Variable repetition rate and wavelength optical pulse source

• US 9,774,163 B2
• Filed: 03/10/2013
• Issued: 09/26/2017
• Est. Priority Date: 01/19/2008
• Status: Active Grant

• Current Assignee: NKT Photonics A/S (NKT A/S)
• Original Assignee: NKT Photonics A/S (NKT A/S)
• Inventors: Clowes, John Redvers, Grudinin, Anatoly Borisovich, Godfrey, Ian Michael
• Primary Examiner(s): Niu, Xinning
• Application Number:
  US13/792,173
• Publication Number:
  US 20130208737A1
• Time in Patent Office: 1,661 Days
• Field of Search: 372 21
• CPC Class Codes: G01N 2021/6419 Excitation at two or more wavelengths
• CPC Class Codes: G01N 2021/6441 with two or more labels
• CPC Class Codes: G01N 21/6458 Fluorescence microscopy fluorescence microscopes per se G02B21/0076 and G02B21/16
• CPC Class Codes: G01N 2201/0697 Pulsed lasers
• CPC Class Codes: G02B 21/16 adapted for ultraviolet illumination ; Fluorescence microscopes G02B21/0076 takes precedence
• CPC Class Codes: G02F 1/3528 for producing a supercontinuum
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• CPC Class Codes: G02F 1/365 in an optical waveguide structure G02F1/377, G02F1/395 take precedence
• CPC Class Codes: H01S 3/0085 Modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/10 Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
• CPC Class Codes: H01S 3/10046 Pulse repetition rate control H01S3/11 takes precedence
• CPC Class Codes: H01S 3/1024 for pulse generation
• CPC Class Codes: H01S 3/108 using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering mode locking using a non-linear element H01S3/1112
• CPC Class Codes: H01S 3/1106 Mode locking
• CPC Class Codes: H01S 3/2308 Amplifier arrangements, e.g. MOPA

Abstract

Variable repetition rate and wavelength optical pulse source, comprising a fixed or variable repetition rate source of supercontinuum pulses; a wavelength tunable optical bandpass filter to filter the supercontinuum pulses at two or more wavelengths, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the optical pulse source can provide variable repetition rate and variable wavelength optical pulses including a series of repetition rates with selected wavelength-varying pulse trains.

Claims

1. Variable repetition rate and wavelength optical pulse source, comprising:

a variable repetition rate source of supercontinuum pulses, said variable repetition rate source of supercontinuum pulses comprising a nonlinear optical element comprising an optical fiber arranged to receive pump pulses and to spectrally broaden the pump pulses to generate the supercontinuum pulses;

said variable repetition rate source of supercontinuum pulses providing nominally identical spectra for different repetition rates; and

a wavelength tunable optical bandpass filter to filter the supercontinuum pulses, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the optical pulse source can provide variable repetition rate and variable wavelength optical pulses.

2. The variable repetition rate and wavelength optical pulse source of claim 1 wherein the wavelength tunable optical bandpass filter is configured to receive a plurality of supercontinuum pulses in a pulse set and to wavelength filter each pulse at a respective one of a corresponding plurality of predetermined wavelengths, to thereby form a wavelength interleaved optical pulse set.

3. The variable repetition rate and wavelength pulse source of claim 1 wherein the wavelength tunable optical bandpass filter is configured to operate in burst mode to provide a pulse train comprising a burst of optical pulses.

4. The variable repetition rate and wavelength optical pulse source of claim 1 wherein the wavelength tunable optical bandpass filter comprises an acousto-optic tunable filter (AOTF).

13. The optical pulse source according to claim 1 configured as a pulsed interleaved excitation apparatus providing first and second interleaved pulses, the first pulse having a wavelength selected to excite a donor molecule and the second pulse having a different wavelength selected to excite an acceptor molecule, the pulse interleaved excitation apparatus comprising said optical pulse source as an illumination source for providing the first and second pulses having different wavelengths.

19. The variable repetition rate and wavelength optical pulse source of claim 1 wherein the pump pulses are launched into the optical fiber without the use of free space optics.

24. The variable repetition rate and wavelength optical pulse source of claim 1 wherein said fixed or variable repetition rate source of supercontinuum pulses comprises a mode locked laser.

5. Variable repetition rate and wavelength optical pulse source, comprising:

a variable repetition rate source of supercontinuum pulses comprising a nonlinear optical element comprising an optical fiber arranged to receive pump pulses and to spectrally broaden the pump pulses to generate the supercontinuum pulses;

a pump pulse source that can provide the pump pulses having different repetition rates, wherein the pulse energy is fixed as pulse to pulse separation is increased with reducing repetition rate; and

a wavelength tunable optical bandpass filter to filter the supercontinuum pulses, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the optical pulse source can provide variable repetition rate and variable wavelength optical pulses.

25. The variable repetition rate and wavelength optical pulse source of claim 5 wherein the pump pulses are launched into the optical fiber without the use of free space optics.

6. A method of producing variable repetition rate and variable wavelength optical pulses, comprising:

providing supercontinuum pulses using a variable repetition rate supercontinuum pulse source, including spectrally broadening pump pulses propagating in an optical fiber;

reducing the repetition rate of the pump pulses, including fixing the pulse energy as the pulse to pulse separation is increased, to thereby provide supercontinuum pulses having a reduced repetition rate; and

filtering the supercontinuum pulses using a wavelength tunable optical bandpass filter, thereby providing optical pulses having different repetition rates and different wavelengths.

