CN103592770A - RGB three-color light beam combiner and manufacturing method thereof - Google Patents

Abstract

The invention relates to an RGB three-color light beam combiner and a manufacturing method of the RGB three-color light beam combiner. The RGB three-color light beam combiner comprises two identical isosceles rectangular prisms, a transmission position phase holographic grating G1 and a reflection position phase holographic grating G2, wherein the transmission position phase holographic grating G1 and the reflection position phase holographic grating G2 take dichromated gelatin as a holographic recording medium. The peak value strip face of the transmission position phase holographic grating G1 is perpendicular to the surface of the corresponding grating, the peak value strip face of the reflection position phase holographic grating G2 is parallel to the surface of the corresponding grating, the bottom surfaces of the two isosceles rectangular prisms are arranged opposite, and the transmission position phase holographic grating G1 and the reflection position phase holographic grating G2 are respectively placed between the two bottom surfaces and packaged through epoxy resin in an adhesion mode. Grating parameters are determined according to the bragg conditions, optimization design is performed on diffraction efficiency of the transmission VPHG and the reflection VPHG by using the Kogelnik coupled-mode theory, the RGB three-color light beam combiner has the advantages of being high in diffraction efficiency and signal to noise ratio and low in scattering and absorption and can effectively improve the use ratio of light energy, and light beam energy loss is small when the beam combiner is used for beam combining.

Description

A kind of RGB tri-coloured light bundling devices and preparation method thereof

Technical field

The present invention relates to a kind of RGB tri-coloured light bundling devices and preparation method thereof, belong to information optics technical field.

Background technology

Body phase holographic grating (VPHG) has that diffraction efficiency is high, wavelength selectivity and the feature such as angular selectivity is strong, signal to noise ratio (S/N ratio) is high, scattering is low, it is low to absorb and cost of manufacture is cheap, in technical fields such as high resolution spectrometer device, wavelength-division multiplex and pulse compressions, has widespread use.

This century from the beginning of, along with the enhancement day by day to superlaser demand, developed to the theory of laser bundling device and experimental study.1999, Massachusetts Institute Technology's Lincoln laboratory has been invented a set of synthesizer, with plane grating, control the light beam that each device sends different wave length simultaneously, make each light beam near field and far field, realize stack (referring to document: Cook C C and Fan T Y Spectral beam combining of Yb-doped fiber lasers in an external cavity.OSA TOPS, Advanced solid lasers, 1999,26:163-166.).2003, the people such as Igor V and Ciapurin are studied transmission-type body grating spectral beam combining scheme parameter optimization, Gaussian beam has been carried out to analogue simulation, and the diffraction characteristic of reflection-type body grating has been carried out analyzing (referring to document: 1. Ciapurin I V Glebov L B, Smimov V I.Spectral combing of high-power fiber laser beams using Bragg grating in PTR glass.Proc.of SPIE, 2004, 5335:116-124. 2. Ciapurin I V, G1ebov L B.Modeling of Gaussian beam diffraction on vo1ume Bragg gratings in PTR glass[C], Proc.SPIE, 2005, 5742:183-194.).2008, the people such as Andrusyak utilize four reflective Volume Bragg gratings (VBG) to realize the Spectral beam combining of Liao Wu road high power light pricker laser instrument (referring to document: Andrusyak O, Ciapurin I, Simirnov V, et al External and Common cavity high spectral Density Beam Combing of high Power Fiber Lasers[c] Proc.SPIE, 2008,6873:687314.).

In recent years, the domestic bundling device research of also having carried out successively for Spectral beam combining.2008, accounting for the people such as raw treasured, Zhao Shanghong is PTR(fotoceram to recording materials) the spectral beam combining of transmitting volume Bragg grating carried out correlative study (referring to document: the research based on transmitting volume Bragg grating spectral beam combining [J]. photoelectron laser, 2008,19 (3): 318-32l.); The people such as Pu Shibing, Jiang Zongfu has set up the physical model of a set of Spectral beam combining based on VBG, numerical simulation the laser of two-way He San road Gauss's line spectrum synthetic (referring to document: the numerical analysis of the Spectral beam combining based on Volume Bragg grating [J]. light laser and the particle beams, 2008,20 (5): 721-724.).2010, the people such as Liu Li, Tan Jichun designed 90 ° of configuration Bragg grating beam optical paths and carried out the laser of two bundle different wave lengths and bundle and two bundles wavelength laser of the same race and bundle experiment (referring to document: beam synthesizing technology research based on Volume Bragg grating and realization [J]-National University of Defense technology journal 2010,32 (2) .).In prior art, bundling device is generally used for the bundle that closes between the less high energy laser beam in wavelength interval.

Summary of the invention

The present invention is directed to the deficiency that prior art exists, provide a kind of simple in structure, preparation cost is cheap, has beam energy loss little, RGB tri-coloured light bundling devices that the efficiency of light energy utilization is high and preparation method thereof.

