CN103532012B - External cavity semiconductor laser - Google Patents

Abstract

An external cavity semiconductor laser, comprising a semiconductor optical amplifier and a collimator lens, a Brewster window, and a rotatable single-cavity all-dielectric thin film Fabry-Pert that are sequentially arranged on the optical path of the output light of the semiconductor optical amplifier Raw optical filter, partial reflector, and actuating mechanism; the incident angle of the outgoing light of the collimator lens incident on the Brewster window is the Brewster angle; the partial reflector is perpendicular to the The optical path of the outgoing light of the single-cavity all-dielectric film Fabry-Perot filter; the actuating mechanism is connected with the transmission of the single-cavity all-dielectric film Fabry-Perot filter and the partial reflector , so that the single-cavity all-dielectric film Fabry-Perot filter is rotated, and the partial reflector is moved along its normal direction. The above-mentioned external cavity semiconductor laser can realize linear and continuous tuning of the output wavelength, and the direction of the output light does not change with the wavelength tuning.

Description

External cavity semiconductor laser

technical field

The invention relates to laser equipment, in particular to an external cavity semiconductor laser.

Background technique

External-cavity semiconductor lasers are low in cost and small in size, and can achieve high-power single-mode emission well. Their products have been widely used in systems such as frequency division multiplexing and coherent optical communication.

At present, a variety of structures have been developed for external-cavity semiconductor lasers. Although they are different, their design principles are the same, that is, insert a light-splitting element into the external cavity, and adjust the light-splitting element and the feedback mechanism outside the cavity to realize the laser wavelength. tuning.

The two traditional external cavity structures are the Littrow structure and the Littman-Metcalf structure based on diffraction gratings. The wavelength of the output beam cannot be linearly tuned, and the direction of the output beam will change with the tuning of the wavelength.

Contents of the invention

Based on this, it is necessary to address the above problems and provide an external cavity semiconductor laser whose output light wavelength can be linearly tuned and whose output light direction does not change with the wavelength tuning.

An external cavity semiconductor laser, comprising:

A semiconductor optical amplifier and a collimator lens, a Brewster window, a rotatable single-cavity all-dielectric thin-film Fabry-Perot filter, and a partial reflector are sequentially arranged on the optical path of the output light of the semiconductor optical amplifier , and the actuating mechanism;

The incident angle at which the outgoing light of the collimating lens is incident on the Brewster window is Brewster's angle;

The partial reflector is perpendicular to the optical path of the outgoing light of the single-cavity all-dielectric film Fabry-Perot filter;

The actuating mechanism is in transmission connection with the single-cavity all-dielectric film Fabry-Perot filter and the partial reflector, so that the single-cavity all-dielectric film Fabry-Perot filter is rotated , and make the partial reflector move along its own normal direction.

In one of the embodiments, it also includes a first plane complete reflection mirror and a second plane complete reflection mirror, the first plane complete reflection mirror is arranged at the outlet of the single-cavity all-dielectric film Fabry-Perot filter On the optical path of the emitted light, the optical path of the reflected light of the first plane complete reflection mirror is perpendicular to the said partial reflection mirror; the second plane complete reflection mirror is arranged on the optical path of the outgoing light of the said partial reflection mirror.

In one of the embodiments, the actuating mechanism includes a transmission rod, a transmission ball and a push block, one end of the transmission rod is connected to the single-cavity all-dielectric film Fabry-Perot filter, and the other end is connected to the The driving ball is connected, and the driving block pushes the driving ball to make the single-cavity all-dielectric film Fabry-Perot filter rotate counterclockwise, and the pushing block approaches and pushes the partial reflector along its The direction in which the incident light is incident moves in the opposite direction.

In one of the embodiments, it further includes a thermoelectric cooler for controlling the temperature of the semiconductor optical amplifier, so that the semiconductor optical amplifier operates at 25°C.

In one of the embodiments, the light outlet of the semiconductor optical amplifier is coated with an antireflection film, and the surface opposite to the light outlet is coated with a high reflection film.

In one of the embodiments, the Brewster window is made of uncoated K9 glass, is circular, has a diameter of 20mm, a physical thickness of 2mm, and the Brewster's angle is 56.6 degrees.

