Abstract
Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. However, the phase noise of widely used conventional signal generators (SGs) will increase as the millimetre-wave frequency increases. Our goal has been to improve commercially available SGs so that they provide a low-phase-noise millimetre-wave signal with assistance from an electro-optics-modulator-based optical frequency comb (EOM-OFC). Here, we show that the phase noise can be greatly reduced by bridging the vast frequency difference between the gigahertz and terahertz ranges with an EOM-OFC. The EOM-OFC serves as a liaison that magnifies the phase noise of the SG. With the EOM-OFC used as a phase noise “booster” for a millimetre-wave signal, the phase noise of widely used SGs can be reduced at an arbitrary frequency f (6 ≦ f ≦ 72 GHz).
Highlights
Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems
We found that the phase noise of signal generators (SGs) 1 from 6 to 72 GHz is reduced as the comb mode number in the electro-optics-modulator-based optical frequency comb (EOM-OFC) increases
When we use mode-locked laser (MLL) 2 and control the carrier-envelope-offset (CEO) and repetition frequency, we can stabilize the centre frequency of the CW LD, its linewidth increases
Summary
Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. Several methods based on photonic technologies have been reported for generating millimetre waves, including whispering-gallery-mode parametric oscillators[7], optical frequency division[8,9,10], optoelectric oscillators[11], on-chip Brillouin oscillators[12], and optical reference cavities[13]. To generate continuously tunable millimetre-wave and microwave signals with ultralow phase noise, we propose a new accessible solution that can greatly reduce the phase noise of widespread commercially available SGs with assistance from the EOM-OFC14–16. The phase noise in our method might not be reduced as much as in previous studies with a fixed frequency, we can achieve continuously tunable millimetre-wave and microwave frequency in a wide range because our method does not need an optical reference cavity, such as a silica high-Q disk or high-finesse Fabry-Pérot cavity. The phase noise of the EOM-OFC mainly originates from that of SG 1’s driving phase/intensity modulators[18]
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