US 5,359,612 AGranted

High repetition rate, mode locked, figure eight laser with extracavity feedback

AssigneeThe United States of America as represented by the Secretary of the Navy

InventorsMichael L. Dennis, Irl N. Duling, III

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Abstract

An optical pulse generator for producing mode-locked optical pulses comprises: a beam splitter; first and second optical loops coupled together by the beam splitter so as to define a figure eight optical path in which a light beam propagating toward the beam splitter in one of the first and second optical loops is split by the beam splitter to form two light beams propagating in opposite directions around the other one of the first and second optical loops; a direction dependent loss element disposed in the first optical loop for reducing the intensity of light propagating in a predetermined direction around the first optical loop; a nonlinear element disposed in the second optical loop and having an intensity dependent nonlinear optical transmission characteristic; an optical gain medium disposed in a selected one of the first and second optical loops; coupling apparatus for coupling pump light into the selected one of said first and second optical loops having the gain medium, and for coupling mode-locked optical pulses out of the optical pulse generator; and a feedback structure, coupled to the coupling apparatus, being responsive to light propagating therethrough for controlling the repetition rate of the mode-locked optical pulses.

Claims25

Dependent claims

An optical pulse generator laser for producing mode-locked optical pulses, said optical pulse generator laser having a cavity comprising:

a beam splitter;
first and second optical loops coupled together by said beam splitter so as to define a figure eight optical path in which a light beam propagating toward said beam splitter in one of said first and second optical loops is split by said beam splitter to form two light beams propagating in opposite directions around the other one of said first and second optical loops;
direction dependent loss means disposed in said first optical loop for reducing the intensity of light propagating in a predetermined direction around said first optical loop;
nonlinear means disposed in said second optical loop and having an intensity dependent nonlinear optical transmission characteristic;
an optical gain medium disposed in a selected one of said first and second optical loops;
means for coupling pump light into said selected one of said first and second optical loops having said gain medium, and for coupling mode-locked optical pulses out of said optical pulse generator laser, said coupling means including:
a fiber wavelength division multiplexer coupler for coupling pump light into said selected one of said first and second optical loops having said gain medium;
and
an output coupler having first and second ports internal to said cavity and third and fourth ports external to said cavity, said output coupler being disposed in said first optical loop for coupling mode-locked optical pulses out of said optical pulse generator laser, said first port being coupled to said direction dependent loss means to enable a first portion of mode-locked optical pulses to pass through said second port to said beam splitter and a second portion of mode-locked optical pulses to be coupled through said third port and out of said optical pulse generator laser, said second port being responsive to light from said beam splitter for enabling that light to pass through said fourth port;
and
feedback means having a variable delay, coupled to said fourth port of said coupling means, being responsive to light from said fourth port for providing feedback of that light propagating therethrough in a manner which is not interferometrically sensitive, for controlling the repetition rate of said mode-locked optical pulses.

8 more elements

An optical pulse generator for producing mode-locked optical pulses, said optical pulse generator comprising:

a beam splitter;
first and second optical loops coupled together by said beam splitter so as to define a figure eight optical path in which a light beam propagating toward said beam splitter in one of said first and second optical loops is split by said beam splitter to form two light beams propagating in opposite directions around the other one of said first and second optical loops;
direction dependent loss means disposed in said first optical loop for reducing the intensity of light propagating in a predetermined direction around said first optical loop;
nonlinear means disposed in said second optical loop and having an intensity dependent nonlinear optical transmission characteristic;
an optical gain medium disposed in a selected one of said first and second optical loops;
means for coupling pump light into said selected one of said first and second optical loops having said gain medium, and for coupling mode-locked optical pulses out of said optical pulse generator, said coupling means including:
a fiber wavelength division multiplexer coupler for coupling pump light into said selected one of said first and second optical loops having said gain medium;
and
an output coupler disposed in the other one of said first and second optical loops and adjacent to said beam splitter for coupling mode-locked optical pulses out of said optical pulse generator;
and
feedback means, coupled to said coupling means, being responsive to light propagating therethrough for controlling the repetition rate of said mode-locked optical pulses, said feedback means including:
an optical fiber coupled at a first end to said output coupler for passing light from said output coupler therethrough, said optical fiber having a second end having a face;
a mirror coated onto said face for reflecting light from said output coupler back through said optical fiber and said output coupler into said other one of said first and second optical loops;
and
means for stretching said optical fiber to produce a desired delay of the light in said optical fiber.

12 more elements

An optical pulse generator for producing mode-locked optical pulses, said optical pulse generator comprising:

a beam splitter;
first and second optical loops coupled together by said beam splitter so as to define a figure eight optical path in which a light beam propagating toward said beam splitter in one of said first and second optical loops is split by said beam splitter to form two light beams propagating in opposite directions around the other one of said first and second optical loops;
direction dependent loss means disposed in said first optical loop for reducing the intensity of light propagating in a predetermined direction around said first optical loop;
nonlinear means disposed in said second optical loop and having an intensity dependent nonlinear optical transmission characteristic;
an optical gain medium disposed in a selected one of said first and second optical loops;
means for coupling pump light into said selected one of said first and second optical loops having said gain medium, and for coupling mode-locked optical pulses out of said optical pulse generator, said coupling means including:
a fiber wavelength division multiplexer coupler for coupling pump light into said selected one of said first and second optical loops having said gain medium;
and
an output coupler disposed in the other one of said first and second optical loops and adjacent to said beam splitter for coupling mode-locked optical pulses out of said optical pulse generator;
and
feedback means, coupled to said coupling means, being responsive to light propagating therethrough for controlling the repetition rate of said mode-locked optical pulses, said feedback means including:
an optical fiber coupled at a first end to said output coupler for passing light from said output coupler therethrough, said optical fiber having a second end;
a mirror butt-coupled to said second end for reflecting light from said output coupler back through said optical fiber and said output coupler into said other one of said first and second optical loops;
and
means for stretching said optical fiber to produce a desired delay of the light in said optical fiber.

12 more elements

An optical pulse generator for producing mode-locked optical pulses, said optical pulse generator comprising:

a beam splitter;
first and second optical loops coupled together by said beam splitter so as to define a figure eight optical path in which a light beam propagating toward said beam splitter in one of said first and second optical loops is split by said beam splitter to form two light beams propagating in opposite directions around the other one of said first and second optical loops;
direction dependent loss means disposed in said first optical loop for reducing the intensity of light propagating in a predetermined direction around said first optical loop;
nonlinear means disposed in said second optical loop and having an intensity dependent nonlinear optical transmission characteristic;
an optical gain medium disposed in a selected one of said first and second optical loops;
means for coupling pump light into said selected one of said first and second optical loops having said gain medium, and for coupling mode-locked optical pulses out of said optical pulse generator, said coupling means including:
a fiber wavelength division multiplexer coupler for coupling pump light into said selected one of said first and second optical loops having said gain medium;
and
an output coupler disposed in the other one of said first and second optical loops and adjacent to said beam splitter for coupling mode-locked optical pulses out of said optical pulse generator;
and
feedback means, coupled to said coupling means, being responsive to light propagating therethrough for controlling the repetition rate of said mode-locked optical pulses, said feedback means including:
an optical fiber coupled to said output coupler for passing light from said output coupler therethrough;
a Bragg grating written directly into said optical fiber for reflecting light from said output coupler back through said optical fiber and said output coupler;
into said other one of said first and second optical loops;
and
means for stretching said optical fiber to produce a desired delay of the light in said optical fiber.

13 more elements

Dependencies are inferred from the claim text.