The technical scheme that realizes the object of the invention is a kind of RGB tri-coloured light bundling devices, the transmissive body phase holographic grating G1 that it comprises two identical isosceles right-angle prisms, the dichromated gelatin of take is holographic recording medium and reflecting body phase holographic grating G2; The peak value stripe surface of transmissive body phase holographic grating G1 is vertical with grating surface, and the peak value stripe surface of reflecting body phase holographic grating G2 is parallel with grating surface; Put in opposite directions the bottom surface of two isosceles right-angle prisms, places respectively transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2 between two bottom surfaces, by epoxy resin bonding, is encapsulated; The material of described isosceles right-angle prism is BK7 glass; Described their incident relation of RGB tri-coloured light is respectively: the light beam of RGB tri-coloured light with close Shu Guang an angle of 90 degrees each other, in RGB tri-coloured light, light beam by grating G1 and G2, is used O with transmission form _{the saturating saturating G2 of G1}represent, in remaining two-beam, light beam incides G1, through diffraction, by transmission after G1, passes through G2, uses O _{the saturating G2 of the G1 that spreads out}represent, another bundle incides G2, through diffraction, by G2, uses O _{g2 spreads out}represent.

RGB tri-coloured light bundling devices described in technical solution of the present invention, are placed in respectively by three λ/2 wave plates between each right angle face of laser instrument and isosceles right-angle prism.

A preparation method who prepares RGB tri-coloured light bundling devices as above, comprises as follows:

1, the structural parameters of transmissive body phase holographic grating G1 are:

(1) empty f1 frequently meets the following conditions: f ₁=1/ Λ ₁, wherein, Λ ₁for the cycle of grating G1, incident light O _{the saturating G2 of the G1 that spreads out}wavelength meet

wherein, θ ₃for incident light O _{the saturating G2 of the G1 that spreads out}with the angle that grating fringe face forms, n ₂refractive index for grating medium; n ₁sin45 °=n ₂sin θ ₃, in formula, n ₁refractive index for isosceles right-angle prism;

(2) refractive index modulation degree Δ n ₁be 0.02～0.04;

(3) grating dielectric thickness d1 meets the following conditions:

Incident light O _{the saturating saturating G2 of G1}and O _{the saturating G2 of the G1 that spreads out}meet the non-oblique incidence of Bragg condition, the diffraction efficiency of reflecting body phase holographic grating TE ripple is thoroughly:

Wherein,

i is positive integer;

Wherein,

i is positive integer;

θ ₁for incident light O _{the saturating G2 of the G1 that spreads out}incident angle in medium, for off-Bragg vector,

for the phase mismatch factor;

2, the structural parameters of reflecting body phase holographic grating G2 are:

(1) empty f frequently ₂=1/ Λ ₂, wherein, Λ ₂for the cycle of grating G2, incident light O _{g2 spreads out}wavelength meet

wherein, θ ₄for incident light O _{g2 spreads out}with the angle that grating fringe face forms, n ₂refractive index for grating medium; n ₁sin45 °=n ₂sin θ ₄, in formula, n ₁refractive index for isosceles right-angle prism;

(2) refractive index modulation degree Δ n ₂=0.02～0.04;

(3) grating dielectric thickness d ₂meet following condition

Incident light meets the non-oblique incidence of Bragg condition, and the diffraction efficiency of reflecting body phase holographic grating TE ripple is:

Wherein, η _{g2 spreads out}=100%, η _{the saturating G2 of the G1 that spreads out}<0.05, η _{the saturating saturating G2 of G1}<0.01, Δ n ₂for grating medium refraction index degree of modulation, d ₂for grating dielectric thickness, θ _bfor incident light O _{g2 spreads out}in medium with the angle of peak value stripe surface.

The principle of definite its foundation of method of body phase holographic grating structural parameters of the present invention is:

1, the bragg condition of body phase holographic grating

When two bundle coherent light beams incide thickness, be d(d>> λ) holographic recording medium on time, two-beam interference organizator phase holographic grating.The grating that object light and reference light record during from the incident of recording medium the same side is transmission hologram grating, and referring to accompanying drawing 1, in figure, (a) is transmissive body phase holographic grating structural representation, is (b) reflecting body phase holographic grating structural representation; The grating recording when as shown in Figure 1, object light and reference light are from the incident of recording medium both sides is reflection holography grating.If adopt symmetrical recording beam path, can obtain non-oblique raster, now the peak value stripe surface of transmissive body holographic grating is vertical with recording medium surface, and the peak value stripe surface of reflection volume holographic grating is parallel with recording medium surface.

