Optical coherence tomography technique

1. A device for optical coherence tomography, or OCT, the device comprising:

a light generator adapted to:

generate a series of input pulses of coherent light, each input pulse of the series having an input pulse; width and an input spectral range; and

change an axial resolution of the device independently of an axial scanning depth of the device by changing the input spectral range;

a single dispersive medium having an input optically coupled to the light generator and an output for output pulses, the dispersive medium being adapted to stretch the input pulse width to an output pulse width of each of the output pulses by chromatic dispersion, the dispersive medium comprising a plurality of taps at different positions along the length of the dispersive medium to provide different dispersion;

an optical coupler adapted to couple the output pulses from the output into a reference arm and into a sample arm, and to superimpose light returning from the reference arm and from the sample arm;

an optical switch adapted to change the axial scanning depth independently of the axial resolution by selectively coupling the light generator to one of the taps as the input or by selectively coupling one of the taps as the output to the optical coupler; and

a detector adapted to detect an intensity of interference of the superimposed light with a temporal resolution of a fraction of the output pulse width.

2. The device of claim 1 , wherein each input pulse in the series has an at least essentially time-independent input center wavelength.

3. The device of claim 1 , wherein each output pulse has at least one of a time-dependent instantaneous output peak wavelength and a time-dependent instantaneous output spectral range.

4. The device of claim 3 , wherein the input spectral range is multiple times broader than the instantaneous output spectral range.

5. The device of claim 1 , wherein the dispersive medium includes an optical fiber.

6. The device of claim 1 , wherein a path of light propagation in the dispersive medium from the input to the output is longer than 1 km.

7. The device of claim 1 , wherein a dispersion parameter of the dispersive medium is greater than 10000 ps/(km·nm).

8. The device of claim 7 , further comprising a field generator adapted to generate an external field acting on the medium, wherein the dispersion parameter of the medium is controlled or controllable by the external field.

9. The device of claim 1 , wherein the detector is further adapted to sample the intensity for a plurality of consecutive fractions corresponding to one output pulse width.

10. The device of claim 9 , wherein the plurality of sampled fractions is at least 500.

11. The device of claim 1 , wherein the fraction is shorter than 200 ns.

12. The device of claim 1 , wherein the detector includes at least one of a photodiode and a balanced detector.

13. The device of claim 12 , wherein the detector further includes a gate unit connected to the photodiode and adapted to read the intensity for each of the fractions.

14. The device of claim 1 , wherein the light generator includes a pulsed titanium-sapphire laser or a pulsed supercontinuum light source.

15. The device of claim 9 , wherein the light generator generates the series of input pulses at a repetition rate and the detector initiates the sampling at the repetition rate.

16. The device of claim 1 , wherein the light generator includes a continuous wave light source and a shutter operatively arranged between the continuous wave light source and the input of the dispersive medium.

17. The device of claim 1 , wherein the optical coupler includes at least one of a beam splitter, an optical fiber coupler, a circulator and a 1-by-2-coupler.

18. A method of performing optical coherence tomography, or OCT, the method comprising:

generating by a light generator a series of input pulses of coherent light, each input pulse of the series having an input pulse width and an input spectral range;

stretching the input pulse width of each of the input pulses to an output pulse width of output pulses by means of chromatic dispersion in a single dispersive medium, the dispersive medium comprising a plurality of taps at different positions along the length of the dispersive medium to provide different dispersion;

changing an axial resolution for the OCT independently of an axial scanning depth for the OCT by changing the input spectral range;

changing the axial scanning depth independently of the axial resolution by selectively coupling the light generator to one of the taps as input or by selectively coupling one of the taps as output to an optical coupler;

coupling by the optical coupler the output pulses into a reference arm and into a sample arm, and superimposing light returning from the reference arm and from the sample arm; and

detecting an intensity of interference of the superimposed light with a temporal resolution of a fraction of the output pulse width.

19. The method of claim 18 , further comprising:

generating an external field acting on the medium, wherein the dispersion parameter of the medium is controlled or controllable by the external field.

20. The method of claim 18 , further comprising:

sampling the intensity for a plurality of consecutive fractions corresponding to one output pulse width.

21. The method of claim 20 , further comprising:

generating a series of input pulses at a repetition rate; and

initiating the sampling at the repetition rate.