CN103887695A - Laser transmitting radial polarized beams based on conical uniaxial crystal - Google Patents

Abstract

A kind of laser based on conical uniaxial crystal outputting radial polarized light beam, its composition includes: uniaxial crystal conical mirror, laser gain medium, plane output coupling mirror and pumping source, the laser gain medium is located between the bottom surface and plane output coupling mirror of the uniaxial crystal conical mirror, the apex angle of the uniaxial crystal conical mirror No and ne is respectively the main shaft refractive index of e light and o light that the uniaxial crystal of the uniaxial crystal conical mirror is made in formula, and the no and ne of the uniaxial crystal should meet following condition: Laser of the present invention has the characteristics that apparatus structure is simple, system stability is good, lasing efficiency is high, output power is high and good beam quality.

Description

Based on the laser of conical uniaxial crystal outputting radial polarized light beam

Technical field

The present invention relates to laser, relate in particular to a kind of laser based on conical uniaxial crystal outputting radial polarized light beam.

Background technology

Radial polarized light beam is a kind of vector light beam, and its light intensity and polarization direction all have the polarization direction at axial symmetry and arbitrfary point place all along radial direction.Radial polarized light beam is because of the character of its a series of uniquenesses that have, and takes the photograph, the field such as biomedicine, electronics acceleration, materials processing all has a wide range of applications in high-resolution imaging, laser light.

Produce at present radial polarized light beam and mainly contain two kinds of methods.A kind of method is passively outside laser cavity to convert linearly polarized light or other forms of polarised light to radial polarisation light.These class methods mainly contain interferes the addition method, wave plate spatial alternation delay method, spiral gradient phase delay device or liquid crystal polarized transformation approach etc.But these chamber external conversion method ubiquities the defects such as beam quality is poor, conversion efficiency is low, device is complicated.Therefore, directly making in recent years the active method of laser outputting radial polarized light beam is a focus of relevant international research.Granted publication number is that the Chinese invention patent application of CN101465512B discloses the thermal birefringence effect in a kind of Nd:YAG of utilization crystal, take special asymmetrical Resonator design to suppress wherein a kind of starting of oscillation of polarised light, realize radial polarisation or tangential polarization Laser output.But this stability of laser cavity resonator based on crystal thermal effect modeling is not high, and can only in specific power interval, realize modeling, the power output of laser can be very restricted.Granted publication number is that the Chinese patent application of CN202333432 discloses the method for utilizing axial-symmetry polarized resonant cavity mirror to make laser output shaft symmetric polarized light beam laser, and this method of utilizing grating mirror modeling also has a lot of reports in the world.But can realize the manufacturing process more complicated of the grating mirror of polarised light modeling radially, cost is very high, not relevant production domesticization product also at present.

Summary of the invention

The present invention is intended to overcome the deficiency of above-mentioned technology, and a kind of laser of outputting radial polarization is provided.The features such as it is simple that this laser has apparatus structure, and the stability of a system is good, and lasing efficiency is high, and power output is high, good beam quality.

Technical solution of the present invention is as follows:

A kind of laser based on conical uniaxial crystal outputting radial polarized light beam, feature is that its formation comprises: uniaxial crystal conical mirror, gain medium, plane output coupling mirror and pumping source, described gain medium between the bottom surface and plane output coupling mirror of described uniaxial crystal conical mirror, the drift angle of described uniaxial crystal conical mirror n in formula _oand n _ebe respectively the e light of uniaxial crystal and the main shaft refractive index of o light of making described uniaxial crystal conical mirror, the n of described uniaxial crystal _oand n _eshould meet following condition:

$\arctan \frac{n_e}{n_o}>\arcsin \frac{1}{n_o}.$

Described can be both uniaxial negative crystal for making the material of uniaxial crystal conical mirror, can be also positive uniaxial crystal.

Described gain medium is single cladded fiber or the doubly clad optical fiber that gas laser medium, laser crystal, laser ceramics, fibre core are mixed with rare-earth activated particle.

