# Integrated Optical Phased Arrays for Beam Forming and Steering
## 4 Configurations
### Other OPAs  
The above-mentioned EF OPAs and WGA-based OPAs are the most common structures for dynamic beam manipulation. Beam forming and steering can also be realized by other OPAs. A bidirectional wide-angle WGA for OPAs with wide FOVs [118], an optical scanning structure based on wavelength division filters [68], and a polarization-division and spatial-division multiplexed nanoantenna array [37] will be discussed here. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \(\mathbf{\lambda}\), \(\mathbf{\mu}\)m & **FOV, \(\mathbf{\alpha}^{*}\times\mathbf{b}^{*}\)** & **Spot, \(\mathbf{\alpha}^{*}\times\mathbf{b}^{*}\)** & **Pick, \(\mathbf{\mu}\)m** & **Array** & **Size, mm\({}^{2}\)** & **Material** & **Shifter** & **Power, mW/\(\pi\)** & **Speed, \(\mathbf{\mu}\)s** & **SLL** & **dB** & **Ref. ** \\ \hline
0.635 & 146 & 0.06 \(\times\) 0.07 & 2 & N/A & 0.5 \(\times\) 0.5 & N/A & N/A & N/A & N/A & 8.7 & [65] \\ \hline
0.905 & \(3\times 17.6\) & 4.3 \(\times\) 0.7 & 3 & 4 \(\times\) 4 & - \(\times\) 0.09 & Si\({}_{3}\)N\({}_{4}\) & TO & 87.6 & N/A & N/A & [99] \\ \hline
1.064 & 11 \(\times\) - & 1.1 & 2 & 16 & N/A & Si\({}_{3}\)N\({}_{4}\) & TO & -95 & -125 & N/A & [93] \\ \hline
1.30 & 80 \(\times\) 17 & 0.14 \(\times\) 0.14 & 7.25 & 128 & 1 & Si & TO & 8 & N/A & 8.9 & [12] \\ \hline
1.55 & 2.3 \(\times\) 14.1 & 27 \(\times\) 2.4 & 2 & 16 & N/A & Si & TO & 8.2 & N/A & N/A & [7] \\ \hline
1.55 & 20 \(\times\) 14 & 1.6 \(\times\) 0.6 & 3.5 & 16 & 4 \(\times\) 0.2 & Si & TO & -215 & N/A & 10 & [96] \\ \hline
1.55 & 6 \(\times\) 6 & N/A & N/A & 8 \(\times\) 8 & N/A & N/A & TO & 8.5 & N/A & N/A & [10] \\ \hline
1.55 & 10 \(\times\) 6.5 & 2 \(\times\) 0.2 & 5.5 & 8 & -\(\times\) 0.5 & InP & EO & N/A & 0.5 & N/A & [79] \\ \hline
1.55 & 20 \(\times\) 15 & 1.2 \(\times\) 0.5 & 4 & 16 & N/A & N/A & TO & 20 & N/A & \textgreater{}10 & [40] \\ \hline
1.55 & 23 \(\times\) 3.6 & 1 \(\times\) 0.6 & 4 & 32 & N/A & Si & EO & 160 & 0.02 & 5.5 & [82] \\ \hline
1.55 & 1.6 \(\times\) 1.6 & N/A & 33 & 8 \(\times\) 8 & N/A & N/A & TO & N/A & N/A & 11 & [86] \\ \hline
1.55 & 1.5 \(\times\) 1.5 & 0.5 \(\times\) 0.5 & 50 & 4 \(\times\) 4 & \(\textless{}1\) & Si & EO & N/A & 0.005 & N/A & [52] \\ \hline
1.55 & 46 & 0.02 \(\times\) 0.02 & 4 & 1024 & 4 \(\times\) 4 & Si\({}_{3}\)N\({}_{4}\) & N/A & N/A & N/A & 10 & [65] \\ \hline
1.55 & 46 \(\times\) 36 & 0.85 \(\times\) 0.18 & 2 & 50 & N/A & Si & TO & 13 As mentioned above, without breaking the up/down symmetry of a WGA, nearly half of the input power radiates downwards. Downward radiation causes a decreased efficiency and fluctuation in the far field [72; 105]. It is difficult to eliminate downward radiation. Meanwhile, it is challenging to realize WGA-based OPAs with high efficiencies and full FOVs. A bidirectional wide-angle WGA for OPAs presented in Figure 9a was used to solve these problems [118]. An FOV of 180\({}^{\circ}\) was achieved by taking advantage of the bidirectional radiation characteristic of the WGA. Additionally, power consumption, control units, and the number of elements of OPAs could be decreased to half due to the bidirectional radiation. This WGA solved the problem of weak intensity of large steering angles simultaneously, and approximately uniform intensity was achieved, making it a promising candidate for high-performance OPAs [118]. An OPA combining microring-based emitters and wavelength division filters presented in Figure 9b realized 2D optical scanning completely through wavelength tuning [68]. The MZIs and microring array separated different wavelengths from the input light and sent them to the corresponding emitters. For this 64-channel structure, an FOV of 6\({}^{\circ}\)\(\times\) 4\({}^{\circ}\) was realized by wavelength tuning from 1.55 to 1.56 \(\upmu\)m [68]. This 2D OPA  
Figure 9: Some structures for beam forming and steering. **(a)** A bidirectional wide-angle WGA for OPAs [118]. **(b)** A 2D 8 \(\times\) 8 optical scanning structure with wavelength division filters and emission array. Reproduced from [68] published by IEEE, 2019.