A Tunable Optical Frequency Reference Module Based on a Volume Holographic Bragg Grating

We present a robust and compact micro-integrated, frequency-tunable, optical frequency reference module developed to improve the long-term frequency stability of lasers in quantum technology and satellite laser communication applications. The module is based on a volume holographic Bragg grating (VHBG) and features a multi-level temperature stabilization concept, packaged into a sealed housing with dimensions of <inline-formula><tex-math notation="LaTeX">96 times 96 times 35 mm³</tex-math></inline-formula>. The module has a frequency tuning range of more than <inline-formula><tex-math notation="LaTeX">65 GHz</tex-math></inline-formula> with a near-linear behavior. We demonstrate short-term frequency stabilities between <inline-formula><tex-math notation="LaTeX">2 times 10⁵ Hz²/Hz</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">4 times 10⁷ Hz²/Hz</tex-math></inline-formula> in the Fourier frequency range from <inline-formula><tex-math notation="LaTeX">20 Hz</tex-math></inline-formula> to <inline-formula><tex-math notation="LaTeX">200 kHz</tex-math></inline-formula>, and a minimum overlapping Allan deviation of <inline-formula><tex-math notation="LaTeX">sigma \(tau =1000 s\) = 1.7 times 10^-10</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">1.5 times 10^-9</tex-math></inline-formula> over 24<inline-formula><tex-math notation="LaTeX"> </tex-math></inline-formula>h. The module can also be operated as a wavemeter and spectrometer, yielding residuals below <inline-formula><tex-math notation="LaTeX">0.33 GHz</tex-math></inline-formula> with second-order polynomial regression calibration, and reliably measuring frequency noise PSDs of lasers whose noise exceeds that of the reference module.