Abstract ▼ AI-Helper

Mid-infrared micro photonic devices including straight/bent waveguides and Y-junction beam splitters are developed on CMOS-compatible AlN-on-silicon platform. A low optical loss of 0.83 dB/cm and efficient 50:50 beam splitting ratio is achieved at ?=2.5 µm. AlN is a semiconductor that has an ...

Mid-infrared micro photonic devices including straight/bent waveguides and Y-junction beam splitters are developed on CMOS-compatible AlN-on-silicon platform. A low optical loss of 0.83 dB/cm and efficient 50:50 beam splitting ratio is achieved at ?=2.5 µm. AlN is a semiconductor that has an ultra-wide operational spectrum covering ultraviolet, visible, NIR and mid-IR wavelengths up to ? = 10 µm. High quality AlN films can be deposited on various CMOS materials, including SiO2, Si, or Sapphire, through metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) or sputteringthat are compatible with standard CMOS processes. Though low loss waveguides and microring resonators made by AlN have been shown in VIS and NIR, its full potential in the use of broadband photonic circuits has not been realized in the Mid-IR (= 2.5 µm) region. Here, we develop AlN mid-IR waveguides that show low optical loss between 2.4 µm and 2.7 µm. as well as a highly efficient 50:50 beam splitter over 200 nm bandwidth that is desired for sophisticated mid-IR photonic circuits. To evaluate our AlN mid-IR devices, we experimentally measure the mode profile and the propagation loss. Fig. 1 (a) illustrates the mode image captured at the waveguide end facet at ? = 2.6 µm. A sharp round spot is clearly resolved which indicates that the fundamental mode is the dominant waveguide mode. The guided mode intensity distribution along the x-axis across the center of the light spot, is plotted and analyzed in Fig. 1 (b). The intensity profile (black solid line) closely fits a Gaussian curve (red dashed line), demonstrating that our experimental result of mode characterization agrees well with the simulation data. The propagation losses are then determined by fitting the optical output powers from waveguides that have different propagation lengths of 2 cm, 3 cm and 4 cm as shown in Fig. 1 (c). From the measurements a propagation loss of 0.83 dB/cm at ? = 2.5 µm is obtained. The low-loss property of our mid-IR devices is attributed to the use of high quality AlN films, as well as optimized fabrication processes that create smooth waveguide sidewalls and consequently reduce scattering loss. Performance of AlN beam splitters is examined since they are critical for multi-channel mid-IR photonic circuits. Fig. 2 (a) and 2 (b) are images recorded from the splitter output at ? = 2.4 µm and ? = 2.6 µm. Two sharp spots from a Y-junction splitter are clearly resolved where every spot represents a guided mode arising from one channel. The intensity distributions across the x axis are measured to evaluate the power splitting ratios. As shown in Fig. 2 (b), two Gaussian-shaped peaks with identical maximum intensities are found at both ? = 2.4 µm and ? = 2.6 µm, which verifies an efficient and uniform 50:50 division ratio.