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

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.