During reproduction, when lighting light wave incides on the peak value stripe surface in volume holographic grating, a part of light will be transmitted diffraction, and another part light will be reflected diffraction.In these diffraction lights, only satisfy condition as the formula (1):

2nΛsinθ _b＝λ (1)

Could strengthen interfere to form diffraction light wave, in formula, λ is lambda1-wavelength in air, the refractive index that n is recording medium, Λ is the grating cycle, θ _bangle for medium intraoral illumination light wave and peak value stripe surface.Referring to accompanying drawing 2, in figure, (a) is the reproduction schematic diagram of transmissive body phase holographic grating provided by the invention, (b) is the reproduction schematic diagram of reflecting body phase holographic grating; As shown in Figure 2, formula (1) is the wavefront reconstruction condition of body phase holographic grating, also claims cloth loudspeaker lattice (Bragg) diffraction conditions.The light diffraction efficiency that meets bragg condition incident is high, can be very low and depart from the light diffraction efficiency of this condition.This character of body phase holographic grating can be used for different wavelengths of light to close bundle.

2, about the diffraction efficiency of transmissive body holographic grating

From Kogelnik coupled wave theory, when lighting light wave is while being direction of vibration perpendicular to the TE ripple (being s polarized light) of the plane of incidence, without the diffraction efficiency that absorbs transmissive body phase grating, be formula (2):

${\mathrm{\&eta;}}_S=\frac{{\sin }^2{(v^2+{\mathrm{\&xi;}}^2)}^{1/2}}{1+{(\mathrm{\&xi;}/v)}^2}---\left(2\right)$

Wherein, correlation parameter is respectively suc as formula shown in (3), (4) and (5):

$v=\frac{\mathrm{\&pi;\&Delta;nd}}{\mathrm{\&lambda;}{\left(\cos {\mathrm{\&theta;}}_1\cos {\mathrm{\&theta;}}_2\right)}^{1/2}}---\left(3\right)$

$\mathrm{\&xi;}=\frac{\mathrm{\&delta;<figure-callout\; id="2"\; label="d"\; filenames="131118163938.png"\; state="\{\{state\}\}">d</figure-callout>}}{2\cos {\mathrm{\&theta;}}_2}---\left(4\right)$

δ＝Δθsin(φ-θ ₀)-ΔλK ²/4πn ₂ (5)

In formula: λ is lambda1-wavelength, θ ₁and θ ₂be respectively the angle of the interior incident light wave of medium and diffraction light wave and z axle, θ ₀incident angle when incident beam meets bragg condition in medium (with the folded angle of Z axis), φ is the angle of grating vector K and Z axis, and Δ n and d are respectively refractive index modulation degree and the thickness of recording medium, and K is grating vector, ξ is off-Bragg vector, and δ is the phase mismatch factor.

3, about the diffraction efficiency of reflection volume holographic grating

From Kogelnik coupled wave theory, when lighting light wave is while being direction of vibration perpendicular to the TE ripple (being s polarized light) of the plane of incidence, without the diffraction efficiency that absorbs reflecting body phase grating, be formula (6):

$\mathrm{\&eta;}=\frac{{\mathrm{sh}}^2{(v^2-{\mathrm{\&xi;}}^2)}^{1/2}}{{\mathrm{sh}}^2{(v^2-{\mathrm{\&xi;}}^2)}^{1/2}+\left[{1-(\mathrm{\&xi;}/v)}^2\right]}---\left(6\right)$

Wherein, correlation parameter is respectively suc as formula shown in (7), (8) and (9):

$v=\frac{\mathrm{\&pi;\&Delta;nd}}{\mathrm{\&lambda;}{\left(\cos {\mathrm{\&theta;}}_1\cos {\mathrm{\&theta;}}_2\right)}^{1/2}}---\left(7\right)$

ξ＝δd/2cosθ ₂ (8)

δ＝Δθ·Κsin(φ-θ ₀)-ΔλΚ ²/4πn ₂ (9)

In formula: θ ₁and θ ₂for the angle of incident light wave in medium and diffraction light wave and z axle, K is grating vector, and φ is the angle of grating vector K and Z axis, and Δ n and d are respectively refractive index modulation degree and the thickness of recording medium, and ξ is off-Bragg vector, and δ is the phase mismatch factor.

Compared with prior art, the invention has the beneficial effects as follows:

1, RGB tri-coloured light bundling device part preparations provided by the invention are simple, and with low cost, can persistence.

2, the diffraction efficiency height of VPHG can reach 100% in theory, and signal to noise ratio (S/N ratio) is high, and scattering is low, absorb low, little for closing the beam energy loss of when bundle, can effectively improve the utilization factor of luminous energy.

