Ultrahigh-reflective optical thin films prepared by reactive magnetron sputtering with RF-induced substrate bias

Area of Science:

• Materials Science
• Optics and Photonics
• Quantum Technologies

Background:

• High-reflectivity (HR) optical thin films are critical components in quantum precision measurement systems.
• Existing fabrication methods may face limitations in achieving the required reflectivity and layer quality for advanced applications.

Purpose of the Study:

• To introduce and validate a new coating technique for fabricating advanced HR optical thin films.
• To demonstrate the capability of this method for producing ultra-high reflectivity mirrors for precision measurements.

Main Methods:

• Employed reactive magnetron sputtering with radio-frequency (RF)-induced substrate bias.
• Utilized RF plasma assistance to achieve atomically flat silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) layers.
• Fabricated a distributed Bragg reflector (DBR) mirror with a specific multilayer structure (air-H{LH}19-substrate).

Main Results:

• Demonstrated the successful deposition of high-quality, atomically flat SiO2 and Ta2O5 layers.
• Achieved an ultra-high reflectivity (HR) of approximately 99.999328% at a center wavelength of 1397 nm.
• The fabricated DBR mirror consisted of alternating SiO2 (171.6 nm) and Ta2O5 (237.8 nm) layers.

Conclusions:

• The novel RF-induced substrate bias sputtering technique is effective for producing superior HR optical thin films.
• This advanced coating method enables the development of next-generation HR reflectors for demanding precision measurement applications.
• The demonstrated ultra-high reflectivity mirrors hold significant potential for advancing quantum precision measurement technologies.