The National Time Service Center of China is developing a compact, highly stable, 698 nm external-cavity diode laser (ECDL) for dedicated use in a space strontium optical clock.
A research team from Xi'an Institute of Optics and Precision Mechanics (XIOPM) and National Time Service Center of the Chinese Academy of Sciences (CAS) presents the optical design, structural design, and preliminary performance of this ECDL. The ECDL uses a narrow-bandwidth interference filter for spectral selection and a cat’s-eye reflector for light feedback.
Schematic of interference-filter external-cavity diode laser (IF-ECDL). (Image by XIOPM)
To ensure long-term stable laser operation suitable for space applications, the connections among all the components are rigid and the design avoids any spring-loaded adjustment.
The frequency of the first lateral rocking eigenmode is 2316 Hz. The ECDL operates near 698.45 nm, and it has a current-controlled tuning range over 40 GHz and a PZT-controlled tuning range of 3 GHz.
The linewidth measured by the heterodyne beating between the ECDL and an ultra-stable laser with 1 Hz linewidth is about 180 kHz. At present, the ECDL has been applied to the principle prototype of the space ultra-stable laser system.
(Original research article “Photonics” (2020) http://dx.doi.org/10.3390/photonics7010012)
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