CN101345392A - Low-loss semiconductor pump laser - Google Patents

Abstract

The invention discloses a low loss semiconductor pumped laser comprising a pumping system outputting light around 1083nm wavelength as fundamental frequency light and a laser cavity including a laser cavity tablet, a laser gain medium and nonlinear frequency-doubling crystal, wherein the laser gain medium is a Nd<3+>-doped laser gain medium. The polarization direction of the frequency-doubling crystal is perpendicular to the direction of optical axis of the laser gain medium to reduce the loss in cavity by arranging the relative position of the laser gain medium optical axis and the axial direction of the nonlinear frequency-doubling crystal or adding a halfwave plate between both using transition emission of Nd<3+> ion <4>F3/2 - <4>I11/2, thereby the loss of frequency-doubling light is reduced to minmum.

Description

A kind of low-loss semiconductor pump laser

Technical field

The present invention relates to laser field, relate in particular to a kind of employing⁴F_3/2→⁴I_11/2Near the emitting fluorescence of the wavelength of 1083nm is as low-loss semiconductor pump laser in the chamber of fundamental frequency light in the transition emission.

Background technology

In the gain medium of Nd ion doping,⁴F_3/2→⁴I_11/2Near in the transition 1064nm fluorescent transition intensity is the strongest, the general 1064nm of employing wavelength as fundamental frequency light to realize frequency multiplication or frequency tripling, to obtain the output of green glow or ultraviolet light, semiconductor pump laser as shown in Figure 1, 2, it comprises thatpumping system 100, laser cavity chamber sheet 101,102,105, uniformdielectric gain medium 103 are as Nd:YAG and non-linear frequency-doubling crystal 104.

For the laser medium material that Nd mixes, the 532nm wavelength around just in time drops on the secondary peak of Nd ionic absorption characteristic peak.Frequency multiplication or frequency tripling output in order to realize the 1064nm wavelength reduce cavity loss, adopt refrative cavity usually or add other optics, and the light that makes the 532nm wavelength is without the laser gain material, to reach the purpose that reduces cavity loss.Utilize these methods, can reduce the loss in the laser cavity, but the structure more complicated, for its application has brought certain degree of difficulty.

For rare earth ion doped system, the level structure of rare earth ion can adopt that central field is approximate to be obtained, and the f layer electronics of rare earth ion be in the shielding action of outer shell, can be similar to such an extent that think free ion.The energy level of rare earth ion can be used like this^2S+1L_JExpression.For free atom or ion under not doing in the outfield, one group of LSJ is only corresponding to an energy level.In gain medium, rare earth ion is subjected to the effect of crystalline field,^2S+1L_JEnergy level splitting becomes many spectral lines.As shown in Figure 2, at Nd³⁺In the ion,⁴F_3/2Multiplet splitting becomes R₁And R₂Article two, spectral line, and⁴I_11/2Multiplet splitting becomes Y₁To Y₆Totally 6 spectral lines.

At Nd:YVO₄In the crystal, the Nd ion occupies D in crystal_2dThe position of point group, according to the transition selective rule, for⁴F_3/2→⁴I_11/2Transition, in the σ polarization spectrum, all transition from the R spectral term to the Y spectral term allow; And in the spectrum of π polarization, have only R₁→ Y₂, Y₄, Y₆, and R₂→ Y₁, Y₃, Y₅Transition is permitted.At doping Nd³⁺In the gain medium of ion, the introducing of impurity influences to some extent to fluorescent radiation, and the transition of forbidding originally also can take place, but its probability is very little, can be without a moment's thought.

According to the Judd-Ofelt theory, calculate and find Nd:YVO₄Crystal is R on the π polarization direction₁→ Y₂(wave number is 9396cm in transition^-1, and 1064mm) transition probability be 0.2291, R on the σ polarization direction₁→ Y₅(wave number is 9230cm in transition^-1, and 1083nm) transition probability be 0.1812 (Luo Zundu, eds.J.Phys.:Condens.Matter vol.6, pp.3737-3748).In the normal temperature fluorometric investigation, can find the existence of this two wave bands transition.

