High spectral purity microwave and terahertz oscillator

Abstract

International audienceWe report on the design of an ultra stable microwave/THz oscillator and on the realization and the characterization of its laser source. The tunable oscillator is expected to show below -150 dB rad2/Hz phase instability at an offset frequency of 10 kHz for a 30 GHz carrier frequency, as well as 18 GHz, 100 GHz, 400 GHz and 1 THz carrier frequencies

Dual frequency laser with two continuously and widely tunable frequencies for optical referencing of GHz to THz beatnotes

“…In this paper, we detail the design of a dual frequency laser sustaining the oscillation of two frequencies that are widely, continuously and independently tunable. In addition, we show that the noise characteristics of this dual frequency laser are compatible with the requirements for optical referencing each wavelength onto a ULE cavity [6].…”

“…The performances of such a laser in terms of noise and frequency control are shown to be perfectly adapted to stabilize independently each frequency to different resonances of a single ULE cavity or even to acetylene ro-vibrational resonances [19]. This laser is indeed designed to be implemented in a larger experiment for THz metrology [6]. Furthermore, the proposed architecture is well suited for direct Pound-Drever-Hall stabilization [20] without external phase modulation due to the intracavity LTO crystals whose modulation bandwidth is designed to be 10 MHz.…”

“…The frequency noise of the electrical oscillator is then up-scaled with the ratio of the beatnote frequency to the RF reference frequency. To overcome this drawback, we have proposed few years ago a technique where both laser lines are simultaneously referenced to two different resonances of a single Ultra Low Expansion (ULE) Fabry-Perot cavity [6,7]. This approach should improve the phase noise of the beat note as compared to that of the up-scaled electrical references.…”

Investigation of the coupling between pump amplitude noise and differential phase noise in an Er,Yb:glass two-polarization dual-frequency solid-state laser

“…The laser under consideration is an Er,Yb:glass laser oscillating at 1550 nm. The optical power of the two optical carriers is 1 mW after injection in the optical fiber [9,13]. The beat-note is tunable over a DC-900 GHz range by rotating the intra cavity etalons [13].…”

“…Yet, when ultrastable and narrow linewidth are required, the amplitude to phase conversion might become the limiting factor even in solid state lasers. We have been involved during the last years in developing a photonic adjustable ultra-stable sub-millimeter and millimeter wave reference based on a dual frequency laser [9] locked to a single ultralow expansion cavity. In this framework the knowledge of the amplitude to phase coupling coefficient is essential in order to ensure the best possible stability of the beat note between the two optical laser lines [10][11][12][13].…”