Described plane output coupling mirror is the level crossing of part reflecting part transmission.

Described pumping source is lamp pumping source, laser pumping source, electric pump source or diode-end-pumped source.

The principle of the invention is as follows:

When a monochromic beam incides the interface of uniaxial crystal and air from uniaxial crystal inside, can produce the reverberation of two bunch polarised lights, and their direction of vibration is mutually vertical, bireflectance phenomenon that Here it is.This orthogonal linearly polarized light in two bundle polarization directions is exactly o light (ordinary light) and e light (abnormal light), the propagation path of o light in uniaxial crystal is consistent at isotropic medium (such as glass) propagation path with light, and deviation can occur the propagation path of e light.The drift angle being processed into for uniaxial crystal materials is α, optical axis is perpendicular to the conical mirror of circular cone bottom surface, can be broken down into o light and e light perpendicular to the light of conical mirror bottom surface incident, can be by reasonably controlling the size of circular cone apex angle α, make e light still be parallel to incident light direction after twice total reflection on taper seat and return, it is parallel with incident direction that the exit direction of o light can not keep.Therefore, the laserresonator that this conical mirror of making through the uniaxial crystal materials of particular design and plane output coupling mirror form, can consume o light loss, makes e light form laser generation, thereby realizes the Laser output of radial polarisation.

The present invention has the following advantages:

1, this laser to gain media without special requirement.Both gas laser be can make, solid or fiber laser also can have been made.

2,, in this laser, the resonant cavity that uniaxial crystal conical mirror forms with plane output coupling mirror can equivalence become average cavity configuration, can realize the Laser output of high light beam quality.

3,, in this laser, in chamber, outside chamber, all do not introduce other extra modeling elements, simple and compact for structure, realizability is strong, operating efficiency is high.

4, in this laser, can introduce easily and adjust Q or locked mode element, realize high-peak power pulse running.

Accompanying drawing explanation

Fig. 1 is the structural representation of outputting radial polarized light beam laser of the present invention.

Fig. 2 be in uniaxial negative crystal e optical index size with the variation schematic diagram of corner dimension between its optical axis.

Fig. 3 is the bireflectance schematic diagram of uniaxial negative crystal conical mirror.

Fig. 4 is the polarisation distribution schematic diagram of radial polarized light beam, and wherein arrow is denoted as polarization direction.

Embodiment

As shown in Figure 1, a kind of laser based on conical uniaxial crystal outputting radial polarized light beam, its formation comprises: uniaxial crystal conical mirror 1, gain medium 2, plane output coupling mirror 3 and pumping source 4, described gain medium 2 between the bottom surface and plane output coupling mirror 3 of described uniaxial crystal conical mirror 1, the drift angle of described uniaxial crystal conical mirror 1 n in formula _oand n _ebe respectively the e light of uniaxial crystal and the main shaft refractive index of o light of making described uniaxial crystal conical mirror 1, the n of described uniaxial crystal _oand n _eshould meet following condition:

$\arctan \frac{n_e}{n_o}>\arcsin \frac{1}{n_o}.$

The resonant tank of arrow logo laser cavity in chamber, plane output coupling mirror 3 right side arrow mark laser outputting cuttings are to polarized laser beam direction.

If the optical axis included angle of the wave normal direction of e light and uniaxial crystal is θ, corresponding refractive index when e light is propagated in uniaxial crystal

$n_e\left(\mathrm{\θ}\right)=\frac{n_o{n}_e}{\sqrt{n_o^2{\sin }^2\mathrm{\θ}+n_e^2{\cos }^2\mathrm{\θ}}}---\left(i\right)$

Wherein, n _oand n _etwo main shaft refractive indexes of uniaxial crystal.

Take uniaxial negative crystal as example, the refractive index size of e light changes as shown in Figure 2 with itself and optical axis included angle θ.