In one of the embodiments, the single-cavity all-dielectric thin-film Fabry-Perot filter is an interference filter, and the film structure of the single-cavity all-dielectric thin-film Fabry-Perot filter is as follows :

Air|(HL) ^P H-2L-H(LH) ^P |Glass

Among them, Air is air, Glass is the substrate, H is the Ta ₂ O ₅ refractive medium layer with a quarter-wavelength optical thickness, L is the SiO ₂ refractive medium layer with a quarter-wavelength optical thickness, and P is the corresponding dielectric layer the number of repetitions.

In one embodiment, the Ta ₂ O ₅ refraction medium layer has a refractive index of 2.06 and a physical thickness of 193.57 nm; the SiO ₂ refraction medium layer has a refractive index of 1.46 and a physical thickness of 273.12 nm. The sheet is a K9 glass substrate with a physical thickness of 2mm and a refractive index of 1.5168, and the number of repetitions of the corresponding dielectric layers is 7.

In one of the embodiments, the substrate of the single-cavity all-dielectric film Fabry-Perot filter is coated with an anti-reflection film, and its film structure is as follows:

Air|(HL) ^P H-2L-H(LH) ^P |Glass|AR

Among them, AR is anti-reflection film.

In one of the embodiments, the partial reflector is made of K9 glass, which is circular and has a diameter of 25.4mm. Its incident surface is concave with a radius of curvature of 500mm. % of the partial reflection film, the exit surface of the partial reflection mirror is a plane, the plane is coated with an anti-reflection film, the concave surface of the partial reflection mirror and the surface of the semiconductor optical amplifier coated with a high reflection film constitute Flat-concave cavity.

In one of the embodiments, the reflectance of the partially reflective film is 60%.

In the above-mentioned external cavity semiconductor laser, the single-cavity all-dielectric film Fabry-Perot filter is rotated by the actuating mechanism, and part of the mirror is moved along its normal direction to adjust the single-cavity all-dielectric film Fabry-Perot filter. The transmission central wavelength of the Perot filter and the external cavity longitudinal mode wavelength of the laser, since the transmission central wavelength and the external cavity longitudinal mode wavelength change linearly with the displacement of the actuator mechanism, it can achieve linear and continuous tuning of the output wavelength, and the tuning It will not affect the optical path, and the direction of the output light will not change with the wavelength tuning.

Description of drawings

Fig. 1 is the structural representation of the external cavity semiconductor laser of an embodiment;

Fig. 2 is a schematic diagram of an actuating mechanism of an embodiment;

Fig. 3 is a diagram showing the variation of the fractional modulus corresponding to the transmission center wavelength of the single-cavity all-dielectric thin-film Fabry-Perot filter according to an embodiment.

detailed description

As shown in Figure 1, a kind of external cavity semiconductor laser comprises a semiconductor optical amplifier 10 and a collimator lens 20, a Brewster window 30, and a rotatable A single-cavity all-dielectric film Fabry-Perot filter 40 , a first planar complete reflection mirror 50 , a partial reflection mirror 60 , a second planar complete reflection mirror 70 , and an actuating mechanism 80 .

The light outlet 11 of the semiconductor optical amplifier 10 is coated with an anti-reflection film with a reflectivity less than 0.01%, and the surface 12 opposite to the light outlet 11 is coated with a high reflection film with a reflectivity greater than or equal to 90%, forming a reflective semiconductor optical amplifier. (RSOA). For the light outlet 11 coated with an anti-reflection coating, the reflectivity of the internal light of the semiconductor optical amplifier 10 should be as low as possible, generally lower than 10 ^-3 order of magnitude; the semiconductor optical amplifier 10 has a higher polarization correlation Gain, the output near-infrared light is mainly TE polarized light (the polarization direction is perpendicular to the horizontal plane, please refer to the paper of Figure 1 and Figure 2 for the horizontal plane), and there is also a small amount of TM polarized light (the polarization direction is parallel to the horizontal plane); in addition , the semiconductor optical amplifier 10 needs to use a thermoelectric cooler (TEC) to control its temperature so that it can run stably at 25°C; meanwhile, the driving current of the semiconductor optical amplifier 10 is set to 230mA. The specific parameters are shown in Table 1.

