CN104795482B - A kind of preparation method of LED photonic crystal - Google Patents

Abstract

The present invention relates to a kind of preparation method of LED photonic crystal, using Nd：The frequency tripled laser Shu Zuowei direct etching laser of YAG laser, wavelength is λ, it is divided into three beams coherent laser through beam splitter, any two beams coherent laser forms identical angle theta between the three beams coherent laser, and the three beams coherent laser is respectively provided with identical polarization direction, and converge in simultaneously on the transparent electrode thin film of LED chip；By giving Nd：One or more pulse of YAG laser, has eventually formed the photonic crystal with some cycles T and pore size.This method can once complete to prepare photonic crystal in chip surface, and technique is simple, convenient and swift, without burying, post-treating and other steps；The prepared photonic crystal cycle is controllable, and the photonic crystal that the cycle is 300nm μm is can obtain by changing the scope of angle theta；Working (finishing) area is big, processing low cost, it is adaptable to mass, large-scale production.

Description

A kind of preparation method of LED photonic crystal

technical field

The invention relates to the field of photonic crystals, and more specifically, to a preparation method of LED photonic crystals.

Background technique

Photonic crystals refer to artificial periodic dielectric structures with photonic band gap characteristics, and photonic crystals are one of the important ways to improve the light extraction efficiency of GaN-based blue LEDs. Theoretically, photonic crystals improve LED light extraction efficiency by utilizing the photonic crystal bandgap structure corresponding to the output light wavelength of the LED, and converting the guided wave mode confined in the light-emitting layer into a radiation mode. For an LED with a given output light wavelength, a photonic crystal with a specific lattice type and geometric structure is prepared on its surface. Generally, the photonic crystal with this structure is required to have a photonic band gap at the light wavelength (or frequency). Most of the existing methods for preparing photonic crystals use electron beam lithography, holographic lithography and other methods, which seem to be relatively easy to implement from the perspective of technology, but for LEDs in the visible light range, the photons of the central wavelength must be within the band gap. The period should be as small as the wavelength fraction, generally more than 100 nanometers. The processing equipment to realize this nanoscale is complex, with many process steps, high cost and small output, which is not convenient for batch and large-scale production.

Contents of the invention

The invention provides a method for preparing LED photonic crystals in order to solve the problems in the prior art that the nano-processing technology for preparing photonic crystals is difficult, the process steps are complicated, the cost is high, and it is not conducive to large-scale production.

The technical solution of the present invention is realized in the following way: a preparation method of LED photonic crystal, said method comprises adopting the three-frequency laser beam of Nd:YAG laser as the direct etching laser, the wavelength is λ, and is divided into three parts by a beam splitter A coherent laser beam, any two coherent laser beams among the three coherent laser beams form the same angle θ, and the three coherent laser beams all have the same polarization direction, and converge on the transparent electrode film of the LED chip at the same time; by giving One or more pulses of Nd:YAG laser, and finally a photonic crystal with a certain period T and aperture size is formed.

Further, the splitting of the beam splitter into three beams of coherent laser light includes the following steps:

a. After the frequency tripled laser beam passes through the diaphragm, it is divided into a first beam and a second beam by a first beam splitter;

b. The first light beam is divided into a third light beam and a fourth light beam through a second beam splitter; the second light beam is divided into a fifth light beam and a sixth light beam through a third beam splitter;

c. The third light beam, the fourth light beam and the fifth light beam are respectively modulated by polarizers and mirrors and converged on the transparent electrode film of the LED chip at the same time, that is, the third light beam passes through the first polarizer and then passes through the second light beam. The seventh beam is reflected by a mirror, the fourth beam is reflected by the second mirror and then the eighth beam is formed by the second polarizer, and the fifth beam is formed by the third polarizer and then reflected by the third mirror The ninth light, finally the seventh light, the eighth light and the ninth light have the same polarization direction and the same phase or the phase difference is an integer multiple of 2π, and converge on the transparent electrode film of the LED chip at the same time .

Further, the sixth light beam is directly input to an optical power meter for detecting and monitoring the power of the Nd:YAG laser.

Further, the relationship between the included angle and the period T of the photonic crystal is

Further, the included angle θ ranges from 10° to 40°.

Further, the more pulses given to the Nd:YAG laser, the larger the aperture of the formed photonic crystal.

Further, the direction of the bisector of the three-dimensional cone angle formed by the seventh light beam, the eighth light beam and the ninth light beam is consistent with the normal direction of the surface of the transparent electrode film of the LED chip.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The process of the present invention can complete the preparation of photonic crystals on the surface of the chip at one time, and the process is simple, convenient and quick, and does not require steps such as masking and post-processing;

(2) The period of the photonic crystal prepared by the present invention is controllable, and a photonic crystal with a period of 300nm-several μm can be obtained by changing the range of the included angle θ. Compared with an LED chip without a photonic crystal, an LED chip with a photonic crystal Luminous power increased by 50-110%;

(3) The process of the present invention has large processing area and low processing cost, and is suitable for batch and large-scale production.