Take uniaxial negative crystal as example, the bireflectance of uniaxial crystal conical mirror as shown in Figure 3 equally.Wherein,

for the semiapex angle of circular cone, θ ₁for the common incidence angle of e light and o light, θ ₂for e reflection of light angle.

Make e light be parallel to incident light direction after interfacial twice total reflection of circular cone and return,

θ ₁+θ ₂=90° （ii）

From the geometrical relationship between the each angle in Fig. 3

Known according to reflection law

n _e(0°)sin(θ ₁)=n _e(90°)sin(θ ₂) （iv）

Comprehensive above various, can determine circular cone drift angle

$\mathrm{\α}=2\arctan \frac{n_e}{n_o}---\left(v\right)$

In addition, want uniaxial crystal conical mirror for laser resonant cavity mirror, on taper seat, should meet total reflection condition perpendicular to the e light of circular cone bottom surface incident:

Comprehensively (i), (iii), (v) and (vi), can obtain two main shaft refractive index ns of uniaxial crystal _oand n _econdition that should be satisfied:

$\arctan \frac{n_e}{n_o}>\arcsin \frac{1}{n_o}---\left(\mathrm{vii}\right)$

Described uniaxial crystal conical mirror 1 is Primary Component of the present invention, for o light is separated with e light.The drift angle of described uniaxial crystal conical mirror

Described uniaxial crystal conical mirror 1 optical axis direction is perpendicular to the bottom surface of conical mirror.Take optical axis uniaxial negative crystal as example, shown in operation principle Fig. 3 of uniaxial crystal conical mirror.

Described can be both uniaxial negative crystal for making the material of uniaxial crystal conical mirror 1, can be also positive uniaxial crystal.

Described uniaxial crystal is at two main shaft refractive index ns of oscillation light wave-wave strong point _oand n _eshould meet

$\arctan \frac{n_e}{n_o}>\arcsin \frac{1}{n_o}.$

Described gain medium 2 can be single covering or the doubly clad optical fiber that gas laser medium, laser crystal, laser ceramics, fibre core are mixed with rare-earth activated particle.

Described plane output coupling mirror 3 is the level crossing of part reflecting part transmission, and for the coupling of the radial polarisation light part producing is exported, its reflectivity can require carry out plated film design according to the output of laser.

Described pumping source 4 makes gain media 2 excite transitions form laser for laser provides energy.Described pumping source can have multiple way of realization, such as lamp pumping, and laser pumping, electric pump, LD(semiconductor laser) pumping etc.

Claims (5)

1. the laser based on conical uniaxial crystal outputting radial polarized light beam, be characterised in that its formation comprises: uniaxial crystal conical mirror (1), gain medium (2), plane output coupling mirror (3) and pumping source (4), described gain medium (2) is positioned between described uniaxial crystal conical mirror (1) bottom surface and plane output coupling mirror (3), the drift angle of described uniaxial crystal conical mirror (1) n in formula _oand n _ebe respectively the e light of uniaxial crystal and the main shaft refractive index of o light of making described uniaxial crystal conical mirror (1), the n of described uniaxial crystal _oand n _eshould meet following condition:

$\arctan \frac{n_e}{n_o}>\arcsin \frac{1}{n_o}.$

2. the laser of outputting radial polarized light beam according to claim 1, described in it is characterized in that is uniaxial negative crystal or positive uniaxial crystal for making the material of uniaxial crystal conical mirror.

3. the laser of outputting radial polarized light beam according to claim 1, is characterized in that described gain medium is single cladded fiber or the doubly clad optical fiber that gas laser medium, laser crystal, laser ceramics, fibre core are mixed with rare-earth activated particle.

4. the laser of outputting radial polarized light beam according to claim 1, is characterized in that described plane output coupling mirror is the level crossing of part reflecting part transmission.

5. according to the laser of the outputting radial polarized light beam described in claim 1 to 4 any one, it is characterized in that described pumping source is lamp pumping source, laser pumping source, electric pump source or diode-end-pumped source.

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