Layered Gallium Monosulfide as Phase‐Change Material for Reconfigurable Nanophotonic Components On‐Chip

• Published in: Advanced optical materials 2024-01, Vol.12 (3), p.n/a
• Main Authors: Gutiérrez, Yael, Dicorato, Stefano, Ovvyan, Anna P., Brückerhoff‐Plückelmann, Frank, Resl, Josef, Giangregorio, Maria M, Hingerl, Kurt, Cobet, Christoph, Schiek, Manuela, Duwe, Matthias, Thiesen, Peter H., Pernice, Wolfram H. P., Losurdo, Maria
• Format: Article
• Language: English
• Subjects: active photonics; Beam steering; chalcogenides; Data processing; Data transmission; Gallium; gallium sulfide; Integrated circuits; Modulators; Neural networks; on‐chip MZI; Optical fibers; optical properties; Phase change materials; Phase modulation; Phase transitions; Photonics; Reconfiguration; Switches
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202301564

The demand for information processing at ultrahigh speed with large data transmission capacity is continuously rising. Necessary building blocks for on‐chip photonic integrated circuits (PICs) are reconfigurable integrated low‐loss high‐speed modulators and switches. Phase change materials (PCMs) provide unique opportunities for integration into PICs. Here, the investigation of layered gallium monosulfide (GaS) as a novel low‐loss PCM from infrared to optical frequencies is pioneered, with high index contrast (Δn ≈0.5) at the optical telecommunication band. The GaS bandgap switches from 1.5 ± 0.2 eV for the amorphous state to 2.1 ± 0.1 eV for the crystalline state. It is demonstrated that the reversible GaS amorphous‐to‐crystalline phase transition can be operated thermally and by picosecond green (532 nm) laser irradiation. The design of a reconfigurable integrated optical modulator on‐chip based on Mach‐Zehnder Interferometers (MZI) with the GaS PCM cell deposited on one of the arms for application is presented at the telecommunication wavelength of λ = 1310 nm, where the standard single mode optical fiber exhibits zero chromatic dispersion, and at λ = 1550 nm, where a minimum optical loss of 0.22 dB km−1 is obtained. This opens the route to applications such as reconfigurable modulators, beam steering using phase modulation, and photonic neural networks. Layered Gallium Sulfide is demonstrated as a novel phase change material for active photonics with its reversible amorphous‐to‐crystalline transition. Its structural and optical properties are statistically assessed, revealing it to be suitable to design a reconfigurable MZI modulator with reduced losses at the telecom wavelength.