CN101060229A - Low noise all solid-state blue laser resonant cavity - Google Patents

Abstract

The disclosed low-noise full-solid blue laser resonant cavity for I-type phase matching multiple frequency crystal comprises: a semi-conductor laser; on the pumping light direction, a coupling lens, a laser crystal with a standard tool and quartz crystal full-wave sheet between the crystal and an I-type phase matching multiple frequency crystal, and an output lens. This invention improves output stability and reduces laser noise efficiently.

Description

Low noise all solid-state blue laser resonant cavity

Technical field

The present invention relates to all solid laser, particularly a kind of low noise all solid-state blue laser resonant cavity.

Background technology

The small-sized blue laser of semiconductor laser pumping intracavity frequency doubling is a kind of technology that fine prospect is arranged, and its scheme is to utilize diode-end-pumped Nd:YAG, suppresses 1064nm and 1319nm starting of oscillation by the plated film means, thereby obtains Nd ³⁺The 946nm transition ( ⁴F _3/2- ⁴I _9/2) laser line, carry out intracavity frequency doubling with frequency-doubling crystal again, thereby obtain the blue laser output that wavelength is 473nm.A subject matter that influences this laser application is that the momentary fluctuation of output is big, and promptly noise is big.Studies show that, this noise mainly because of the many longitudinal modes of fundamental frequency light in frequency-doubling crystal with frequency effect, and the intercoupling of two polarized components of non-polarized Raman laser.Based on this theory, a direct method of elimination or minimizing laser noise forces the laser single-frequency operation exactly.The frequency-selecting method of having reported at present comprises:

Short cavity menu longitudinal mode method is made up of semiconductor laser 1, coupling mirror 2, laser crystal 3, the frequency-doubling crystal output cavity mirror 6 of holding concurrently as Fig. 1;

F-P etalon menu longitudinal mode method is made up of semiconductor laser 1, coupling mirror 2, laser crystal 3, etalon 15, frequency-doubling crystal 6, etalon 16, output cavity mirror 7 as Fig. 2;

Orthogonal polarization modes menu longitudinal mode method is made up of semiconductor laser 1, coupling mirror 2, laser crystal 3, frequency-doubling crystal 6, quarter wave plate 17, output cavity mirror 7 as Fig. 3;

Birefringence filter plate menu longitudinal mode method is made up of semiconductor laser 1, coupling mirror 2, laser crystal 3, polarizer 18, quartz crystal full-wave plate 5, frequency-doubling crystal 6, output cavity mirror 7 as Fig. 4;

Travelling-wave cavity menu longitudinal mode method is made up of semiconductor laser 1, coupling mirror 2, input cavity mirror 19, laser crystal 3,1/2 wave plate 20, TGG Faraday rotator 21, speculum 22, speculum 23, frequency-doubling crystal 6, output cavity mirror 7 as Fig. 5.

Short cavity method menu longitudinal mode method needs restricted room long, and this has just limited endovenous laser crystal, frequency-doubling crystal and other various size of component, thereby makes power output very little and operational mode is single, only is fit to be applied in the microchip laser; F-P etalon menu longitudinal mode method generally need be inserted two etalons simultaneously just can reach desirable frequency-selecting effect, and this just makes that loss is excessive, thereby has limited the laser transformation efficiency; The ability of orthogonal polarization modes menu longitudinal mode method elimination Mode Coupling is not good enough, and long-term working stability is not enough; Birefringence filter plate method suppresses the limited in one's ability of many longitudinal modes running, single-frequency operation stable not good enough; Travelling-wave cavity method structure is too complicated, adjusts the difficulty height, is not suitable for producing in batches.

Summary of the invention

The object of the present invention is to provide a kind of low noise all solid-state blue laser resonant cavity that is applicable to the semiconductor laser pumping intracavity frequency doubling, so that better solve its noise problem.

