CN102005688A - Method for preparing slab waveguide laser device in neodymium-doped lutecium vanadate crystal - Google Patents

Abstract

The invention relates to a method for preparing a slab waveguide laser device in a neodymium-doped lutecium vanadate crystal, belonging to the technical field of optoelectronic device preparation. The method mainly comprises the following steps of: forming a slab waveguide in the neodymium-doped lutecium vanadate crystal and realizing the laser output on the slab waveguide. A femtosecond laser the pulse repetition rate of which is 200 KHz, the energy of which is 2-17 millijoule/pulse and the write-in speed of which is 0.2-15mm/second is adopted to form the slab waveguide in the neodymium-doped lutecium vanadate crystal. After laser resonant cavity film coating is carried out on the end surface of the waveguide, a pumping laser is utilized to carry out pumping on the neodymium-doped lutecium vanadate slab waveguide to output an infrared laser the wave length of which is 1063+/-1 or 1340+/-1nm.

Description

Method for preparing strip waveguide laser device in neodymium-doped lutetium vanadate crystal

technical field

The invention relates to a method for preparing a strip waveguide laser device in a neodymium-doped lutetium vanadate crystal, belonging to the technical field of optoelectronic device preparation.

Background technique

Neodymium-doped lutecium vanadate (Nd doped lutecium vanadate, or Nd:LuVO ₄ for short) crystal is a widely used laser gain medium, with strong polarization absorption, large stimulated emission cross section, high absorption coefficient, Broad absorption band, small dependence on pump wavelength, low lasing threshold. It can generate laser with a wavelength of 1064 or 1340 nanometers, and has important applications in laser processing, integrated optics, and optical communications. A waveguide is a basic element of integrated optics, which is defined as a high-refractive-index region with a high refractive index relative to the circumferential medium. In waveguides, light beams are confined to propagate in high-refractive-index media due to the principle of total reflection. According to the way light is restricted in the waveguide, it can be divided into planar waveguide (restricting the propagation of light in one direction) and strip waveguide (restricting the propagation of light in two directions). The waveguide prepared by the gain medium material is pumped under certain conditions, and the waveguide laser can be output. The waveguide structure can confine the energy of light in a very small cross-sectional area, and can achieve high energy density at low incident energy, so the pumping threshold of waveguide lasers is much lower than that of bulk materials. Moreover, in the waveguide, the overlapping area of the pump light and the waveguide laser is large, so that a large pumping efficiency can be achieved. In addition, the ratio of the length of the waveguide to the diameter of the end face is large, which is conducive to heat dissipation and greatly reduces the thermal effect of the waveguide laser. There are many ways to prepare waveguides, such as ion implantation, pulsed laser deposition, femtosecond laser writing, diffusion, etc. In 2005 and 2007, "Journal of Crystal Growth" and "Applied Surface Science" respectively reported the preparation of Nd: _LuVO planar waveguide by pulsed laser deposition technology and ion implantation technology (Journal of Crystal Growth 281, 426 (2005), Applied Surface Science 253, 9311(2007)), etc. There is no report on the fabrication of strip waveguides. There are also no reports on waveguide lasers.

Contents of the invention

The invention provides a method for fabricating a strip waveguide in a neodymium-doped lutetium vanadate (hereinafter abbreviated as Nd:LuVO ₄ ) crystal by direct writing with a 350 fs femtosecond laser and realizing the output waveguide laser.

1) Polishing the two surfaces perpendicular to the crystal axis of the neodymium-doped lutetium vanadate crystal, that is, the c-axis direction, and cleaning the polished sample;

2) Use a femtosecond laser to burn the sample along the a or b-axis direction of the crystal through any polished surface to produce two traces with a distance of 20 or 30 microns, and form a strip waveguide between the two traces; The pulse repetition frequency of the second laser is 200 kHz, the energy is 2 to 17 microjoules per pulse, the writing speed is 0.2 to 15 millimeters per second femtosecond laser, the wavelength is 1047 nanometers, and the pulse width is 350 femtoseconds;

3) polishing the two end faces of the crystal perpendicular to the direction of the strip waveguide;

4) Coating a laser resonant cavity film on the polished end face to form a strip-shaped neodymium-doped lutetium vanadate crystal waveguide laser device;

5) Using a light source to pump a strip waveguide of a neodymium-doped lutetium vanadate crystal to generate waveguide laser light with a wavelength of 1063±1 nm or 1340±1 nm.

Using femtosecond laser writing is low cost, strong arbitrariness, and high controllability; the change of the refractive index in the waveguide region and the adjustment of the waveguide mode can be realized by adjusting the energy, pulse, and writing speed of the femtosecond laser. The output of waveguide lasers can be enhanced by precisely tuning the matching of coupling modes.

