Summary of the invention
The object of the present invention is to provide preparation facilities and the method thereof of the anti-reflection structure of a kind of sub-wavelength, for solving the graphical complicated process of preparation of window material in prior art, the technical problem that light transmittance is undesirable.
For achieving the above object, technical scheme proposed by the invention is:
The preparation facilities of the anti-reflection structure of a kind of sub-wavelength of the present invention, it comprises: computer control module, laser instrument, optical delivery assembly, galvanometer assembly, focusing system components, and processing platform; Described optical delivery assembly, galvanometer assembly, focusing system components are arranged along laser optical path successively, the laser parameter of laser instrument transmitting is controlled by described computer control module, and control galvanometer assembly and processing platform action, laser beam is scanned the surface of the work to be added be positioned on processing platform, prepares anti-reflection structure.
Wherein, it is for sapphire, zinc sulphide, zinc selenide, the preparation of the patterned structures of diamond and these window materials of magnesium fluoride.
Wherein, the optical maser wavelength that described laser instrument is launched is 355-1064nm.
Wherein, described galvanometer assembly is preferably 3D galvanometer.
A preparation method for structure that sub-wavelength is anti-reflection, it comprises the following steps:
The first step, according to preparation condition, environment for use parameter, application EFFECTIVE MEDIUM THEORY, obtains structure and the size of sub-wavelength;
Second step, according to laser parameter determination Laser output path;
3rd step, opens laser instrument, prepares the anti-reflection structure of sub-wavelength on workpiece to be processed surface.
Wherein, described sub-wavelength parameter comprises the cycle, dutycycle and height.
Wherein, when preparing for the anti-reflection structure of 3 ~ 5 mu m waveband sapphire surface, the cycle of sub-wavelength is 1.4 μm, and dutycycle is 0.52, is highly 2.9 μm.
Wherein, described laser instrument is psec or altra-fast fs laser instrument.
Compared with prior art, the advantage of the preparation facilities of the anti-reflection structure of this invention sub-wavelength is: equipment is simple, technique is simple, without the need to preparing mask plate, can accurately control sub-wavelength structure size, machining accuracy is less than characteristic size, and preparation efficiency is high, one step completes, LASER Light Source can efficiency of selection high, cost is low.
Detailed description of the invention
Below with reference to accompanying drawing, elaboration is further given to the present invention.
Refer to Fig. 1, the preparation facilities of structure that a kind of sub-wavelength of the present invention is anti-reflection, it comprises: computer control module 7, laser instrument 1, optical delivery assembly 2, galvanometer assembly 4, focusing system components 5, and processing platform 6; Described optical delivery assembly 2, galvanometer assembly 4, focusing system components 5 along laser optical path arrangement, control laser instrument 1 by computer control module 7, according to process requirements, control laser parameter by computer control module 7 successively.And control galvanometer assembly 4 and processing platform 6 action, make laser beam at workpiece surface scan to be added, prepare anti-reflection structure.Preferably, in this embodiment, be also provided with a speculum 3 at optical delivery assembly 2 between galvanometer assembly 4, speculum 3 for changing laser transfer direction, thus reduces the space occupied of this equipment.Wherein, the workpiece to be added of this enforcement is sapphire 8, and sapphire 8 is positioned on processing platform 6, can rotate with processing platform.
Optical delivery assembly 2 is generally beam expanding lens device, is expanded by laser beam, to obtain less focal beam spot.Galvanometer assembly 4 is made up of X galvanometer, Y galvanometer and Z axis linear module, and the Main Function of galvanometer assembly 4 guides light beam downwards, and by controlling the three-dimensional motion that can realize laser beam.Light beam is after focusing system 5, and light beam focuses on work piece surface.
In other embodiments, the preparation facilities of structure that this sub-wavelength is anti-reflection also can be used for sapphire, zinc sulphide, zinc selenide, the preparation of the patterned structures of diamond and these window materials of magnesium fluoride.
Preferably, laser instrument 1 psec or altra-fast fs laser instrument.The optical maser wavelength that laser instrument 1 is launched can be 355-1064nm.Computer control module 7 controls the start and stop of laser instrument 1, and the laser parameter controlling laser instrument transmitting is arranged, and its laser parameter controlled comprises electric current, frequency, sweep speed, machined parameters etc.
Preferably, galvanometer assembly 4 is generally 3D galvanometer.Laser scanning methods can be regulated on three-dimensional.Computer control module 7 also controls the action of galvanometer assembly 4 and processing platform 6 simultaneously, first will the anti-reflection structure graph prepared at sapphire surface be needed to import in computer, by the motion of computer controlled damping mirror assembly 4 and processing platform 6, thus realize graphically preparing accurately.
