Ultralow noise mode-locked laser and RF sinewave source

• US 7,978,740 B1
• Filed: 10/05/2007
• Issued: 07/12/2011
• Est. Priority Date: 01/06/2004
• Status: Active Grant

• Current Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Original Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Choi, Myoun-Taek, Gee, Sangyoun, Delfyett, Peter J.
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): King; Joshua
• Application Number:
  US11/973,366
• Time in Patent Office: 1,376 Days
• Field of Search: 372/18, 372/29.02
• US Class Current: 372/29.02
• CPC Class Codes: H01S 3/06791 Fibre ring lasers fibre laser gyrometers G01C19/72
• CPC Class Codes: H01S 3/08036 using intracavity dispersive, polarising or birefringent elements
• CPC Class Codes: H01S 3/107 using electro-optic devices, e.g. exhibiting Pockels or Kerr effect H01S3/1061, H01S3/1063, H01S3/1065 take precedence
• CPC Class Codes: H01S 3/1109 Active mode locking
• CPC Class Codes: H01S 3/1121 Harmonically mode locking lasers, e.g. modulation frequency equals multiple integers or a fraction of the resonator roundtrip time
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/136 by controlling devices placed within the cavity

Abstract

Systems, devices and methods of generating both a precision electrical timing signal as well as a precision optical timing signal. A novel, modified opto-electronic loop oscillator is used to drive a harmonic mode-locked laser. A novel opto-electronic loop has a larger “Q” factor by increasing the electrical loop oscillating frequency ω₀ by using a beat note created by the selection of two optical longitudinal modes from the mode-locked laser. The beat note is detected and divided down to drive a modulator that mode-locks the laser. The frequency division stage also reduces the noise.

Claims

1. An opto-electronic oscillator to drive a harmonic mode-locked laser, comprising:

an automatically self-starting optical loop forming an optical ring laser to produce an optical timing signal to drive the harmonic mode-locked oscillator, the optical loop responsive to an electrical modulation signal to drive the opto-electronic oscillator in resonance to produce coherent optical oscillation greater than approximately 12.4 GHz, the optical loop producing a periodic comb of phase locked longitudinal modes;

an optical delay to inject a delay in the periodic comb of phase locked longitudinal modes;

a Fabry-Perot Etalon in the optical loop to filter the delayed periodic comb of phase locked longitudinal modes to suppress a supermode noise and allow only two longitudinal modes;

an optical coupler to couple an opto-electronic feedback loop with said optical ring laser to couple the two longitudinal modes from the optical loop to the electrical loop, and produce an optical beat note pulse from the two longitudinal modes,

an optical delay in the opto-electronic feedback loop to delay the produced optical beat note pulse, a photo detector for detecting and converting said delayed optical beat note pulse into an electrical signal, and an electrical divider dividing the electrical signal by an integer to create a timing signal to control the optical loop; and

an optical modulator driven by the divided electrical signal coupling said optical ring laser with said opto-electronic feedback loop to generate said electrical control modulation signal to drive said optical ring laser in resonance to produce an optical timing signal to drive the harmonic mode-locked laser.

2. The device as in claim 1, wherein said optical modulation is in phase with said optical oscillation in said ring laser and causes mode-locking of said optical oscillation in said ring laser at a selected harmonic frequency that is a multiple of the fundamental frequency of said ring laser.

3. The device as in claim 1, wherein said optical feedback loop includes an optical coupler disposed relative to said ring laser, said optical coupler operable to split an output of said laser into a first portion as laser output and a second portion as an optical timing signal that is modulated by said electrical modulation signal causing an optical modulation in said optical oscillation in said optical ring laser.

4. The device as in claim 1, further comprising an optical filter disposed relative to said ring laser, said optical filter operable to pass selected longitudinal modes of said ring laser to said opto-electronic feedback loop.

5. The device as in claim 1, wherein said opto-electronic feedback loop includes a photo detector responsive to said optical signal, said photo detector deployed relative to said ring laser and operable to convert said optical signal into said electrical modulation signal.

6. The device as in claim 5, further comprising an electrical divider circuit operable to perform a mathematical division on the output of said photo detector and produce said electrical modulation signal.

7. The device as in claim 1, wherein said opto-electronic feedback loop includes a microwave coupler, said microwave coupler operable to split an output of said electrical modulation signal into a first portion as opto-electronic feedback loop output and a second portion as an electrical timing signal.