Automatic Frequency Control Of Lasers In Optical Frequency Synthesizer

Optical frequency synthesizers（OFSs）can transfer the frequency stability and accuracy of a reference oscillator at a specific frequency（such as an optical clock）to any other designed frequency with high fidelity.They play an increasingly important role in scientific research and technology,such as the applications of optical atomic clocks,precision spectroscopy and measurement.Automatic control of OFSs is the key to its practical applications.In this paper,we study the automatic frequency control of the reference oscillator and the output laser of an OFS.For the reference laser of the OFS,we use a microcontroller unit as the logic control element to control an analog circuit of loop filter（also called analog-digital hybrid PID controller）.Thereby we realize automatic laser frequency scan and automatic laser frequency stabilization to the resonance of an ultra-stable optical reference cavity.The reference laser of the OFS can realize laser frequency locking and relocking within 0.5 s.After locking,the laser linewidth is 0.3 Hz,and the frequency stability reaches 6×10^-16 at 1s averaging time.Moreover,we propose a scheme for laser frequency control of the output laser of the OFS.With the help of a computer,the laser frequency is coarsely set to a desired wavelength automatically according to the reading of a wave meter.An error signal for locking the output laser is automatically generated in an optical frequency divider based on an optical frequency comb.Finally,with the analog-digital hybrid PID controller,the output laser can be frequency-stabilized to the reference laser of the OFS.The preliminary researches in this thesis provide ideas for the automatic control of OFSs.