System and method for providing chirped electromagnetic radiation

• US 20070189341A1
• Filed: 02/14/2006
• Published: 08/16/2007
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: Aeva, Inc.
• Original Assignee: Digital Signal Corporation (StereoVision Imaging, Inc.)
• Inventors: Belsley, Kendall
• Granted Patent: US 8,081,670 B2
• Time in Patent Office: Days
• US Class Current: 372/10
• 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:

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 receiving electromagnetic radiation from the optical cavity, and being controllable to either dump the received electromagnetic radiation away from the optical cavity or to return the received electromagnetic radiation back to the optical cavity.

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.

14. A method of controllably chirping electromagnetic radiation, the method comprising:

forming an optical cavity;

introducing electromagnetic radiation into the optical cavity at an initial frequency;

shifting the frequency of the electromagnetic radiation within the optical cavity from the initial frequency at a substantially linear chirp rate;

opening an optical switch to dump a portion of the electromagnetic radiation stored within the optical cavity out of the optical cavity; and

introducing electromagnetic radiation into the optical cavity at the initial frequency.

15. The method of claim 14, further comprising amplifying the electromagnetic radiation within the optical cavity.

16. The method of claim 14, further comprising outputting a portion of the electromagnetic radiation within the cavity to a device.

17. The method of claim 14, wherein the step of shifting the frequency of the electromagnetic radiation within the optical cavity comprises diffracting the electromagnetic radiation within the optical cavity.

18. The method of claim 14, wherein the optical cavity comprises a ring cavity.

19. The method of claim 14, wherein the steps of opening a switch to dump a portion of the electromagnetic radiation and introducing electromagnetic radiation into the optical cavity at the initial frequency are performed simultaneously.