Description of drawings

Fig. 1 is a schematic diagram of the optical path for preparing LED photonic crystals by the method of the present invention.

Among them, G, aperture, F1, the first beam splitter, F2, the second beam splitter, F3, the third beam splitter, B1, the first polarizer, B2, the second polarizer, B3, the third Polarizer, S1, first reflector, S2, second reflector, S3, third reflector L, optical power meter.

detailed description

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

As shown in Figure 1, the three-frequency laser beam (355nm) of Nd:YAG laser is used as the direct etching laser. On the GaN chip, photonic crystals with different periods and different depths of the triangular lattice are prepared on the ITO layer. After the frequency tripled laser beam passes through the diaphragm G, it is divided into a first beam and a second beam through the first beam splitter F1; the first beam is divided into a third beam and a fourth beam through the second beam splitter F2; The second beam is divided into a fifth beam and a sixth beam by the third beam splitter F3; the sixth beam is directly input to the optical power meter L for detecting and monitoring the power of the Nd:YAG laser. The third light beam, the fourth light beam and the fifth light beam are respectively modulated by polarizers and reflectors and converged on the transparent electrode film of the LED chip at the same time, that is, the third light beam passes through the first polarizer B1 and then passes through the first polarizer B1. The seventh beam is reflected by the mirror S1, the fourth beam is reflected by the second mirror S2 and then passed through the second polarizer B2 to form the eighth beam, and the fifth beam is reflected by the third beam after passing through the third polarizer B3 The mirror S3 reflects to form the ninth light beam, and finally the seventh light beam, the eighth light beam and the ninth light beam have the same polarization direction and the same phase or the phase difference is an integer multiple of 2π, and are converged on the LED chip at the same time On the transparent electrode film, the direction of the bisector of the three-dimensional cone angle formed by the three beams of light is consistent with the normal direction of the surface of the transparent electrode film of the LED chip. Any two coherent laser beams among the three coherent laser beams form the same angle θ, the angle range is 10°-40°, and the relationship between the angle and the period T of the photonic crystal is: The larger the angle θ is, the smaller the period of the photonic crystal is, the more pulses are given to the Nd:YAG laser, and the larger the aperture of the formed photonic crystal is. When the included angle θ=23.68°, T=0.51 μm, the LED chips with photonic crystal and without photonic crystal are tested, and the LED of this embodiment emits light when the threshold voltage is above 2.4V and within the voltage range of 2.8-4.0V 90% more power.

Example 2

As shown in Figure 1, the three-frequency laser beam of Nd:YAG laser is used as the direct etching laser. On the GaN chip, photonic crystals with different periods and different depths of the triangular lattice are prepared on the ITO layer. The three After the frequency-doubled laser beam passes through the diaphragm G, it is divided into a first beam and a second beam through the first beam splitter F1; the first beam is divided into a third beam and a fourth beam through the second beam splitter F2; The second beam is divided into a fifth beam and a sixth beam by the third beam splitter F3; the sixth beam is directly input to the optical power meter L for detecting and monitoring the power of the Nd:YAG laser. The third light beam, the fourth light beam and the fifth light beam are respectively modulated by polarizers and reflectors and converged on the transparent electrode film of the LED chip at the same time, that is, the third light beam passes through the first polarizer B1 and then passes through the first polarizer B1. The seventh beam is reflected by the mirror S1, the fourth beam is reflected by the second mirror S2 and then passed through the second polarizer B2 to form the eighth beam, and the fifth beam is reflected by the third beam after passing through the third polarizer B3 The mirror S3 reflects to form the ninth light beam, and finally the seventh light beam, the eighth light beam and the ninth light beam have the same polarization direction and the same phase or the phase difference is an integer multiple of 2π, and are converged on the LED chip at the same time On the transparent electrode film, the direction of the bisector of the three-dimensional cone angle formed by the three beams of light is consistent with the normal direction of the surface of the transparent electrode film of the LED chip. Any two coherent laser beams among the three coherent laser beams form the same angle θ, and the range of the included angle is 10°-40°. When the included angle is preferably 13.68°, the relationship between the included angle and the period T of the photonic crystal is: T = 867nm. The higher the number of pulses given to the Nd:YAG laser, the larger the aperture of the formed photonic crystal. The LED chips with and without photonic crystals were tested, and the luminous power of the LED in this embodiment increased by 50% when the threshold voltage was above 2.4V and within the voltage range of 2.8-4.0V. Example 3

