Patent Application
20180292684
The present invention pertains to a laser oscillation device and, more particularly, to a laser oscillation device which uses a wedge cell capable of continuous wavelength tuning lasing in a predetermined wavelength region.
In general, as a laser oscillation device, a cell having a uniform thickness is used. Conventional laser oscillation devices are made by using cholesteric liquid crystals injected into a cell having a uniform thickness in order to realize wavelength tuning and then using pitch or UV tight which varies depending on the temperature of the liquid crystal.
However, the cholesteric liquid crystal structure used in the conventional laser oscillation device functions as a laser resonator, and a cell having a uniform thickness interval corresponds to a Fabry-Perot laser cavity having a fixed length of the laser resonator. Thus, in the case of rasing using a conventional laser oscillation device, the laser shows oscillation of the laser line in a wide wavelength range, but confronts the result of discontinuous laser wavelength variation, that is, discontinuous laser wavelength oscillation.
In order to solve such a problem, in case of the conventional art, a cholesteric liquid crystal having two different pitches in a wedge-shaped cell is injected from both sides of the cell and then a continuous pitch gradient is formed by using diffusion and laser wavelength can be generated.
However, in the case of a general liquid crystal, after a few months, the gradient due to the density of molecules formed disappears due to molecular diffusion, and the change of the laser wavelength is disappeared. Further, in the case of the polymerized liquid crystal, there is a problem that it is difficult to make a process of continuously changing the concentration of the molecules and a long production time is required.
The present disclosure is purposed to provide a laser oscillation device which generates a continuous laser wavelength by forming pitch gradient by a temperature difference in a wedge cell.
The laser oscillation device according to an exemplary embodiment includes a first substrate; a second substrate which is provided above the first substrate and forms a wedge cell between the second substrate and the first substrate; a liquid crystal layer, formed by a liquid crystal having the same pitch, which is injected into the wedge cell; and a temperature controller which is connected to both sides of the wedge cell and controls the temperatures of both sides of the wedge cell to be different from each other.
The injected liquid crystal may form a continuous pitch gradient by a difference of temperature of the wedge cell.
The liquid crystal could be polymerized by radiating UV or applying heat after the pitch gradient may be formed.
The laser oscillation device may further include at least two spacers provided on both sides of the first substrate and the second substrate to form the wedge cell.
The height of the at least two spacers which correspond to a distance between the first substrate and the second substrate may be different from each other.
The liquid crystal may be cholesteric liquid crystal composed of nematic liquid crystal and chiral dopant, and wherein the pitch may be determined based on relative concentration ratio of the nematic liquid crystal and the chiral dopant.
As described above, according to various embodiments of the present invention, it is possible to provide a laser oscillation device that generates a continuous laser wavelength which can be semi-permanently used, and can reduce the manufacturing time of the laser oscillation device.
The present embodiment will be further described with reference to the enclosed drawings.
Referring to
In order to fabricate the laser oscillation device 100, a cell must be made first. To do this, a polyimide is coated on the upper surface of the first substrate 110 and the lower surface of the second substrate 120 and the coated polyimide film is rubbed-polyimide to form liquid crystal alignment layers 115 and 125. The liquid crystal alignment layers 115 and 125 may be formed of various materials such as polyamide, polyamide-imide and polyphenylene oxide as well as polyimide.
After the rubbing process, a first spacer 130 and a second spacer 140 having different sizes (for example, different in height (h1, h2)) are provided between the first substrate 110 and the second substrate 120 to form a wedge cell in a hollow stale between the first substrate 110 and the second substrate 120. That is, in order to form a wedge-shaped cell between the first substrate 110 and the second substrate 120, the first spacer 110 and the second spacer 120 are provided on both sides between the first substrate 110 and the second substrate 120.
When the wedge-shaped cells are formed as shown in
The cholesteric liquid crystal is produced by mixing a nematic liquid crystal with a chiral dopant. The pitch of the liquid crystal can be determined according to the ratio of the nematic liquid crystal mixed with the cholesteric liquid crystal to the chiral dopant. At this time, various laser dyes can be added to the cholesteric liquid crystal as necessary to broaden or narrow the laser wavelength band.
The laser dye can use a dye having a fluorescence spectral range in a region where laser oscillation is to be continuously performed. That is, laser dyes having a fluorescence spectral range can be added to each cholesteric liquid crystal in a region where laser tuning is to be performed.