Table 1

The collimator lens 20 is used to collimate the near-infrared light into near-infrared parallel light, and the incident angle of the outgoing light incident on the Brewster window 30 is Brewster's angle.

The Brewster window 30 is made of uncoated K9 glass, which is circular, with a diameter of 20mm and a physical thickness of 2mm. The angle between the sheet 30 and the horizontal plane is 33.4 degrees, so that the near-infrared parallel light is incident on the Brewster window 30 at a Brewster angle of 56.6 degrees, so as to filter out the TM polarized light in the parallel light beam , so as to ensure that the final output of the laser is pure TE polarized light.

The single-cavity all-dielectric film Fabry-Perot filter 40 is arranged on the outgoing light path of the Brewster window 30 and can rotate around an axis 9 perpendicular to the light path.

The single-cavity all-dielectric film Fabry-Perot filter 40 is a narrow-band interference filter, and the film structure of the single-cavity all-dielectric film Fabry-Perot filter is as follows:

Air|(HL) ^P H-2L-H(LH) ^P |Glass

Among them, Air is air, and Glass is the substrate, which is made of K9 glass with a physical thickness of 2mm and a refractive index of 1.5168; H is Ta with a quarter-wavelength optical thickness, a refractive index of 2.06, and a physical thickness of 193.57nm. ₂ O ₅ refraction medium layer; L is a quarter-wavelength optical thickness, a refractive index of 1.46, and a physical thickness of 273.12nm SiO ₂ refraction medium layer, P is the number of repetitions of the corresponding medium layer, preferably 7, at this time Multiple vibration longitudinal modes in the external cavity can be filtered, leaving only a single longitudinal mode output.

In order to prevent the light beam from reflecting back and forth in the substrate, an anti-reflection coating can be coated on the substrate, and the film structure of the single-cavity all-dielectric film Fabry-Perot filter 40 after coating is Air|(HL) ^PH -2L-H(LH) ^P |Glass|AR, wherein AR is an anti-reflective coating.

As shown in FIG. 2 , the central transmission wavelength of the single-cavity all-dielectric film Fabry-Perot filter 40 can be changed by changing its inclination angle θ: the larger the inclination angle θ, the smaller the transmission central wavelength. Moreover, for transverse electric field light (TE polarized light) or transverse magnetic field light (TM polarized light), the transmission central wavelength of the single-cavity all-dielectric film Fabry-Perot filter 40 and the cosine of its inclination angle θ are within a certain range There is a linear relationship inside.

The first plane complete reflection mirror 50 is located on the outgoing optical path of the single-cavity all-dielectric film Fabry-Perot filter 40, and the optical path of the reflected light of the first plane complete reflection mirror 50 is perpendicular to the The partial reflection mirror 60; the second plane complete reflection mirror 70 is located on the outgoing light path of the partial reflection mirror 60, and the outgoing light of the partial reflection mirror 60 is the output light of the laser, which is completely reflected by the second plane Output after reflection by mirror 70.

The partial reflector 60 is made of K9 glass, which is circular and has a diameter of 25.4 mm. Its incident surface is a concave surface with a radius of curvature of 500 mm. The concave surface is coated with a partial reflective film with a reflectivity of 50% to 90%. The outgoing surface of the partial reflector 60 is a plane, and the plane is coated with an anti-reflection film; the concave surface of the partial reflector 60 and the surface of the semiconductor optical amplifier 10 coated with a high-reflection film form a flat-concave resonant cavity, so that the resonant cavity forms With stable oscillation, the light beam will be focused and reflected back to the light source after it is incident on the concave surface of the partial reflector 60 . When the reflectivity of the partial reflection film is 60%, the output laser wavelength value, line width and output power of the flat-concave resonator will reach the best.

The actuating mechanism 80 is in transmission connection with the single-cavity all-dielectric film Fabry-Perot filter 40 and the partial reflector 60, so that the single-cavity all-dielectric film Fabry-Perot filter The optical sheet 40 rotates, and the partial reflector 60 is moved along its normal direction, so as to adjust the transmission center wavelength of the single-cavity all-dielectric thin-film Fabry-Perot filter 40 and the longitudinal axis of the external cavity of the laser. mode wavelength, thereby linearly tuning the wavelength of the output laser.

