CN1334625A - Optical parametric oscilaltor with reflectivity-variable cavity - Google Patents

Abstract

An optical parametric oscillator with reflectivity varying cavity consists of input reflector, non-linear crystal and output reflector, the non-linear crystal is on the place between the two reflectors. The reflectivity varying film series composed of at least three films are applied on the surface of a reflector chosen one of them from output or input reflector. The coated surface faces to the crystal. The thickness of at least one film is curvilinear, the films among film series are made of inorganic optical filming materials. Since the values of reflectivity of input or output reflector to outpt light are varied as a curve along the radial, the angle of divergence of beam is diminished effectively, hence the quality of the output laser beam is improved.

Description

Optical parametric oscilaltor with reflectivity-variable cavity

Technical field:

The present invention relates to a kind of optical parametric oscilaltor with reflectivity-variable cavity, more particularly, is to adopt the external cavity type optical parametric oscillator of reflectivity-variable eyeglass as resonator mirror, the radially curved variation of the reflectance value of this kind variable reflectivity mirror.Use the optical parametric oscillator of this kind chamber mirror under the pump laser source effect, can export and have the very laser of high light beam quality.Belong to laser technology field.

Background technology:

Optical parametric oscillator is a kind of device for non-linear optical, and it adopts nonlinear crystal as nonlinear crystal.Nonlinear crystal places resonant cavity, produces the parameter transfer process under the effect of pump light, and forms the laser output that wavelength is different from pump light by the oscillation action of resonant cavity.The resonant cavity of optical parametric oscillator has various ways in the prior art, Fig. 1 (a) has provided the simplest a kind of form, constitute by nonlinear crystal 2 and two plane mirrors 1 and 3 that are placed on its two ends, wherein the rete of input mirror 1 surface plating has very high transmitance to pump light, and output light (being flashlight) is had high reflectance; The rete of outgoing mirror 3 inner surfaces plating has certain transmitance to flashlight, and can select high permeability or high reflectance dual mode to the transmitance of pump light.

The optical parametric oscillator resonant cavity also has other multiple organization plans, and the ring cavity structure that is made of speculum 1,3 and ring cavity speculum 4 for example is as Fig. 1 (b); Has the unsteady cavity structure that the speculum 1,3 of certain curvature constitutes by the surface, as Fig. 1 (c).1 and 3 identical among its lumen mirror 1 and 3 plated film mode and Fig. 1 (a), the rete on the annular chamber speculum 4 requires that flashlight is had high reflectance simultaneously.Structure shown in Fig. 1 (b), 1 (c) only is the simplest unsteady cavity and annular chamber schematic diagram, annular chamber that optical parametric oscillator can adopt and unsteady cavity also have other various ways, and can design other multiple optical elements to realize having the output of special properties in the chamber.In addition, by can directly realize having the resonant cavity of certain geometry cavity type at the plane of crystal plated film of particular configuration.

Yet there is a problem in common optical parametric oscillator, and Here it is, and the beam quality of optical parametric oscillator output is very poor, and beam divergence angle is very big.This problem fails to obtain fine solution always, has greatly limited the practical application of optical parametric oscillator.

Summary of the invention:

The objective of the invention is to design a kind of optical parametric oscilaltor with reflectivity-variable cavity, by being at external cavity type optical parametric oscillator outgoing mirror or the inboard plating of input mirror reflectivity-variable film, improve the parametric oscillation process of optical parametric oscillator, realize that preferably horizontal film is selected in the chamber, make the laser beam of output have higher beam quality, reduce the angle of divergence of light beam greatly, can carry out the effect spread that has of longer distance.

Description of drawings:

Fig. 1 is the cavity configuration schematic diagram of optical parametric oscillator prior art, and wherein: (a) being the ordinary straight cavity configuration, (b) is typical ring cavity structure, (c) is typical unsteady cavity structure;

Fig. 2 is several typical reflectivity curves that can adopt in the optical parametric oscillator variable reflectivity mirror.

Fig. 3 (a) is the structure chart of embodiment one, and the film layer structure of outgoing mirror 3 is wherein represented with Fig. 3 (b).

Fig. 4 (a) is the structure chart of embodiment two, and the film layer structure of outgoing mirror 3 is wherein represented with Fig. 4 (b).

Among Fig. 1-Fig. 4, the 1st, input mirror, the 2nd, nonlinear crystal, the 3rd, outgoing mirror, the 4th, the ring cavity speculum, 5 is 2 rank Gaussian curves, 6 is 4 rank Gaussian curves, and 7 is 6 rank Gaussian curves, the 8th, and saddle-shaped curve, the 9th, K9 glass, the 10th, zirconium dioxide 1/4 wave film, the 11st, silica 1/4 wave film, the 12nd, zirconium dioxide graded films, the 13rd, zinc sulphide 1/4 wave film, the 14th, magnesium fluoride 1/4 wave film, the 15th, the zinc sulphide graded films, 16 are reflectivity-variable film system.

