Rewritable Photonic Integrated Circuit with Phase Change Materials

Abstract

We propose a low loss (Sb2S3: 28.7 dB/mm and Sb2Se3: 1.20 dB/mm) rewriteable photonic integrated circuit using phase change materials that is written by nanosecond laser pulses.

Rewritable Photonic Integrated Circuit Canvas Based on Low-Loss Phase Change Material and Nanosecond Pulsed Lasers

“…Here, we experimentally demonstrate a low-loss and rewritable PIC platform using laser-written Sb 2 S 3 . A dielectric-assisted waveguide structure 8,26 is used to lower the optical propagation loss while enhancing the endurance and reliability of PCMs. We first demonstrate arbitrary patterning on the PCM canvas with a fine resolution of 600 nm line pitch, to demonstrate the rewritable capability of our platform, then write laser-written waveguides between pairs of predefined grating couplers.…”

“…The propagation loss was then measured via a cutback measurement as 0.01722 dB/μm, comparable to the 0.010 dB/μm loss in simulation. 8 While this loss is ∼1000 times larger than current commercial silicon photonic waveguides, 27 this loss is acceptable to create waveguides of submm length. Our rewritable and low-cost platform shows a promising path to democratizing PIC prototyping for designers without access to a nanofabrication facility, which will enhance PIC education and accelerate rapid PIC prototyping.…”

“…The PIC canvas was fabricated by depositing multiple materials on a silicon substrate in the order of 3.5 μm SiO 2 , 15 nm Sb 2 S 3 , 20 nm Al 2 O 3 and 400 nm Si 3 N 4 (see Supplementary Section S2 for fabrication process steps), as shown in the inset of Figure 1a. This multilayer design enables the low-loss dielectric-assisted waveguide mode (see Supplementary Figure S2) 8 and is key to low-loss waveguiding. We started with a c-Sb 2 S 3 PIC canvas by annealing the chip at 325 °C on a hot plate.…”

“…A linearly fitted trendline had a slope of 17.2 dB/mm, which matched well with the theoretical value of 10 dB/mm. 8 This variation could be attributed to several factors, such as (1) the anisotropy of c-Sb 2 S 3 crystals, (2) mode leakage during propagation, (3) variation in the grating couplers, (4) misalignment between the axis of the writing laser and the chip, and (5) variation in the waveguide widths and cladding thicknesses. Among the etched Si 3 N 4 waveguides, there was a standard deviation from the mean of 3.5 dB, implying variation in the material and gratings.…”

“…This follows from the fundamental trade-off between the propagation loss and the mode confinement, incurred by the finite extinction coefficient of Sb 2 S 3 . 8 A thicker Sb 2 S 3 film leads to a more confined optical mode, but at expense of a higher propagation loss due to the increased mode interaction with lossy c-Sb 2 S 3 (see optical mode simulation in Supplementary Section S1). To mitigate this loss-confinement trade-off and enable sufficient confinement for waveguide bends, we need to further reduce the loss of the PCM canvas.…”