System and method for providing chirped electromagnetic radiation

• US 8,081,670 B2
• Filed: 02/14/2006
• Issued: 12/20/2011
• Est. Priority Date: 02/14/2006
• Status: Active Grant

• Current Assignee: Aeva, Inc.
• Original Assignee: Digital Signal Corporation (StereoVision Imaging, Inc.)
• Inventors: Belsley, Kendall
• Primary Examiner(s): Stultz, Jessica
• Assistant Examiner(s): King, Joshua
• Application Number:
  US11/353,124
• Publication Number:
  US 20070189341A1
• Time in Patent Office: 2,135 Days
• Field of Search: 372 10- 13, 372/28, 372/94
• 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:

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 that receives electromagnetic radiation from 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 form the optical cavity via the first output, and the optical switch being configured in a second state to return substantially all of the received electromagnetic radiation from 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 form 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 for 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 has a second input that receives electromagnetic radiation from a radiation source, and is operable in the second state to either dump substantially all of the electromagnetic radiation received from the radiation source via the second input away from the optical cavity, and is operable in the first state to direct substantially all of the electromagnetic radiation received from the radiation source via the second input into the optical cavity.

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

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 operable in the first state to dump the received electromagnetic radiation away from the optical cavity for a period of time that is substantially equal to a period of time required for electromagnetic radiation to travel 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:

introducing electromagnetic radiation into an 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;

operating an optical switch in a first state for a first period of time, the optical switch disposed within the optical cavity, the optical switch having a first output, a second output, and an input coupled to the optical cavity that receives electromagnetic radiation from the optical cavity, wherein when the optical switch operates in the first state, substantially all of the electromagnetic radiation received by the optical switch is dumped away from the optical cavity via the first output, wherein the first period of time is greater than or substantially equal to a period of time required for electromagnetic radiation to travel the optical length 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 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 optical switch is further operable when open to introduce electromagnetic radiation into the optical cavity at the initial frequency.

20. 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 separate from the frequency shifter, the optical switch having a first input and a second input, the first input coupled to the optical cavity to receive electromagnetic radiation from the optical cavity, the second input coupled to a radiation source outside the optical cavity to receive electromagnetic radiation from the radiation source, the optical switch having a first output coupled to the optical cavity to provide electromagnetic radiation from either the first input or the second input to the optical cavity and a second output configured to dump electromagnetic radiation away from the optical cavity, and the optical switch being configured in;

a first state in which the electromagnetic radiation received by the optical switch from the optical cavity via the first input is returned to the optical cavity via the first output of the optical switch while the electromagnetic radiation received by the optical switch from the radiation source via the second input is dumped away from the optical cavity via the second output of the optical switch; and

a second state in which the electromagnetic radiation received by the optical switch form the optical cavity via the first input is dumped away from the optical cavity via the second output of the optical switch while the electromagnetic radiation received by the optical switch form the radiation source via the second input is returned to the optical cavity via the first output of the optical switch, wherein the optical switch is configured in the second state for a period of time that is greater than or substantially equal to a period of time required for electromagnetic radiation to travel the optical length of the optical cavity causes the frequency of the electromagnetic radiation within the optical cavity to return to the initial frequency.

21. The system of claim 20, wherein the electromagnetic radiation received from the radiation source is at an initial frequency such that:

operation of the optical switch in the first state causes the frequency of the electromagnetic radiation within the optical cavity to linearly shift further and further away from the initial frequency as the electromagnetic radiation is circulated back through the optical cavity through the optical switch.