If 3, RGB provided by the invention tri-coloured light bundling device parts increase λ/2 these bundling devices of wave plate, when being applicable to RGB tri-coloured light and being P polarized light, close bundle, at laser projection system, there is potential application foreground.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of transmission position phase provided by the invention and reflecting body phase holographic grating structure;

Fig. 2 is the reproduction schematic diagram of transmission position phase provided by the invention and reflecting body phase holographic grating;

The structure of the RGB tri-coloured light bundling devices that Fig. 3 provides for the embodiment of the present invention 1 and use light path schematic diagram;

Fig. 4 is that in the embodiment of the present invention 1, ruddiness and blue light close bundle schematic diagram through transmissive body phase holographic grating G1;

Wavelength-diffraction efficiency (+1 grade) scatter chart of the transmissive body phase holographic grating G1 that Fig. 5 provides for the embodiment of the present invention 1;

The ruddiness that Fig. 6 provides for the embodiment of the present invention 1, blue light and green glow three beams combiner schematic diagram;

The diffraction efficiency curve figure of the reflecting body phase holographic grating G2 that Fig. 7 embodiment of the present invention 1 provides;

The structure of the RGB tri-coloured light bundling devices that Fig. 8 provides for the embodiment of the present invention 2 and use light path schematic diagram;

Wavelength-diffraction efficiency (+1 grade) scatter chart of the transmissive body phase holographic grating G1 that Fig. 9 embodiment of the present invention 2 provides;

Wavelength-diffraction efficiency (+1 grade) scatter chart of the reflecting body phase holographic grating G2 that Figure 10 provides for the embodiment of the present invention 2;

The structure of the RGB tri-coloured light bundling devices that Figure 11 provides for the embodiment of the present invention 3 and use light path schematic diagram;

Wavelength-diffraction efficiency (+1 grade) scatter chart of the transmissive body phase holographic grating G1 that Figure 12 embodiment of the present invention 3 provides;

Wavelength-diffraction efficiency (+1 grade) scatter chart of the reflecting body phase holographic grating G2 that Figure 13 provides for the embodiment of the present invention 3.

Embodiment

Below in conjunction with drawings and Examples, technical solution of the present invention is further elaborated.

Embodiment 1

Referring to accompanying drawing 3, it is the structure of the RGB tri-coloured light bundling devices that provide of the present embodiment and uses light path schematic diagram; In the present embodiment, RGB tri-coloured light wavelength are respectively ruddiness λ _r=635nm, green glow λ _g=532nm, blue light λ _b=473nm, carries out the design of Structural Parameters of transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2.RGB tri-coloured light bundling devices comprise by two identical isosceles right-angle prism P1 and P2, transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2.Grating G1 and the G2 non-inclination peak value stripe surface grating for obtaining with symmetrical light path record, the peak value stripe surface of grating G1 is vertical with grating surface, and the peak value stripe surface of grating G2 is parallel with grating surface.Put in opposite directions the bottom surface of two identical isosceles right-angle prisms, places respectively transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2 therebetween, with epoxy resin bonding, encapsulates.RGB tri-coloured light (be s polarized light, vibration plane is perpendicular to the plane of incidence) are normally incident in respectively on three right angle faces of two isosceles right-angle prisms with the angle of 90 ° each other.(wavelength is λ to ruddiness _r) and blue light (wavelength is λ _b) through transmissive body phase holographic grating G1, now G1 is to λ _rdiffraction efficiency maximum and to λ _bdiffraction efficiency minimum, and due to λ _rincident angle on G1 and angle of diffraction are Mirror Symmetry with respect to peak value stripe surface, and λ _bmainly with transmission form through G1, so after G1 λ _rwith λ _bexit direction consistent, enter reflecting body phase holographic grating G2 after closing bundle.The λ of G2 to this incident _rand λ _bdiffraction efficiency all minimum, and (wavelength is λ to green glow _g) diffraction efficiency maximum, and due to λ _gincident angle on G2 and angle of diffraction are also Mirror Symmetry with respect to peak value stripe surface, and λ _rand λ _bmainly with transmission form through G2, so after G2 λ _rand λ _bwith λ _gexit direction consistent.Finally, the vertical outgoing from a right angle face of isosceles right-angle prism P2 in the same direction of RGB tri-coloured light, thus realize the beam function that closes of RGB tri-coloured light.

If RGB tri-coloured light are p polarized light (being that vibration plane is parallel to the plane of incidence), can before each coloured light enters isosceles right-angle prism, first by λ/2 wave plate, be converted into s polarized light, and then close bundle.

Grating G1 and G2 all adopt dichromated gelatin (DCG, refractive index n ₂=1.52) as holographic recording medium, and be non-inclination striped concave grating.According to optical wavelength of all kinds, light beam incident and exit direction, require to determine respectively the empty frequency of grating G1 and G2.Adopt Kogelnik coupled wave theory and G-solver software (theoretical based on rigorous coupled wave) respectively the refractive index modulation degree Δ n of grating G1 and G2 and the thick d of glue to be optimized and to be chosen, to reach diffraction of light efficiency of all kinds requirement.In bundling device, prism material used is that (refractive index is n to BK7 glass ₁=1.5168).

