Multiple laser source, and systems for use thereof

• US 6,654,401 B2
• Filed: 03/17/2001
• Issued: 11/25/2003
• Est. Priority Date: 08/08/2000
• Status: Expired due to Fees

• Current Assignee: F & H Applied Science Associates Incorporated
• Original Assignee: F & H Applied Science Associates Incorporated
• Inventors: Contarino, Vincent Michael, Li, Yifei, Cavalheiro Vieira, Amarildo Jesus, Herczfeld, Peter Robert, Mullen, Linda Jeanne
• Primary Examiner(s): Ip, Paul
• Assistant Examiner(s): MENEFEE, JAMES A
• Application Number:
  US09/811,320
• Publication Number:
  US 20020018494A1
• Time in Patent Office: 983 Days
• Field of Search: 372/9, 372/12, 372/70-71
• US Class Current: 372/70
• CPC Class Codes: H01Q 3/2676 Optically controlled phased array
• 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 3/2383 Parallel arrangements
• CPC Class Codes: H01S 5/0623 using the beating between two closely spaced optical frequencies, i.e. heterodyne mixing

Abstract

A chirp signal source includes first and second lasers formed on a solid-state chip or substrate. Each of the lasers has a resonator or cavity which incorporates or includes electrooptic material which changes refractive index in response to an electric field. The lasers are pumped, and the resulting laser beams are coupled to a light-to-electric converter which combines the light beams to generate an electrical difference frequency. The change in refractive index allows the lasers to be swept or chin,ed at a much higher rate than thermal or piezoelectrically operated lasers. This structure has the advantages of tending to reduce temperature effects on the difference frequency. It has the further advantage of a high sweep rate, which can be used to improve the signal-to-noise ratio. A radar or lidar ranging system according to an aspect of the invention uses multiple solid-state lasers, which are thermally coupled together.

Claims

1. A laser arrangement, comprising:

a first solid-state laser formed on a chip, said first solid-state laser having a particular cavity length, at least a portion of said cavity of said first solid-state laser including electrooptic material;

a second solid-state laser also formed on said chip, and having said particular cavity length, at least a portion of said cavity of said second solid-state laser including said electrooptic material;

first and second optical pumps having nominally the same pump frequency;

optical coupling means coupled to said first and second optical pumps and to said first and second solidstate lasers, for pumping said first and second lasers with similar pump light, whereby said first and second lasers produce first and second laser light beams;

a light-to-electric converter which, in the presence of plural light signals at different frequencies or wavelengths, generates electrical signals at frequencies related to the difference; and

second optical coupling means coupled to said first and second lasers, and coupled to said light-to-electric converter, for coupling said first and second laser light beams to said light-to-electric converter, whereby said light-to-electric converter generates at least one electrical difference signal.

2. An arrangement according to claim 1, further comprising:

an electrode associated with at least a portion of said electrooptic material of said second laser, for, when electrically energized, electrooptically affecting the length of said cavity of said second laser by virtue of index of refraction effects, thereby affecting the wavelength of said laser light beam of said second laser, which in turn affects said electrical difference signal.

3. An arrangement according to claim 2, further comprising:

an electrode associated with at least a portion of said electrooptic material of said first laser, for, when electrically energized, electrooptically affecting the length of said cavity of said first laser by virtue of index of refraction effects, thereby affecting the wavelength of said laser light beam of said first laser, which in turn affects said electrical difference signal;

a source of fixed electrical bias coupled to said electrode associated with said second laser, and

a source of information signal coupled to said electrode associated with said first laser, for simultaneously generating an information signal spectrum about a frequency established by said fixed bias.

4. An arrangement according to claim 1, wherein said first and second optical pumps comprise:

a single pump light source; and

signal dividing means coupled to said single pump light source, for dividing pump light from said single pump light source into a first portion and a second portion, corresponding to said first and second optical pumps.