Technical solution of the present invention is as follows:

A kind of low noise all solid-state blue laser resonant cavity, the pump direction that comprises semiconductor laser and send along this semiconductor laser with optical axis the coupling mirror that sets gradually, laser crystal, I class phase matched frequency-doubling crystal, the output cavity mirror, it is characterized in that between described laser crystal and I class phase matched frequency-doubling crystal, being placed with etalon and quartz crystal full-wave plate, described laser crystal left side is coated with to the antireflective film of pump light with to the multilayer dielectric film of the high reflectance of fundamental frequency light, the right side is coated with the anti-reflection deielectric-coating to fundamental frequency light, described output cavity mirror left side is coated with the deielectric-coating to the high reflectance of fundamental frequency light, the right side is coated with the antireflective film to frequency doubled light, has constituted laserresonator between the left side of described laser crystal and the output cavity mirror; Described quartz crystal full-wave plate and I class phase matched frequency-doubling crystal constitute the birefringence filter plate, and described quartz crystal full-wave plate, I class phase matched frequency-doubling crystal and etalon all are coated with the antireflective film to fundamental frequency light.

The thickness d of described etalon, surface reflectivity R and laser incident angle α satisfy following two relational expressions:

1. the transmissivity of F-P etalon $T\left(\mathrm{\λ}\right)=\frac{1}{1+\frac{4R}{{(1-R)}^2}{\sin }^2\left(\frac{\mathrm{\δ}}{2}\right)},$

2. incident laser gain live width ${\mathrm{\&Delta;v}}_m=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A20071004084600081.png,A20071004084600082.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{nd}\cos \left(\frac{\mathrm{\&alpha;}}{n}\right)},$

In the formula: $\mathrm{\&delta;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}*2\mathrm{nd}\cos \mathrm{\&theta;}$ Be phase difference by adjacent two light beams of F-P etalon surface reflection;

λ is the wavelength in the incident laser vacuum;

N is a F-P etalon d refractive index;

θ is ray refraction angle in the F-P etalon;

C is the light velocity in the vacuum.

Principle of the present invention is as follows:

Use the frequency-selecting of F-P etalon, the transmissivity of F-P etalon changes with wavelength, and the transmissivity of F-P etalon is:

$T\left(\mathrm{\&lambda;}\right)=\frac{1}{1+\frac{4R}{{(1-R)}^2}{\sin }^2\left(\frac{\mathrm{\&delta;}}{2}\right)},$

In the formula: R is the surface reflectivity of F-P etalon;

$\mathrm{\&delta;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}*2\mathrm{nd}\cos \mathrm{\&theta;}$ Be phase difference by adjacent two light beams of F-P etalon surface reflection;

λ is the wavelength in the incident laser vacuum;

D is a F-P etalon thickness;

N is a F-P etalon d refractive index;

θ is ray refraction angle in the F-P etalon.

F-P etalon free spectral range scope is:

${\mathrm{\&Delta;v}}_m=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="A20071004084600081.png,A20071004084600082.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\mathrm{nd}\cos \left(\frac{\mathrm{\&alpha;}}{n}\right)},$

Wherein: α is the etalon angle of inclination.

By selecting suitable R, d and α make free spectral range and incident laser gain live width basically identical, and make in the gain live width and only contain two transmitance maximums, and then this etalon has played the effect of restriction incident laser bandwidth.Simultaneously, I class phase matched frequency-doubling crystal has had effect partially to incident laser, can regard an optical polarizer as, and it and quartz crystal full-wave plate have constituted birefringent filter.Incident laser becomes linearly polarized light through behind this frequency-doubling crystal, and this linearly polarized light is broken down into o light and e light through behind the quartz crystal, and the phase difference of this o light and e light round trip in quartz crystal is: δ=4 π l (n _o-n _e)/λ,

In the formula: l is a quartz crystal thickness, n _oAnd n _eBe o light under the different longitudinal mode correspondences and the refractive index of e light in quartz crystal, λ is the wavelength in the incident laser vacuum.Have only the longitudinal mode that satisfies δ=m π (m is a positive integer), turn back to the polarisation of light direction longitudinal mode identical with former polarization direction of polarizer, this polarizer just is zero to its loss.Polarizer has also just suppressed these longitudinal modes to other longitudinal modes existence losses in various degree, has reached the frequency-selecting effect.