The design procedure of body phase holographic grating bundling device is as follows:

1, the optimal design of the definite and diffraction efficiency of transmissive body phase grating G1 parameter

Referring to accompanying drawing 4, it is that in the present embodiment, ruddiness and blue light close bundle schematic diagram through transmissive body phase holographic grating G1; As shown in Figure 4, the effect of transmissive body phase holographic grating G1 is that to realize wavelength be λ _rruddiness and wavelength be λ _bblue light close bundle.When ruddiness and blue light are during in the incident of transmissive body phase holographic grating G1 surface normal both sides, for make blue light mainly with transmission form by grating G1 ruddiness after grating G1 diffraction with blue combiner, should make grating G1 at λ _rthe diffraction efficiency at place is maximum and at λ _bthe diffraction efficiency at place is minimum.

(1) empty f's frequently determines

As ruddiness λ _rfrom a right angle face vertical incidence of prism P1, the incident angle that arrives grating G1 surface is 45 °.Can be in the hope of λ by refractive index theorem _rincidence angle θ in grating medium ₃shown in formula (10):

n ₁sin45°＝n ₂sinθ ₃ (10)

For making grating G1 at λ _rplace obtains high-diffraction efficiency, need meet Bragg diffraction condition, and formula (1) is shown in formula (11):

λ _R＝2n ₂Λ ₁sinθ ₃ (11)

Obtaining thus the empty of transmissive body phase grating G1 is frequently: f ₁=1/ Λ ₁=3378lp/mm.

(2) optimization of diffraction efficiency

When incident light meets Bragg condition and is incident to non-inclination striped concave grating, i.e. δ=0, ξ=0, by (2) formula, obtaining now transmissive body phase holographic grating is shown in formula (12) to the diffraction efficiency of TE ripple (being s polarization):

$\mathrm{\&eta;}={\sin }^{2}v={\sin }^2\left(\frac{\mathrm{\&pi;\&Delta;nd}}{\mathrm{\&lambda;}\cos {\mathrm{\&theta;}}_1}\right)---\left(12\right)$

From (12) formula, diffraction efficiency of grating is relevant with recording medium refractive index modulation degree d with recording medium refractive index modulation degree Δ n.When grating G1 is maximum to the diffraction efficiency of ruddiness, need to meet formula (13):

$\frac{\mathrm{\&pi;\&Delta;nd}}{{\mathrm{\&lambda;}}_R\cos {\mathrm{\&theta;}}_1}=i\frac{\mathrm{\&pi;}}{2},(i=\mathrm{1,2},....)---\left(13\right)$

From (2), for making the diffraction efficiency of blue light minimum, mainly with transmission form, pass through G1, need to meet formula (14):

(υ _B ²+ξ _B ²) ¹/ ²＝iπ(i=1,2,...) (14)

Conventionally refractive index modulation degree Δ n is controlled in 0.02～0.04 scope.Optimization by refractive index degree of modulation Δ n and the thick d of glue is selected, and utilize respectively wavelength-diffraction efficiency distribution curve that Kogelnik coupled wave theory and G-solver software calculates transmissive body phase holographic grating G1 as shown in Figure 5, now, recording medium refractive index modulation degree Δ n ₁=0.02, recording medium thickness d ₁=11.4um.

Referring to accompanying drawing 5, it is wavelength-diffraction efficiency (+1 grade) distribution curve (f=3378lp/mm, Δ n=0.02, d=11.4um) of the present embodiment transmissive body phase holographic grating G1; As seen from Figure 5, for the frequency body phase holographic grating of high-altitude, the diffraction efficiency curve being calculated by Kogelnik coupled wave theory and G-solver software (theoretical based on rigorous coupled wave) is consistent.Transmissive body phase holographic grating G1 is at λ _r=635nm place diffraction efficiency approaches 100%, and at λ _b=473nm place diffraction efficiency is close to 0, and therefore, in grating G1, Red and blue light passes through with the form of 1 order diffraction and 0 order diffraction (being transmission) respectively.And due to Red and blue light with 90 ° of angle outgoing each other the surface to grating G1, and incident angle and the angle of diffraction of ruddiness in G1 medium is Mirror Symmetry with respect to peak value stripe surface, therefore, Red and blue light is consistent in the exit direction on grating G1 surface, to close the form of bundle, is incident to grating G2.

Result of calculation obtains the parameter of the present embodiment transmissive body phase holographic grating G1: empty f frequently ₁=1/ Λ ₁=3378lp/mm, recording medium refractive index modulation degree Δ n ₁=0.02, recording medium thickness d ₁=11.4um.

