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EP-4740275-A1 - LASER DEVICE

EP4740275A1EP 4740275 A1EP4740275 A1EP 4740275A1EP-4740275-A1

Abstract

The present invention relates to a laser device (10) comprising a housing (12) in which the following elements are arranged: - a laser cavity (20) bounded by a reflecting mirror (M1) and a partially reflecting mirror (M2), the partially reflecting mirror forming the exit of the laser cavity for a laser beam amplified in the laser cavity, - an optical fibre (22) able to convey the laser beam between the exit of the laser cavity and the world outside the housing, the optical fibre being fastened to the housing at least at one fastening point (P1, P2), and - a selective component (24) able to select the wavelength of the laser beam output from the laser device, the selective component being positioned in the optical fibre at the exit of the laser cavity and upstream of the one or more fastening points.

Inventors

  • LOPEZ, THIERRY

Assignees

  • 3SP Technologies

Dates

Publication Date
20260513
Application Date
20240702

Claims (12)

  1. 1. Laser device (10) comprising a housing (12) in which the following elements are arranged: - a laser cavity (20) delimited by a reflecting mirror (M1) and a partially reflecting mirror (M2), the partially reflecting mirror (M2) forming the output of the laser cavity (20) for a laser beam amplified in the laser cavity (20), - an optical fiber (22) capable of conveying the laser beam between the exit of the laser cavity (20) and the exterior of the housing (12), the optical fiber (22) being fixed to the housing (12) at at least one fixing point (P1, P2), and - a selective component (24) capable of selecting the wavelength of the laser beam at the output of the laser device (10), the selective component (24) being positioned in the optical fiber (22) at the output of the laser cavity (20) and upstream of the fixing point(s) (P1, P2).
  2. 2. Laser device (10) according to claim 1, in which the selective component (24) is a Bragg grating.
  3. 3. A laser device (10) according to claim 1 or 2, wherein the housing (12) has an outlet (26), the optical fibre (22) being fixed to the housing (12) at a first and a second fixing point (P1, P2), the first fixing point (P1) being between the outlet of the laser cavity (20) and the outlet of the housing (12), the second fixing point (P2) coinciding with the outlet (26) of the housing (12), the selective component (24) being positioned between the outlet of the laser cavity (20) and the first fixing point (P1).
  4. 4. Laser device (10) according to any one of claims 1 to 3, in which the selective component (24) is positioned at a distance less than or equal to 1 millimeter from the output of the laser cavity (20).
  5. 5. Laser device (10) according to any one of claims 1 to 4, in which the face of the partially reflecting mirror (M2) facing the optical fiber (22) is optimized to transmit, into the laser cavity (20), a laser beam at the selection wavelength of the selective component (24).
  6. 6. Laser device (10) according to any one of claims 1 to 5, in which the reflection spectrum of the selective component (24) has a chosen bandwidth to retain only one or two laser modes of the laser beam, advantageously only one mode of the laser beam.
  7. 7. Laser device (10) according to any one of claims 1 to 6, in which the reflection spectrum of the selective component (24) has a bandwidth less than or equal to five times the free spectral range (FSR) of the laser cavity (20), preferably less than or equal to 0.5 nanometers, preferably less than or equal to 0.3 nanometers.
  8. 8. Laser device (10) according to any one of claims 1 to 7, in which the reflection spectrum of the selective component (24) is apodized.
  9. 9. Laser device (10) according to any one of claims 1 to 8, in which the optical fiber (22) comprises an optic (32) capable of focusing the laser beam in the optical fiber (22), the optic (32) being positioned in the optical fiber (22), between the output of the laser cavity (20) and the selective component (24), the optic (32) preferably being a lens machined in the optical fiber (22).
  10. 10. Laser device (10) according to any one of claims 1 to 9, in which the laser cavity (20) is a rectilinear cavity.
  11. 11. A laser device (10) according to any one of claims 1 to 9, wherein the laser cavity (20) is a curved cavity.
  12. 12. The laser device (10) of any one of claims 1 to 11, wherein the laser housing (12) has a length less than or equal to the length of the laser cavity (20) plus 8 millimeters.