Description of drawings

Fig. 1 is a process flow diagram of the present invention;

Fig. 2 Schematic diagram of the fabrication process of neodymium-doped lutetium vanadate crystal waveguide by femtosecond laser direct writing;

Fig. 3 is the generation schematic diagram that neodymium-doped lutetium vanadate crystal stripe waveguide laser produces;

In the figure: 1. Femtosecond laser, 2. Neodymium-doped lutetium vanadate crystal, 3. Strip waveguide, 4. Laser writing trace, 5. Pump light, 6. Polarizer, 7. Input end of laser resonator Coating, 8. Coating at the output end of the laser resonator, 9. Convex lens, 10. Waveguide laser.

Detailed ways

Embodiment 1: Method for preparing strip waveguide laser device in neodymium-doped lutetium vanadate crystal

1) Polishing the two surfaces perpendicular to the crystal axis direction (c-axis) of the neodymium-doped lutetium vanadate crystal (2), and cleaning the polished sample;

2) Use a femtosecond laser (1) to burn the sample along the a-axis direction of the crystal through any polished surface to produce two traces with a distance of 30 microns. A strip waveguide (3) is formed between the two traces. Use a femtosecond laser (1) with a pulse repetition frequency of 200 kHz, an energy of 8 μJ/pulse, a writing speed of 1 mm/s, a wavelength of 1047 nm, and a pulse width of 350 femtoseconds.

3) Polishing the two end faces of the crystal perpendicular to the direction of the strip waveguide.

4) Coating the laser cavity film (7, 8) on the polished end face. The resonant cavity film in the direction of passing light is required to pass through 99% of light with a wavelength of 790-810 nanometers, and reflect 99% of light with a wavelength of 1055-1090 nm (7). The requirement for the resonant cavity film in the output direction is that the wavelength is 790- 99% reflection of light at 810 nanometers, and 95% reflection (8) of light with a wavelength of 1055-1090 nanometers, forming a strip-shaped neodymium-doped lutetium vanadate crystal waveguide laser device;

A titanium sapphire laser is used to generate continuous pump light (5) with a center wavelength of 808 nanometers to pump a strip waveguide (3) of a neodymium-doped lutetium vanadate crystal to generate waveguide laser light with a wavelength of 1063±1 nanometers.

Embodiment 2: Method for preparing strip waveguide laser device in neodymium-doped lutetium vanadate crystal

1) Polishing the two surfaces perpendicular to the crystal axis direction (c-axis) of the neodymium-doped lutetium vanadate crystal (2), and cleaning the polished sample;

2) Use a femtosecond laser (1) to burn the sample along the a-axis direction of the crystal through any polished surface to produce two traces with a distance of 30 microns. A strip waveguide (3) is formed between the two traces. Use a femtosecond laser (1) with a pulse repetition frequency of 200 kHz, an energy of 9 microjoules/pulse, a writing speed of 2 mm/s, a wavelength of 1047 nm, and a pulse width of 350 femtoseconds.

3) Polishing the two end faces of the crystal perpendicular to the direction of the strip waveguide.

4) Coating the laser cavity film (7, 8) on the polished end face. The resonant cavity film in the direction of passing light is required to pass through 99% of light with a wavelength of 790-810 nanometers, and reflect 99% of light with a wavelength of 1330-1350 nm (7). The requirement for the resonant cavity film in the output direction is that the wavelength is 790- 99% reflection of light at 810 nanometers, and 95% reflection (8) of light at a wavelength of 1330-1350 nanometers, forming a strip-shaped neodymium-doped lutetium vanadate crystal waveguide laser device;

5) Using a Ti:Sapphire laser to generate continuous pump light with a central wavelength of 808 nm (5) to pump the waveguide (3) of a neodymium-doped lutetium vanadate crystal to generate waveguide laser light with a wavelength of 1340±1 nm.

Claims (2)

1. a method for preparing strip waveguide laser device in neodymium-doped lutetium vanadate crystal, is characterized in that, preparation method is as follows: 1) Polishing the two surfaces perpendicular to the crystal axis of the neodymium-doped lutetium vanadate crystal, that is, the c-axis direction, and cleaning the polished sample; 2) Using a femtosecond laser, burn the sample along the a or b axis of the crystal through any polished surface to produce two traces with a distance of 20 or 30 microns, and form a strip waveguide between the two traces; 3) polishing the two end faces of the crystal perpendicular to the direction of the strip waveguide; 4) Coating a laser resonant cavity film on the polished end face to form a strip-shaped neodymium-doped lutetium vanadate crystal waveguide laser device; 5) Using a light source to pump a strip waveguide of a neodymium-doped lutetium vanadate crystal to generate waveguide laser light with a wavelength of 1063±1 nm or 1340±1 nm. 2. according to the method for preparing strip waveguide laser device in neodymium-doped lutetium vanadate crystal according to claim 1, it is characterized in that: the pulse width of described femtosecond laser is 350 femtoseconds, and pulse repetition frequency is 200 kilohertz, the energy is 2-17 microjoules per pulse, the writing speed is 0.2-15 millimeters per second, and the wavelength is 1047 nanometers.

Images