As shown in Figure 1, the three-frequency laser beam of Nd:YAG laser is used as the direct etching laser. On the GaN chip, photonic crystals with different periods and different depths of the triangular lattice are prepared on the ITO layer. The three After the frequency-doubled laser beam passes through the diaphragm G, it is divided into a first beam and a second beam through the first beam splitter F1; the first beam is divided into a third beam and a fourth beam through the second beam splitter F2; The second beam is divided into a fifth beam and a sixth beam by the third beam splitter F3; the sixth beam is directly input to the optical power meter L for detecting and monitoring the power of the Nd:YAG laser. The third light beam, the fourth light beam and the fifth light beam are respectively modulated by polarizers and reflectors and converged on the transparent electrode film of the LED chip at the same time, that is, the third light beam passes through the first polarizer B1 and then passes through the first polarizer B1. The seventh beam is reflected by the mirror S1, the fourth beam is reflected by the second mirror S2 and then passed through the second polarizer B2 to form the eighth beam, and the fifth beam is reflected by the third beam after passing through the third polarizer B3 The mirror S3 reflects to form the ninth light beam, and finally the seventh light beam, the eighth light beam and the ninth light beam have the same polarization direction and the same phase or the phase difference is an integer multiple of 2π, and are converged on the LED chip at the same time On the transparent electrode film, the direction of the bisector of the three-dimensional cone angle formed by the three beams of light is consistent with the normal direction of the surface of the transparent electrode film of the LED chip. Any two coherent laser beams form the same angle θ between the three coherent laser beams, and the range of the included angle is 10°-40°. When the included angle is preferably 26.68°, the relationship between the included angle and the period T of the photonic crystal is: The photonic crystal period is 456nm. The higher the number of pulses given to the Nd:YAG laser, the larger the aperture of the formed photonic crystal. The LED chips with and without photonic crystals were tested, and the luminous power of the LED in this embodiment increased by 110% when the threshold voltage was above 2.4V and within the voltage range of 2.8-4.0V.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (6)

1. a kind of preparation method of LED photonic crystal, it is characterised in that methods described includes using Nd：The frequency tripling of YAG laser Laser beam is as direct etching laser, and wavelength is λ, is divided into through beam splitter between three beams coherent laser, the three beams coherent laser Any two beams coherent laser forms identical angle theta, and the three beams coherent laser is respectively provided with identical polarization direction, and converges simultaneously On the transparent electrode thin film of LED chip；By giving Nd：One or more pulse of YAG laser, having eventually formed has Some cycles T and pore size photonic crystal；

The beam splitter is divided into three beams coherent laser and comprised the following steps：

A, the frequency tripled laser beam are divided into the first light beam and the second light beam after diaphragm (G) by the first beam splitter (F1)；

B, first light beam are divided into the 3rd light beam and the 4th light beam by the second beam splitter (F2)；Second light beam passes through Three beam splitters (F3) are divided into the 5th light beam and the 6th light beam；

C, the 3rd light beam, the 4th light beam and the 5th light beam after polarizer, speculum modulation respectively by converging simultaneously On the transparent electrode thin film of the LED chip, i.e. the 3rd light beam is anti-by the first speculum (S1) by the first polarizer (B1) Penetrate to form the 7th beam light, the 4th light beam forms the 8th beam light after reflecting through the second speculum (S2) through the second polarizer (B2), with And the 5th light beam reflect to form the 9th beam light by the 3rd speculum (S3) by the 3rd polarizer (B3), last 7th beam The integral multiple that light, the 8th beam light and the 9th beam light have identical polarization direction and same phase or phase difference is 2 π, and together When converge on the transparent electrode thin film of the LED chip.

2. the preparation method of LED photonic crystal according to claim 1, it is characterised in that the 6th light beam is directly defeated Enter to light power meter (L), for detecting and monitoring Nd：The power of YAG laser.

3. the preparation method of LED photonic crystal according to claim 1, it is characterised in that the angle and photonic crystal Relation between cycle T is

4. the preparation method of LED photonic crystal according to claim 1, it is characterised in that the scope of the angle theta is 10 °~40 °.

5. the preparation method of LED photonic crystal according to claim 1, it is characterised in that give the Nd：YAG laser The number of pulses of device is more, and the aperture of the photonic crystal of the formation is bigger.

6. the preparation method of LED photonic crystal according to claim 1, it is characterised in that the 7th light beam, the 8th light The angular bisector direction and the transparent electrode thin film surface of the LED chip for the three-dimensional cone angle that beam and the 9th light beam three are formed Normal direction it is consistent.