Description

DESCRIPTION TITLE: Laser device The present invention relates to a laser device. Known from the state of the art are laser devices comprising, in a housing, a laser cavity capable of generating a transverse single-mode laser beam and a single-mode optical fiber capable of conveying the laser beam generated by the cavity to the output of the housing. To select and stabilize the wavelength of the laser beam generated by the laser cavity, it is known to use a component, such as a Bragg grating, in particular a Bragg grating inscribed in an optical fiber (in English "Fiber Bragg Grating", abbreviated to FBG). Such a component is traditionally positioned in the optical fiber, outside the housing. Currently, a challenge is to gain compactness by integrating external components into the housing, in particular the FBG. However, the integration of the FBG into the package causes significant wavelength jumps and power jumps when the laser diode current varies, which degrade the spectral and power stability of the laser beam at the fiber output. This is problematic for some envisaged applications, including Erbium-doped fiber amplifier (EDFA) pumping applications, but also frequency doubling and optical metrology applications, such as optical clock experiments. There is therefore a need for a laser device that is compact while maintaining good spectral and power stability of the laser beam at the fiber output. For this purpose, the present description relates to a laser device comprising a housing in which the following elements are arranged: a laser cavity delimited by a reflecting mirror and a partially reflecting mirror, the partially reflecting mirror forming the output of the laser cavity for a laser beam amplified in the laser cavity, - an optical fiber capable of carrying the laser beam between the exit of the laser cavity and the exterior of the housing, the optical fiber being fixed to the housing at at least one fixing point, and a selective component capable of selecting the wavelength of the laser beam at the output of the laser device, the selective component being positioned in the optical fiber at the output of the laser cavity and upstream of the fixing point(s). According to particular embodiments, the device comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations: - the selective component is a Bragg grating; - the housing has an outlet port, the optical fiber being fixed to the housing at a first and a second fixing point, the first fixing point being between the outlet of the laser cavity and the outlet port of the housing, the second fixing point coinciding with the outlet port of the housing, the selective component being positioned between the outlet of the laser cavity and the first fixing point; - the selective component is positioned at a distance less than or equal to 1 millimeter from the output of the laser cavity; - the face of the partially reflecting mirror facing the optical fiber is optimized to transmit, into the laser cavity, a laser beam at the selection wavelength of the selective component; - the reflection spectrum of the selective component has a bandwidth chosen to retain only one or two laser modes of the laser beam, advantageously a single mode of the laser beam; - the reflection spectrum of the selective component has a bandwidth less than or equal to five times the free spectral interval of the laser cavity, preferably less than or equal to 0.5 nanometers, preferably less than or equal to 0.3 nanometers; - the reflection spectrum of the selective component is apodized; - the optical fiber comprises an optic suitable for focusing the laser beam in the optical fiber, the optic being positioned in the optical fiber, between the output of the laser cavity and the selective component, the optic preferably being a lens machined in the optical fiber; - the laser cavity is a rectilinear cavity; - the laser cavity is a curved cavity; and - the laser housing has a length less than or equal to the length of the laser cavity plus 8 millimeters. Other features and advantages of the invention will become apparent upon reading the following description of embodiments of the invention, given by way of example only and with reference to the drawings which are: - [Fig 1] figure 1, a schematic sectional view of an example of a laser device, - [Fig 2] Figure 2, a graphical representation of an example of the modes of a laser beam generated by a laser cavity, and superimposed the reflection spectrum of a first selective component and a second selective component (Bragg gratings), the first and second selective components having different bandwidths (1.2 nm versus 0.25 nm), - [Fig 3] figure 3, a graphical representation of an example of the evolution of the optical power and of the derivative of the optical power as a function of the laser current for a laser device having a selective FBG component positioned less than 1 mm from t