The cholesteric liquid crystal having the same pitch is injected into the wedge-shaped cells between the first substrate 110 and the second substrate 120. After a predetermined period of time, a laser resonator may be formed. Specifically, a laser resonator array in which the length of the pitch continuously increases and decreases in the X-axis direction after a certain period of time is passed from injecting the cholesteric liquid crystal at room temperature may be formed. In this case, one or more pigments may be added to the cholesteric liquid crystal. Also, the pitch can be proportional to the thickness (d) of the wedge-shaped cell. That is, as the thickness (d) of the wedge-shaped cell increases, the length of one pitch may increase.
Referring to
Further, the position of the band gap can be determined by adjusting the relative concentration ratio of the nematic liquid crystal and the chiral dopant in the case of the cholesteric liquid crystal. In the case of using a pump beam as the laser, the laser whose tuning wavelength is continuously tuned can be oscillated by moving the position of the pump beam from the side where the thickness (d) of the wedge-shaped cell from a larger thickness to a smaller thickness.
In addition, this laser oscillation device can actively change the laser wavelength generated by using a cholesteric liquid crystal wedge type cell to which a dye is added. Specifically, by making one cholesteric liquid crystal wedge-shaped cell have a high temperature at one end and a low temperature at the other end, a temperature gradient is formed in the cell to form a pitch gradient of the liquid crystal by temperature It is possible to generate a continuous laser wavelength.
According to an embodiment of the present invention, after the cholesteric liquid crystal is injected into the wedge-shaped cell, the temperature of both sides of the wedge-shaped cell is controlled differently, and the continuous wavelength variable Polymer Cholesteric Liquid Crystal (PCLC) can be fabricated by irradiating UV light or applying heat at the time when the resonator is formed. The time at which the continuous wave-length variable resonator is formed, that is, the time at which UV light or heat is applied, can be determined by a choice of a person designing the invention, and the person designing the invention can select a different viewpoint for each desired wavelength variable region.
Referring to
Referring to
In addition, the cholesteric liquid crystal forms a continuous pitch gradient by the combination of the wedge-shaped cell structure and the temperature gradient, thereby forming a continuous laser resonator array to continuously generate the laser wavelength in a wide wavelength region.
Referring to
In addition, when a resonator is fabricated by forming a temperature gradient in the form of a wedge-shaped cell, the length of the resonator can be continuously varied, and a cholesteric liquid crystal having a pitch corresponding to a mode for continuously varying the length of the resonator may form pitch gradient in a resonate and continuously oscillate lasing.
In addition, the continuously tunable lasing interval can be adjusted by changing the relative concentration ratio of the nematic liquid crystal and chiral dopant, or by changing the point at which the solidification is performed by irradiating the UV. Therefore, even when fabricating a laser oscillation device using UV curable PCLC, it is possible to continuously change the wavelength in a section of several hundred nanometers or more, that is, 100 nm or more.
According to the present invention, it is possible to realize a continuous wide-wavelength variable lasing in a visible region (VIS region) by using cholesteric or polymeric cholesteric in a non-polymeric form, and this principle may be applied to both the ultraviolet rays (UV) region, visible rays (VIS) region, or infrared rays (IR) region, and it is possible to realize continuous wavelength modulation in a range of several tens of nanometers or several hundreds of nanometers.
That is, according to the present invention, it is possible to manufacture a laser capable of continuously variable wavelength lasing in a range of several hundreds nm or more in a wedge-shaped optical device fabricated from a cholesteric liquid crystal and a laser dye. In particular, since the present invention can continuously generate a monochromatic laser line in a range of about 100 nm or more without any additional optical element, it is possible to manufacture a tunable laser of an ultrasmall size and high efficiency, and this can be used independently as a laser source.
The present invention is also more efficient than the conventional continuous variable tunable laser system, Optical Parametric Oscillator (OPO), and provides all of the advantages offered by conventional cholesteric liquid crystal lasers. Accordingly, the present invention can be applied not only to lasers but also to optical science, spectroscopic optical devices, and optical industry, and in particular, it can increase the signal transmission efficiency of optical communication when applied to optical communication.
The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the inventive concept. The exemplary embodiments may be readily applied to other types of device or apparatus. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the inventive concept, and many alternatives, modifications, and variations will be apparent to those skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0075881 | May 2015 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2016/000836 | 1/27/2016 | WO | 00 |
