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">$96\,\times \,96\,\times \,35\,\text{mm}^{3}$</tex-math></inline-formula>. The module has a frequency tuning range of more than <inline-formula><tex-math notation="LaTeX">$\text{65}\,\text{GHz}$</tex-math></inline-formula> with a near-linear behavior. We demonstrate short-term frequency stabilities between <inline-formula><tex-math notation="LaTeX">$2 \times 10^{5}\,\text{Hz}^{2}/\text{Hz}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$4 \times 10^{7}\,\text{Hz}^{2}/\text{Hz}$</tex-math></inline-formula> in the Fourier frequency range from <inline-formula><tex-math notation="LaTeX">$\text{20}\,\text{Hz}$</tex-math></inline-formula> to <inline-formula><tex-math notation="LaTeX">$\text{200}\,\text{kHz}$</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">$\text{0.33}\,\text{GHz}$</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.