Specifically, the actuating mechanism 80 includes a transmission rod 81, a transmission ball 82 and a push block 83, one end of the transmission rod 81 is connected to the single-cavity all-dielectric film Fabry-Perot filter 40, and the other One end is connected with the driving ball 82, and the pushing block 83 can reciprocate left and right on the horizontal plane. When the pushing block 83 moves to the right along the horizontal direction, it will push the transmission ball 82, so that the single-cavity all-dielectric film Fabry-Perot filter 40 rotates counterclockwise around the axis 9; meanwhile, the pushing block 83 will slowly approach and connect to the partial reflector 60 when moving to the right, and then push the partial reflector 60 to move backward (that is, to move in the opposite direction of its incident light). When the pushing block 83 moves forward on the horizontal plane, it will drive the partial reflector 60 to move along the direction of its incident light; The elastic recovery device carried can make it rotate clockwise around the axis 9 along with the movement of the pushing block 83 .

Specifically, the transmission ball 82 can be made into a standard sphere with a smooth surface, and the frictional resistance is very small. To ensure the sensitivity of the movement of the single-cavity all-dielectric film Fabry-Perot filter 40 driven by the pushing block 83 . Driving the pushing block 83 left and right along the horizontal direction can make the single-cavity all-dielectric film Fabry-Perot filter 40 rotate around the axis 9; driving the pushing block 83 forward and backward along the horizontal direction can also make the partial reflector 60 synchronized back and forth movement.

The elastic recovery device can apply a clockwise elastic force (recovery force) to the single-cavity all-dielectric film Fabry-Perot filter 40, when the pushing block 83 deviates from the initial position (that is, position 1 in Figure 2) When the single-cavity all-dielectric film Fabry-Perot filter 40 and the partial reflector 60 are driven to move, the elastic force will be overcome. When the push block 83 returns to the initial position, the single-cavity all-dielectric film Fabry-Perot filter The sheet 40 follows the movement of the pushing block 83 due to the elastic force.

It can be understood that the first planar complete transmitter 50 and the second planar complete reflector 70 can also be simplified, as long as the position of the partial reflector 60 is changed, and the partial reflector 60 is perpendicular to the single-cavity all-dielectric film The output light path of the Fabry-Perot filter 40, and the actuating mechanism 80 can push the partial reflector 60 to move along the opposite direction of its incident light. Mirror 60 outputs directly.

As shown in Figure 2, the position when the single-cavity all-dielectric film Fabry-Perot filter 40 is perpendicular to the outgoing light path of the Brewster window is recorded as the initial position (position 1 in Figure 2), when When the push block 83 (not shown in FIG. 2 ) starts to advance from the initial position, two movements will occur simultaneously: 1) counterclockwise rotation of the single-cavity all-dielectric film Fabry-Perot filter 40; 2) Forward movement of the partially reflective mirror 60 (the opposite direction of its incident light incidence). The counterclockwise rotation of the single-cavity all-dielectric film Fabry-Perot filter 40 will gradually reduce its transmission center wavelength; the forward movement of the partial mirror 60 will gradually reduce the round-trip optical path of the entire laser system. , so that the wavelength of the external cavity longitudinal mode gradually decreases. It can be proved that when the push block 83 is pushed from the initial position to a certain area, the transmission center wavelength of the single-cavity all-dielectric film Fabry-Perot filter 40 will decrease synchronously with the wavelength of a certain external cavity longitudinal mode . At this time, the laser will output a single longitudinal mode laser with continuously adjustable wavelength (no mode hopping), and the tuning will not affect the optical path, and the direction of the output beam will not change with the tuning of the wavelength. Moreover, the laser has a simple structure and low cost.

