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This invention is a method and apparatus for optical-to-microwave conversion and synthesis of lightwaves directly with electronics. The invention's electronic synthesizer for light creates a frequency comb in which all the modes of the comb are directly traceable to one electronic signal. It is composed of four essential pieces: an electro-optic modulation (EOM) frequency comb, novel optical-domain filtering of electronic noise, a new design for the nonlinear optics needed for spectral broadening of >1 picosecond (ps) optical pulses, and an f-2f nonlinear interferometer for carrier-phase detection. The invention works by imposing a microwave-electronic modulation onto a continuous-wave (CW) laser to create an EOM frequency comb. The electronic modulation transforms the CW laser into a train of optical pulses at the microwave rate. We then use two novel optical-domain processes that enable electronic synthesis of light, optical filtering of electronic noise and spectral broadening with >1 ps pulses to generate a coherent supercontinuum. With the supercontinuum, we use the f-2f technique for carrier-phase detection, which directly links the CW laser frequency to the microwave-electronic modulation signal.

The invention's EOM frequency comb will enable diverse applications, including electro-optical signal conversion, spectroscopic detection of molecules, coherent optical communications and optical imaging, and as a diagnostic tool for medical imaging. Our invention brings highly unique features to these applications from a widely tunable frequency comb with wide mode spacing to a coherent optical-microwave interface to robust, deterministic frequency comb generation.

Patent Abstract: 

This invention is a method and apparatus for electronic synthesis of light based on an electro-optic modulation (EOM) frequency comb. The invention provides a phase-coherent link between light and microwave radiation using linear electro-optics. It is composed of four interconnected components. In the first component, the invention utilizes periodic electro-optic modulation at microwave rates to transform a continuous-wave (CW) laser into a train of picosecond light pulses. The second component is nonlinear-fiber broadening of this EOM frequency comb to produce a supercontinuum with 160 THz of bandwidth. The third component is optical filtering of the EOM comb that virtually eliminates electronic-noise-induced decoherence of the supercontinuum. The fourth component is f-2f self-referencing that yields the carrier-envelope offset frequency of the EOM comb, which enables measurement and control of the CW laser frequency calibrated by the SI definitions of time and frequency.


This invention introduces the concept of lightwave synthesis directly with electronics. The overall concept of this invention involving electro-optic modulation (EOM) comb system design and mitigation of electronic noise is completely new – that an electronically derived frequency comb, the EOM comb, can be used to synthesize and count cycles of light. This invention hinges upon two new innovations: optical filtering of electronic thermal noise and ultrabroadband supercontinuum generation with >1 ps optical pulses. These are new, critical, innovative, and enabling features. Additionally, the EOM frequency comb invention offers a new technological route for synthesis of lightwaves that offers important features that do not currently exist. In particular, the EOM comb synthesizer supports high mode spacing in the 10+ GHz range that targets applications in communications, spectroscopy, and sensing in which optically resolving comb modes is critical. EOM combs also offer wide frequency tuning to match application needs.


Scott Papp, Scott Diddams, Katja Eha, and Daniel Cole

Patent Number: 
Technology Type(s): 
Laser and Optics, Manufacturing, Electronics, Optical Frequency Measurements, Micro- and Optoelectronics, Healthcare
Internal Laboratory Ref #: 
Patent Issue Date: 
August 14, 2018
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