5. An arrangement according to claim 4, where said signal dividing means comprises a half-silvered mirror and a prism.

6. An arrangement according to claim 4, where said signal dividing means comprises a directional coupler.

7. A radar system, said radar system comprising:

a chirp signal source, said chirp signal source including;

a first solid-state laser formed on a chip, said first solid-state laser having a particular optical cavity length, at least a portion of said cavity of said first solid-state laser including electrooptic material;

a second solid-state laser also formed on said chip, and having said particular optical cavity length, at least a portion of said cavity of said second solid-state laser including said electrooptic material;

first and second optical pumps having nominally the same pump frequency;

optical coupling means coupled to said first and second optical pumps and to said first and second solid-state lasers, for pumping said first and second lasers with similar pump light, whereby said first and second lasers produce first and second laser light beams;

a light-to-electric converter which, in the presence of plural light signals at different frequencies or wavelengths, generates electrical signals at frequencies related to the difference; and

second optical coupling means coupled to said first and second lasers, and coupled to said light-to-electric converter, for coupling said first and second laser light beams to said light-to-electric converter, whereby said light-to-electric converter generates at least one electrical difference signal;

said radar system further comprising;

a chirp signal source coupled to said electrooptic material of at least one of said first and second lasers, for causing the frequencies of said first and second laser light beams to relatively change with time;

means for transmitting said electrical difference signal toward a target;

means for receiving at least a portion of said electrical difference signal received from said target;

mixing means coupled to said light-to-electric converter and to said means for receiving, for mixing together said electrical difference signals produced by said light-to-electric converter with said electrical difference signal received from said target, for generating a difference frequency signal indicative of the range of said target; and

processing means coupled to said mixing means for evaluating said difference frequency signal indicative of the range of said target.

8. A lidar system, said lidar system comprising:

a chirp signal source, said chirp signal source including;

a first solid-state laser formed on a chip, said first solid-state laser having a particular optical cavity length, at least a portion of said cavity of said first solid-state laser including electrooptic material;

a second solid-state laser also formed on said chip, and having said particular optical cavity length, at least a portion of said cavity of said second solid-state laser including said electrooptic material;

first and second optical pumps having nominally the same pump frequency;

optical coupling means coupled to said first and second optical pumps and to said first and second solid-state lasers, for pumping said first and second lasers with similar pump light, whereby said first and second lasers produce first and second laser light beams;

a light-to-electric converter which, in the presence of plural light signals at different frequencies or wavelengths, generates electrical signals at frequencies related to the difference; and

second optical coupling means coupled to said first and second lasers, and coupled to said light-to-electric converter, for coupling said first and second laser light beams to said light-to-electric converter by way of a target, whereby said light-to-electric converter generates at least one electrical difference signal;

said lidar system further comprising;

a chirp signal source coupled to said electrooptic material of at least one of said first and second lasers for causing said first and second laser light beams to change in frequency relative to each other;

means for transmitting said first and second laser light beams toward a target;

means for receiving at least a portion of said first and second light beams received from said target; and

processing means coupled to said light-to-electric converter for evaluating said difference frequency signal indicative of the range of said target.

9. A communication system, said communication system comprising:

a chirp signal source, said chirp signal source including;

a first solid-state laser formed on a chip, said first solid-state laser having a particular optical cavity length, at least a portion of said cavity of said first solid-state laser including electrooptic material;

a second solid-state laser also formed on said chip, and having said particular optical cavity length, at least a portion of said cavity of said second solid-state laser including said electrooptic material;

first and second optical pumps having nominally the same pump frequency;

optical coupling means coupled to said first and second optical pumps and to said first and second solid-state lasers, for pumping said first and second lasers with similar pump light, whereby said first and second lasers produce first and second laser light beams;

a light-to-electric converter which, in the presence of plural light signals at different frequencies or wavelengths, generates electrical signals at frequencies related to the difference; and

second optical coupling means coupled to said first and second lasers, and coupled to said light-to-electric converter, for coupling said first and second laser light beams to said light-to-electric converter, whereby said light-to-electric converter generates at least one electrical difference signal;

said communication system further comprising;

an information signal source coupled to said electrooptic material of at least one of said first and second lasers for causing said electrical difference signal to be responsive to said information;

and means for receiving at least a portion of said electrical difference signal, and for extracting said information from said electrical difference signal.