Design And Manufacture Of Low-noise Power Supply And Frequency Locking Module For Optical Frequency Combs

Optical frequency comb is a frequency source based on mode-locked laser and frequency stabilization circuit.It uses the principle of PLL in the microwave field to lock the frequency of the pulsed laser to a frequency source with high stability to ensure high stability of the pulse frequency.The locked optical frequency comb forms a direct link between the optical frequency and the microwave frequency,which the researchers call optical gears.Due to the high frequency accuracy of locked optical frequency comb,it is widely used as an optical clock in precision measurement and other fields,such as optical metrology,frequency chain generation,optical atomic clock,high-precision spectroscopy and more accurate GPS technology,etc.The application of strong potential technology.The power supply is a source of energy for the operation of the system.Low noise and low ripple power supply are critical to the operation of the system.Especially for precision equipment,the noise of the power supply will directly affect the noise of the entire system.There are many sensitive devices inside the optical frequency comb system.In order to meet the miniaturization of the optical frequency comb and low noise frequency output,a low noise compact power supply is indispensable for optical frequency combs.At present,the frequency lock part of the optical frequency comb system developed in China is huge in size.The frequency signal processing and phase lock and lock control steps are locked by a lock-in amplifier and a ready-made servo system instrument,and there is no special lock circuit design for the system.This caused the entire system to be very bloated.In order to apply optical frequency combs to more fields,a miniaturized low-noise power supply and a compact frequency locking module are particularly important.In this paper,a low-dropout linear regulator is used to design and fabricate a low-noise power supply module for the optical frequency comb system.At the same time,the lock circuit of the optical frequency comb output light repetition frequency and carrier envelope offset frequency signal is designed and manufactured.The specific research work includes the following two parts:In the first part,the use of Altium Designer software to design a small volume of low-noise power supply module,the use of low-dropout linear regulator and common-mode filter design to suppress the larger ripple in the switching power supply,and then suppress the power supply noise of the closed-loop system,respectively The ripple of each power supply module is measured.The output ripple of each power supply module is suppressed to within 1mV.Experiments have found that a low-ripple power supply module can effectively suppress the frequency offset compared to a photodetector directly powered by a switching power supply.Probe light phase noise from 10Hz to 1KHz.In the second part,we design a microwave circuit module with compact structure repetition frequency and carrier envelope offset frequency signal processing and frequency identification.The module can successfully amplify,divide,filter and phase-check the repetition frequency and the carrier envelope offset frequency.After the phase-detection output signal is collected by the FPGA,the frequency can be effectively locked.The standard deviation of the frequency drift after the repetition frequency is locked is 0.092mHz,and the standard deviation of the frequency deviation after the carrier envelope offset frequency is locked is 2.5mHz.The low-noise power module and frequency-locked loop circuit designed and fabricated in this paper have a compact structure,can provide good low-noise power supply for the optical frequency comb system,and at the same time lock the output frequency of the optical frequency comb on the external reference source instead of The frequency processing link in the lock-in amplifier of the optical frequency comb in the first generation greatly reduces the overall volume of the optical frequency comb system,and provides a useful reference for a more compact and even portable fiber optical frequency comb system in the future.