Assuming that at the initial position, the total length of the round-trip optical path of the entire external cavity (that is, the total length of the initial round-trip optical path of the external cavity) is OPL (0); when the push block 83 (not shown in Figure 2) is pushed forward by x (mm ) (arriving at position 2 in Figure 2), the amount of change in the round-trip optical path length of the external cavity is OPD(x); the physical thickness of the substrate of the single-cavity all-dielectric film Fabry-Perot filter 40 is h, The refractive index of the substrate is n, and the distance from the center of the rotating shaft 9 to the center of the sphere 82 is L. According to Figure 2, the expression of OPD(x) is:

$\mathrm{<span\; class="notranslate">\; OPD</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; hL</span>}}{\sqrt{{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; wxya</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; wxya</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>\sqrt{{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; wxya</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; wxya</span>}}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Then, when the pushing block 83 is pushed forward by x (mm) from the initial position, the total round-trip optical path length of the new external cavity is OPL(x)=OPL(0)-OPD(x). Thus, the total length of the round-trip optical path of the external cavity after the pushing block 83 is pushed to a new position can be obtained.

Simultaneously, after the pushing block 83 advances x (mm), by the following formula, the rotation angle θ of the single-cavity all-dielectric film Fabry-Perot filter 40 can be obtained,

$\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Here θ is also the incident angle of the laser beam at the single-cavity all-dielectric film Fabry-Perot filter 40 at this time. For a given single-cavity all-dielectric film Fabry-Perot filter 40, its transmission center wavelength λ _s (x) is a function of its beam incident angle θ, since the incident angle θ has been obtained, so at this time The λ _s (x) of is also a fixed value, which can be calculated accordingly. According to the transmission characteristics of the single-cavity all-dielectric film Fabry-Perot filter 40 and the lasing principle of the external cavity semiconductor laser, the change of the transmission center wavelength of the single-cavity all-dielectric film Fabry-Perot filter 40 There is a quasi-linear relationship with the change of the wavelength of the external cavity longitudinal mode of the external cavity semiconductor laser.

Therefore, the fractional longitudinal mode corresponding to the transmission center wavelength of the single-cavity all-dielectric thin-film Fabry-Perot filter 40 is defined as m _s (x), and when the pushing block 83 is pushed forward by x (mm), Have

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; OPL</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

As x changes continuously, m _s (x) also changes.

Here, h=2(mm), n=1.5168.

If the distance from the center of the axis 9 to the center of the sphere of the transmission ball 82 is 81mm, then the total length of the round trip optical path of the initial external cavity of the laser (that is, from the concave surface of the semiconductor optical amplifier 10 that is coated with a high reflection film to the concave surface of the partial reflector 60 The round-trip optical path length) OPL(0) is 449.9mm. Then, when the pushing block 83 is pushed forward by 5.9~6.7mm, the output wavelength of the external cavity semiconductor laser will be in the range of continuous adjustment without mode hopping. The displacement of 83 changes linearly. Due to the long round-trip optical path of the external cavity of the external cavity semiconductor laser, a relatively narrow output laser linewidth can be obtained. In the actual output performance test, as the pushing block 83 is pushed forward by 5.9~6.7mm, the output wavelength of the external cavity semiconductor laser shows a basic linear change in the range of 1547.203~1552.426nm, and the output power is relatively stable. Between 40~50microwatts, the output longitudinal mode is always a single longitudinal mode, and its line width is relatively stable between 100~150MHz. Based on the above parameters, we can package and shape the external cavity semiconductor laser 100 . Of course, the above parameters can have ±5% fluctuation.

