System and method for providing chirped electromagnetic radiation

• US 8,891,566 B2
• Filed: 12/19/2011
• Issued: 11/18/2014
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: Aeva, Inc.
• Original Assignee: Digital Signal Corporation (StereoVision Imaging, Inc.)
• Inventors: Belsley, Kendall L.
• Primary Examiner(s): Maldonado, Julio J
• Assistant Examiner(s): King, Joshua
• Application Number:
  US13/329,595
• Publication Number:
  US 20120189027A1
• Time in Patent Office: 1,065 Days
• Field of Search: 372/10, 372/11, 372/12, 372/13, 372/28, 372/94, 356/482, 356/486
• US Class Current: 372/28
• CPC Class Codes: G01S 17/26 wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals
• CPC Class Codes: G01S 17/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/4911 Transmitters
• CPC Class Codes: G02F 1/11 based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves acousto-optical deflection G02F1/33
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction
• CPC Class Codes: G02F 2203/25 Frequency chirping of an optical modulator; Arrangements or methods for the pre-set or tuning thereof
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: H01S 3/1062 using a controlled passive interferometer, e.g. a Fabry-Perot etalon
• CPC Class Codes: H01S 3/1103 Cavity dumping
• CPC Class Codes: H01S 3/235 Regenerative amplifiers

Abstract

A system and method for controllably chirping electromagnetic radiation from a radiation source includes an optical cavity arrangement. The optical cavity arrangement enables electromagnetic radiation to be produced with a substantially linear chirp rate and a configurable period. By selectively injecting electromagnetic radiation into the optical cavity, the electromagnetic radiation may be produced with a single resonant mode that is frequency shifted at the substantially linear chirp rate. Producing the electromagnetic radiation with a single resonant mode may increase the coherence length of the electromagnetic radiation, which may be advantageous when the electromagnetic radiation is implemented in various applications. For example, the electromagnetic radiation produced by the optical cavity arrangement may enhance a range, speed, accuracy, and/or other aspects of a laser radar system.

Claims

1. A system for controllably chirping electromagnetic radiation, the system comprising:

a first coherent laser radar section comprising;

a laser source that generates a first laser beam,

an interferometer that splits the first laser beam into a first target beam and a first local oscillator beam, and generates a first combined target beam from a first reflected portion of the first target beam and the first local oscillator beam;

a second coherent laser radar section comprising;

a laser source that generates a second laser beam,

an interferometer that splits the second laser beam into a second target beam, incident on the target at the same location as the first target beam, and a second local oscillator beam, and generates a second combined target beam from a second reflected portion of the second target beam and the second local oscillator beam; and

a processor configured to determine a range and a Doppler velocity of the target unambiguously from the first combined target beam and the second combined target beam,

wherein each of the first laser source and the second laser source further comprises;

at least one optical element that forms an optical cavity;

a frequency shifter disposed within the optical cavity, wherein the frequency shifter receives electromagnetic radiation from the optical cavity, and outputs a frequency shifted portion of the received electromagnetic radiation back to the optical cavity; and

an optical switch disposed within the optical cavity, the optical switch having an input coupled to the optical cavity, the optical switch having a first output and a second output, and the optical switch being configured in a first state to dump substantially all of the received electromagnetic radiation from the input away from the optical cavitiy via the first output, and the optical switch being configured in a second state to return substantially all of the received electromagnetic radiation form the input back to the optical cavity via the second output,

wherein, while the optical switch is configured in the second state, the frequency of the electromagnetic radiation within the optical cavity linearly shifts further and further away from the initial frequency as the electromagnetic radiation is circulated through the optical cavity, and

wherein the optical switch is configured in the first state for a period of time that is greater than or substantially equal to a period of time required from electromagnetic radiation to travel the optical length of the optical cavity thereby returning the frequency of the electromagnetic radiation within the optical cavity to the initial frequency.

2. The system of claim 1, wherein the optical switch receives electromagnetic radiation from a radiation source, and is controllable to either dump the electromagnetic radiation received from the radiation source away from the optical cavity or to direct the electromagnetic radiation received from the radiation source into the optical cavity.

3. The system of claim 2, wherein when the optical switch returns the electromagnetic radiation received from the optical cavity back to the optical cavity, the optical switch dumps the electromagnetic radiation received from the radiation source.

4. The system of claim 1, further comprising an optical amplifier.

5. The system of claim 4, wherein the optical amplifier has a gain large enough to overcome one or more cavity losses of the optical cavity.

6. The system of claim 1, wherein a portion of the electromagnetic radiation within the optical cavity is output from the optical cavity to a device.

7. The system of claim 6, wherein the portion of the electromagnetic radiation within the optical cavity that is output from the optical cavity is output from frequency shifter to the device.

8. The system of claim 7, wherein the frequency shifter receives electromagnetic radiation from the optical cavity, and diffracts the received electromagnetic radiation such that the portion of the electromagnetic radiation that is output from the optical cavity is zero order diffracted by the frequency shifter.

9. The system of claim 1, wherein the frequency shifter receives electromagnetic radiation from the optical cavity, and diffracts the received electromagnetic radiation such that the frequency shifted portion of the received electromagnetic radiation that is output back to the optical cavity is first order diffracted by the frequency shifter.

10. The system of claim 1, wherein the optical cavity comprises a ring cavity.

11. The system of claim 1, wherein the at least one optical element comprises at least one of a mirror, a lens, a prism, or an optical fiber.

12. The system of claim 1, wherein the optical switch is controllable to dump the received electromagnetic radiation away from the optical cavity for a period of time that is substantially equal to the optical length of the optical cavity.

13. The system of claim 1, wherein the frequency shifter comprises an acousto-optic Bragg cell.