Fig. 1. Comparison of OCT imaging technique with other imaging techniques

Fig. 2. Classification of OCT technique^[20]

Fig. 3. Axial resolution and lateral resolution in OCT. (a) Relationship between axial resolution and spectral width; (b) relationship between lateral resolution and lens numerical aperture

Fig. 4. Correspondence between discrete optical devices and integrated optical devices

Fig. 5. PIC-based OCT in visible light band. (a) AWG device applied to OCT at 800 nm^[24]; (b) multiple cascaded AWG device^[25]; (c) first in vivo retinal imaging using PIC-based OCT system^[22]; (d) PIC-based SS-OCT in visible light band^[26]

Fig. 6. PIC-based TD-OCT in O band. (a) PIC-based OCT^[28]; (b) a low-cost, handheld, battery-powered multimodal skin imaging system using PIC and MEMS technologies^[29]

Fig. 7. PIC-based SD-OCT in O band. (a) Cross-sectional OCT imaging of multi-layered scattering model^[31]; (b) integrating a 50∶50 broadband non-uniform directional coupler with an AWG on the same chip, employed for in vivo human skin imaging for the first time^[31]; (c) MZI with four beam splitters and a reference arm with a length of 190 mm were designed based on the silicon nitride platform^[32]; (d) tunable delay line based on Si₃N₄ waveguide thermal-optical effect, imaging of human right ventricle by using delay line^[23]

Fig. 8. PIC-based SS-OCT in O band. (a) Ultra-compact silicon photonics-based integrated interferometer designed for SS-OCT^[34]; (b) incorporating both the sample and reference arms into a common path configuration in SS-OCT, and integrating an on-chip micro-ball lens into the PIC, thereby eliminating the need for additional optical elements between the chip and the sample, and realizing imaging of multilayered tissue phantom^[36]

Fig. 9. PIC-based OCT in C band. (a) PIC-based SS-OCT system^[38]; (b) on-chip integrated coherent receiver designed for SS-OCT^[40]