Vibration Property of a Cryogenic Optical Resonator within a Pulse-Tube Cryostat

• Main Authors: Yanxia Ye, Leilei He, Yunlong Sun, Fenglei Zhang, Zhiyuan Wang, Zehuang Lu, Jie Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Sensors
• Subjects: optical resonator; in situ vibration measurement; cryogenic temperature; vibration sensitivity
• Online Access: https://www.mdpi.com/1424-8220/21/14/4696
• ISSN: 1424-8220

Cryogenic ultrastable laser cavities push laser stability to new levels due to their lower thermal noise limitation. Vibrational noise is one of the major obstacles to achieve a thermal-noise-limited cryogenic ultrastable laser system. Here, we carefully analyze the vibrational noise contribution to the laser frequency. We measure the vibrational noise from the top of the pulse-tube cryocooler down to the experiment space. Major differences emerge between room and cryogenic temperature operation. We cooled a homemade 6 cm sapphire optical resonator down to 3.4 K. Locking a 1064 nm laser to the resonator, we measure a frequency stability of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.3</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>15</mn></mrow></msup></mrow></semantics></math></inline-formula>. The vibration sensitivities change at different excitation frequencies. The vibrational noise analysis of the laser system paves the way for in situ accurate evaluation of vibrational noise for cryogenic systems. This may help in cryostat design and cryogenic precision measurements.