Laser oscillation device

1. A laser oscillation device comprising:

a first substrate which has a flat surface;

a second substrate which has a flat surface and is disposed above the first substrate in such a manner that a wedge cell having a thickness-change direction is formed between the first substrate and the second substrate; and

a liquid crystal layer which is formed by two or more liquid crystals which are doped by one or more laser dyes and injected into the wedge cell and have different pitches,

wherein the wedge cell forms a different thickness by the flat surface of the first substrate and the flat surface of the second substrate,

wherein the two or more liquid crystals diffuse in the wedge cell having the different thickness to form consecutive pitch gradients to form a one-dimensional laser cavity array with a continuously changing cavity length,

wherein, in the wedge cell along the thickness-change direction of the wedge cell, a continuous linear increase in optical pitch is caused by diffusion, a pitch gradient matching with a slope of the cell thickness, and

wherein the first substrate and the second substrate are coated with alignment layers.

2. The laser oscillation device of claim 1 , wherein after the consecutive pitch gradients are formed, ultraviolet (UV) rays are radiated or heat is applied to polymerize the two or more liquid crystals.

3. The laser oscillation device of claim 1 , further comprising at least two different thickness spacers which are disposed on sides of the first and second substrates to form the wedge cell.

4. The laser oscillation device of claim 3 , wherein heights of the at least two different thickness spacers corresponding to a distance between the first and second substrates are different from each other, and

wherein a distance between the two different thicknesses spacers is such that the pitch gradient is a continuous pitch gradient that matches with the slope of the cell thickness.

5. The laser oscillation device of claim 1 , wherein the two or more liquid crystals are respectively injected into a side of the wedge cell having a thick thickness and another side of the wedge cell having a thin thickness in opposite directions.

6. The laser oscillation device of claim 1 , wherein:

the two or more liquid crystals are cholesteric compounds with laser dyes or cholesteric liquid crystals which are formed of a nematic liquid crystal, chiral dopant, and laser dyes; and

the different pitches are determined by a relative concentration ratio between the nematic liquid crystal and the chiral dopant.

7. The laser oscillation device of claim 1 , wherein the one-dimensional laser cavity array with the pitch gradient provides a continuous laser wavelength tuning in a broad spectral range, with a tuning resolution of Δλ<1 nm by a laser pumping.

8. The laser oscillation device of claim 1 , wherein the substrates are planar and coated with alignment layers which are rubbed.