The course of work of resonant cavity of the present invention is as follows:

Send pump light by coupling mirror incident laser crystal by semiconductor laser, the fluorescence that is ejected vibration in the resonant cavity of laser crystal left side and output cavity mirror composition produces many longitudinal modes fundamental frequency light; I class phase matched frequency-doubling crystal and the quartz crystal full-wave plate optically active to fundamental frequency light have constituted the birefringence filter plate, I class phase matched frequency-doubling crystal, quartz crystal full-wave plate and etalon acting in conjunction curb the unnecessary longitudinal mode composition outside the center die of this fundamental frequency light, only keep center die, make fundamental frequency light be the vibration of single longitudinal mode form; Single longitudinal mode fundamental frequency light is through forming the output of single longitudinal mode multiple frequency light after the non-linear frequency multiplication effect of frequency-doubling crystal 6.

The present invention has considered that simultaneously structure is comparatively simple, and cavity loss can not be excessive and low noise laserresonator design requirement such as single longitudinal mode steady operation, the invention has the advantages that:

(1) with respect to the travelling-wave cavity method, structure is comparatively simple, only inserts two additional optical elements altogether, and can satisfactorily finish low noise output steady in a long-term requirement equally, and this makes the batch process of laser become possibility;

(2) with respect to the short cavity method, owing to do not require the chamber is long, so can place more optical elements, and longer laser crystal and frequency-doubling crystal etc., thus power output can be improved;

(3) with respect to cross-polarization method and birefringence filter method, how much not complicated on the structure, but the present invention combines the frequency-selecting effect of etalon and birefringence filter plate, makes that single longitudinal mode output is more stable, can satisfy actual needs;

(4) with respect to F-P etalon method, owing to only adopt 1 etalon, under the similar situation of frequency-selecting effect, effectively reduce loss, and reduced laser and adjusted difficulty, this just embodies the better synthesis effect.

Description of drawings

Fig. 1 is the semiconductor laser pumping intracavity frequency doubling low noise all solid-state blue laser resonant cavity schematic diagram of short cavity method frequency-selecting in the background technology

Fig. 2 is the semiconductor laser pumping intracavity frequency doubling low noise all solid-state blue laser resonant cavity schematic diagram of F-P standard general laws frequency-selecting in the background technology

Fig. 3 is the semiconductor laser pumping intracavity frequency doubling low noise all solid-state blue laser resonant cavity schematic diagram of cross-polarization modulus method frequency-selecting in the background technology

Fig. 4 is the semiconductor laser pumping intracavity frequency doubling low noise all solid-state blue laser resonant cavity schematic diagram of birefringence filter method frequency-selecting in the background technology

Fig. 5 is the semiconductor laser pumping intracavity frequency doubling low noise all solid-state blue laser resonant cavity schematic diagram of travelling-wave cavity method frequency-selecting in the background technology

Fig. 6 is an embodiment of the invention assembling schematic diagram

Embodiment

The invention will be further described below in conjunction with embodiment and accompanying drawing.