Gain medium Nd:YVO as shown in Figure 3₄Fluorescence curve, single crystal fiber (a), monocrystalline (b) (D.ReyesArdilaeds.J.Crystal Growth vol.233 pp.253-258).Frequency doubled light so that near the fundamental frequency light the 1083nm is produced just drops on crystal σ polarization direction⁴I_9/2→⁴G_7/2+⁴G_9/2On the ABSORPTION EDGE of absorptive transition, crystal almost is equivalent to the absorption of material itself to the absorption of this wavelength light, and loss is little; And on the π polarization direction, this wave band also drops on⁴I_9/2→⁴G_7/2+⁴G_9/2In the absorptive transition scope, also belong to Nd³⁺The characteristic absorption of ion, loss is big.For the crystal of other isostructure optical axis, also there is similar phenomenon, as: Nd:LuVO₄, Nd:GdVO₄Deng.

Summary of the invention

The object of the invention provide a kind of with near the wavelength light 1083nm as fundamental frequency light, the little low-loss semiconductor pump laser of loss simple in structure, energy.

The present invention adopts following structure: wavelength light was as fundamental frequency optical pumping system, laser cavity near semiconductor pump laser comprised output 1083nm, laser cavity comprises laser cavity chamber sheet, gain medium and non-linear frequency-doubling crystal, and gain medium is for mixing Nd³⁺Gain medium, adopt Nd³⁺Ion⁴F_3/2→⁴I_11/2The transition emission, wherein

A. adopt a class phase matched when non-linear frequency-doubling crystal, and when adopting o+o → e structure, non-linear frequency-doubling crystal axially and the optical axis of gain medium be parallel to each other, the relative gain medium of frequency doubled light is the σ polarization;

B. adopt a class phase matched when non-linear frequency-doubling crystal, and when adopting e+e → o structure, non-linear frequency-doubling crystal axially vertical mutually with the optical axis of gain medium, the relative gain medium of frequency doubled light is the σ polarization;

C. when non-linear frequency-doubling crystal adopts two class phase matched, and when adopting o+e → o structure, between non-linear frequency-doubling crystal and gain medium, insert half-wave plate, the optical axis of half-wave plate places optical direction, and on the middle separated time of gain medium optical axis and the non-linear frequency-doubling crystal angle between axially, making frequency doubled light be equivalent to gain medium is o light.

Above-mentioned laser cavity is discrete laser cavity or micro-piece type laser cavity.

The above-mentioned gain medium that mixes Nd3+ refers to Nd:YVO4, Nd:GdVO4, Nd:LuVO4.

The present invention adopts said structure, at different non-linear frequency-doubling crystals, by gain medium optical axis and the axial relative position of non-linear frequency-doubling crystal are set, perhaps between the two, add half-wave plate, make the polarization direction and the gain medium optical axis direction of its frequency doubled light orthogonal, to reduce cavity loss, drop to minimum thereby make frequency doubled light get loss.This structure has greater advantage to the simplification of structure in high-power frequency multiplication or frequency tripling laser.

Description of drawings

Now in conjunction with the accompanying drawings the present invention is further elaborated:

Fig. 1 is the structural representation of one of existing semiconductor pump laser;

Fig. 2 is two a structural representation of existing semiconductor pump laser;

Fig. 3 is the schematic diagram of gain medium Nd:YVO4 fluorescence curve;

Fig. 4 is the structural representation of one of semiconductor pump laser of the present invention;

Fig. 5 is two a structural representation of semiconductor pump laser of the present invention;

Fig. 6 is three a structural representation of semiconductor pump laser of the present invention.

