Non‐Volatile Reconfigurable Integrated Photonics Enabled by Broadband Low‐Loss Phase Change Material

Abstract

Phase change materials (PCMs) have long been used as a storage medium in rewritable compact disk and later in random access memory. In recent years, integration of PCMs with nanophotonic structures has introduced a new paradigm for non‐volatile reconfigurable optics. However, the high loss of the archetypal PCM Ge2Sb2Te5 in both visible and telecommunication wavelengths has fundamentally limited its applications. Sb2S3 has recently emerged as a wide‐bandgap PCM with transparency windows ranging from 610 nm to near‐IR. In this paper, the strong optical phase modulation and low optical loss of Sb2S3 are experimentally demonstrated for the first time in integrated photonic platforms at both 750 and 1550 nm. As opposed to silicon, the thermo‐optic coefficient of Sb2S3 is shown to be negative, making the Sb2S3–Si hybrid platform less sensitive to thermal fluctuation. Finally, a Sb2S3 integrated non‐volatile microring switch is demonstrated which can be tuned electrically between a high and low transmission state with a contrast over 30 dB. This work experimentally verifies prominent phase modification and low loss of Sb2S3 in wavelength ranges relevant for both solid‐state quantum emitter and telecommunication, enabling potential applications such as optical field programmable gate array, post‐fabrication trimming, and large‐scale integrated quantum photonic network.

On-Chip Integrated Photonic Devices Based on Phase Change Materials

“…Given that these are newer platforms, there has not been a lot of progress in this direction, but they are promising. The Sb 2 S 3 -and GSSTbased switches reported lower insertion losses of 0.48 dB and 0.135 dB [47,155], device lengths of 8 µm and 5 µm, and extinction ratios of 30 dB and 20 dB, respectively. Sb 2 Se 3based modulators using ring resonators as the basic structure demonstrated an insertion loss of 0.45 dB and switching energy of 185 nJ for an electrically switched device [158].…”

“…In the case of Sb 2 S 3 and Sb 2 Se 3 , a ZnS:SiO 2 (20%:80%) layer is used on top which prevents the loss of the sulfur/selenium atom [24]. In some recent publications, Fang and his colleagues reported successfully using a silicon nitride (Si 3 N 4 ) cap on top of Sb 2 S 3 PCM [47], while Faneca and colleagues also successfully demonstrated the use of an Si 3 N 4 cap on GST [48]. The method seems advantageous concerning the cost of the fabrication process and the complexity of the fabrication process, as deposition of Si 3 N 4 through plasma-enhanced chemical vapor deposition (PECVD) is a standardized practice.…”

“…Power consumption in GST-based systems is an important issue, which has led to some researchers exploring other platforms such as Sb 2 S 3 [45,47], Sb 2 Se 3 [158], and GSST [155] for switching and modulation applications. Given that these are newer platforms, there has not been a lot of progress in this direction, but they are promising.…”

Nonvolatile programmable silicon photonics using an ultralow-loss Sb 2 Se 3 phase change material

“…In several recent studies, the antimony-based chalcogenides Sb 2 S 3 ( 18 , 19 , 20 ) and Sb 2 Se 3 ( 21 ) have been identified as a family of highly promising ultralow-loss PCMs for photonic applications. The materials exhibit no intrinsic absorption losses ( k < 10 −5 ) in either phase over the telecommunications transmission band and show low switching temperatures around 200°C for Sb 2 Se 3 and 270°C for Sb 2 S 3 ( 21 ) while remaining nonvolatile at operating temperatures.…”

High Q Resonant Sb2S3-Lithium Niobate Metasurface for Active Nanophotonics

“… (GST) and are probably the commonest PCMs in nanophotonics [ 4 , 5 , 6 ]. They are widely used in applications such as dynamic thermal emission [ 7 , 8 , 9 , 10 ], light modulation [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ], beam steering [ 18 , 19 ], polarization conversion [ 20 ], colour display [ 21 , 22 , 23 ] and various tunable metasurfaces and metadevices [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Customized laser has already been used to write, erase, and rewrite GST films into two-dimensional binary or gray-scale functional patterns, which would induce local refractive index changes and construct nanophotonic devices [ 36 ].…”