2, the parameter of reflecting body phase grating G2 is determined and the optimal design of diffraction efficiency

Referring to accompanying drawing 6, it is the present embodiment ruddiness, blue light and green glow three beams combiner schematic diagram; As shown in Figure 6, the effect of reflecting body phase holographic grating G2 is to λ _rand λ _bdiffraction efficiency minimum, to λ _g1 order diffraction efficiency maximum, i.e. λ _rand λ _bmainly with transmission form, pass through grating G2, and λ _gwith diffraction form, by grating G2, finally realize the bundle that closes of RGB tri-coloured light.

(1) empty f's frequently determines

As green glow λ _g=532nm is from a right angle face vertical incidence of prism P2, and the incident angle that arrives grating G2 surface is 45 °.Can be in the hope of λ by refractive index theorem _gincidence angle θ in grating medium ₄for formula (15):

n ₁sin45°＝n ₂sinθ ₄ (15)

For making grating G2 at λ _gplace obtains high-diffraction efficiency, need meet Bragg diffraction condition, and formula (1) can obtain formula (16):

${\mathrm{\&lambda;}}_G=2{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="131118163938.png"\; state="\{\{state\}\}">n</figure-callout>}}_2{\mathrm{\&Lambda;}}_2\cos {\mathrm{\&theta;}}_4=2{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="131118163938.png"\; state="\{\{state\}\}">n</figure-callout>}}_2{\mathrm{\&Lambda;}}_2\sqrt{1-{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="131118163938.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&theta;}}_4}---\left(16\right)$

Obtaining thus the empty of reflecting body phase grating G2 is frequently: f ₂=1/ Λ ₂=4049lp/mm.

(2) optimal design of diffraction efficiency

When incident light meets the non-oblique incidence of Bragg condition, i.e. δ=0, ξ=0, by (6) formula, obtaining the now diffraction efficiency of transmissive body phase holographic grating TE ripple is formula (17):

${\mathrm{\&eta;}}_G={\mathrm{th}}^2\left(\frac{\mathrm{\&pi;\&Delta;nd}}{{\mathrm{\&lambda;}}_G\sin {\mathrm{\&theta;}}_b}\right)---\left(17\right)$

In formula: Δ n is DCG medium refraction index degree of modulation, and d is grating thickness, θ _bangle for medium intraoral illumination light wave and peak value stripe surface.From the character of hyperbolic tangent function, when Δ nd is enough large, diffraction efficiency theoretical value just can reach 100%.When making green glow η reach maximum, make the diffraction efficiency of Red and blue light minimum.Conventionally by refractive index modulation degree and the thick parameter control of glue, be: Δ n=0～0.04, d=0～50um.

Optimization by refractive index degree of modulation Δ n and the thick d of glue is selected, and utilizes respectively diffraction efficiency curve that Kogelnik coupled wave theory and G-solver software calculates reflecting body phase holographic grating G2 referring to accompanying drawing 7; Now, recording medium refractive index modulation degree Δ n ₂=0.03, recording medium thickness d ₂=24um.As seen from Figure 7, the diffraction efficiency curve that adopts Kogelnik coupled wave theory and G-solver software (theoretical based on rigorous coupled wave) to calculate is consistent.Grating G2 is at λ _gthe diffraction efficiency at=532nm place is 100%, at λ _r=635nm place and λ _b=473nm place diffraction efficiency is close to 0.Therefore, in grating G2, Red and blue light passes through with the form of 0 order diffraction (being transmission), and green glow passes through with the form of 1 order diffraction, and due to λ _gincident angle on G2 and angle of diffraction are also Mirror Symmetry with respect to peak value stripe surface, therefore, three coloured light exit direction on grating G2 is consistent, final vertical outgoing from a right angle face of isosceles right-angle prism P2 in the same direction, thus realize the beam function that closes of RGB tri-coloured light.

The parameter that result of calculation obtains the present embodiment reflecting body phase grating G2 is: empty f frequently ₂=1/ Λ ₂=4049lp/mm, recording medium refractive index modulation degree Δ n ₂=0.03, recording medium thickness d ₂=24um.

The present embodiment provides a kind of novel RGB tri-coloured light bundling device parts that transmission and reflecting body phase holographic grating be core devices of take.Take DCG as holographic recording medium, according to bragg condition, determine the frequently empty of two gratings, adopt Kogelnik coupled wave theory and G-solver software to be optimized design to the diffraction efficiency of transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2, obtained G1 at ruddiness λ _rthe diffraction efficiency at=635nm place reaches 100%, at blue light λ _b=473nm place diffraction efficiency approaches 0, and G2 is at ruddiness λ _gthe diffraction efficiency at=532nm place reaches 100%, at ruddiness λ _r=635nm and blue light λ _bthe diffraction efficiency at=473nm place approaches 0 result.This two grating and two isosceles right-angle prisms is combined, when RGB tri-coloured light (are s polarized light, be that vibration plane is perpendicular to the plane of incidence) while being normally incident in respectively three right angle faces of two isosceles right-angle prisms with the angle of 90 ° each other, the vertical outgoing from a right angle face of isosceles right-angle prism in the same direction of final RGB tri-coloured light, thus realize the beam function that closes of RGB tri-coloured light.