See also Fig. 6, Fig. 6 is the assembling schematic diagram of one embodiment of the invention, as seen from the figure, low noise all solid-state blue laser resonant cavity of the present invention, the pump direction that comprises semiconductor laser 1 and send along this semiconductor laser 1 with optical axis the coupling mirror 2 that sets gradually, laser crystal 3, I class phase matched frequency-doubling crystal 6, output cavity mirror 7, it is characterized in that between described laser crystal 3 and I class phase matched frequency-doubling crystal 6, being placed with etalon 4 and quartz crystal full-wave plate 5, described laser crystal 3 left sides are coated with to the antireflective film of pump light with to the high-reflecting film of fundamental frequency light, the right side is coated with the antireflective film to fundamental frequency light, described output cavity mirror 7 left sides are coated with the high-reflecting film to fundamental frequency light, the right side is coated with the antireflective film to frequency doubled light, has constituted laserresonator between the left side of described laser crystal 3 and the output cavity mirror 7; Described quartz crystal full-wave plate 5 constitutes the birefringence filter plate with I class phase matched frequency-doubling crystal 6, and described quartz crystal full-wave plate 5, I class phase matched frequency-doubling crystal 6 and etalon 4 all are coated with the antireflective film to fundamental frequency light.

Described semiconductor laser 1, coupling mirror 2, laser crystal 3, etalon 4, quartz crystal full-wave plate 5, I class phase matched frequency-doubling crystal 6, laser output cavity mirror 7 are installed in laser housing 8 successively respectively and place on coupling mirror support 9 in this laser housing 8, laser crystal bearing 10, etalon bearing 11, full-wave plate bearing 12, frequency-doubling crystal bearing 13, the output cavity mirror bearing 14.

Semiconductor laser 1 adopts the semiconductor laser element of 808nm wavelength output; Coupling mirror 2 adopts the suitable condenser lens of focal lengths, is fixed on the coupling mirror bearing 9 that aluminium alloy makes with glue.

Laser crystal 3 is the Nd:YAG crystal, and this crystal left side is coated with the high saturating deielectric-coating (HT to the 808nm pump light ₈₀₈＞95%) and the high inverse medium film (HR of 946nm fundamental frequency light ₉₄₆＞99.5%), simultaneously to 1064nm and the high saturating (HT of 1319nm _1064,1319＞70%), and as the left end of laserresonator; This crystal right side is coated with the high saturating deielectric-coating (HT to 946nm ₉₄₆＞95%), laser crystal 3 usefulness heat-conducting glues are fixed on above the laser crystal support 10 that aluminium alloy makes.

F-P etalon 4 mainly is made up of the flat glass plate of two precisions and the space collar between plate.Space collar is formed by the very little fused silica material fine finishining of the coefficient of expansion.Etalon is fixed on the etalon support 11 that aluminium alloy makes with glue, as mentioned before, its surface reflectivity, angle of inclination and thickness have determined the modeling effect, under the situation of surface reflectivity and thickness decision, available screw is finely tuned by the etalon angle so that it meets best modeling effect.5 liang of surfaces of quartz crystal full-wave plate are coated with the high transmittance film (HT of 946nm ₉₄₆＞95%), blended rubber is fixed on the full-wave plate support 12 that aluminium alloy makes.

I class phase matched frequency-doubling crystal 6 is three lithium borates (LBO) crystal, and two surfaces are coated with the high transmittance film (HT of 946nm and 473nm ₉₄₆＞95%, HT ₄₇₃＞95%).6 pairs of 946nm laser of frequency-doubling crystal also play a part polarizer, combine the frequency-selecting effect of performance birefringence filter plate with quartz crystal full-wave plate 5.These frequency-doubling crystal 6 usefulness heat-conducting glues are fixed on the frequency-doubling crystal support 13 that aluminium alloy makes.

The left end concave surface of output cavity mirror 7 is coated with 946nm high-reflecting film (HR ₉₄₆＞99.5%) and the antireflective film (AR of 1064nm, 1319nm, 473nm _1064,1319＜30%, AR ₄₇₃＜10%), and, form flat-concave cavity as the right-hand member of laserresonator; The plane plating 473nm antireflective film (AR of right-hand member ₄₇₃＜10%).Output cavity mirror 7 usefulness glue are fixed on the output cavity mirror support 14 that aluminium alloy makes.

