![]() ![]() The operation principle of VIDG-PCSELs is illustrated in Fig. Further details of the device structure are presented in the supplementary information. The top-view image of the device captured using an optical microscope and the cross-sectional scanning electron microscopy (SEM) image of the device are displayed in Fig. 1a), were varied from 0 o to 45° (0°, 30°, and 45°) to observe the corresponding changes in the output beam. The azimuthal angles of the gratings, which are defined as the grating strip angles with respect to the x-axis (Fig. 1b) to identify each optical mode without confusion. A simple metal grating with a period of 8 μm and FF of 37.5% was applied as the optical diffraction element (Fig. The square-latticed PC comprising of periodic circular air holes with a lattice constant ( a) of 275 nm and a filling factor (FF) of 18% was designed for a lasing wavelength of 940 nm. ![]() The major components of the structure are the epitaxial wafer, PC layer, ITO cladding layer, and vertically integrated diffraction structure. The characteristics of the laser, such as the output-light power–current–voltage (L–I–V) curves, near and far field patterns, and PC band structures were also measured and analyzed.įigure 1a displays the schematic of the VIDG-PCSEL structure. The integrated structure has a negligible influence on the lasing threshold and spectra, and the beam direction is altered according to our expectations. In this study, various designs of vertically integrated diffractive gratings on PCSELs (VIDG-PCSELs) were investigated for determining the correspondence between the output beam deflection angle and the designed structure. The aforementioned mechanism is used to obtain vertically integrated optical diffraction elements on PCSELs for achieving beam steering and a high output power. The original circular output beam in the surface normal direction is then split into two beams with deflection angles of 4–5° with respect to the vertical direction. A periodic structure is naturally formed in the ITO cladding layer as the thickness of the layer increases to 400 nm 26. ![]() This layer exhibits the function of current injection and optical confinement. The ITO layer exhibits a higher electrically conductive nature and a lower refractive index than typical semiconductors. The designed structure is based on PCSELs with a low-cost indium-tin-oxide (ITO) cladding layer according to our previous report 2, 26. ![]() To reduce the output power loss at the interconnection of optical elements while maintaining the device size on the chip scale, we propose the use of vertically integrated diffractive elements on PCSELs for static beam steering. However, the efficiency of these devices will be suffered due to its mechanism of light deflection. Recently, beam-steering systems with chip-scale dimensions, such as optical phase arrays 15, 16, 17, 18, 19, slow-light waveguide 20, 21, tunable meta-surfaces 22, 23, 24, and composite photonic-crystal (PC) structures 25, 26, 27, 28 have been proposed. The resulting system is typically bulky and costly. In the current commercial Lidar or 3D sensing devices, laser light sources are combined with external optical and mechanical elements to steer the output beam for scanning 13, 14. The surface-emitting configuration also facilitates wafer level testing and (2D) integration of the laser array 11, 12. Moreover, due to the two dimensional (2D) distributed feedback lasing mechanism over the entire plane area 6, 7, 8, the optical density of these lasers is relatively low to prevent a catastrophic optical damage at high output powers 9, 10. PCSELs exhibit a large output power on a single device, single wavelength, surface-emitting direction, circular beam shape, and small beam divergence. Photonic-crystal surface-emitting lasers (PCSELs) are considered to be ideal light sources for applications such as light detection and ranging (Lidar) and three-dimensional (3D) sensing 1, 2, 3, 4, 5. ![]()
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