A preparation method for structure that sub-wavelength is anti-reflection, it comprises the following steps:
First step S1, according to preparation condition, environment for use parameter, application EFFECTIVE MEDIUM THEORY, obtains structure and the size of sub-wavelength;
Second step S2, according to laser parameter determination Laser output path;
3rd step S3, opens laser instrument, prepares the anti-reflection structure of sub-wavelength on workpiece to be processed surface.
Wherein, described sub-wavelength parameter comprises the cycle, dutycycle and height.The account form application EFFECTIVE MEDIUM THEORY of sub-wavelength parameter calculates, and distance is calculated as follows:
The determination in cycle:
Anti-reflection in order to enable patterned structures carry out in broadband, polarizers of big angle scope, and have higher transmitance, and to polarization state not Ning'an, its cycle should meet following formula
Wherein Λ x is the cycle in x direction, and Λ y is the cycle in y direction, and ns is refractive index of substrate, and ni is air refraction, and λ is incident wavelength.
Be Sapphire Substrate in the present embodiment, n
s=1.67, anti-reflection scope is 3-5 μm, and incident wavelength is got
So the patterned structures cycle should meet
But the cycle is not the smaller the better, because the cycle is less, prepare more difficult, preparation accurately can be under some influence.So when meeting anti-reflection requirement, because making structural cycle maximize as far as possible, therefore sapphire should close to 1.40 μm at the anti-reflection structural cycle of 3-5 mu m waveband.
The determination of dutycycle:
According to EFFECTIVE MEDIUM THEORY formula,
Wherein ni is air refraction, n
sfor refractive index of substrate, n
2Dfor equivalent refractive index.
According to the reflectivity of the anti-reflection structure of sapphire sub-wavelength and the relation of equivalent refractive index: when namely equivalent refractive index is 1.29, reflectivity is minimum, and antireflective effect is best.
Can be obtained by formula, when dutycycle is 0.52, equivalent refractive index is 1.29, and now antireflective effect is best, is consistent with theory.Therefore, design sapphire be substrate in the sub-wavelength of 3-5 mu m waveband anti-reflection structure time, dutycycle should be 0.52.
The determination of height:
Have coating theory known, the optical thickness of film material is 1/4th of incident wavelength, namely when height h=3.75/4X1.29 μm=0.726 μm of sub-wavelength structure, has best antireflective effect.
Prepared by patterned structures:
In graphics software, draw the patterned structures (for cylindricality) of above-mentioned parameter: the cycle is 1.40 μm, dutycycle is 0.52, is highly 2.9 μm.Imported in the machining software of computer, setting laser motion path.And suitable laser parameter is set, electric current, power, frequently, sweep speed etc., start processing.Process Computer controls Laser output, and along optical delivery system, speculum, enter galvanometer system and optical focusing system afterwards, laser focusing falls on a sapphire substrate, and starts to process according to the path of setting.Now, laser beam can be selected to be moved by vibration mirror scanning according to processing work size, also can while laser beam be moved by vibration mirror scanning, platform drives workpiece motion s (for adding man-hour on a large scale).
The detection of transmitance:
By Fourier infrared spectrograph test sapphire and graphic sapphire in the transmitance of 3-5 mu m waveband, result is as follows: Sapphire Substrate this be 88% in 3-5 mu m waveband transmitance, preparing after above-mentioned patterned structures is more than 99% in 3-5 mu m waveband transmitance.
In above-mentioned case study on implementation, Sapphire Substrate also can change into is other backing materials, as zinc sulphide, zinc selenide, diamond, magnesium fluoride etc.Also the transmitance of its all band can be prepared in, as the anti-reflection structure of near-infrared, visible waveband.Calculate and preparation method same as described above, the centre wavelength numerical value of the refractive index and corresponding wave band that only need substitute into respective material carries out analog computation, and chooses applicable laser processing parameter and carry out processing.
Preferably, described laser instrument is psec or altra-fast fs laser instrument.
Refer to accompanying drawing 3, the structural representation that it is anti-reflection structure when being cylindric, the anti-reflection structure on workpiece 8 surface to be added is cylindric 81.In other embodiments, structure that this is anti-reflection also can be pyramid-shaped, coniform etc.
Foregoing; be only preferred embodiment of the present invention; not for limiting embodiment of the present invention; those of ordinary skill in the art are according to central scope of the present invention and spirit; can carry out corresponding flexible or amendment very easily, therefore protection scope of the present invention should be as the criterion with the protection domain required by claims.