Fig. 3 is " m _s (x)-x " graph, can be seen from the figure, along with pushing block 83 from initial position, begin to advance gradually, the transmission center wavelength of single-cavity all-dielectric film Fabry-Perot filter 40 The corresponding fractional longitudinal modulus will first increase and then decrease. There is a smooth transition region between increase and decrease, and the fractional longitudinal modulus in this region remains basically stable, indicating that in this region, the single-cavity all-dielectric film Fabry-Perot filter 40 The transmission center wavelength of is changing synchronously with the wavelength of a certain external cavity longitudinal mode. That is to say, in this region, the output wavelength of the external cavity semiconductor laser is continuously adjustable without mode hopping.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. An external cavity semiconductor laser, characterized in that, comprising: A semiconductor optical amplifier and a collimator lens, a Brewster window, a rotatable single-cavity all-dielectric thin-film Fabry-Perot filter, and a partial reflector are sequentially arranged on the optical path of the output light of the semiconductor optical amplifier , and the actuating mechanism; The incident angle at which the outgoing light of the collimating lens is incident on the Brewster window is Brewster's angle; The partial reflector is perpendicular to the optical path of the outgoing light of the single-cavity all-dielectric film Fabry-Perot filter; The actuating mechanism is in transmission connection with the single-cavity all-dielectric film Fabry-Perot filter and the partial reflector, so that the single-cavity all-dielectric film Fabry-Perot filter is rotated , and make the partial reflector move along its normal direction; Wherein, the actuating mechanism includes a transmission rod, a transmission ball and a push block, one end of the transmission rod is connected with the single-cavity all-dielectric film Fabry-Perot filter, and the other end is connected with the transmission ball , the pushing block pushes the transmission ball to make the single-cavity all-dielectric film Fabry-Perot filter rotate counterclockwise, and the pushing block approaches and pushes the partial reflection mirror along its incident light incident reflection direction to move. 2. The external cavity semiconductor laser according to claim 1, further comprising a first plane complete reflection mirror and a second plane complete reflection mirror, the first plane complete reflection mirror being arranged on the single-cavity all-dielectric On the optical path of the light emitted by the thin-film Fabry-Perot filter, the optical path of the reflected light of the first plane complete reflection mirror is perpendicular to the said partial reflection mirror; the second plane complete reflection mirror is arranged on the said part The optical path of the light emitted by the reflector. 3. The external cavity semiconductor laser according to claim 1 or 2, further comprising a thermoelectric cooler for controlling the temperature of the semiconductor optical amplifier, so that the semiconductor optical amplifier operates at 25°C. 4. The external cavity semiconductor laser according to claim 3, characterized in that, the light exit port of the semiconductor optical amplifier is coated with an anti-reflection film, and the surface opposite to the light exit port is coated with a high reflection film. 5. external cavity semiconductor laser according to claim 4, is characterized in that, described Brewster window is made of uncoated K9 glass, is circular, and its diameter is 20mm, and physical thickness is 2mm, so The Brewster's angle is 56.6 degrees. 6. external cavity semiconductor laser according to claim 5, is characterized in that, described single-cavity all-dielectric film Fabry-Perot filter is an interference filter, and its film system structure is as follows: Air|(HL) ^P H-2L-H(LH) ^P |Glass Among them, Air is air, Glass is the substrate, H is the Ta ₂ O ₅ refractive medium layer with a quarter-wavelength optical thickness, L is the SiO ₂ refractive medium layer with a quarter-wavelength optical thickness, and P is the corresponding dielectric layer the number of repetitions. 7. The external cavity semiconductor laser according to claim 6, characterized in that, the Ta ₂ O _The refractive index of the refraction medium layer is 2.06, and the physical thickness is 193.57nm, and the refractive index of the SiO ₂ Refraction medium layer is 1.46, the physical thickness is 273.12nm, the substrate is a K9 glass substrate, the physical thickness is 2mm, the refractive index is 1.5168, and the number of repetitions of the corresponding dielectric layer is 7. 8. external cavity semiconductor laser according to claim 7, is characterized in that, the substrate of described single-cavity all-dielectric film Fabry-Perot optical filter is coated with anti-reflection film, and described single-cavity all-dielectric film The film structure of the Fabry-Perot filter is as follows: Air|(HL) ^P H-2L-H(LH) ^P |Glass|AR Among them, AR is anti-reflection film. 9. The external-cavity semiconductor laser according to claim 8, wherein the partial reflector is made of K9 glass and is circular with a diameter of 25.4mm, its incident surface is concave, and its radius of curvature is 500mm. A partial reflective film with a reflectivity of 50% to 90% is coated on the top, the exit surface of the partial reflector is a plane, and an anti-reflection film is coated on the plane, and the concave surface of the partial reflector is in contact with the semiconductor The surface of the optical amplifier coated with a high reflection film constitutes a flat-concave resonant cavity. 10. The external cavity semiconductor laser according to claim 9, wherein the reflectivity of the partially reflective film is 60%.