MODE LOCKED LASER SYSTEM

• US 20110134942A1
• Filed: 07/29/2009
• Published: 06/09/2011
• Est. Priority Date: 07/29/2008
• Status: Active Grant

• Current Assignee: Legato Laser Technology Ltd.
• Original Assignee: Legato Laser Technology Ltd.
• Inventors: Cohen, Guy, Karni, Yoram
• Granted Patent: US 8,494,016 B2
• Time in Patent Office: Days
• US Class Current: 372/18
• CPC Class Codes: H01S 5/065 Mode locking; Mode suppression; Mode selection ; Self pulsating
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/4062 with an external cavity or using internal filters, e.g. Talbot filters
• CPC Class Codes: H01S 5/4068 with lateral coupling by axially offset or by merging waveguides, e.g. Y-couplers
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

A laser resonator cavity is presented. The laser resonator cavity comprises an optical manipulator of different longitudinal modes propagating along different optical paths. The optical manipulator is configured for adjusting a difference in optical lengths of the different optical paths thereby adjusting a frequency spacing between the different longitudinal.

Claims

1. A laser resonator cavity which is characterized by a general optical length and comprising an optical manipulator of different longitudinal modes propagating along different optical paths, said optical manipulator being configured for adjusting a difference in optical lengths of the different optical paths thereby adjusting a frequency spacing between the different longitudinal modes such that said frequency spacing is independent of said general optical length.

2. The laser resonator cavity of claim 1, wherein said optical manipulator is configured for adjusting at least one of spatial shape, temporal shape and repetition rate of an output pulse.

3. The laser resonator cavity of claim 2, wherein the output of the cavity is in the form of short pulses.

4. The laser resonator cavity of claim 1, wherein said manipulator comprises at least one of the following:

a dispersion control assembly, and at least one spectral beam splitters/combiners.

5. The laser resonator cavity of claim 1, wherein the spectral beam splitter/combiner assembly is configured and operable to combine light components of the different spatially separated longitudinal modes propagating along the different optical paths into a combined light beam and to separate a combined light beam into the different longitudinal mode components to propagate along the different spatially separated optical paths.

6. The laser resonator cavity of claim 5, comprising a mode locking assembly accommodated in the optical path of the combined light beam.

7. The laser resonator cavity of claim 2, wherein said manipulator comprises an intensity control assembly.

8. The laser resonator cavity of claim 4, wherein said manipulator comprises an intensity control assembly, thus enabling control of both amplitude and frequency of the different longitudinal modes.

9. The laser resonator cavity of claim 8, wherein the intensity control assembly comprises a plurality of intensity control units arranged across the different optical paths of the different longitudinal modes propagating within the cavity, the intensity control units being configured to adjust relative intensities of each of the different longitudinal modes propagating in the different paths separately.

10. The laser resonator cavity of claim 1, wherein the dispersion control assembly comprises different dispersion control media in the paths of the different longitudinal modes thereby independently adjusting the optical lengths of each of the different modes.

11. The laser resonator cavity of claim 1, configured to define at least first and second optical regions, wherein the first optical region is configured to create a spatial overlap between the different longitudinal modes thereby forming a pulsed laser beam, and the second optical region is configured to create spatial dispersion of the different longitudinal modes with said frequency spacing, thereby enabling separate manipulation of the different longitudinal modes within said second optical region.

12. The laser resonator cavity of claim 11, wherein said second optical region is defined by the accommodation of the optical manipulator.

13. The laser resonator cavity of claim 1, configured for controlling one or more properties of a frequency comb of the different longitudinal modes, said one or more properties comprising at least the frequency spacing between the consequent longitudinal modes of the frequency comb, thereby enabling control of a frequency of output pulses of the cavity and an output pulse shape.

14. The laser resonator cavity of claim 1, comprising one or more gain media comprising an array of optical gain sources arranged along an axis substantially perpendicular to an optical axis of the cavity and being accommodated in the different optical paths of the different longitudinal modes propagating within the cavity for separately amplifying the different longitudinal modes.

15. The laser resonator cavity of claim 14, wherein said one or more gain media is located in a first region of the cavity where the optical paths of the different longitudinal modes overlap, or in a second optical region where the optical path of the different longitudinal modes are spatially separated.

16. The laser resonator cavity of claim 1, comprising light collection optics interposed between a spectral beam splitter/combiner assembly and the optical manipulator, and configured to direct the different spatially separated longitudinal modes from said one or more gain media onto said spectral beam splitter/combiner.

17. The laser resonator cavity of claim 6, wherein said mode locking assembly comprises a saturable absorber.

18. The laser resonator cavity of claim 1, wherein the length of the optical path slightly increases with an increase of the frequency of the longitudinal mode.

19. The laser resonator cavity of claim 1, wherein the length of the optical path slightly decreases with an increase of the frequency of the longitudinal mode.

20. The laser resonator cavity of claim 1, wherein the differences in the optical lengths are adjusted by optical properties and spatial arrangement of elements in the cavity such that frequencies (f_k=f₀+kδ

) of the different longitudinal modes are spaced by constant equal amount δ

.

21. The laser resonator cavity of claim 4, wherein said dispersion control assembly comprises a multitude of dispersion control units which are arranged across the different optical paths of the different longitudinal modes propagating within the cavity, and which are configured to adjust the optical length of each of said different paths separately.

22. The laser resonator cavity of claim 21, wherein the dispersion control units have controllable optical length.

23. The laser resonator cavity of claim 21, wherein the dispersion control units are made of one or more materials having refraction index or indices varying in response to application of an external electric field.

24. The laser resonator cavity of claim 14, wherein said one or more gain media has one of the following configurations:

(a) comprises an array of semiconductor edge emitting laser sources;

(b) comprises a broad area semiconductor edge emitting laser source;

(c) comprises an array of semiconductor vertically emitting laser sources;

(d) comprises spaced apart laser gain medium regions having different lasing properties.

25. A laser resonator cavity comprising at least first and second optical regions, configured such that the first optical region creates a spatial overlap between light waves of different longitudinal modes thereby forming a pulsed laser beam, and the second optical region creates spatial dispersion of the laser longitudinal modes with a frequency spacing between consequent longitudinal modes being independent of a general optical length of the cavity, thereby enabling separate manipulation of the different longitudinal modes within said second optical region such that the optical length of the optical path of the longitudinal mode increases with the frequency of the longitudinal mode, while the frequency spacing between the longitudinal modes is substantially equal, thereby providing ultrashort pulsed output of the cavity.

26. A laser resonator cavity comprising an intracavity optical manipulator for manipulating different longitudinal modes propagating along different optical paths in the cavity, said optical manipulator being configured for adjusting frequency spacings between the different longitudinal modes by manipulating optical lengths of the different optical paths such that the optical path length varies with the frequencies of the longitudinal modes as a monotonic function corresponding to increase or decrease of the optical length with an increase in the frequency of the longitudinal mode.

27. A laser resonator cavity characterized by a general optical length and configured for controlling one or more properties of a frequency comb of longitudinal modes of light waves propagating through the cavity, said one or more properties comprising a frequency spacing between the consequent longitudinal modes of the frequency comb, thereby enabling control the frequency of output pulses of the cavity and an output pulse shape, the frequency spacing being independent of said general optical length.