Can be by increasing λ/2 wave plate, when being also applicable to RGB tri-coloured light and being p polarized light (being that vibration plane is parallel to the plane of incidence), this bundling device closes bundle.Because body phase holographic grating has, diffraction efficiency is high, signal to noise ratio (S/N ratio) is high, scattering is low and absorb the performances such as low, and novel bundling device provided by the invention is conducive to improve the utilization factor of luminous energy, at laser projection system, has potential application foreground.

Embodiment 2

Referring to accompanying drawing 8, it is the structure of the body phase holographic grating bundling device that provides of the present embodiment and uses light path schematic diagram; In the present embodiment, their incident relation of RGB tri-coloured light is respectively:

Grating G1: (wavelength is λ to ruddiness _r) and green glow (wavelength is λ _g) through transmissive body phase holographic grating G1, now G1 is to λ _gdiffraction efficiency maximum and to λ _rdiffraction efficiency minimum.

Grating G2: (wavelength is λ to ruddiness _r), (wavelength is λ to green glow _g) and blue light (wavelength X _b) through reflecting body phase holographic grating G2, the now λ of G2 to this incident _rand λ _gdiffraction efficiency all minimum, and (wavelength is λ to blue light _b) diffraction efficiency maximum.

1, grating G1 parameter determines

Referring to accompanying drawing 9, it is wavelength-diffraction efficiency (+1 grade) distribution curve of the present embodiment transmissive body phase holographic grating G1; Fig. 9 is known, and transmissive body phase holographic grating G1 is at λ _g=532nm place diffraction efficiency approaches 100%, and at λ _r=635nm place diffraction efficiency is close to 0, and therefore, in grating G1, green glow and ruddiness pass through with the form of 1 order diffraction and 0 order diffraction (being transmission) respectively.And due to green glow and ruddiness with 90 ° of angle outgoing each other the surface to grating G1, and incident angle and the angle of diffraction of green glow in G1 medium is Mirror Symmetry with respect to peak value stripe surface, therefore, green glow is consistent in the exit direction on grating G1 surface with ruddiness, to close the form of bundle, is incident to grating G2.By the method for embodiment 1, draw G1 parameter: f=4040lp/mm, Δ n=0.02, d=9.5um.

2, grating G2 parameter determines

Referring to accompanying drawing 10, it is wavelength-diffraction efficiency (+1 grade) distribution curve of the present embodiment reflecting body phase holographic grating G2; In grating G2, ruddiness and green glow pass through with the form of 0 order diffraction (being transmission), and blue light passes through with the form of 1 order diffraction, and due to λ _bincident angle on G2 and angle of diffraction are also Mirror Symmetry with respect to peak value stripe surface, therefore, three coloured light exit direction on grating G2 is consistent, final vertical outgoing from a right angle face of isosceles right-angle prism P2 in the same direction, thus realize the beam function that closes of RGB tri-coloured light.By the method for embodiment 1, draw G2 parameter: f=4554lp/mm, d=20um, Δ n=0.03.

Embodiment 3

Referring to accompanying drawing 11, it is the structure of the body phase holographic grating bundling device that provides of the present embodiment and uses light path schematic diagram; In the present embodiment, their incident relation of RGB tri-coloured light is respectively:

Grating G1: (wavelength is λ to blue light _b) and green glow (wavelength is λ _g) through transmissive body phase holographic grating G1, now G1 is to λ _bdiffraction efficiency maximum and to λ _gdiffraction efficiency minimum.

Grating G2: blue light (wavelength X _b), (wavelength is λ to green glow _g) and ruddiness (wavelength is λ _r) through reflecting body phase holographic grating G2, the now λ of G2 to this incident _band λ _gdiffraction efficiency all minimum, and (wavelength is λ to ruddiness _r) diffraction efficiency maximum.

1, grating G1 parameter determines

Referring to accompanying drawing 12, it is wavelength-diffraction efficiency (+1 grade) distribution curve of the present embodiment transmissive body phase holographic grating G1; As shown in Figure 12, transmissive body phase holographic grating G1 is at λ _b=473nm place diffraction efficiency approaches 100%, and at λ _g=532nm place diffraction efficiency is close to 0, and therefore, in grating G1, blue light and green glow pass through with the form of 1 order diffraction and 0 order diffraction (being transmission) respectively.And due to blue light and green glow with 90 ° of angle outgoing each other the surface to grating G1, and incident angle and the angle of diffraction of green glow in G1 medium is Mirror Symmetry with respect to peak value stripe surface, therefore, blue light is consistent in the exit direction on grating G1 surface with green glow, to close the form of bundle, is incident to grating G2.By embodiment 1 method, obtain G1 parameter: f=4543lp/mm, Δ n=0.02, d=8.5um.

