 nm corresponds to the 'clear-out' function in 88 Sr + trapped ion quantum bits [21,28]. The input light will then propagate through the waveguide, and coupled out to free-space through the grating.…”

“…To have more 'converged' beam profiles, beam profiles from mixed pitch gratings with R = 20 µm are also included in the 'converged' category. From our prior study on mixed pitch gratings, the mixing of grating pitch only affects the beam waist along the x-axis, with minimal impact on the beam morphology along the y-axis [22]. Thus, all beam profiles from R = 20 µm mixed pitch gratings can be categorized as 'converged' beam profile images.…”