###### Abstract  
The tri-comb-based multi-heterodyne detection technique has been proven to be a powerful tool for precision metrology, e.g., laser ranging and spectroscopy. However, in existing tri-comb generation methods, it is difficult to provide a large and variable difference in tri-comb repetition rates. In this paper; we propose a multidimensional multiplexing mode-locked laser based on a dual-ring integrative structure. Combining the dimensions of sub-ring multiplexing and wavelength multiplexing, two modes of tri-comb generation can be achieved with the dual-ring single cavity laser. The generated combs are identified based on the relative intensity of the pulse trains and optical spectrum, and the repetition rates of dual-combs from the same sub-ring are distinguished based on dispersion analysis. With repetition rates of approximately 47 MHz and 49.6 MHz, the minimum and maximum repetition rate difference of the generated tri-comb can be changed from 2.38 kHz and 2.59526 MHz to 2.74 kHz and 2.59720 MHz merely by switching the operation mode of the dual-ring integrated mode-locked laser. The obtained results indicate that our method can offer a powerful scheme for future multi-comb generation and its application in multi-heterodyne detection-based laser ranging and spectroscopy.  
f A Multidimensional Multiplexing Mode-Locked Laser Based on a Dual-Ring Integrative Structure for Tri-Comb Generation  
1 Center of Ultra-Precision Optoelectronic Instrument Engineering, Harbin Institute of Technology, Harbin 150080, China, [EMAIL_ADDRESS] (R.Y.); [EMAIL_ADDRESS] (H.S.); [EMAIL_ADDRESS] (H.L.); [EMAIL_ADDRESS] (J.X.); [EMAIL_ADDRESS] (J.W.); [EMAIL_ADDRESS] (H.F.); [EMAIL_ADDRESS] (H.Y.); [EMAIL_ADDRESS] (J.T.)  
Key Lab of Ultra-Precision Intelligent Instrumentation (Harbin Institute of Technology), Ministry of Industry and Information Technology, Harbin 150080, China  
Postdoctoral Research Station of Optical Engineering Harbin Institute of Technology, Harbin 150080, China  
Correspondence: [EMAIL_ADDRESS]  
12 October 2020; 19 November 2020; Published: 21 November 2020  
###### Abstract  
The tri-comb-based multi-heterodyne detection technique has been proven to be a powerful tool for precision metrology, e.g., laser ranging and spectroscopy. However, in existing tri-comb generation methods, it is difficult to provide a large and variable difference in tri-comb repetition rates. In this paper; we propose a multidimensional multiplexing mode-locked laser based on a dual-ring integrative structure. Combining the dimensions of sub-ring multiplexing and wavelength multiplexing, two modes of tri-comb generation can be achieved with the dual-ring single cavity laser. The generated combs are identified based on the relative intensity of the pulse trains and optical spectrum, and the repetition rates of dual-combs from the same sub-ring are distinguished based on dispersion analysis. With repetition rates of approximately 47 MHz and 49.6 MHz, the minimum and maximum repetition rate difference of the generated tri-comb can be changed from 2.38 kHz and 2.59526 MHz to 2.74 kHz and 2.59720 MHz merely by switching the operation mode of the dual-ring integrated mode-locked laser. The obtained results indicate that our method can offer a powerful scheme for future multi-comb generation and its application in multi-heterodyne detection-based laser ranging and spectroscopy.  
frequency comb generation; mode-locked laser; tri-comb; multi-heterodyne detection; metrology; spectroscopy; laser ranging +
Footnote †: journal: Applied Physics Letters