Ultralow noise mode-locked laser and RF sinewave source

• US 7,492,795 B1
• Filed: 01/05/2005
• Issued: 02/17/2009
• Est. Priority Date: 01/06/2004
• Status: Expired due to Fees

• Current Assignee: University of Central Florida (State University System of Florida)
• Original Assignee: University of Central Florida Research Foundation Inc. (State University System of Florida)
• Inventors: Delfyett, Peter J, Gee, Sangyoun, Choi, Myoung-Taek
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): King; Joshua
• Application Number:
  US11/029,974
• Time in Patent Office: 1,504 Days
• Field of Search: 372/29.011
• US Class Current: 372/29.011
• 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. A method of generating precise optical timing signals having a frequency greater than approximately 12.4 GHz from a mode locked laser source comprising the steps of:

Automatically self-starting an optical loop of a mode locked laser source optoelectronic loop oscillator operating at greater than approximately 12.4 GHz;

Producing a periodic comb of phase-locked longitudinal modes from the mode locked laser source;

Selecting two of said phase-locked longitudinal modes from said optical loop of the mode locked laser source;

Producing a beat note from said selected two phase-locked longitudinal modes;

Delaying the produced beat note in a delay line, having a length of about 100 meters, between an optical circulator of the optical loop and a photodiode of an electrical loop said delay line coupling the electrical loop with the optical loop;

Detecting said delayed beat note pulses at the electrical loop coupled with the optical loop and generating an electrical beat pulse;

Dividing said electrical beat pulses by a selected integer to form an electrical controlling signal;

Controlling an optical modulator coupling said optical loop with said electrical loop with said electrical controlling signal to mode lock said laser source on a selected harmonic of a fundamental frequency of said optical loop; and

Coupling said harmonic of said laser source to an optical output as the optical timing signal to drive a harmonic mode-locked laser.

2. The method of claim 1, further comprising the step of:

using a Fabry-Perot Etalon to suppress a supermode noise of the harmonically mode-locked laser source generated as a result of operation greater than approximately 12.4% GHz.

3. The method of claim 1, further comprising the step of:

filtering the divided electrical beat pulses.

4. A method of generating precise microwave timing signals from a self-starting mode-locked laser optoelectronic oscillator comprising the steps of:

Producing a periodic comb of phase-locked longitudinal modes from the self-starting optical loop of the mode-locked laser optoelectronic oscillator mode locked at greater than approximately 12.4 GHz

Selecting two of said phase-locked longitudinal modes from said optical loop;

Producing a beat mode from said selected two phase-locked longitudinal modes;

Delaying the beat mode in a delay line, having a length of about 100 meters, between an optical circulator of the optical loop and a photodiode of an electrical loop;

Detecting said delayed beat mode pulses and generating an electrical beat pulse in the electrical loop of said optoelectronic oscillator;

Dividing said electrical beat pulses mode by a selected integer to form an electrical controlling signal;

Controlling an optical modulator coupling said optical loop with said electrical loop with the said electrical controlling signal whereby said laser is locked on a selected harmonic of the fundamental frequency of the optical loop; and

Coupling said electrical controlling signal to an output as a microwave timing signal.

5. The method of claim 4, further comprising the step of:

suppressing a supermode noise of the harmonically mode-locked laser.

6. The method of claim 4, further comprising the step of filtering the divided electrical beat pulses.

7. The method of claim 5, wherein the suppressing step further includes the step of:

using a Fabry-Perot Etalon as a filter in the optical loop to suppress the supermode noise generated by the greater than 12.4 GHz operation.

8. A method of generating precise optical and electrical timing signals for a mode-locked laser and RF sinewave source comprising the steps of:

Automatically self-starting an optical loop and an electrical loop of an optoelectronic oscillator from background noise;

Generating a beat pulse signal from a laser source in an optical loop of the optoelectronic oscillator, the optical loop operating at greater than approximately 12.4 GHz;

Coupling the generated beat pulse signal from an optical circulator of said optical loop to a filter, which filters the beat pulse and couples said beat pulse into a delay line, having a length of about 100 meters, between said filter and a photodiode of the electrical loop of the optoelectronic oscillator;

The electrical loop operating at a frequency greater than approximately 12.4 GHz;

Converting the filtered and delayed beat pulse signal into an electrical drive timing signal in the electrical loop including dividing the electrical drive timing signal by an integer; and

Modulating the laser source with the electrical drive timing signal so that the laser source is mode-locked to a selected harmonic of a fundamental frequency of the laser source.

9. An optical timing signal generating system for lasers comprising:

An automatically self-starting optical loop laser source for generating an optical beat pulse signal, the optical loop operating at greater than approximately 12.4 GHz;

A modifier for modifying the beat pulse signal into an electrical drive timing signal in an electrical loop coupled with the optical loop, the modifier comprising;

An optical filter for filtering the optical beat pulse signal coupled, from an optical circulator of said optical loop, into the electrical loop;

An optical delay device, including an optical delay line, having a length of about 100 meters, between said filter and a detector, of the electrical loop, for adding a delay to the filtered optical beat pulse signal;

the detector for detecting the filtered and delayed optical beat pulse signal and converting optical beat pulse signal to an electrical drive timing signal; and

A modulator for modulating the laser source with the electrical drive timing signal so that the laser source is mode-locked to a selected harmonic of a fundamental frequency of the laser source.