The specific embodiment:

Embodiment one:

Such as Fig. 3 (a), the optical parametric oscillator geometric configuration adopts the unsteady cavity structure, and nonlinear crystal 2 is KTP (KTiOPO₄), Work in the noncritical phase matching mode. Pump light is the pulse laser of wavelength 1.064 μ m. The plating of the left side of outgoing mirror 3 with With the corresponding reflectivity-variable film of wavelength 1.57 μ m system, the duplicature of right side plating has high permeability to the light of 1.57 mum wavelengths. The reflectivity-variable curve adopts 2 rank Gaussian curves 5 among Fig. 2. The output wavelength of embodiment one is near 1.57 μ m.

The reflectivity-variable film structure of outgoing mirror 3 inboards such as Fig. 3 (b), wherein 9 is substrate, material is K9 glass; 10 are Zirconium dioxide 1/4 wave film, thickness are about 0.20 μ m, and 11 is silica 1/4 wave film, and thickness is about 0.27 μ m. 1/4 Wave film refers to that the light path of rete is 1/4 respective wavelength. Rete 10 and 11 can adopt common vapour deposition method processing.

Axial symmetry graded profile zirconium dioxide film centered by the outermost rete 12, material adopts zirconium dioxide, in the rete The thickness at heart place is about 0.20 μ m, and thickness therefrom successively decreases at the mind-set edge, and near 0, this rete is adopted at the thickness of edge Method with electron gun evaporation is processed. The film system that rete 10,11,12 consists of is to wavelength 1.57 μ m reflection of light rates Be desired curve, film is that the reflectance value of center is about 50%.

The concrete chamber shape parameter of embodiment one has passed through certain optimization, can export to have the very laser of high light beam quality Bundle. Like this, through after the propagation of certain distance, hot spot and normal optical parametric oscillator phase specific area that embodiment one produces Greatly dwindle, and can satisfy the actual requirement in the fields such as laser ranging, spectrum, optical communication.

Embodiment two:

Embodiment two geometric configurations adopt simple straight chamber, and such as Fig. 4 (a), nonlinear crystal 2 is periodically poled lithium niobate, Pump light is the continuous laser of wavelength 0.53 μ m. Outgoing mirror 3 left sides are coated with the reflectivity-variable with wavelength 0.78 μ m photophase Film system, the duplicature on right side has high permeability to the light of 0.78 mum wavelength. The reflectivity-variable curve adopts 4 among Fig. 2 Rank Gaussian curve 6. The output wavelength of embodiment two is near 0.78 μ m.

The reflectivity-variable film structure of outgoing mirror 3 inboards such as Fig. 4 (b), wherein 9 is substrate, material is K9 glass; 13 Be zinc sulphide 1/4 wave film, thickness is about 0.08 μ m, and 14 is magnesium fluoride 1/4 wave film, and thickness is about 0.14 μ m. Rete 13 and 14 adopts common vapour deposition method processing.

Axial symmetry graded profile ZnS-film centered by the rete 15 that is clipped in the middle, material adopts zinc sulphide, rete center The thickness at place is about 0.08 μ m, and thickness therefrom successively decreases at the mind-set edge, at the thickness of edge near 0. This rete adopts The method of electron gun evaporation is processed. The film system that rete 13,14,15 consists of to wavelength 0.78 μ m reflection of light rate is Desired curve, film are that the reflectance value of center is about 90%.

Embodiment two:

The red beam of output high light beam quality, because beam divergence angle is littler than the output beam of normal optical parametric oscillator, This light beam has bigger effective propagation distance, can use in the fields such as illumination, colored demonstration.

Claims (2)

1, a kind of optical parametric oscilaltor with reflectivity-variable cavity, comprise input reflection mirror, nonlinear crystal and output reflector, wherein nonlinear crystal places in the middle of two speculums, it is characterized in that, in wherein said output reflector or the input reflection mirror any one, its inboard is coated with the reflectivity-variable film system that is made of three above retes towards the surface of nonlinear crystal, wherein having a thicknesses of layers at least is shaped form, and the thickness at curve peak place is $d=\frac{\mathrm{\λ}}{4n}$ , wherein d is a thickness, and λ is the optical parametric oscillator output wavelength, and n is the refractive index of film material.

As the said optical parametric oscilaltor with reflectivity-variable cavity of claim 1, it is characterized in that 2, film material is any in silicon dioxide, zirconium dioxide, magnesium fluoride or the zinc sulphide.

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