ASE Swept Source with Self-Tracking Filter for OCT Medical Imaging

• US 20110051143A1
• Filed: 05/08/2010
• Published: 03/03/2011
• Est. Priority Date: 09/03/2009
• Status: Active Grant

• Current Assignee: Excelitas Technologies Corporation (Excelitas Technologies Holdings LLC)
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Atia, Walid A., Flanders, Dale C., Kuznetsov, Mark E.
• Granted Patent: US 8,526,472 B2
• Time in Patent Office: Days
• US Class Current: 356/451
• CPC Class Codes: F21V 9/20 Dichroic filters, i.e. devices operating on the principle of wave interference to pass specific ranges of wavelengths while cancelling others
• CPC Class Codes: G01B 9/02004 using frequency scans
• CPC Class Codes: G01B 9/02091 Tomographic interferometers, e.g. based on optical coherence
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 5/005 Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/0064 Anti-reflection components, e.g. optical isolators
• CPC Class Codes: H01S 5/0078 for frequency filtering
• CPC Class Codes: H01S 5/02216 Butterfly-type, i.e. with electrode pins extending horizontally from the housings
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/02325 Mechanically integrated components on mount members or optical micro-benches
• CPC Class Codes: H01S 5/5018 using two or more amplifiers or multiple passes through the same amplifier
• CPC Class Codes: H01S 5/5036 the arrangement being polarisation-selective
• CPC Class Codes: H01S 5/5063 operating above threshold

Abstract

An integrated swept wavelength tunable optical source uses a narrowband filtered broadband signal with an optical amplifier and self-tracking filter. This source comprises a micro optical bench, a source for generating broadband light, a tunable Fabry Perot filter, installed on the bench, for spectrally filtering the broadband light from the broadband source to generate a narrowband tunable signal, an amplifier, installed on the bench, for amplifying the tunable signal. The self-tracking arrangement is used where a single tunable filter both generates the narrowband signal and spectrally filters the amplified signal. In some examples, two-stage amplification is provided. The use of a single bench implementation yields a low cost high performance system. For example, polarization control between components is no longer necessary.

Claims

1. A swept optical source, comprising:

a tunable filter for spectrally filtering light from a source to generate a tunable optical signal that is spectrally tuned over a scanband; and

an optical amplifier for amplifying the tunable optical signal with the amplified tunable optical signal being filtered by the tunable filter.

2. A swept source as claimed in claim 1, wherein the source comprises a broadband source that generates light over the scanband.

3. A swept source as claimed in claim 1, wherein the source comprises an amplified spontaneous emission source that generates light over the scanband.

4. A swept source as claimed in claim 1, wherein the tunable filter is a Fabry Perot tunable filter.

5. A swept source as claimed in claim 1, wherein the tunable filter is a micro electro mechanical system Fabry Perot tunable filter.

6. A swept source as claimed in claim 1, wherein in a passband of the tunable optical filter is less than 20 GigaHertz (FWHM).

7. A swept source as claimed in claim 1, wherein in a passband of the tunable optical filter is less than 5 GigaHertz (FWHM).

8. A swept source as claimed in claim 1, further comprising a tuning controller that drives the tunable filter to tune over the scanband at a speeds greater than 10 kiloHertz.

9. A swept source as claimed in claim 1, further comprising a tuning controller that drives the tunable filter to tune over the scanband at speeds greater than 100 kiloHertz.

10. A swept source as claimed in claim 1, wherein the optical amplifier comprises a semiconductor optical amplifier.

11. A swept source as claimed in claim 1, further comprising a reflector for reflecting the tunable optical signal to pass through the optical amplifier a second time and back to the tunable filter.

12. A swept source as claimed in claim 1, further comprising a loop including the optical amplifier for directing the tunable optical signal back to the tunable filter.

13. A swept source as claimed in claim 1, further comprising a polarization rotation system for rotating a polarization of the tunable optical signal between being filtered by the tunable filter.

14. A swept source as claimed in claim 13, wherein the polarization rotation system includes a non-reciprocal polarization rotation element.

15. A swept source as claimed in claim 13, wherein the polarization rotation system includes a halfwave plate.

16. A swept source as claimed in claim 1, wherein the filtering by the tunable filter of the tunable optical signal is co-directional with the filtering of the amplified tunable optical signal by the tunable filter.

17. A swept source as claimed in claim 1, wherein the filtering by the tunable filter of the tunable optical signal is contra-directional with the filtering of the amplified tunable optical signal by the tunable filter.

18. A method for generating a tunable optical signal, comprising:

spectrally filtering light to generate a tunable optical signal with a tunable filter that is spectrally tuned over a scanband;

amplifying the tunable optical signal to generate an amplified tunable optical signal; and

spectrally filtering the amplified tunable optical signal with the same tunable filter.

19. A method as claimed in claim 18, further comprising generating the light with a broadband source that generates light over the scanband.

20. A method as claimed in claim 18, wherein the tunable filter is a Fabry Perot tunable filter.

21. A method as claimed in claim 18, further comprising tuning the tunable filter over the scanband at a speeds greater than 10 kiloHertz.

22. A method as claimed in claim 18, further comprising tuning the tunable filter over the scanband at a speeds greater than 100 kiloHertz.

23. A method as claimed in claim 18, further comprising directing the tunable optical signal back to the tunable filter using a loop.

24. A method as claimed in claim 18, further comprising directing the tunable optical signal back to the tunable filter using a reflector.

25. A tunable amplifier, comprising:

a tunable filter for spectrally filtering light to generate a tunable optical signal that is spectrally tunable over a spectral band; and

an optical amplifier for amplifying the tunable optical signal with the amplified tunable optical signal being filtered by the tunable filter.

26. A swept optical source, comprising:

a tunable filter for spectrally filtering light from a source to generate a tunable optical signal that is spectrally tuned over a scanband;

an optical amplifier for amplifying the tunable optical signal in a first pass; and

a reflector for reflecting the tunable optical signal to pass through the optical amplifier in a second pass.

27. An optical coherence analysis system, comprising:

a swept source including a tunable filter for spectrally filtering light from a source to generate a tunable optical signal that is spectrally tuned over a scanband and an optical amplifier for amplifying the tunable optical signal with the amplified tunable optical signal being filtered by the tunable filter; and

a Michelson interferometer for dividing the amplified tunable optical signal between a reference arm and a sample arm and generating an interference signal by combining the optical signal from the reference arm and the sample arm; and

a detector system for detecting the interference signal.