Method and apparatus for preparing femtosecond optical filament interference direct writing volume grating/chirped volume grating

Patent metadata

Field	Value
Publication number	US-11899229-B2
Application number	US-202117230428-A
Country	US
Kind code	B2
Filing date	Apr 14, 2021
Priority date	Apr 15, 2020
Publication date	Feb 13, 2024
Grant date	Feb 13, 2024

Abstract

The present disclosure discloses a method and apparatus for preparing a femtosecond optical filament interference direct writing volume grating/chirped volume grating. The method is characterized in that optical filaments are formed in glass by using femtosecond pulse laser, and plasma is controlled to quickly scan in the glass and etch a volume grating or chirped volume grating structure by adjusting the focal length of convex lens, laser energy and movement of motor machine. The apparatus includes a femtosecond pulse laser module, a pulse chirp management module, a pulse time domain shaping module, a laser separation and interference module, a glass volume grating processing platform module and a camera online imaging module.

First claim

What is claimed is:

1. A method for preparing a femtosecond optical filament interference direct writing volume grating or a chirped volume grating, wherein femtosecond pulse laser is configured to interfere in glass to form a section of optical filament that is several times a Rayleigh length of a light spot; a plasma, produced by multiphoton ionization of the medium caused by a femtosecond pulse laser, is controlled to rapidly scan in the glass and etch out a structure of the volume grating or the chirped volume grating by adjusting a focal length and laser energy of a focusing lens; and the femtosecond pulse laser has two or more beams, such that the two or more beams reunite at a focal point behind a converging lens after time domain synchronization to generate interference to form a plasma grating or a chirped plasma grating in the glass near the area of focal point.

2. An apparatus for preparing a femtosecond optical filament interference direct writing volume grating or a chirped volume grating, wherein the apparatus comprises a femtosecond pulse laser module, a pulse chirp management module, a pulse time domain shaping module, a laser separation and interference module, a glass volume grating processing platform module and a camera online imaging module; wherein the femtosecond pulse laser module comprises: a femtosecond laser or a picosecond laser, and an adjustable power attenuator; the pulse chirp management module comprises: a first diffraction grating, a second diffraction grating, a mirror with high reflectivity at incident angle of 0°, a first planar mirror, and a second planar mirror; the pulse time domain shaping module comprises a plurality of planar mirrors, a third diffraction grating, a concave mirror, and a pulse shaping template; the laser separation and interference module comprises a plurality of planar mirrors, an optical path collimator, a beam splitting device, a time domain delay controller and a converging lens; the glass volume grating processing platform module comprises: a glass sample and an electrically controlled displacement platform; the camera online imaging module comprises: two convex lenses, a CCD camera and a computer;
the femtosecond pulse laser generated by the femtosecond pulse laser module is incident to the pulse chirp management module; the pulse chirp management module is configured to manage the time-domain chirp or spatial dispersion of incident laser pulse; the pulse time domain shaping module is configured to manipulate incident time domain waveform to modulate the spatial distribution of formed plasma grating; an output laser from prior module is then incident to the laser separation and interference module; the laser separation and interference module is configured to separate the incident laser pulse into two or more beams, the two or more beams of pulses reunite at a focal point behind the converging lens after time domain synchronization to generate interference, and a plasma grating or a chirped plasma grating is formed in the glass near the area of focal point; the glass samples are placed on glass volume grating processing platform module; the glass volume grating processing platform module is configured to move the glass sample and scan the shape of glass volume grating etched by laser induced plasma grating or laser induced chirped-plasma grating; the camera online imaging module is configured to monitor a laser processing condition in the glass sample in real time.

3. The apparatus according to claim 2 , wherein the adjustable power attenuator is a circular rotary neutral density attenuation sheet, a combination of half-wave plate and a Gland prism or a combination of half-wave plate and a polarization beam splitter.

4. The apparatus according to claim 2 , wherein the first diffraction grating and the second diffraction grating in the pulse chirp management module are transmissive diffraction gratings, reflective diffraction gratings or dispersion prisms.

5. The apparatus according to claim 2 , wherein the third diffraction grating in the pulse time domain shaping module is a transmission grating, a reflection grating, a volume grating or a dispersion prism.

6. The apparatus according to claim 2 , wherein the pulse shaping template is an acousto-optic modulator, a liquid crystal spatial modulator, a moving mirror or a deformable mirror.

7. The apparatus according to claim 2 , wherein the beam splitting device is a micro-array mirror configured to divide the pulse laser into a plurality of beams according to a power ratio, a combination of a half-wavelength wave plate and a polarization beam splitter, and a combination of one or more planar beam splitters.

8. The apparatus according to claim 2 , wherein the time domain delay controller comprises a displacement stage and two planar mirrors, and is configured to adjust a time domain difference between the laser pulses to achieve time domain synchronization of a plurality of laser pulses while passing through the focal point of the converging lens.

9. The apparatus according to claim 2 , wherein the converging lens is a plano-convex cylindrical lens, a double-glued cylindrical lens, a circular lens, a micro-lens array or a conical lens.

10. The apparatus according to claim 2 , wherein the glass sample is a six-sided polished rectangular parallelepiped made of fused silica glass, K9 glass, calcium fluoride glass or zinc sulfide crystal.

Assignees

• Chongqing Institute Of East China Normal Univ
• Roi Optoelectronics Tech Co Ltd
• Univ East China Normal

Inventors

• Zeng Heping
• Nan Junyi
• Hu Mengyun
• Yan Ming

Classifications

• G02B5/1857 Primary

  using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams · CPC title

• G03H1/0402

  Recording geometries or arrangements (G03H1/0443, G03H1/0476, G03H1/16 take precedence) · CPC title

• G03H2001/0268

  Inorganic recording material, e.g. photorefractive crystal [PRC] · CPC title

• G03H2222/33

  Pulsed light beam · CPC title

• G03H2240/52

  Exposure parameters, e.g. time, intensity · CPC title