26. The method of claim 6 further comprising launching the pump pulses into the optical fiber without the use of free space optics.

7. Variable repetition rate and wavelength optical pulse source, comprising:

a variable repetition rate source of supercontinuum pulses;

a wavelength tunable optical bandpass filter to filter the supercontinuum pulses at two or more wavelengths, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the wavelength tunable optical filter can be modulated, synchronously with the source of supercontinuum pulses, at the operating frequency of the source of supercontinuum pulses or at a lower frequency, wherein the optical pulse source can provide variable repetition rate and variable wavelength optical pulses including a series of repetition rates with selected wavelength-varying pulse trains; and

wherein the source of supercontinuum pulses comprises an optical pump laser operable to generate optical pump pulses at a pump pulse repetition rate;

a nonlinear optical element;

a gating device, provided between the pump laser output and the nonlinear optical element, and arranged to selectively control the launch of pump pulses into the nonlinear optical element at a variable, lower repetition rate, to thereby selectively control the repetition rate of optical supercontinuum pulses generated within the nonlinear optical element.

8. The variable repetition rate and wavelength optical pulse source of claim 7 wherein the nonlinear optical element comprises a microstructured optical fiber.

9. The variable repetition rate and wavelength optical pulse source according to claim 7 wherein the optical pump laser comprises a fiber oscillator and wherein the source of supercontinuum pulses comprises an optical fiber amplifier configured to receive pump pulses from the modelocked fiber oscillator and operable to amplify the pump pulses, the optical fiber amplifier being provided between the gating device and the fiber oscillator.

10. The variable repetition rate and wavelength optical pulse source according to claim 8 wherein the optical pump laser comprises a fiber oscillator and wherein the source of supercontinuum pulses comprises an optical fiber amplifier configured to receive pump pulses from the modelocked fiber oscillator and operable to amplify the pump pulses, the optical fiber amplifier being provided between the gating device and the fiber oscillator.

11. The variable repetition rate and wavelength optical pulse source of claim 9 wherein the source of supercontinuum pulses comprises a further optical amplifier provided between the gating device and the nonlinear optical element.

12. The variable repetition rate and wavelength optical pulse source according to claim 10 wherein the source of supercontinuum pulses comprises a further optical amplifier provided between the gating device and the nonlinear optical element.

14. A method of producing variable repetition rate, wavelength-varying optical pulses, comprising:

providing supercontinuum pulses using a variable repetition rate supercontinuum pulse source, including spectrally broadening pump pulses propagating in an optical fiber;

reducing the repetition rate of the supercontinuum pulses to provide supercontinuum pulses having a reduced repetition rate, including providing nominally identical spectra for different repetition rate supercontinuum pulses; and

filtering the supercontinuum pulses at two or more wavelengths using a wavelength tunable optical bandpass filter, thereby providing optical pulses having different repetition rates and different wavelengths.

15. The method of claim 14, wherein filtering the supercontinuum pulses at two or more wavelengths comprises:

receiving, at the wavelength tunable optical bandpass filter, a plurality of supercontinuum pulses in a pulse set; and

wavelength filtering each pulse at a respective one of a corresponding plurality of predetermined wavelengths, to thereby form a wavelength interleaved optical pulse set.

16. The method of claim 14, comprising providing a pulse train comprising a burst of optical pulses by operating the wavelength tunable optical bandpass filter in a burst mode.

17. The method of claim 14 comprising launching the pump pulses into the optical fiber without the use of free space optics.

18. Variable repetition rate and wavelength optical pulse source, comprising:

a fixed or variable repetition rate source of supercontinuum pulses;

a wavelength tunable optical bandpass filter to filter the supercontinuum pulses at two or more wavelengths, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the optical pulse source can provide variable repetition rate and variable wavelength optical pulses including a series of repetition rates with selected wavelength-varying pulse trains, including providing one wavelength for one pulse and a second wavelength for the next pulse, wherein said optical pulse source can form a wavelength interleaved optical pulse train.

20. The variable repetition rate and wavelength optical pulse source of claim 18 wherein said fixed or variable repetition rate source of supercontinuum pulses comprises a fixed repetition rate source of supercontinuum pulses.

21. The variable repetition rate and wavelength optical pulse source of claim 18 wherein said fixed or variable repetition rate source of supercontinuum pulses comprises a variable repetition rate source.

22. The variable repetition rate and wavelength optical pulse source of claim 18 wherein said fixed or variable repetition rate source of supercontinuum pulses comprises a mode locked laser.

23. Variable repetition rate and wavelength optical pulse source for providing output optical pulses, comprising:

a fixed or variable repetition rate source of supercontinuum pulses;

a wavelength tunable optical bandpass filter to filter the supercontinuum pulses at two or more wavelengths, wherein said source of supercontinuum pulses and said wavelength tunable optical bandpass filter are configured such that the optical pulse source can provide variable repetition rate and variable wavelength optical pulses including a series of repetition rates with selected wavelength-varying pulse trains, including selective control of the spectral profile of each output optical pulse.