2, grating G2 parameter determines

Referring to accompanying drawing 13, it is wavelength-diffraction efficiency (+1 grade) distribution curve of the present embodiment reflecting body phase holographic grating G2.In grating G2, blue light and green glow pass through with the form of 0 order diffraction (being transmission), and ruddiness passes through with the form of 1 order diffraction, and due to λ _rincident angle on G2 and angle of diffraction are also Mirror Symmetry with respect to peak value stripe surface, therefore, three coloured light exit direction on grating G2 is consistent, final vertical outgoing from a right angle face of isosceles right-angle prism P2 in the same direction, thus realize the beam function that closes of RGB tri-coloured light.By embodiment 1 method, draw G2 parameter: f=3392lp/mm, d=30um, Δ n=0.03.

Claims (3)

1. RGB tri-coloured light bundling devices, is characterized in that: the transmissive body phase holographic grating G1 that it comprises two identical isosceles right-angle prisms, the dichromated gelatin of take is holographic recording medium and reflecting body phase holographic grating G2; The peak value stripe surface of transmissive body phase holographic grating G1 is vertical with grating surface, and the peak value stripe surface of reflecting body phase holographic grating G2 is parallel with grating surface; Put in opposite directions the bottom surface of two isosceles right-angle prisms, places respectively transmissive body phase holographic grating G1 and reflecting body phase holographic grating G2 between two bottom surfaces, by epoxy resin bonding, is encapsulated; The material of described isosceles right-angle prism is BK7 glass; Described their incident relation of RGB tri-coloured light is respectively: the light beam of RGB tri-coloured light with close Shu Guang an angle of 90 degrees each other, in RGB tri-coloured light, light beam by grating G1 and G2, is used O with transmission form _{the saturating saturating G2 of G1}represent, in remaining two-beam, light beam incides G1, through diffraction, by transmission after G1, passes through G2, uses O _{the saturating G2 of the G1 that spreads out}represent, another bundle incides G2, through diffraction, by G2, uses O _{g2 spreads out}represent.

2. a kind of RGB tri-coloured light bundling devices according to claim 1, is characterized in that: three λ/2 wave plates are placed in respectively between each right angle face of laser instrument and isosceles right-angle prism.

3. a preparation method who prepares RGB tri-coloured light bundling devices as claimed in claim 1, is characterized in that:

The structural parameters of transmissive body phase holographic grating G1 are:

(1) empty f1 frequently meets the following conditions: f ₁=1/ Λ ₁, wherein, Λ ₁for the cycle of grating G1, incident light O _{the saturating G2 of the G1 that spreads out}wavelength meet

wherein, θ ₃for incident light O _{the saturating G2 of the G1 that spreads out}with the angle that grating fringe face forms, n ₂refractive index for grating medium; n ₁sin45 °=n ₂sin θ ₃, in formula, n ₁refractive index for isosceles right-angle prism;

(2) refractive index modulation degree Δ n ₁be 0.02～0.04;

(3) grating dielectric thickness d ₁meet the following conditions:

Incident light O _{the saturating saturating G2 of G1}and O _{the saturating G2 of the G1 that spreads out}meet the non-oblique incidence of Bragg condition, the diffraction efficiency of reflecting body phase holographic grating TE ripple is thoroughly:

Wherein,

i is positive integer;

wherein,

i is positive integer;

θ ₁for incident light O _{the saturating G2 of the G1 that spreads out}incident angle in medium,

for off-Bragg vector,

for the phase mismatch factor;

The structural parameters of reflecting body phase holographic grating G2 are:

(1) empty f frequently ₂=1/ Λ ₂, wherein, Λ ₂for the cycle of grating G2, incident light O _{g2 spreads out}wavelength meet

wherein, θ ₄for incident light O _{g2 spreads out}with the angle that grating fringe face forms, n ₂refractive index for grating medium; n ₁sin45 °=n ₂sin θ ₄, in formula, n ₁refractive index for isosceles right-angle prism;

(2) refractive index modulation degree Δ n ₂=0.02～0.04;

(3) grating dielectric thickness d ₂meet following condition

Incident light meets the non-oblique incidence of Bragg condition, and the diffraction efficiency of reflecting body phase holographic grating TE ripple is:

Wherein, η _{g2 spreads out}=100%, η _{the saturating G2 of the G1 that spreads out}<0.05, η _{the saturating saturating G2 of G1}<0.01, Δ n ₂for grating medium refraction index degree of modulation, d ₂for grating dielectric thickness, θ _bfor incident light O _{g2 spreads out}in medium with the angle of peak value stripe surface.

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