Embodiment

See also shown in Fig. 4 or 5, wavelength light is as fundamental frequencyoptical pumping system 100,laser cavity 10 near the present invention includes output 1083nm,laser cavity 10 comprises laser cavity chamber sheet 101,102,gain medium 103 and non-linear frequency-doubling crystal 104, and gain medium is for mixing Nd³⁺Gain medium, be commonly referred to as Nd:YVO₄, Nd:GdVO₄, Nd:LuVO₄Etc. a series of Nd³⁺The gain medium that mixes adopts Nd³⁺Ion⁴F_3/2→⁴I_11/2Transition emission is wherein adopted a class phase matched when non-linear frequency-doubling crystal 104, and when adopting o+o → e structure, non-linear frequency-doublingcrystal 104 axially and the optical axis ofgain medium 103 be parallel to each other, therelative gain medium 103 of frequency doubled light is the σ polarization; When non-linear frequency-doubling crystal 104 adopts a class phase matched, and when adopting e+e → o structure, non-linear frequency-doubling crystal 104 axially vertical mutually with the optical axis ofgain medium 103, therelative gain medium 103 of frequency doubled light is the σ polarization; Therelative gain medium 103 of frequency doubled light dropped to minimum for the σ polarization thereby make frequency doubled light get loss near two states all must be proved 1083nm.

See also shown in Figure 6, when non-linear frequency-doubling crystal 104 adopts two class phase matched, and when adopting o+e → o structure, between non-linear frequency-doubling crystal 104 andgain medium 103, insert half-wave plate 106, the optical axis of half-wave plate 106 places optical direction, and on the middle separated time of the angle ofgain medium 103 optical axises and non-linear frequency-doubling crystal 104 between axially, establish the optical axis of half-wave plate 106 and the angle of optical direction and be

The angle ofgain medium 103 optical axises and optical direction is 90 °, and non-linear frequency-doubling crystal 104 angles axial and optical direction are θ, promptly

So utilize the wave plate structure, the frequency doubled light that produces is rotated a certain angle, make frequency doubled light be equivalent to gainmedium 103 and be o light, to reduce cavity loss.

Above-mentioned laser cavity is discrete laser cavity or micro-piece type laser cavity.

The present invention is particularly useful for the microchip intracavity frequency doubling laser of tight structure.

Claims (3)

1, a kind of low-loss semiconductor pump laser, wavelength light is as fundamental frequency optical pumping system, laser cavity near comprising output 1083nm, laser cavity comprises laser cavity chamber sheet, gain medium and non-linear frequency-doubling crystal, gain medium is the gain medium that mixes Nd3+, adopt Nd3+ ion 4F3/2 → 4I11/2 transition emission, it is characterized in that:

A. adopt a class phase matched when non-linear frequency-doubling crystal, and when adopting o+o → e structure, non-linear frequency-doubling crystal axially and the optical axis of gain medium be parallel to each other, the relative gain medium of frequency doubled light is a polarization;

B. adopt a class phase matched when non-linear frequency-doubling crystal, and when adopting e+e → o structure, non-linear frequency-doubling crystal axially vertical mutually with the optical axis of gain medium, the relative gain medium of frequency doubled light is a polarization;

C. when non-linear frequency-doubling crystal adopts two class phase matched, and when adopting o+e → o structure, between non-linear frequency-doubling crystal and gain medium, insert half-wave plate, the optical axis of half-wave plate places optical direction, and on the middle separated time of gain medium optical axis and the non-linear frequency-doubling crystal angle between axially, making frequency doubled light be equivalent to gain medium is o light.

2, a kind of low-loss semiconductor pump laser according to claim 1 is characterized in that: its laser cavity is discrete laser cavity or micro-piece type laser cavity.

3, a kind of low-loss semiconductor pump laser according to claim 1 is characterized in that: its gain medium that mixes Nd3+ refers to Nd:YVO4, Nd:GdVO4, Nd:LuVO4.

Images