Semiconductor laser 1, coupling mirror support 9, laser crystal bearing 10, etalon bearing 11, full-wave plate bearing 12, frequency-doubling crystal bearing 13, output cavity mirror bearing 14 all are fixed on the laser housing 8 that aluminium alloy makes.

This resonant cavity course of work is as follows:

Send pump light by coupling mirror 2 incident laser crystal 3s by semiconductor laser 1, the fluorescence that is ejected vibration in the resonant cavity of laser crystal 3 left sides and output cavity mirror 7 compositions produces many longitudinal modes fundamental frequency light; I class phase matched frequency-doubling crystal 6 and the quartz crystal full-wave plate 5 optically active to fundamental frequency light have constituted the birefringence filter plate, I class phase matched frequency-doubling crystal 6, quartz crystal full-wave plate 5 and etalon 4 actings in conjunction curb the unnecessary longitudinal mode composition outside the center die of this fundamental frequency light, only keep center die, make fundamental frequency light be the vibration of single longitudinal mode form; Single longitudinal mode fundamental frequency light is through forming the output of single longitudinal mode multiple frequency light after the non-linear frequency multiplication effect of frequency-doubling crystal 6.

Claims (3)

1, low noise all solid-state blue laser resonant cavity, the pump direction that comprises semiconductor laser (1) and send along this semiconductor laser (1) with optical axis the coupling mirror (2) that sets gradually, laser crystal (3), I class phase matched frequency-doubling crystal (6), output cavity mirror (7), it is characterized in that between described laser crystal (3) and I class phase matched frequency-doubling crystal (6), being placed with etalon (4) and quartz crystal full-wave plate (5), described laser crystal (3) left side is coated with to the antireflective film of pump light with to the multilayer dielectric film of the high reflectance of fundamental frequency light, the right side is coated with the anti-reflection deielectric-coating to fundamental frequency light, described output cavity mirror (7) left side is coated with the deielectric-coating to the high reflectance of fundamental frequency light, the right side is coated with the antireflective film to frequency doubled light, has constituted laserresonator between the left side of described laser crystal (3) and the output cavity mirror (7); Described quartz crystal full-wave plate (5) constitutes the birefringence filter plate with I class phase matched frequency-doubling crystal (6), and described quartz crystal full-wave plate (5), I class phase matched frequency-doubling crystal (6) and etalon (4) all are coated with the antireflective film to fundamental frequency light.

2, low noise all solid-state blue laser resonant cavity according to claim 1 is characterized in that described semiconductor laser (1), coupling mirror (2), laser crystal (3), etalon (4), quartz crystal full-wave plate (5), I class phase matched frequency-doubling crystal (6), laser output cavity mirror (7) are installed in laser housing (8) successively respectively and place on coupling mirror support (9) in this laser housing (8), laser crystal bearing (10), etalon bearing (11), full-wave plate bearing (12), frequency-doubling crystal bearing (13), the output cavity mirror bearing (14).

3, low noise all solid-state blue laser resonant cavity according to claim 1 is characterized in that thickness d, surface reflectivity R and the laser incident angle α of described etalon (4) satisfies following two relational expressions:

1. the transmissivity of F-P etalon $T\left(\mathrm{\&lambda;}\right)=\frac{1}{1+\frac{4R}{{(1-R)}^2}{\sin }^2\left(\frac{\mathrm{\&delta;}}{2}\right)},$

2. incident laser gain live width ${\mathrm{\&Delta;v}}_m=\frac{c}{2\mathrm{nd}\cos \left(\frac{\mathrm{\&alpha;}}{n}\right)},$

In the formula: $\mathrm{\&delta;}=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}*2\mathrm{nd}\cos \mathrm{\&theta;}$ Be phase difference by adjacent two light beams of F-P etalon surface reflection;

λ is the wavelength in the incident laser vacuum;

N is a F-P etalon d refractive index;

θ is ray refraction angle in the F-P etalon.

C is the light velocity in the vacuum.

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